WO2012082717A2 - Porous metal dendrites for high efficiency aqueous reduction of co2 to hydrocarbons - Google Patents

Abstract

A porous metal catalyst having a high BET surface area for converting carbon dioxide to a hydrocarbon and a method and a system for converting carbon dioxide to a hydrocarbon where the method and system utilize a metal catalyst and optionally an ion exchange resin.

Description

Porous Metal Dendrites for High Efficiency Aqueous Reduction of C0₂ to

Hydrocarbons

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit of USSN 61/422,510 filed December 13, 2010, and hereby incorporated by reference in its entirety.

BACKGROUND

Existing carbon infrastructure costs can be viewed as running contrary making a transition from a fossil fuel economy to alternative energy sources. Thus, intermediate solutions which abate C0₂ emissions while also producing valuable products can be useful. The use of electrolytic cells in the reduction of C0₂ to methane and other hydrocarbons, electrolytic ally, at room temperatures, with a saturated solution of carbon dioxide and an electrolyte, can be an economic means of producing natural gas from carbon dioxide.

SUMMARY

One aspect of the presently disclosed subject matter provides a porous metal dendrite having a high BET surface area. The BET surface area is at least 20 m²/g, but 30 m²/g, or 40 m²/g can be preferred. The dendritic structure of the porous metal dendrite has a fractal like multi-level random structure and a portion of the structure is highly resolved to provide the high surface area. A portion of the dendrite is resolved at least 50 ran, but 30 nm orlO nm can be preferred. The metal can be any metal that is capable of reducing C0₂ to hydrocarbons while stable in the system the reduction takes place. For example, the metal is selected from the group consisting of zinc, iron, copper, chromium, platinum, gold, silver, cobalt, nickel, tin, combination of transition metal and ionic salts thereof..

In one embodiment, the porous metal dendrite is oxidized so that a portion of the metal dendrite is oxidized. In one embodiment, the porous metal dendi'ite has a outer perimeter area and the oxidized portion is at or near the outer perimeter area. The oxidized metal is metal halide or metal oxide. In another embodiment, the oxidized metal is copper chloride or copper oxide

In one embodiment, a method of preparing the metal porous dendrite with a high surface area by utilizing a metal chlorophyllin salt wherein the metal is selected from the group consisting of zinc, iron, copper, platinum, gold, silver, cobalt, nickel, and tin. In one embodiment, the metal porous dendrite with a high surface area by providmg a metal derivative, a metal chlorophyllin salt and an acid including but not limited to sulfuric acid, HC1, acetic acid, nitric acid in an aqueous solvent, wherein the metal derivative is derived from a metal selected from the group consisting of zinc, iron, copper platinum, gold, silver, cobalt, nickel, tin, combination of transition metal and ionic salts thereof providing a substrate in the solution; and providing a plurality of electrical pulses to the solution to obtain electrodeposition of the porous metal dendrite with a high surface area. In one embodiment, the metal derivative is copper sulfate.

In one embodiment, a method for capturing carbon dioxide from a dilute or concentrated gaseous stage and converting it to by using an ion exchange resin that contains a metal catalyst, submerging at least a portion of the ion exchange resin in an electrolyte water solution, and electrochemically converting carbon dioxide to a hydrocarbon. The ion exchange resin can cyclically move from the gaseous phase to the electrolyte water solution and vice versa. The metal catalyst is a catalyst capable of reducing carbon dioxide to a hydrocarbon such as zinc, iron, copper platinum, gold, silver, cobalt, nickel, tin, combination of transition metal and ionic salts thereof. In one embodiment, the metal catalyst is silver, copper, copper chloride or copper oxide. The metal catalyst can be incorporated into the ion exchange resin in various ways. For example, a power or plate supported form of the metal catalyst can be used. Alternatively, the catalyst can be incorporated in form of wire or mesh.

In one embodiment, a system for extracting and converting carbon dioxide to a hydrocarbon (e.g., ethylene) that includes a first electrode a first electrode that is in contact with the electrolyte water solution, an ion exchange resin containing a metal catalyst for C0₂ reduction, wherein at least a portion of the ion exchanged resin is cyclically exposed to a gaseous stage containing C0₂ and submerged in the electrolyte water solution, and a second electrode that is either directly or indirectly in contact with the ion exchange resin.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 depicts a cyclic voltametry (CV) of copper and platinum electrodes immersed in a 0.1 M sodium bicarbonate solution saturated with carbon dioxide, The A) red line graph is a CV of a piece of copper foil 0.2 grams in mass, while B) the blue line is a CV of porous copper dendritic electrode with a mass of 5 mg. Current densities for the porous copper is much higher, despite the differences in mass. As reproduced in black and white, the "red" line (A) are the two lines that have the highest i/A at about -1.5 volts and the "blue lines" (B) are the two lines that have the lowest i/A at about- 1.5 volts.

Figure 2 is a photograph of copper deposits grown at 150 mA/cm² with

PVA.

Figure 3 is a photograph of copper deposits grown at 150 mA/cm² with no additive.

Figure 4 is a photograph of copper grown with a PEG additive on glassy carbon.

Figure 5 is a cyclic voltametry (CV) a high acid copper solution lOg L Cu, and 32g L of sulfuric acid (left diagram) and CV of high acid copper solution lOg/L Cu and 32 g/L sulfuric acid with 1% chlorophyllin additive.

Figure 6 is a photograph of chlorophllyn residue on porous structure during reverse pulse application, magnified 400 times. The chlorophllyn membrane is attracted to the anode, and is selectively pulled off of the growing fractal front while remaining in the recessed regions, containing loss of surface area while increasing growth of surface area.

Figure 7 is a photograph of copper particles formed with chlorophyllin additive and 10 alternating pulses of -0.32 A/cm² and 0.1 A/cm². Copper structures can be resolved down to 50 nm, and take on a non-spherical form which display higher surface areas.

Figure 8 is a photograph of copper particles formed with chlorophyllin additive and 10 alternating pulses of -0.32 A/cm² and 0.1 A/cm². Copper structures can be resolved down to 50 nm, and take on a non-spherical form which provide higher surface areas.

Figure 9 is a photograph of a dendritic fractal cluster produced under a pulsating regime of 500 pulses with a current density of 0.69 A/cm².

Figure 10 is a photograph of a dendritic structure after a pulsating regime of 1000 pulses with a current density of 0.69 A/cm².

Figure 11 is a photograph showing the beginnings of the dendritic copper foam beginning to form. Figure 12 is a photograph of copper PDS for visual characterization magnified 30 times.

Figure 13 is a photograph of copper PDS magnified 300 times and

5000 times.

Figure 14 is a photograph of a dendrite structure magnified 20,000 times.

Figure 15 is an illustrative diagram of a system for capturing and converting C0₂ to a hydrocarbon.

Figure 16 is an illustrative drawing of an ion exchanging resin incorporating a metal catalyst.

DESCRIPTION

The presently disclosed electrolytic cell system can further include an electrolyte source capable of being introduced into a region in between the first electrode and the second electrode of the electrolytic cell system. In one embodiment, the electrolyte is selected from a bicarbonate salt (e.g., potassium hydrogen carbonate), sodium chloride, carbonic acid, hydrogen, potassium and methanol.

The presently disclosed electrolytic cell system can further include a source of a metal porphyry salt capable of being introduced into a region in between the first electrode and the second electrode of the electrolytic cell system. For example, the metal porphyrin salt can be a metal chlorophyllin salt, such as copper chlorophyllin.

Another aspect of the presently disclosed subject matter provides an electrode for an electrolytic ceil system comprising a substrate with a metal porous dendritic structure applied thereon. The metal can be selected from platinum, gold, silver, zinc, cobalt, nickel, tin, palladium and copper.

In one embodiment, the carbon dioxide is obtained from an air stream, a combustion exhaust stream, or a pre-existing carbon dioxide source.

The efficiency of a metal catalyst directly relates to the surface area of the catalyst. Thus, obtaining a larger surface area of a catalyst is very important. The metal porous dendrites presently disclosed contain higher surface areas than the conventional dendrite structures and allows for the rapid electrochemical reduction of C0₂ to hydrocarbons more than 100 times better than copper foil per gram. The 2 · unique structures of the dendrite provide BET surface areas of 20-40 m /g or higher. This high surface areas can be results of the highly resolved fractal structures of the dendrite, which can be resolved as low as 10 nm, which is nearly a full order of magnitude smaller than those previously reported in the literature. .

A SEM scan of a copper deposits grown at 10 mA/cm² with PVA as an additive is shown in Figure 2 and without any additive in Figure 3. Both do not show any formation of fractal structure. When PEG is used as an additive, large and poorly resolved dendritic structures were formed (Figure 4).

It is found that when a metal chlorophyllin is used, the fractal structure formation was substantially promoted. For example, Figure 6-14 show copper porous dendrites grown with copper chlorophyllin. SEM photographs are taken of the structures after a short number of pulses, as well as longer pulses. From these photographs, it can be seen that the addition of chlorophyllin resulted in the further branching of the nucleating copper particles. Photographs are given from spherical nucleation of copper obtained without additives, to the nucleation of copper with more structure on smaller scales with chlorophyllin as an additive. Nucleation without additives can be controlled to 100 nm. However, using a chlorophyllin additive, structures can be resolved to 50 nm and particles take on a popcorn-like structure. A CV of plating solution with chlorophyllin and without chlorophyllin shows that chlorophyllin increases the resistivity of the solution significantly. Because of the small concentrations of chlorophyllin added to achieve this effect, it is likely that the resistance effect occurs at the electrode surface rather than due to lowering the conductivity of the electrolyte itself. In Figures 5 below, the figure on the left shows a high acid copper solution without the addition of chlorophyllin. The second graph on the right of Figure 5 shows the same high acid copper solution with chlorophyllin. In Figure 5, the top line refers to copper plating and the bottom line refers to copper dissolution. A close examination of the CV shows that the two initial peaks in the forward sweep and reverse sweep occur at the same potentials. However, in the forward sweep of the electrolyte with chlorophyllin, the peak oxidation of copper into ionic form is suppressed, and the final peak occurs at a potential that is 0.3 volts higher than in the solution without the additive. This shows that some another process is occurring at the anode during reduction of copper. This likely occurs due to adhered chlorophyllin desorbing off the surface of the electrodes as potential increased. Furthermore, the peak plating current is also lower in the solution with chlorophyllin, giving support to the idea that chlorophyllin increases the resistivity of the system by preventing the flow of ions.

