CN114068950B - Ultra-fine sub-nano gold composite material electrocatalyst based on porous carbon support and preparation method and application thereof - Google Patents
Ultra-fine sub-nano gold composite material electrocatalyst based on porous carbon support and preparation method and application thereof Download PDFInfo
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Abstract
The invention discloses an ultrafine sub-nano gold composite material electrocatalyst based on porous carbon support and a preparation method and application thereof, wherein the preparation method comprises the following steps: mixing porous carbon, chloroauric acid (III) serving as a metal salt precursor and water to obtain a first mixture, stirring until the first mixture is uniformly mixed, adding a sodium borohydride aqueous solution serving as a reducing agent, stirring uniformly to obtain a second mixture, filtering, and washing to obtain the superfine sub-nano gold composite material electrocatalyst. The invention synthesizes the porous carbon supported superfine sub-nano gold composite material electrocatalyst by using a template method, has simple and feasible reaction operation, simple required equipment and high repeatability, and the prepared composite material has the advantages of high yield, good electrochemical stability, large electrochemical active area and the like, and can be widely applied to the field of electrocatalytic alcohol oxidation reaction.
Description
Technical Field
The invention belongs to the technical field of alcohol oxidation reaction electrocatalytic materials, and particularly relates to an ultrafine sub-nano gold composite material electrocatalyst based on porous carbon support, and a preparation method and application thereof.
Background
In recent years, fuel cells have been widely focused on as clean energy sources in the fields of power supply, catalysis and the like, and have an important role in protecting the environment. The direct alcohol fuel cell is a novel fuel cell which is widely focused and studied in a plurality of fields such as power supply, catalysis and the like in recent years, and is a power generation energy device which directly takes alcohol as fuel and converts chemical energy generated during alcohol oxidation reaction into electric energy, and the working principle is very simple, and the direct alcohol fuel cell mainly comprises a cathode, an anode, a proton exchange membrane, a bipolar plate and the like. In operation, alcohol is catalytically oxidized to CO at the anode 2 Simultaneously generates electrons and protons, wherein the protons pass through the proton exchange membrane from the anode to the cathode, and reduce oxygen in the cathode chamber under the action of a catalyst to generate H 2 O. The electrons reach the cathode from the anode via the external circuit, and do work via the external circuit to form an electric loop. The fuel of methanol or ethanol has the advantages of rich sources, low price, low toxicity, liquid state, easy carrying and storage, higher electrochemical activity and combustion efficiency, working at room temperature, light weight, small volume, simple structure, convenient maintenance, low pollution, easy operation and the like, and compared with the gas fuel (methanol 4.82 kWhL) -1 Ethanol 6.34kWhL -1 Hydrogen at 20MPa 0.53kwh l -1 ) Has a relatively high energy density. Therefore, the direct alcohol fuel cell is widely used in portable devices as a small power station, a power source for vehicles, and portable devicesHas wide application prospect in the fields of national defense, energy, communication and the like, and is favored by the industry in recent years. However, the practical use of direct alcohol fuel cells is somewhat limited by the fact that the catalyst performance is too low. The oxidation of alcohols requires a catalyst with high activity and has a high overpotential, which is mainly due to the fact that intermediate products such as CO generated during the oxidation of alcohols become attachments to severely poison the electrode surface, and thus the temperature needs to be increased to increase the oxidation rate, but this greatly limits the use effect of direct alcohol fuel cells at room temperature. Commercial Pt/C catalysts commonly used at present are easy to poison to influence the stability of the catalyst, so that the catalytic performance is reduced, the electrooxidation kinetics are slower, and the electrooxidation kinetics can only reach about 10 -4 Current densities on the order of a/mg and are extremely susceptible to deactivation after multiple applications, resulting in rapid current density drops. In addition to platinum, gold electrodes are also used as catalysts for alcohol oxidation. However, the polished gold electrode has a smooth surface, but the catalytic active sites are less exposed, so that the alcohol oxidation electrocatalytic performance (current density) is greatly limited, and the poisoning resistance is also weak.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide a preparation method of an ultrafine sub-nano gold composite material electrocatalyst based on porous carbon support, which is simple, convenient and feasible, high in yield and good in reproducibility.