In an embodiment represented by this example, copper chlorophyllin is found to have a considerable effect upon the structure of the copper crystals. Chlorophyllin undergoes anodic attraction during alternating pulses, creating a situation in which the chlorophyllin coats the developing dendritic fractal structure, creating regions of even higher thermodynamic instability allowing additional growth of dendrites on the already complex surface. Figure 6 shows an anodic pulse, and the resulting chlorophyllin film coating the copper electrode.

The chlorophyllin can produce this effect because it is selectively pulled from the fractal structure in a way that exposes surfaces to rough, protruding points which promote additional dendritic growth. Based on the electrochemistry of chlorophyllin, and its effect on the electrodeposition of copper, proper surface areas can be determined on which reactions can occur. Copper nanostructures are resolved down to length scales as low as 10 nanometers, nearly a full order of magnitude smaller than those previously reported in the literature. Figure 7 and figure 8 show a highly structured dendritic copper particle resolved to 500 nm. These particles have much higher complexities than other particles reported in the literature, and most likely form due to the interaction of the process with copper chlorophyllin. Figures 9 and Figure 10 show the result of dendritic agglomeration after 500 pulses and 1000 pulses.

The result of high current densities running through the relatively low number of nucleating particles results in higher formation of hydrogen bubbles, since the potentiostat is set, in this embodiment, to deliver a constant current rather than a constant potential. Thus the total current is distributed over a much smaller surface area. While dendrites still formed at current densities insufficient to produce hydrogen, hydrogen bubbles serve as a template for the formation or micropores as well as the protrusion of dendrites into the micropores. Because the interface of gas and liquid in bubbles form thin channels of liquid, the growth of copper becomes diffusion limited, creating dendritic structures of varying crystal structures. Furthermore, this dendritic pore forms a single, conductive crystal, with the potential to vibrate and transmit phonons through its structure. Figure 11 shows the incipient formation of copper PDS after 2000 pulses. Figure 12 shows the final copper PDS grown on glass carbon. The diameter of the pore is about 2 mm and it protrudes about 1 mm off the surface of the glass carbon. Figure 13 shows close-ups of the fully formed copper PDS, which take the form of buds, leaves, stalks and stems. The space between pore openings are filled with dendritic copper, structured down to only a few nanometers, as shown in Figure 4. The outside surface of PDS can be further controlled based on, for example, a program of finishing pulses.

Multiple BET surface areas are taken. It appears that due to the high reactivity of the copper dendritic powder with air, measurements varied from 19.2 meters square per gram to 41.2 meters squared per gram. Weighing errors are also likely due to the small amount of dendritic powder available to be weighed. However, the median measurement is 29.45, and this corresponds well to 20 meters square per gram previously reported as the BET measurement of a copper tin foam alloy grown under similar conditions, and due to the hydrogen bubble templating. The increased surface area can be due to the dendritic structures protruding from the pores— structures which the Cu-Sn alloy does not possess.

A <150 micron copper powder (Aldrich 99.999% pure <150 micron powder) is tested, a surface area of 1.28 is obtained. However with the fractal powder a BET surface area of 4.26 is obtained despite the visibly larger particle sizes. When the structure is held intact on a piece of glassy carbon, the BET surface area is almost 1 order of magnitude higher, with readings ranging between 19.5 m /gram and 41.2 m /gram. The high range in the results could be due to errors in degassing the samples. Because of the low stability of the samples used in this Example, degassing at temperatures above 150°C caused the sample to fall apart, constrict, or otherwise disappear. Thus, degassing is conducted at a relatively low temperature and not all gas can have been equally driven away from the samples. However, this error would tend to bias measurements downwards rather than upwards since sample absorptiveness and sample mass will be underestimated.

Table 1. Sample Mass v. BET Measurement A comparison of BET surface measurements gives insight into the different surface areas of powders. Using 2 grams of copper powder, <150 microns in diameter, this powder has a surface area of only 1.14 meters squared per gram. Even this is a high reading, as there exist reports of copper powders with surface areas as low as .5 meters squared per gram. Even dendritic powder grown under high current densities showed a surface area of 4. 5 meters squared per gram. Thus, the dendritic structures themselves, as well as the arrangement of the dendritic metals into a foam, both contribute to the increased absorptivity of the dendritic foam. This lends further support to the unique and positive geometries of the dendritic microporous foam, along with the combination of dendritic structures and micropores, both contributing to the gas absorption capabilities of the foam.

The average pore size of the foam in this example is 10 to 50 microns, which is consistent with those reported in the literature. In certain embodiments that employ higher system pressures, pore sizes can be reduced through the reduction in bubble size of template hydrogen gas. While not being bound by any particular theory, it is believed that the tips of dendrites could be resolved to 50 nanometers, and display a highly textured surface which is also self-similar across multiple scales.

The high surface area, as well as the electrical conductivity of this material, are noteworthy. The use of these structures in the reduction of C0₂ to ethylene, methane, and/or other hydrocarbons electrolytically, at room temperatures, with nothing more than a saturated solution of carbon dioxide and sodium bicarbonate, can be a highly economic means of producing natural gas from carbon dioxide.

In one embodiment, the method includes introducing an electrolyte saturated with C0₂ to an electrolytic cell that includes a substrate with a metal plated thereon, and applying electricity to the electrolytic cell to electrochemically reduce the C0₂. The metal can be selected from, for example, Pt, Au, Ag, Zn, Co, Pb, Ni, Pd and Cu. In one embodiment the substrate is plated with a metal porous dendritic structure, such as a copper porous dendritic structure. Substrates can include, but are not limited to, glassy carbon and titanium. Electrolytes can include, but are not limited to, sodium chloride, sodium carbonate, sodium bicarbonate and potassium hydrogen carbonate.

The presently disclosed subject matter also provides an electrolytic cell system that includes an electrolyte saturated with carbon dioxide, a cathode that includes a substrate with a metal plating, and a source of electricity capable of being applied to the electrolytic cell. The metal can be selected from, for example, Pt, Au, Ag, Zn, Co, Ni and Cu. h one embodiment the substrate is plated with a metal porous dendritic structure, such as a copper porous dendritic structure. Substrates can include, but are not limited to, glassy carbon and titanium.

In one embodiment, a metal porous dendritic structure is obtained using a metal porphyrin salt. As used herein, "porphyrin" refers to a cyclic structure composed of four pyrrole rings together with four nitrogen atoms and two replaceable hydrogens for which various metal atoms can readily be substituted. Porphyrins canr be substituted or unsubstituted. An example of a porphyrin is chlorophyllin. Porphyrins, many of which are naturally-occurring, can be obtained from commercial sources. Alternatively, porphyrins can be synthesized. See, e.g., P. Rothemund (1936): "A New Porphyrin Synthesis. The Synthesis of Porphyrin," J. Am, Chem. Soc. 58 (4): 625-627; P. Rothemund (1935): "Formation of Porphyrins from Pyrrole and Aldehydes". J. Am. Chem. Soc. 57 (10): 2010-2011, each of which hereby incorporated by reference.

In one embodiment of the presently disclosed subject matter, an electrode is prepared by pulse and reverse pulse plating a substrate with a copper porous dendritic structure using a copper chlorophyllin salt as one of the copper sources. This electrode can be used in the methods and systems described herein.

Metal Porous Dendritic Structures (PDS) (e.g., Copper Porous Dendritic Structures) can be a high performance material in the catalysis of carbon dioxide as well as air capture and electrolytic reduction of C0₂ due to the high surface areas as well as the absorptive catalytic capacity of Copper PDS. For example, copper PDS can solve one of the major difficulties in the electrolytic reduction of C0₂, as presented in the literature - constructing a electrode which maximizes adsorption of gaseous C0₂ in the reduction reaction with H₂ on the cathode surface. This can allow a commercially feasible process linking electrolytic reduction with air capture, and, in certain embodiments, create a standard temperature and pressure (STP) Fischer Tropsch (FT) device.

Electrodes can be created using a plating mechanism which has been described. See, e.g., Nikolic ND, KI Popov, Lj. J. Pavlovic, MG Pavlovic. "The Effect of Hydrogen Codeposition on the Morphology of Copper Electro deposits. I. The Concept of Effective Overpotential:" Journal of Electroanalytical Chemistry, 558 (2006) 88-98, which is hereby incorporated by reference.

According to one non-limiting embodiment, a bath of copper sulfate and sulfuric acid solution (10 g/L Cu, 32 g/L H2SO4) can be prepared. An Autolab 4800 Potentiostat can be used with a glassy carbon and copper PDS cathode and a platinum wire anode. Copper Chlorophyllin salt (C₃ H₃]CuN₄0₆.3Na Sigma Commercial Grade) can be added to the solution at 1% by weight. Because chlorophyllin is characterized by anodic attraction, the reverse pulse regime creates regions of chlorophyllin membranes covering the dendritic structures, creating additional diffusion-limited growth of dendrites of a smaller scale. Pulse and reverse pulse electrodeposition can be used to form microporous, copper PDS (SEM photos included). A current density of pulsating regimes of -.015 and .01 can be used, which translates into a current density of -.32 A/m² and .21 A/m² of 15 ms and 5 ms respectively. This regime can be repeated numerous times (e.g., 10,000 times), which creates a small pore on the glassy carbon. A microporous corral structure results.

The presently disclosed subject matter provides electrodes grown in this manner, as well as electroless plating of other noble metals such as, but not limited to, Pt, Au, Ag, as well as other metals such as Zn, Co, Ni to the copper template to electrochemically reduce C0₂ to hydrocarbons (e.g., ethylene) using electricity in an electrolytic cell which can use sodium bicarbonate or potassium bicarbonate as the electrolyte, or methanol. C0₂ can be dissolved into electrolyte using a membrane, such as a liquid cell membrane. In certain embodiments, potentials can vary from, for example, -.5 V to -3 V vs. SHE.

Embodiments of the presently disclosed subject matter provides rapid electrochemical reduction of C0₂ to hydrocarbons at current efficiencies of more than, for example, 100 times more than copper foil per gram. Unique products can also be produced on the electrode including C₂ to C₆ hydrocarbons, formate, ethylene, propane, and methanol. In one embodiment, ethylene is the primary hydrocarbon produced by the electrolytic cell system.

Using the pulse reverse pulse technique along with copper chlorophyllin additive, BET surface areas were measured between 20 to 41 m /gram. Use of these electrodes can profitably produce valuable hydrocarbons from carbon dioxide, producing near carbon neutral fuels, while also taking advantage of future and existing carbon credits for offsetting emissions. The presently disclosed subject matter provides for the electrolytic reduction of carbon dioxide. Further embodiments provide a process linking electrolytic reduction with air capture, creating a standard temperature and pressure (STP) Fischer Tropsch (FT) device. The mechanics of dendrite formation and review of the theoretical literature on fractal catalyst simulations is also provided.

Porous dendritic metal foams can be used in electrocatalytic applications, particularly the conversion of C0₂ directly to useful hydrocarbons, such as ethylene. Furthermore, because these catalysts are both produced and applied in an electrochemical environment, any lost catalyst area can be rapidly regenerated in situ. These possible applications extend to porous copper, platinum, and gold structures on reactions such as the electrocatalytic reduction of C0₂ to C₂-C6 hydrocarbons, methanol, CO, hydrogen, formate, and other organic compounds, with hydrocarbons being produced at large molar percentages and current densities. The high surface area, coupled with the microporous structure creates outsized absorptivity, while the continuous structure of the foam allows for high electrical conductivity. Finally, continuous absorption of product species leads to further conversion of methane to higher hydrocarbons. BET surface characterization and SEM scans show that dendritic structures have higher surface areas than bulk materials as well as non- dendritic powders. Furthermore, the electrocatalytic and catalytic activities are tested using cyclic voltammetry and calculations indicate that copper PDS have nearly a full order of magnitude higher BET surface area than dendritic powder, and more than 100 times the electrochemical activity on reduction of carbon dioxide to methane and other hydrocarbons than commercial copper foil.

The reduction of carbon dioxide using a metal catalyst can be efficiently conducted by using an ion exchange resin where the metal catalyst is incorporated into the ion exchange resin. Figure 15 illustrates an example system. In the system, a rolled resin catalyst system 100 is utilized. The catalyst includes an ion exchange resin 101 contains a metal catalyst 102, which can be a plated catalyst or powdered catalyst. (Figure 16). Copper wire mesh 103 can be used to structure the catalyst assembly. The resin containing a catalyst is rolled on a cathode or conductive rod 200 so that rotation of the rolled resin catalyst allows the resin is cyclically exposed to the air and then submerged in an electrolyte water solution 300 to which an anode 400 is comiected. When the resin is wetted and exposed to the air, the resin captures carbon dioxide as the moisture evaporates. Then, the resin is submerged into the electrolyte water solution, which causes the captured carbon dioxide to be leased When electricity is applied to electrodes, electrochemical reduction takes place producing hydrocarbons. Depending on the catalyst impregnated into the resin, the result product canr differ.

The catalytic resin receives a pulse of electricity, which catalyzes a reaction between the hydrogen in the water and the gaseous carbon dioxide being released from the resin 100. This works mainly for three reasons. 1) Because the resins are conductive and amalgamated with conductive catalysts, the electric current conduct throughout the surface of the catalytic resins. 2) The reduction reaction occurs due to a three-phase reaction between electrolyte, gaseous carbon dioxide adsorbed to the surfaces of the solid catalyst. Thus, the mechanism where the resin releases the bicarbonates into gaseous carbon dioxide is perfectly fitted to take advantage of this mechanism as the carbon is in gaseous rather than solid form at the surface of the catalytic resin. Finally, because the amalgamated catalytic metals, particularly the oxides and chlorides of copper, as well as the previously described porous dentritic structure copper catalysts, the transfer of gaseous carbon dioxide to the surface of the catalysts occurs naturally upon release. Furthermore, it has been found that the inclusion of copper oxides have increased the absorptive of other carbon capture absorbers. Since oxides of copper are in fact better absorbers and catalytic surfaces for the conversion of carbon dioxide to hydrocarbons, oxidation and deactivation of catalytic surfaces during exposure to air is not an issue.

The disclosed subject matter is further described by means of the examples, presented below. The use of such examples is illustrative only and in no way limits the scope and meaning of the disclosed subject matter or of any exemplified term. Likewise, the disclosed subject matter is not limited to any particular embodiments described herein. Indeed, many modifications and variations of the presently disclosed subject matter will be apparent to those skilled in the art upon reading this specification.

One purpose of the growth phase of the experiments are to grow fractal surfaces which can be tested for catalytic activity. Initially, only titanium and glassy carbon produced dendritic structures on their surfaces in this particular example. This is due to the low nucleation densities achieved on the surface of these two substrates. Low nucleation densities result in high current densities, which also have correspondingly high electric potentials. Ultimately glassy carbon is used as substrate for experiments because of the low nucleation densities achieved due to the low conductivity of the glassy carbon, as well as the repeatability of the surface of glassy carbon. Low nucleation densities on the surface of titanium are due to inconsistent oxidation patterns. Finally, glassy carbon is a substrate of choice in the literature when studying copper crystal growth.

A bath of copper sulfate and sulfuric acid solution (10 g L Cu, 32 g/L H2SO4) is prepared. An Autolab 4800 Potentiostat is used with a glassy carbon with copper PDS cathode and a platinum wire anode. Copper chlorophyllin salt (0₃₄Η₃ι CuN₄0₆,₃Na Sigma Commercial Grade) is added to the solution at 1% by weight. Because chlorophyllin is characterized by anodic attraction, as observed through visual inspection, the reverse pulse regime creates regions of chlorophyllin membranes covering the dendritic structures, creating additional diffusion-limited growth of dendrites of a smaller scale by limiting the exposure of cathodic surface area and concentrating a high current density on the tips of new dendrites while preventing structures previously grown from smoothing out with more copper particles. The surface of dendrites after an anode phase of a pulse is shown below to demonstrate the chlorophyllin anodic attraction. Other additives used in experiments were PVA, PEG, and PVP. Results of nucleation for each can be displayed.

Pulse and reverse pulse electrodeposition are used to form microporous, copper PDS. A current of pulsating regimes of -.015 A and .01 A are used, which translated into a current density of -.32 A/m². and .21 A/m² of 1 ms and 5 ms respectively. This regime is repeated 10,000 times, which creates a small pore on the glassy carbon substrate. A microporous corral structure results. The conceptual advantages of pulse and reverse pulse plating for standard electroplating applications is discussed in a review by Chandrasekar and Pushpavanam (2007). It creates dissolution, and the potential of new nucleations. Other metals such as zinc and iron, which are known to produce dendrites, can also be used as templates for copper and other metal electrodes through electroless plating.

To measure the surface area of the copper PDS, as well as to provide a comparison with other copper powders and structures, BET surface area measurements were conducted. The theory of BET surface area measurements can be found in Brunauer, S., P. H. Emmett and E. Teller, J. Am. Chem. Soc, 1938, 60, 309. doi: 10.1021/ja01269a023, which is hereby incorporated by reference. The substrate is removed carefully from the electrolyte. If too many pulses are used, pores can lose their structural integrity. Too few pulses, and the pores can be too readily oxidized upon contact with air. Pores are rinsed with deionized water to remove residues of sulfuric acid, then acetone is used to remove deionized water and prevent redissolution of copper PDS. The pore is degassed for a period of six hours at 100°C in a Quantchrome Nova 3000 Surface Area Analyzer under a nitrogen atmosphere to prevent oxidation. When degassed at significantly higher temperatures, the PDS can lose its structure, or can be oxidized into a hard brown crust. When degassed at lower temperatures, residues can react with copper and can turn the powder into a blue residue.

Additional dendritic powder, which are dendritic copper grown at high current densities without a pulsing regime, are collected and analyzed as free copper which did not remain on substrate. Furthermore, commercially available spherical copper powder is also analyzed. After sample is degassed, pores are then measured for BET surface area by scraping dendritic pores from glassy carbon substrate into a sealed vacuum tube which is evacuated to set pressures, and partial vapor pressures measured with a transducer at each pressure point.

The resulting foam was collected in free form from a tube chamber within the electrolytic cell. This setup is necessary to maintain the high current densities necessary to produce the foam, while also allowing for the flow of copper ions into the cell. Once the tube is filled with copper, the resulting product is washed with deionized water and placed in an argon atmosphere to prevent oxidation of copper powder. A copper corral structure is also grown on a glassy carbon substrate. The BET surface area of the intact coral structure is measured. Cyclic voltametry is performed on the copper electrode on the oxidation of C0₂ to methanol to compare the activity of the fractal catalyst with the activity of a flat geometry deposit.