The invention also aims to provide the superfine sub-nano gold composite material electrocatalyst obtained by the preparation method, which has high-exposure sub-nano multi-catalytic active sites, large electrochemical active area, high current density and excellent poisoning resistance effect, can be used as alcohol oxidation electrocatalyst, and has good stability.
The aim of the invention is achieved by the following technical scheme.
The preparation method of the superfine sub-nano gold composite material electrocatalyst based on porous carbon support comprises the following steps:
mixing porous carbon, chloroauric acid (III) serving as a metal salt precursor and water to obtain a first mixture, stirring until the first mixture is uniformly mixed, adding sodium borohydride aqueous solution serving as a reducing agent, stirring uniformly to obtain a second mixture, filtering, and washing to obtain an ultrafine sub-nano gold composite material electrocatalyst (Au@NPC), wherein the ratio of sodium borohydride to chloroauric acid in the sodium borohydride aqueous solution is 1:1, wherein the ratio of the mass parts of the porous carbon to the mass parts of the chloroauric acid is (800-850): 1.
In the above technical scheme, when the unit of the parts by weight of the substances is mmol, the unit of the parts by weight is mg.
In the technical scheme, the chloroauric acid is added in the form of an aqueous solution of chloroauric acid.
In the above technical scheme, the concentration of chloroauric acid in the first mixture is 0.09-0.12 mM.
In the above technical scheme, ethanol is used for washing.
In the above technical solution, the method for preparing the porous carbon includes: and (3) burning the ZIF-8 crystal for 6-7 hours at 550-800 ℃ in a nitrogen or inert gas environment, cooling to room temperature of 20-25 ℃, soaking in hydrochloric acid for etching, washing with ultrapure water, and drying to obtain black powder which is the porous carbon, wherein the concentration of hydrochloric acid is 5-7M.
In the technical scheme, the speed of adding the sodium borohydride aqueous solution is 5-10 mu L/s.
In the technical scheme, the concentration of sodium borohydride in the sodium borohydride aqueous solution is 8-12 mmol/L.
The ultra-fine sub-nano gold composite material electrocatalyst obtained by the preparation method.
The superfine sub-nano gold composite material electrocatalyst comprises porous carbon and sub-nano gold growing in porous carbon pore channels.
In the technical scheme, the size of the porous carbon is 150-700 nm, and the size of the sub-nano gold is 1.5-2.3 nm.
In the technical scheme, the BET surface of the superfine sub-nano gold composite material electrocatalystThe average of the products was 56m 2 ·g -1 BET surface area of porous carbon is 300-650 m 2 ·g -1 。
The application of the superfine sub-nano gold composite material electrocatalyst in improving the anti-poisoning capability of the catalyst. The invention synthesizes the porous carbon supported superfine sub-nano gold composite material electrocatalyst by using a template method, has simple and feasible reaction operation, simple required equipment and high repeatability, and the prepared composite material has the advantages of high yield, good electrochemical stability, large electrochemical active area and the like, and can be widely applied to the field of electrocatalytic alcohol oxidation reaction.