In the third section of the experiment, copper PDS grown on glassy carbon substrate is tested as a electrocatalyst for the reduction of carbon dioxide to higher hydrocarbons. A sealed electrolytic cell is constructed isolating the anode from the cathode so that samples of gas produced could be collected.

A 0.1 M Na₂C0₃ is prepared with deionized water, and saturated with carbon dioxide by bubbling gas through solution for one hour. A piece of commercially available, thin copper foil (Alfa Aesar Cu foil Puratronic, 99.9999% (metal basis), 0.25 mm thick) is used as an electrode in the reduction process. A MetroOhm Autolab 4800 potentiostat is used, and a platinum wire counterelectrode is used as well. Gas phase products are analyzed using gas chromotography. A volume of 100 ml is extracted from the cell after running the cell for 10 minutes to purge all air from the system. The production of hydrogen and CO is not detected by the GC. Its weight is determined to be 0.2 grams, which is approximately 40 times the weight of the copper dendritic electrode, which had a weight of 0.00503 grams. However, it's apparent surface area is the same when projected to a two dimensional plane.

This solution was then used as electrolyte for tests. Γη the literature, regardless of the electrolyte used, whether it was KHCO₃, Na₂C0₃, or simply salt, the resulting products did not change (Shibata et al 2008). A copper foil sheet was prepared to have roughly the same surface area as the substrate of glassy carbon. A cyclic voltametry was conducted to determine the difference in activities between the copper foil electrode and the copper PDS electrode. Gas was collected from the sealed cathodic chamber and removed with a syringe. The resulting gases were analyzed using an Agilent Gas Chromatography to confirm the production of methane and ethylene. Furthermore, visual inspect found that there was an oil slick on the surface of the water, though this substance was not analyzed.

It is found that reactions are occurring at the surface of copper fractal catalysts which do not occur on the copper foil catalyst. Furthermore, it is also found that fractal catalysts have a high surface area which also have a high electrical conductance. Finally, it shows that fractal catalysts are two orders of magnitude more efficient per gram than copper foil.

A copper gas diffusion electrode is fabricated which addresses one of the major needs for improvement— making room temperature and pressure, aqueous electrochemical reduction of carbon dioxide to higher hydrocarbons feasible; this electrode is at least two orders of magnitude more active per gram than an equivalent copper foil. Furthermore, a CV (Cyclic Voltametry) demonstrated that additional reactions occur in the copper PDS electrode as compared to a copper foil electrode, giving some support to the hypothesis that geometrical effect can play a significant role in selectivity of products. A method was found to grow surfaces which are significantly more complex, as measured by BET surface area, than those produced in the literature using techniques which have not yet been reported, namely the addition of chlorophyllin. The interface of the copper surface also can be used as a template for other catalysts, providing the potential for creating unique electrocatalytic alloys. Copper PDS electrodes demonstrated electrochemical reduction of CO₂ to hydrocarbons with a peak occurring at a slightly lower potential. Because this process occurs due to adsorption on electrode surfaces, it is possible the gaseous diffusion electrodes would produce higher yields than a simple foil electrode. Copper PDS has very significant surface area and a very low volumetric density. In addition, copper PDS displays many irregularities on its surface, a condition that has been found to be conducive to catalytic reactions, perhaps due to local concentrations in electric field potentials at boundary discontinuities. It is interesting to note that when these structures were placed into the saturated solution of sodium bicarbonate, bubbles nucleated at a far higher rate on the structures, than elsewhere in the solution or other electrodes.

When the CV is run comparing the copper PDS electrode and a copper foil electrode, an interesting effect is detected. It is immediately apparent that the copper structured into a fractal produced rates of reduction higher than the electrode with a mass almost 40 times greater than the copper dendrite. This is unexpected. The peaks occur at nearly the same places for both the copper foil and the copper foam, though the copper foam displays a slightly lower peak voltage, making the process energetically more efficient. The PDS peak is relatively longer, which can imply there are two competitive processes occurring: the production of methane and perhaps other higher hydrocarbons from hydrogen and carbon dioxide. As the potentials increase, the higher activity of the copper PDS, as compared to the copper foil is apparent. The copper PDS is almost 4 times more efficient, and almost 160 times more efficient per gram.

Finally, the CV showed another interesting effect for copper PDS gaseous diffusion electrodes. On the negative sweep of the CV, the oxidation peaks for the copper gas diffusion electrode differed from the peaks of the foil electrode. The gas diffusion electrodes showed two peaks, while the foil electrode only showed a single peak. The dual peaks implies that two reverse reactions are occurring, each of a slightly different reaction energy, as shown in Figure 1.

It is interesting that significant production of side reactions occur, and are likely due to the porous structure of the electrode, since the gas reactions only occur when gas is captured on the porous electrode and adsorbed onto the surface of the catalytic metal. Highly dispersed metal particles are not a better geometry when compared with a porous structure, given the requirements of gaseous adhesion for electrolytic conversion of carbon dioxide to occur. Instead, the unique, fractal geometry of the internal surface of the structure creates a reaction surface, which also traps individual reactant and product gas molecules and confines them within what is essentially a knudsen diffusion regime, though the scalar accuracy of this non-binding proposal can be verified with simulations. The production of ethylene and methane were confirmed with gas chromatography with dendritic copper grown at high current densities.

Direct electrochemical reduction of C0₂ allows for a simpler process and also, by avoiding high temperature and pressure reactors, also provides the process production rates to take advantage of baseload surplus electricity (Gatrell 2008), Because of the high absorptivity of these structures, the absorptive resins, in one particular embodiment, are to be used in an electrolytic cell, optionally functionalized onto the copper, to produce a direct means electrolytic reduction of C0₂ to ethylene, methane and/or other hydrocarbons on the surface of the resin support.

Copper and platinum display catalytic activity on various toxic and undesirable substances, pollutants, residues, and greenhouse gases. Copper is a particularly good catalyst because of its relative low cost, as well as its proven applications in the breakdown and detoxification of organic compounds. High surface area copper can provide rapid decomposition and neutralization of toxins such as hydrazine, trichloroethylene, nitrobenzene, and phenols, as well as the potential for applications in other fields, such as the electrolytic reduction of carbon dioxide to methane, methanol, and other hydrocarbons, and rapid, high current energy generation in fuel cells. Solely for purpose of convenience, this section will discuss the electrolytic reduction of C0₂ on copper electrodes.

The electrochemical reduction of C0₂ on a Cu electrode has gained attention for the removal and conversion of C0₂ to more useful products, the electrocatalytic activity of Cu electrodes, and the electrode activity as a function of different electrolyte concentrations, temperatures and pressures. See Lee, Jaeyoung, Yongsug Tak: "Electrocatalytic activity of Cu electrode in electroreduction of C0₂; Electrochimica Acta 46 2001 3015-3022; Cabrera, Carlos ., Hector De. Jesus Cardona, and Cynthia del Moral: "Voltammetric study of C0₂ reduction at Cu electrodes under different KHC0₃ concentrations, temperatures, and C0₂ Pressures." Journal of Electroanalytical Chemistry 513 (2001) 45-51. The creation of porous gas electrodes, which facilitate the conversion of saturated C0₂ to unsaturated C0_2t is one major need in improving the efficiency and commercial feasibility of electrolytic reduction of carbon dioxide to ethylene, methane, methanol as well as formic acid and other hydrocarbons. It is hypothesized by Gattrell et al (2006) that the reduction of C0₂ to CH₄ occurs not from dissolved C0₂ but from gas phase C0₂, due to adsorbed C0₂ on the surface of the electrode, as well as the adsorption of CH₄ and higher hydrocarbons on the surface of the gas electrode. The first reaction is C0₂+e- - C0_2aci_s . For many other catalysts which have high CO adsorption, the production of CO is favored. CO+ both physisorbs and chemisorbs onto copper and is enhanced by surface defects and can form temporary carbonate structures with the copper.

The reactions involved for the electrolytic reduction of C0₂ to higher chain hydrocarbons are given below; all reactions are given vs. Standard Calomel Electrode. (Collin and Sauvage 1989):

C0₂ + 2 H⁺ + 2 e ^" - CO +2H₂0 E°— -.52 V.

C0₂ + 2 H⁺ + 2 e ^" ^ HC00H E^0,= -,61 V.

C0₂ + 8 H⁺ + 8 e ^" -> HCHO+H₂0 E⁰'- -.48 V.

C0₂ + 8 H⁺ + 8 e ^" -» C¾OH+H₂0 E°'= -.38 V.

C0₂ + 8 H⁺ + 8 e ^" -» CH₄+2H₂0 E⁰'- -.24 V. A rough calculation of the cost of methane can be calculated. A high current efficiency of 60% hydrocarbons, with the balance being hydrogen, formate, and CO can be achieved using a simple copper foil. Under complete conversion of C0₂ to methane, one would obtain 44 grams C0₂ per 16 grams of methane. The price of 1 mmBTU of natural gas is $4,304 (www.nymex.com). There are 97 cubic feet in 100000 BTU of natural gas and thus there are 970 cubic feet in 1 mmBTU of natural gas. This converts to 27467.341 liters. Using the ideal gas law, PV=nRT, the number of moles of methane can be determined. Thus, there are 1225.49 moles in 1 mmBTU of natural gas. Which will require the same amount of moles of carbon dioxide to produce. Assuming the cost of carbon dioxide is $100/ton and 1 ton is 1000 kg, 1 ton of C0₂ would produce 1000000 g 53922g - 18.5453 mmBTUs of natural gas. Thus, based on the raw material cost of carbon dioxide, the market value of the product would be 18.5453*4.304 - $79.82. With a carbon offset price of $35 per ton of C0₂ it is conceivable that natural gas can be produced from C0₂ profitably if the cost of caseload electricity would be negligible in this process. This also assumes a 60% efficiency with other valuable products which produce, neglected in the analysis, 1 mol of CO₂ would require 8 mols of electrons or 13.33 coulombs of energy. Assuming 1 cent per kilowatt hour, it would cost 13.33 cents per kilomol of C0₂ produced, since each mole of C0₂ requires 13.33 coulombs of electricity operating at 60%o efficiency. The minimum current that can be used in the reaction would be on the order of .5* 10^" assuming a resistance of 100 ohms. Based on this number, the minimum power requirements for the reaction to proceed is 100*(.5*10^" ) or .0025 watts or .0000025 kilowatts. To reduce 1 ton of C0₂ to methane would require 13.33*1225.5*18.55 Columbs. At an amperage of .5*10^~2 C/second as the lower bound, 1 ton of C0₂ would require (13.33 * 1225.5* 18.55) / .005 = 60606244.7 seconds or 16326 hours. Thus 16326*.0000025= .040815 kilowatt hours. Of course one would not expect the reaction to proceed at such low amperages, and one could turn up the reaction rates very significantly and still only incur relatively reasonable electricity costs. The primary costs are C0₂ feed stock, and water.

Interestingly, a mixture of Fischer Tropsch products of up to C₆ hydrocarbons are produced from C0₂ at room temperature. Carbon chain products are observed for copper electrodes which had been polished under an acid solution. See Shibata, Hirokazu Jacob A. Moulijn and Guido Mul: Enabling Electrocatalytic Fischer-Tropsch Synthesis from carbon dioxide Over Copper-Based Electrodes. Gattrell et al (2007) propose that five cells connected in series would be able to convert 97% of Carbon Dioxide fed into the system producing a final product of hythane. Other studies have been conducted on the effect of copper crystal structure on selectivities (Hori et al 2003) and the effect of alloying other metals to copper (Mho et al 2000).

Other methods of electrocatalytic conversion of C0₂ involve alternative metals such as Ti0₂, Pt, as well as using methanol as an electrolyte instead of water (Centi et al 2007). Higher H⁺ concentration increased the yield of hydrocarbons in the reduction of C0₂. The results at different temperatures and KHCO₃ concentrations support the idea of the presence of CO as an adsorbed intermediate and the existence of a region of lower pH near the electrode surface, respectively. Different pressures also change the current efficiency and products at the copper electrode. Voltammetric study of C0₂ reduction at Cu electrodes under different KHCO₃ concentrations, temperatures and C0₂ pressures (DeJesus-Cardona et al 2002).

Hori et al (1993) tested the selectivity of various metals for CO production from C0₂ and found that Au > Ag > Cu > Zn » Cd > Sn > In > Pb > Ti > Hg, though copper is still the best producer of hydrocarbons electrolytically. Mediation with metal porphyrins is also studied and found to be an effective means of electrolytic reduction of C0₂. See, Ogura, Kotaro, Ichiro Yoshida: Electrocatalytic Reduction of C0₂ to Methanol part 9: Mediation with Metal Porphyrins." Journal of Molecular Catalysis, 47 (1998) 51-57, hereby incorporated by reference. Copper chlorophyllin, which will reduce carbon dioxide in air at the same rate as a leaf, is of particular note. Losada et al (1995) used polymer films of polypyrrole cobalt(II) to reduced C0₂ electrolytically.

While poisoning of catalyst has been reported to occur as a major problem of deposition (Yano et al 2001), Hori et al (2005) determined that the deactivation of copper electrodes are, in reality, due to impurities in the prepared solution which could be eliminated through pretreatment. Bockris discusses the importance of preelectrolysis of electrolyte solutions when studying electrode processes in detail (Bockris 1993, Bokris 1970), Catalyst poisoning is not detected on the surface of the catalyst by the CV. The CV shows the current flow as a function of potential. Current is directly proportional to the reduction of C0₂ to CH₄.

One of the major difficulties with using electrochemical cells for industrial conversion of C0₂ to hydrocarbons is the large geometries necessary for foil electrodes to produce industrial quantities. These structures are especially useful for electrocatalytic application which require high interfacial surface areas or high absorptions of gas reactant species. The extraordinarily high activity potential of the presently disclosed copper chlorophyllin catalyst is due to the high surface area of the dendritic structures as well as the micropores and nanopores in the scaling, self- similar structure, which allows for rapid absorption of reactant species. These structures absorb a notable amount of gas, as determined by a BET test.

Aqueous electroreduction of C0₂ to ethylene, methane and other hydrocarbons could be a significant strategy for upgrading the value of C0₂ to enhance the economic feasibility of air capture and other CCS (carbon capture and storage) technologies. This is particularly true with ionic resin exchange membranes which capture C0₂, as the technology requires the immersion of the C0₂ saturated membranes into water to facilitate the desorption of C0₂. During the desorption process, the resulting solution can be saturated with C0₂ and fed into an electrolytic cell for the conversion of the gas into hydrocarbons. This could be facilitated with copper dendritic gas diffusion electrodes, which would allow for a high efficiency conversion with the minimal use of copper, a catalyst that is already cheap and plentiful.

Furthermore, Fisher-Tropsch (FT) synthesis can also be conducted from the higher hydrocarbons produced from the initial copper electrodes. Fisher Trospch synthesis can also be conducted electrolytically at room temperature. The limiting factor again is the solubility of the gas in the electrolyte, as well as the ability of electrodes to adhere gaseous reactant species.

Through the use of double templating, copper dendrites can be converted to thermo dynamically preferred metals such as gold, silver, and platinum. Furthermore, by producing zinc dendrites, electrolytically, a similar process can be used to produce iron and cobalt dendritic electrodes which produce similar gaseous effects. Table 2 below gives the reduction potentials of important electrolytic reduction reaction which can be utilized with double templating to produce gaseous electrodes with high efficiencies.

Table 2: Standard Potentials. Source: Handbook of Chemistry and Physics, 86' Edition. Any metal with a more positive electromotive potential can undergo electroless plating, in which metal ions which have a higher EMF will spontaneously exchange ions with the metal of a lower EMF. Thus, from the porous copper structure, platinum, silver, palladium and gold can be plated electrolessly to form dendritic pores of a similar structure. Furthermore, if zinc leaves are grown instead of copper leaves, a larger array of potential porous dendritic electrodes could be produced from a wide variety of metals, since zinc has a relatively low EMF. Thus, an electroless process could be used to replace zinc with chromium, iron, nickel or cobalt, all of which can play significant roles in Fischer Tropsch synthesis.

A further application of the presently disclosed subject matter is the use of carbon nanotubes as electrodes for the further refining of hydrocarbons into FT synthetic fuels. Since the experiments performed are conducted on glassy carbon, a relatively low surface area substrate with a low conductivity and activity (Rozwadowskp 1979), improvements in current efficiencies for reduction of carbon dioxide can be obtained if glassy carbon substrates are replaced with a carbon nanotube substrate as a heterogeneous catalyst support due to the increased absorptive, conductance, and electrochemical activity of nanotubes (Planeix 1994). Many uses of nanostructured electrodes have already been found for electrolytic applications (Wang 2004) for such applications as sensors (Pietrobon et al 2009, Welch et al 2006), fuel cells (Lien et al 2005), and fuel conversion (Tong 2007) and reforming of methane (Pawelec 2006). Direct plating of metal catalyst particles has found some success, though chemical means have been the dominant method of electrode preparation (Yao et al 2004, Yang et al 2009). Nanotubes are already a promising route for high pressure and temperature FT synthesis (Prinsloo et al 2002, Serp et al 2003), including the direct impregnation of high activity catalysts such as cobalt (Choi et al 2002) onto carbon nanotube structures, which has been shown to increase yields of lighter hydrocarbons and lower the peak temperatures of the reaction (Tavasoli et al 2008, Lu 2007) as well as selectivities of specific hydrocarbons (Lordi et al 2001). A combination of the capacity of nanotubes to adsorb and store hydrogen (Mishra et al 2008), as well as its demonstrated high electrochemical activity when decorated with noble and near noble metals (Sun et al 2005, Tang et al 2004, Li et al 2004, Tsai et al 2007, Georgakilas et al 2007) along with the ability of porous copper dendrite to adsorb carbon dioxide and hydrocarbons, make the combination of the two particularly interesting for reduction of C0₂ as well as FT synthesis. No studies on CNT electrolytic reduction of C0₂ have been reported in the literature.

This section will review electrochemical mechanisms of producing fractals and dendrites as well as other shape-controlled nanoparticles. It will first discuss electrodeposition and some of the dendritic structures produced with this process. It will then discuss sonochemistry and sonoelectrochemistry as another means of producing fractal nanostructures. Finally, the mechanisms of fractal formation for copper is briefly discussed.

Electrodeposition has found application for creating nanostructures with unique properties. Electrodeposition provides a high degree of control and repeatability for production of nanoparticles, including shape control as well as size control, depending upon the applied currents and potentials, as well as nucleation characteristics of electrode materials. See Liu, H, F. Favier, K Ng, MP Zach, and RM Penner: "Size Selective Electrodeposition of Meso-scale Metal Particles: a general method." Electrochimica Acta 47 (2001) 671-677; Radisic, Aleksandar Philippe M. Vereecken, James B. Hannon, Peter C. Searson, and Frances M. Ross: "Quantifying Electrochemical Nucleation and Growth of Nanoscale Clusters Using Real-Time Kinetic Data, Nanoletters (2006) Vol. 6 No 2. 238-242.