Drawings
FIG. 1 (a) is a diagram showing the transmission electron microscope characterization of the ultra-fine sub-nano gold composite electrocatalyst obtained in example 3, with a scale size of 200nm;
FIG. 1 (b) is a Raman spectrum diagram of the ultra-fine sub-nano-gold composite electrocatalyst obtained in examples 1 to 4;
FIG. 2 is an electron microscope topography of the ultra-fine sub-nano gold composite electrocatalyst obtained in example 3 (the inset is an electron diffraction image of the composite), wherein i is an electron microscope image under a 100nm scale, and ii is an electron microscope image under a 20nm scale after i is enlarged;
FIG. 3 is an X-ray powder diffraction (PXRD) diagram of the ultra-fine sub-nano-gold composite electrocatalyst, porous carbon and ZIF-8 obtained in example 3;
FIG. 4 is an X-ray photoelectron spectrum of the ultra-fine sub-nano gold composite electrocatalyst obtained in example 3, FIG. 4i is an Au4f energy spectrum of the ultra-fine sub-nano gold composite electrocatalyst obtained in example 3, FIG. 4ii is a C1s energy spectrum of the ultra-fine sub-nano gold composite electrocatalyst obtained in example 3, and FIG. 4iii is a full energy spectrum of the ultra-fine sub-nano gold composite electrocatalyst obtained in example 3;
FIG. 5 (a) is a nitrogen adsorption diagram of ZIF-8 and porous carbon (NPC) obtained in example 3;
FIG. 5 (b) is a nitrogen adsorption diagram of the ultra-fine sub-nano-gold composite electrocatalyst obtained in example 3;
FIG. 6 (a) shows the results of examples 1 to 4 for the ultra-fine sub-nano-gold composite electrocatalyst0.5M H 2 SO 4 Cyclic voltammograms in the electrolyte;
FIG. 6 (b) is a graph showing the electrochemical activity area of the ultra-fine sub-nano-gold composite electrocatalyst obtained in examples 1 to 4;
FIG. 7 (a) is a cyclic voltammogram of the methanol oxidation reaction of the ultra-fine sub-nano-gold composite electrocatalyst obtained in examples 1 to 4;
FIG. 7 (b) is a timing chart of the methanol oxidation reaction of the ultra-fine sub-nano-gold composite electrocatalyst obtained in examples 1 to 4;
FIG. 7 (c) is a cyclic voltammogram of the ethanol oxidation reaction of the ultra-fine sub-nano-gold composite electrocatalyst obtained in examples 1 to 4;
FIG. 7 (d) is a timing chart of ethanol oxidation reaction of the ultra-fine sub-nano-gold composite electrocatalyst obtained in examples 1 to 4.
Detailed Description
The technical scheme of the invention is further described below with reference to specific embodiments.
Silver nitrate (AgNO) 3 99.5% or more) and 2-methylimidazole (99% or more), purchased from Tianjin Bote chemical trade Co., ltd;
methanol (CH) 3 OH, 99% or more), ethanol (CH 3 CH 2 OH, 99% or more), obtained from Tianjin metallocene chemical industry trade company;
perfluorosulfonic acid polymer solution (mass fraction 5%) from Shanghai sigma chemical industry trade company;
commercial Pt/C (20%) catalyst (commercial platinum carbon), available from alfa eastern chemical trade company, inc;
hydrochloric acid (HCl, 36%) and sulfuric acid (H) 2 SO 4 More than or equal to 98 percent) from wealth chemical reagent limited company;
chloroauric acid (III) (AuCl 3 ·HCl·4H 2 O, content in hydrochloric acid 23.5-23.8%) from Ala-dine;
sodium borohydride (NaBH) 4 99.5%) from Komi chemical Co.
The size of the ZIF-8 crystals used in the examples described below was (1.6.+ -. 0.2) μm, its preparation method: 5mL of a metal salt zinc nitrate hexahydrate methanol solution (25 mmol.L) -1 ) 5mL of a methanol solution (25 mmol.L) of the organic ligand 2-methylimidazole -1 ) Put into a 20mL reaction flask, stand at room temperature for reaction for 3 hours, observe the bottom gray precipitate, further centrifuge at 3000rpm for 3 minutes, wash with water three times, and dry in a 60 ℃ oven for 3 hours to obtain ZIF-8 crystals. The ZIF-8 crystal can be specifically referred to in the literature: chem.Commun.,2013,49,2521-2523.
The microporous filter membrane is a polyethersulfone water-based filter membrane with pore diameters of 0.45 and 0.8 μm and is purchased from Jinteng laboratory equipment Co., ltd.