Furthermore, this technique is well understood, and is both economical and fast. Finally, the product of electrodeposition can be harvested directly from electrodes rather than slowly seperated out of a mixture, which is often the case in the production of nanoparticles through chemical means. Electrodeposition has been used to produce nanowires directly on carbon nanotubes. Electrodeposition goes a long way towards solving the problem most nanoparticles face: the lack of stability that other methods such as chemical reduction as well as the method of microwave irradiation which are more difficult to structure into a stable, rep eatable configurations. Particles can be deposited directly onto a supporting structure such as nanotubes. Catalytic metals relevant to FT synthesis can be deposited unto carbon nanotubes and other carbon substrates such as glassy carbon as supports include platinum and platinum-ruthenium, gold and silver. See, e.g., Auer E, Freund A, Pietsch J, Tacke T: Carbons as Supports for Industrial Precious Metal Catalysts. Appl Catal A. 1998; 173: 259-71.

Sonoelectrochemistry has also been used to produce fractal and dendritic nanostructures. In order to understand this method, Sonochemistry must first be discussed, and involves using an ultrasonic horn to agitate' liquid systems. Sonochemical effects occur because of acoustic cavitation which form as the peaks and troughs of an ultrasonic wave pass rapidly through the liquid medium creating regions of rarification and attenuation. See Adewuyi, Yusuf G: "Sonochemistry: Environmental Science and Engineering Applications." Ind Eng. Chem Res. 2001 40(22), 4681-4715 DOI 10.1021/ie0100961; Mason, Timothy J., "Large Scale Sonochemical Processing: Aspiration and Actuality." Ultrasonics Sonochemistry 7 (2000) 145-149. This causes formation of bubbles, which are then caused to implode by the moving pressure wave of sound. This results in two regions of enhanced chemical activity: in the gas within the bubbles which reach temperatures of up to 5200 K, and along the boundary between the water and the gas phase, which can reach temperatures of 1900K. Hydrodynamic models of cavitation also estimate pressures to reach between 1000-10000 bars. See Suslick, ennth S. Taeghwan Hyeon, and Mingming Fang: "Nanostructured Materials Generated by High-Intensity Ultrasound: Sonochemical Synthesis and Catalytic Studies." Chem. Material. 1996 8, 2172-2179. (Suslick et al 1986).

Sonochemistry has been used to produce iron oxide nanoparticles when they are ligands of organic particles. These iron nanoparticles of 20 nm clusters of 2-3nm smaller subcomponents displayed kinetics of up to 10 times higher than the bulk form. Furthermore, this method is also reported to improve iron selectivity when loaded onto a silica substrate through sonification. Sonification also produces OH radicals which explains many of its effects in the environmental engineering practices, such as photocatalysis of pollutants. However, this also gives it potential for functionalizing the surface of carbon nanotubes as well as the surfaces of electrodes and catalyst supports for catalyzing reactions such as methanation. See Tong, Hao, Hu Lin Li, Xiao Gang Zhang: Ultrasonic Synthesis of Highly Dispersed Pt Nanoparticles Supported on MWCNTs and Their Electrocatalytic Activity Towards Methanol Oxidation. Carbon 45 (2007) 2424-2432.

Sonoelectrochemistry couples the power ultrasound to electrochemistry. Kinetics and cavitation are the two main avenues through which sonoelectrochemistry produce its unique results on the nanoscale. Microjets are generated at the electrode surface by the cavitation events with speeds of up to 100 m/sec. The setup should include an ultrasonic immersion horn probe in which the horn tip can be placed inside the electrochemical cell, producing a sono electrochemical cell. The other components would be a graphite counter electrode, Ar inlet degassing unit, Pyrex reservoir to maintain thermal conditions, a Titanium tipped sonic horn, an SCE reference electrode, and Pt 102 resistance thermocouple. A thorough review of the setup can be found in Compton Richard G, John C. Eklund, Frank Marken, Thomas 0 Rebbitt, Richard P. Akkermans and David N. Waller. "Dual Activation: Coupling Ultrasound to Electrochemistry -- An Overview." Electrochimica Acta Vol 42 No 18 pp 2919-2927, which is hereby incorporated by reference.

According to the literature, sonication enhances current densities of the electrochemical system. Even uncontrolled electrode geometries placed in an ultrasonic bath, enhancing currents to 10 times high than unsonicated electrodes. On glassy carbon electrode surfaces, significant pitting is observed. However, activation of the carbon is also observed, and is theorized to arise from OH- radicals produced in the cavitation bubble, which then react with the surface of the glassy carbon electrode. This activation is not likely due to increased BET surface area. OH- fictionalization of glassy electrodes led to higher rates of electrodeposition of Pb0_2. Other aspects which can be controlled are the frequency and intensity, pulsing intervals and lengths, gases in dissolved in solution, pressure and temperature, concentration of solute, and geometry and location of sonic sources. The enhanced reactions spurred by sonoelectrochemical practices are due to a thinning of the diffusion layer between the electrolyte and electrode. Sono electrification of CNTs with SbSI has been used to prepare nanorods with the CNT matrix and Co/Fe alloys are also produced with this method. Nowak et al (2009) in their study use the high pressures and temperatures formed by the cavitation bubbles to form nanorods within the CNTs.

Additives such as PVA have been used in the sonochemical process to prevent the agglomeration of particles as they are deposited. Hass et al (2008) used a sonoelectrochemical method to synthesize copper dendrite nano structures. See Haas, Iris, Sangaraju Shanmugam, and Aharon Gedanken, "Synthesis of Copper Dendrite Nanostractures by a Sonoelectrochemical Method." Chem Eur. J. 2008, 14, 4696 - 4703. Because sonochemistry relies on ultrasonic pulses that produce small bubbles which collapse very quickly (Compton 1997), this can explain why dendritic structures form. Lead Oxide nanostructures are created using ultrasonic pulses on a glassy carbon electrode (Garcia et al 1 98). It is likely that these dendritic structures form as a powder, which are later linked together on the carbon matrix by the interaction between the polymer chains which hold the particles together and prevent them from agglomerating, as well as the interaction between the PVA and the carbon matrix. PVA functions by forming a polymer matrix which creates this effect, while the -OH group allows for electric interaction between particles, which would be prevented from occurring by the surfactant PVP. They concluded that neither the electrode, nor the pulseform or pretreatment made any difference in the dendritic structures formed, and instead these formed only after on the carbon-copper matrix used in TEM studies. Haas reported that the BET surface area of the dendritic structure is less than 2 m²/gram.

Haas does not explain the mechanism of dendrite and fractal formation beyond suggesting the electronic interaction. However, given the results of the formation of copper dendrite foam, it seems likely that dendritic powder formation occurs due to the same mechanism, whereby bubble formation create diffusion limited conditions which promote the formation of dendritic structures. Their method is interesting in that they have a 300 ms pulse of electricity followed by a 250 ultrasonic pulse. The electric pulse causes the copper to be reduced into a polymer matrix formed on the PVA, which is then ablated off the electrode by the ultrasonic pulse. Then searching for the deposition of dendritic fractal structures which had dimensions between 1.74 and 1.76, and had details of up to 50 nm in resolution, these dendrites are dependent upon the interaction between the colloid solution and the interface on which it is prepared to be scanned rather than from any inherent activity from the sono electrochemical cell. The major contribution of the sono electrochemical cell is to create nanoparticles from reduction of copper, and then the stabilization of these nanoparticles by the PVA. Intriguingly, the dendritic structures only formed on a copper carbon grid, which is used as preparation material for TEM study. Perhaps, by creating a electrical matrix on the surface of carbon nanotubes, it can be possible to load nanotubes with dendrites. The use of surfactants has also been reported to create tin nanorods in conjunction with a sonochemical method (Qiu et al 2005). Dendritic crystal growth occurs in electrochemical conditions far from thermodynamic equilibrium. Dendrites tend to grow under mass transport limited conditions. At conditions far from thermodynamic equilibrium, surface energy is no longer the dominant factor in crystal formation (Choi, Kyoung-shin 2008). Dendrites are also the most efficient way to distribute surface area in a three dimensional structure while maintaining a coherent, single structure. Other dispersion methods optimize the total catalytic surface area, without maintaining a coherent shape that also preserves the charge transport properties of the metal. While interest in the formation of non-noble nanoparticles and structures have been growing due to the relatively high stability of copper nanoparticles, the presently disclosed subject matter relates to uses of porous copper dendritic structures. One advance in copper dendritic structures has come where the porous dendritic structures grown under high current densities can be used as a template to electrolessly exchange copper ions with platinum ions, creating a dendritic structure that is fully platinum. These structures have been shown to increase the current density of the electrocatalytic reduction of O2 over 2.5 times.

This section will discuss crystal growth in copper and the conditions necessary for dendrite formation to occur. High ionic concentrations will not necessarily affect the crystal growth rate, as the current applied determines the amount of a substance deposited. However, the concentration will affect whether deposition occurs in a mass transport limited regime. The literature suggests that branching growth even at low overpotentials result from an uneven distribution of potential across the surface of the crystal structure. The reduction of Cu²⁺ to Cu⁺ depends on the concentration of Cu²⁺ as the Nernst equation shows:

E_red=E°-.05916xlog([Cu⁺]/[Cu²⁺] at T= 298.15 K. 11)

This mechanism can be used to produce dendrites at low overpotentials in low ion concentrations. Different crystal growth regimes can be established depending on the over potential. The growth rate of crystals depends upon the overpotential applied to the electrochemical system. The overpotential, is defined as

The higher the overpotential, the further the system is from equilibrium.

Mass transport is the most important factor in dendritic crystal growth. Mass transport-limited growth occurs when the rate of crystal growth is greater than the availability of ions in the immediate mass transport boundary layer. Imperfections in the crystal faces create a nonlinear effect in these conditions, as the apexes of the imperfections grow at a higher rate than the receded faces, further increasing the differences between the apexes and valleys of the crystal faces. At high overpotentials in relatively low concentrations of metal ions, a diffusion boundary layer forms around the electrode, which leads the deposition into a mass transport limited regime. High overpotentials also increase the number of crystal branches as well as the total surface area per volume.

Some factors will prevent the system from reaching a diffusion limited regime. At high concentrations of metal ions, the transport regime cannot become diffusion limited. Higher temperatures also tend to increase the size of the boundary layer and mitigate the depletion zone, thus leading the system to remain outside the diffusion limited regime for higher overpotentials. This is true in the growth of zinc crystals as discussed in the literature. At higher temperatures, the rate of mass transport and the rate of diffusion across the boundary layer increase. Finally, any other factors which tend to contribute to mass transfer, such as stirring rates or short plating pulses would also mitigate the growth of dendrites. Furthermore, capping protruding edges would also tend to reduce the formation of dendrites, by directing crystal growth toward non-dendritic protrusions on the electrode.

The effect of organic additives on dendrite growth has been studied. One means to study the interaction of additives and crystal growth is to introduce additives into the plating solution after initial growth has already occurred. This allows for the study of crystal faces which might have otherwise been dissolved by the additive. Additives change crystal structure primarily by changing the kinetics and thermodynamics of crystal growth. PVP has been used to prevent the growth of dendrites (Haas 2006) by capping the protruding nucleations. PVP is attracted to the cathode, and is a non polar capping agent, preventing electric interaction between ions and nucleated metals. PEG and PVA on the other hand, do not necessarily promote the growth of dendrites, but change the morphology of the deposits. Finally, chlorophillin is an interesting substance because it both contains a copper core, while also displaying anodic attraction. No studies have been conducted on chlorophyllin to date, as known to the inventors.

Choi, Kyoung-Shin (2008) discusses shape control through electrodeposition and the use of additives. Different crystal planes have different chemical and physical properties. Furthermore, control of branch growth also changes the distribution of crystals and the connectivity which can play a critical role in the optimization of surface structure. Surfactants such as sodium dodecyl sulfate absorbs to the {111} crystal plane, which slows the growth of branch structures, as the {1 11 } plane is the furthest protruding plane. On the other hand CI- interact with the {100} direction, resulting in retardation of growth along this axis. The degree of hinderance depends upon the concentration of additives. Initially it is thought that pH is the dominant influence in shape evolution, though later studies showed that the Cl- ion is the determining factor (Choi, Kyoung-Shin (2008)).

There have only been a few studies published about the control of copper morphology on the nano and micro scales. Dendrites tend to grow under mass transport limited conditions, far from thermodynamic equilibrium where surface energy is no longer the dominant factor in crystal formation (Choi 2008). Imperfections in the crystal faces creates a nonlinear effect in these conditions, as the apexes of the imperfections grow at a higher rate than the receded faces, further increasing the differences between the apexes and valleys of the crystal faces. Furthermore, as reported by Nikolic et al (2009), as well as Shin et al (2003), when mass transfer limited deposition occurs in the hydrogen evolution regime, evolving hydrogen bubbles form a template around which copper dendrites can form. Manipulating the pause-to-pulse ratio gives greater control over the size of micropores, while variation on voltages can give some control over the morphology of the dendrites (Nikolic 2007). The resulting foam maintains its structural integrity, unlike other dendritic deposits. When grown without additives, Shin reported copper is structured down to hundreds of nanometers. Nikolic et al (2006) reports that the size of the copper grains decrease with increasing over potentials of 550 mV to lOOOmV. A similar copper-tin foam structure is characterized using BET surface measurements to have 20 m²/gram (Shin and Liu 2005).

Dendrites form a tree-like structure with a backbone as well as leaves. The physical connection between the crystals of the leaves as well as the backbone crystal allow nanocrystals to act as a single crystal, conducting phonons and electrons as a single structure (Choi 2008). The continuous structure of metallic dendritic structures can provide the first clue as to novel catalyst actions as will be further sketched out in this thesis. Porous dendritic structures occur because of mass transport limited branching growth. The hydrogen bubbles evolved during electrodeposition of copper at high potentials results in the formation of diffusion limited regions near the cathode. These diffusion limited regions produce branching structures while the bubbles create a template for the development of porous dendritic structures. Recently, Copper PDS have been synthesized from copper, as well as other metals such as tin, to form metallic foam with high surface area and high adsorptive characteristics. Many experts in catalysis dismiss the notion of dendritic surfaces as being economically viable for applications due to the assumed short lifetimes of their surfaces. While fractal distributions of catalytic metals have been proposed, only a few multi-scale structures which display self similarity have been synthesized. Furthermore, these structures are usually too delicate to find practical use. However, copper PDS have a higher stability than other fractal distributed catalysts grown at the submicron scale, as these dendritic structures are structured on both a microscale and macroscale and form a continuous structure, rather than a powder. Anectdotal observations of the structure recorded an ability to resist oxidation while maintaining cohesion within an aqueous environment. These structures are completely metallic and display surface areas which are orders of magnitudes higher than metals in their bulk form. Their shape follow fractal geometries, which display self-similarity across multiple scales, and surfaces which grow with the complexity of the surface roughness. PDS have the potential to capture the theoretical effects of fractal surfaces. Studies have demonstrated that catalytic metals arranged in a fractal geometry show higher kinetic rates at lower temperatures.

Because of the complex interfaces displayed by fractal surfaces, theorists have posited that these surfaces could possess unique applications for catalysis, as well as unique mass and heat transfer properties. Rates of reactions are affected by diffusion effects as well as surface area effects. Geometric effects have also been discussed, and become significant at smaller scales. Catalyst surfaces have been found to have a random fractal, or multi-fractal geometry. Furthermore, catalyst surfaces in simulations have been found to have a significant effect on the rates of reactions of the catalysts, especially those limited by knudsen diffusion, where diffusion occurs along a long pore and collisions occur frequently (Sheintuch 2001). However, these theoretical studies only quantified existing catalyst supports and their conclusions mainly pertained to issues of mass transfer, rather than to the kinetic effect different fractal geometries of metal catalysts themselves might have on catalytic reactions.

Computer simulations have been conducted in exploring the potential effects of fractal surfaces. Authors have posited that heterogeneous fractal surfaces and fractal pore structures can produce novel effects such as enhanced mass transfer and selectivity. Pfeifer and Avnir (1983) state in their article a power law relating the size of an object R and fractal dimension D to its chemical interaction property.

A ~ s^(2~D)/2 for monolayer coverage with s = cross sectional area of particles. 1) A ~ R°^~3 for adsorbates, where R is the radius of particles 2) dV/dp ~p^{2 D} for pores where dV is the infinitesimal pore volume with radius >dp. 3)

The dendritic porous copper foam would have a combination of contributions from equation 1) and equation 3). These power laws state: that the more complicated the surface, the higher the surface area available for adsorption; and, that the larger the radius and the larger the fractal dimension, the higher the chemical interaction property. Furthermore in Avnir (1991) the catalyst activity is described with another relatively intuitive equation:

A~R^D where A is the chemical activity of the particle 4).

Other studies have made correlations between the activity of a catalyst and its fractal dimension, as a higher fractional dimension implies a more complex surface with more surface area. The justification for this is that porous dendritic structures are controlled fractal surfaces, rather than random fractal surfaces. Meankin's (1986) simulation of catalyst selectivity in random fractals finds small effects due to the unique geometries of random fractals. However, controlled fractal surfaces, can have very specific effects on different types of chemical reactions catalyzed by the base metals beyond those found by Meakin. For example, the porous dendritic structures described in this paper, might have a geometry which deflects gas particles into paths which maximize the number of impacts with the catalyst surface.

The mechanisms simulated are based on the inner recesses of the fractals to have a higher ability to absorb a particle of a specific size, and thus create new products. However, the fundamental mechanism of action would be similar: that though the distribution of catalysis events is equal on all surfaces, the distribution of diffusion absorption events varies greatly as some surfaces are harbored from certain objects (Meakin 1986), perhaps because of their geometry.

Under certain geometries with involutions, the concentrations of different species of chemicals depending on their molecular mass, would be limited by the depth of scale. It is possible a specific geometry will catalyze a specific reaction to completion very quickly so that production rates are fast which the dominant products produced at one scale, the products reactions occurring on another. There is a multi component recursive product chain of products produced in one of the involutions, as on reactant becomes the reactants on the next. The consumptions of small products, creates a gradient for new monomers to diffuse into the regions, and the random kinetic activity between inflowing monomers will displace new monomers. Certain regions of the fractal surface become inaccessible to diffusion gradients (Meakin 1986). There regions can act as a harbor for creation of a specific type of chemical species.

One can assume that metals are delocalized electron shells which have the capacity to absorb kinetic energy from surrounding molecules, while also imparting electronic energy to reacting species. If one were to assume that metals, which are high conductors of heat, do not possess kinetic energy when in solid state, then each molecule that strikes the surface of the delocalized shell of an electron will impart some fraction of its energy, 1/f, to metal surface plus a constant, c, amount of energy which is the attractive surface energy of the metal. The reacting species will subsequently slow down. Species which have a low enough kinetic energy below the surface binding energy of the metal will stick to the surface of the metal. When two demobilized reactant molecules come in contact on the surface of the metal, the vibrational energy their reaction creates can be high enough for them to leave the surface of the metal.