Examples 1 to 4
The preparation method of the superfine sub-nano gold composite material electrocatalyst based on porous carbon support comprises the following steps:
in a reaction glass bottle, 5mg of porous carbon and 50. Mu.L of aqueous chloroauric acid solution (III) (the concentration of chloroauric acid in the aqueous chloroauric acid solution is 10 mmol.L) -1 ) Mixing with 5mL of water to obtain a first mixture, wherein the concentration of chloroauric acid in the first mixture is 0.11mM, stirring the first mixture for 1h until the mixture is uniform, enabling a metal salt precursor chloroauric acid to enter porous carbon pore channels, dropwise adding 50 mu L of sodium borohydride aqueous solution serving as a reducing agent (the speed of adding the sodium borohydride aqueous solution is 8 mu L/s), and the concentration of sodium borohydride in the sodium borohydride aqueous solution is 10 mmol.L -1 Stirring uniformly to obtain a second mixture, filtering the second mixture by using a microporous filter membrane, centrifuging at a speed of 2000rpm for 3 minutes, washing the solid obtained by centrifugation by using ethanol for 3 times, and drying in a 60 ℃ oven for 6 hours to obtain the superfine sub-nano gold composite material electrocatalyst (Au@NPC), wherein the ratio of sodium borohydride to chloroauric acid in the sodium borohydride aqueous solution is 1:1, the ratio of the mass parts of the porous carbon to the mass parts of the chloroauric acid is 834:1, the unit of the mass parts of the substances is mmol, and the unit of the mass parts is mg.
Wherein, the method for preparing the porous carbon (NPC) comprises the following steps: placing a ceramic boat filled with ZIF-8 crystals in a quartz tube of a tube furnace, heating to T ℃ from room temperature at a heating rate of 5 ℃/min under a nitrogen environment, preserving heat at T ℃ for 6 hours, naturally cooling to room temperature of 20-25 ℃, soaking in hydrochloric acid with a concentration of 6M for 3 times (each specific operation is ultrasonic vibration in an ultrasonic cleaner for 20 minutes, the aim is to remove metal substances), washing with ultrapure water for 3 times, and drying in vacuum at 60 ℃ for 24 hours to obtain black powder which is porous carbon. Wherein, the value of T is shown in Table 1.
TABLE 1
The porous carbon obtained in example 1 had the following dimensions: (213.2±22.5) nm; the sub-nano gold grows in the porous carbon pore canal and is finally embedded in the porous carbon pore canal, and the size of the sub-nano gold is (1.9+/-0.4) nm. Porous carbon BET surface area of 305m 2 ·g -1 Its Raman peak is 1345cm -1 、1460cm -1 、1595cm -1 ，1345cm -1 And 1595cm -1 Peak ratio of 0.75; BET surface area of the obtained superfine sub-nano gold composite material electrocatalyst is 56m 2 ·g -1 The diffraction peaks were: 24.4 °, 38.2 °,44.3 °,64.6 °, 77.8 °.
The porous carbon obtained in example 2 had the following dimensions: (625.4 + -37.8) nm; the sub-nano gold grows in the porous carbon pore canal and is finally embedded in the porous carbon pore canal, and the size of the sub-nano gold is (1.9+/-0.4) nm. Porous carbon BET surface area of 325m 2 ·g -1 Its Raman peak is 1345cm -1 、1460cm -1 、1595cm -1 ，1345cm -1 And 1595cm -1 Peak ratio of 0.82; BET surface area of the obtained superfine sub-nano gold composite material electrocatalyst is 56m 2 ·g -1 The diffraction peaks were: 24.4 °, 38.2 °,44.3 °,64.6 °, 77.8 °.
The porous carbon obtained in example 3 had the following dimensions: (574.3+ -146.6) nm; the sub-nano gold grows in the porous carbon pore canal and is finally embedded in the porous carbon pore canal, and the size of the sub-nano gold is (1.9+/-0.4) nm. Porous carbon BET surface area of 630m 2 ·g -1 Its Raman peak is 1345cm -1 、1595cm -1 Peak ratio was 0.94; by a means ofThe BET surface area of the ultra-fine sub-nano gold composite material electrocatalyst is 56m 2 ·g -1 The diffraction peaks were: 24.4 °, 38.2 °,44.3 °,64.6 °, 77.8 °.