If this is true, then a fractal geometry would be significantly better than another standard Euclidian geometry. Surface area is not the primary detenninant of catalyst activity, in itself. Rather, surface area is only important in increasing the number of collisions with reactant molecules. However, an optimized 2 dimensional coating of catalyst particles will still be of a lower efficiency than a porous fractal geometry because fractal geometries maximize the collisions per molecule by directing the trajectory of molecules after the collision towards another metal surface in the vicinity, whose angle directs particles towards another internal wall of the porous dendritic cage. Reactant molecules are trapped within the interfacial spaces and slow down dramatically faster because of multiple collisions. Because of the potential for multiple collisions, even molecules which are moving with initial kinetic energy which exceeds the surface binding energy of the metal, can be demobilized after multiple collisions with the surface of the metal. If we assume a flat surface, as is the case with most catalyst loading geometries, then we should assume a fast moving molecule will likely have at most a single collision. Especially if the loading of catalyst particles are only a small percentage of the total surface area on a supporting structure. Since reactant molecules can only have a single collision, their kinetic energy cannot exceed c. However, for multiple collisions, a molecule can have kinetic energy

where i is the total number of collisions for a given molecule and E is the initial kinetic energy of the molecule upon entering the cage. It will also gain energy from collisions with other molecules and collisions with infrared photons emitted by the surface of the metal. However, if the catalyst surface is a polycrystalline with higher heat and phonon conductivity than the surrounding region, and it is connected to an effectively infinite heat sink, the infrared radiation given off by the metallic catalyst surface would likely not exceed ambient temperatures, despite what is an effective hot spot trap within the fractal pore, since the metal can be said to absorb the kinetic energy throughout its delocalized electron shell, and only has average excitation equal to the average kinetic energy it absorbs.

The pore can become a hotspot because when first exposed to the ambient environment with a given temperature T, which has a corresponding Kinetic energy KE, carried primarily by the movement of molecules. As these molecules come into contact with the opening of the hole, it has a probability p for every unit of time t of getting trapped by the cage. Furthermore, there is a probability q that a particle will escape from the trap where q depends on the number of particles trapped by the cage t with q<p. At some point, p and q will equilibrate and the average number of particles per unit volume will be greater within the fractal trap than outside the fractal trap. Furthermore, particles can constantly lose kinetic energy based on each collisions with the surface of the metal, as the metal carries away the energy from particles with higher kinetic energy. Thus, if the average number of collisions for a molecule within some involution of the fractal surface is S, and assuming a uniform distribution of energies. The proportion of molecules which could be captured by a surface with binding energy B would be those molecules which have an energy E < B. If we assume a normal Gaussian distribution for the kinetic energy of particles within the system, then the proportion of particles which have an energy less than B for a flat surface would be the cumulative density function of a normal Gaussian distribution where x equal in this case to the normalized number f R p \ f p

f / and the probability of binding would be

5)

On the other hand, assuming there is a slight loss of kinetic energy by particles in a collision where f is the average proportion of energy lost for each particle after a collision with a metallic surface, while also including energies gained from random collisions with infrared radiation and collisions with other molecules. Assuming that one closes off the opening of the pore system to prevent any new particles from entering, then the new average kinetic energy of the pocket would be £ * ( ! - /)'^' 6)

Since the average kinetic energy of the system is shifted to a lower energy if one assumes a closed set of particles and a heat sink attached to the metal phonon conductor. Regarding the heat sink, the fractal structure, since it is a continuous structure, will have an increase of kinetic energy transferred through it as phonons, though it does not violate the second law, since these phonons are attached to a glassy carbon surface, which is catalyzed at relatively low temperatures of approximately 200 degrees Celsius.

The probability of a particle exceeding the binding energy of the metal is: )'^')/(# * ( 1 - /)'^")

7)

Finally, the difference between a fiat catalyst surface, and a surface which is arranged in a fractal trap would be:

ίi - E)jE

One simulation (Phillips et al 2003) conducted with Fluent CFD using

Gambit mesh generator, utilized the Cantor set generator, a 76% reduction in the active surface area, the calculated drop in mass transfer to the active surfaces is only reduced by 2.25% when the reactions are diffusion limited. With each iteration, the total length is shortened by 1/3. However, even after infinite iterations, where the effective length is 0, under this study, the simulations show that the total rate of mass transfer falls asymptotically to a fixed value.

The present disclosed subject matter is not to be limited in scope by the specific embodiments described herein. Indeed, various modifications of the disclosed subject matter in addition to those described herein will become apparent to those skilled in the art from the foregoing description and the accompanying figures.

Claims

What is claimed:

1. A porous metal dendrite having a high BET surface area, comprising:

a fractal like dendritic structure , wherein the BETsurface area is at least 20 m /g.

2. The porous metal dendrite according to claim 1 wherein the BET surface area is at least 30 m² /g.

3. The porous metal dendrite according to claim 1 wherein the BET surface area is at least 40 m² /.

4. The porous metal dendrite according to claim 1, wherein a portion of the dendritic structure is resolved to at least 50 nm.

5. The porous metaldendrite according to claim 1, wherein a portion of the dendritic structure is resolved to at least 30 nm.

6. The porous metal dendrite according to claim 1, wherein a portion of the dendritic structure is resolved to at least 10 nm.

7. The porous metal dendrite according to claim 1, wherein the metal is selected from the group consisting of zinc, iron, copper platinum, gold, silver, cobalt, nickel, tin, combination of transition metal, and ionic salts thereof.

8. The porous metal dendrite according to claim 1, wherein the metal is copper.

9. The porous metal dendrite accordmg to claim 1, wherem at least a portion of the dendritic structure is oxidized.

10. The porous metal dendrite according to claim 9, wherein dendritic structure has a outer perimeter area and the oxidized portion is at or near the outer perimeter area.

11. A porous metal dendrite having a high median surface area wherein the porous metal dendrite is prepared by using a chlorophyllin derivative as a nucleation additive.

12. The porous metal dendrite according to claim 11, wherein the metal is selected from the group consisting of zinc, iron, copper platinum, gold, silver, cobalt, nickel, tin, combination of transition metal and ionic salts thereof and the chlorophyllin derivative comprises a metal chlorophyllin salt.

13. The porous metal dendrite according to claim 9, wherein the metal is copper and the chlorophyllin derivative comprises a copper chlorophyllin salt.

14. The porous metal dendrite according to claim 11, wherein the metal dendrite has a fractal like multi-level random structure, wherein a portion of the structure is resolved to at least 50 nm.

15. The porous copper dendrite according to claim 14, wherein the portion of the structure is resolved to at least 30 run.

16. The porous copper dendrite according to claim 14 wherein the portion of the structure is resolved to at least 10 nm.

17. A method of preparing a porous metal dendrite with a high surface area having, comprising:

(a) providing a metal derivative, a metal chlorophyllin salt and an acid in an aqueous solvent, wherein the metal derivative is derived from a metal selected from the group consisting of zinc, iron, copper platinum, gold, silver, cobalt, nickel, tin, combination of transition metal, and ionic salts thereof;

(b) providing a substrate in the solution; and

(c) providing a plurality of electrical pulses to the solution to obtain electrodeposition of the porous metal dendrite with a high surface area.

18. The method according to claim 17, wherein the metal derivative comprises a copper derivative.

19. The method according to claim 18, wherein the copper derivative comprises copper sulfate.

20. The method according to claim 17, wherein the acid comprises sulfuric acid.

21. The method according to claim 17, where the metal chlorophyllin salt comprises a copper chlorophyllin salt.

22. The method according to claim 17, wherein the electrical pulses comprise a first pulse having a first current density and a second pulse having a second current density, and wherein the first and second current densities are different.

23. The method according to claim 20, wherein the first and second pulses are applied for different time durations.

24. A method for converting carbon dioxide to a hydrocarbon, comprising,

(a) capturing carbon dioxide from a gaseous stage by using an ion exchange resin, wherein the ion exchange resin contains a metal catalyst;

(b) submerging at least a portion of the ion exchange resin in an electrolyte water solution; and

(c) electrochemically converting carbon dioxide to a hydrocarbon.

25. The method according to claim 24, wherein the ion exchange resin cyclically moves between the gaseous stage and the electrolyte water solution.

26. The method according to claim 25, wherein the gaseous stage is atmosphere.

27. The method according to claim 24, the metal catalyst comprises one or more metal selected from the group consisting of zinc, iron, copper platinum, gold, silver, cobalt, nickel, tin, combination of transition metal and ionic salts thereof.

28. The method according to claim 27, the metal catalyst comprises copper, copper chloride or copper oxide.

29. The method according to claim 24, wherein the metal catalyst comprises a porous metal dendrite having a high BET surface area and a fractal like dendritic structure, wherein the BETsurface area is at least 20 m² /g.

30. A system for extracting and converting carbon dioxide to a hydrocarbon, comprising:

a container of an electrolyte water solution;

a first electrode that is in contact with the electrolyte water solution;

an ion exchange resin containing a metal catalyst for C0₂ reduction, wherein at least a portion of the ion exchanged resin is cyclically exposed to a gaseous stage containing C0₂ and submerged in the electrolyte water solution; and

a second electrode that is either directly or indirectly in contact with the ion exchange resin.

31. The system according to claim 30, wherein the metal catalyst comprises one or more metal selected from the group consisting of zinc, iron, copper platinum, gold, silver, cobalt, nickel, tin, combination of transition metal and ionic salts thereof.

32. The method according to claim 30, the metal catalyst comprises copper, copper chloride or copper oxide.

33. The method according to claim 32, wherein the metal catalyst comprises a porous metal dendrite having a high BET surface area and a fractal like dendritic structure, wherein the BETsurface area is at least 20 m² /g.