The porous carbon obtained in example 4 had the following dimensions: (341.1 + -62.6) nm; the sub-nano gold grows in the porous carbon pore canal and is finally embedded in the porous carbon pore canal, and the size of the sub-nano gold is (1.9+/-0.4) nm. Porous carbon BET surface area 502m 2 ·g -1 Its Raman peak is 1345cm -1 、1595cm -1 Peak ratio was 1.02; BET surface area of the obtained superfine sub-nano gold composite material electrocatalyst is 56m 2 ·g -1 The diffraction peaks were: 24.4 °, 38.2 °,44.3 °,64.6 °, 77.8 °.
The ultra-fine sub-nano gold composite electrocatalyst obtained in examples 1 to 4 was further characterized as follows:
(1) Porous carbon supported electron microscope morphology characterization
A proper amount of superfine sub-nano gold composite material electrocatalyst is selected and dissolved in ethanol to obtain a sample solution, and the sample solution is instilled on a copper mesh and a silicon wafer (sold by electron microscope company) by using a 5 mu L pipetting gun. The copper mesh loaded with the sample solution presents transmission electron imaging under the effect of transmission electron beam of a transmission electron microscope, the appearance and the size of the porous carbon support are characterized, the porous carbon is formed by calcining ZIF-8 serving as a template and a sacrificial agent at a high temperature, and the size is about 200-600 nm and is mainly in a dodecahedron appearance. See FIG. 1 (a) (instrument model: tecnai F20). Raman spectra were measured using a Raman spectrometer after instillation on the wafer, showing the formation of porous carbon, showing 1345 and 1595cm -1 Two typical peaks at 1460cm -1 Additional peaks 1345 and 1595cm -1 Is composed of defect mode (d band) and E 2g Mode (g-band) induced, lower ratio indicates higher graphitization degree of carbon, 1460cm -1 The adsorption of C-H from ZIF-8 is achieved, and carbonization effect without peak is better. See FIG. 1 (b) (instrument model number Renishaw InVia Reflex spectroscopy).
(2) Electron microscope morphology characterization of composite electrocatalyst
And (3) a proper amount of superfine sub-nano gold composite material electrocatalyst is selected and dissolved in ethanol to obtain a sample solution, the sample solution is instilled on a copper mesh (sold by electron microscopy company) by using a 5 mu L pipetting gun, transmission electron imaging is respectively presented under the effect of transmission electron beams of an electron microscope, the appearance and the size of the porous carbon supported superfine sub-nano gold composite material electrocatalyst are characterized, the porous carbon size is about 200-600 nm, the morphology of a dodecahedron is mainly adopted, and sub-nano gold grows in porous carbon pore channels and the size is-2 nm. See FIG. 2 (instrument model: tecnai F20).
(3) Characterization of composite electrocatalyst by X-ray powder diffraction (PXRD)
The PXRD characterization of the ultra-fine sub-nano gold composite electrocatalyst shows that the ultra-fine sub-nano gold composite electrocatalyst has reliable phase purity, proves the formation of sub-nano gold and the structure of porous carbon, provides guarantee for the application of the ultra-fine sub-nano gold composite electrocatalyst as an electrocatalyst, and is shown in figure 3 (the PXRD characterization of the porous carbon obtained in example 3 is shown, and the instrument model is Bruker GADDS XRD).
(4) Elemental analysis characterization of composite electrocatalyst
The element analysis characterization of the ultra-fine sub-nano gold composite material electrocatalyst is carried out by an X-ray photoelectron spectroscopy test of sample powder, and shows that Au4f peaks are 83.6eV and 87.6eV, zn 2p peaks are 1021.2 and 1044.1eV, so that the atomic ratio of gold to carbon in the ultra-fine sub-nano gold composite material electrocatalyst can be calculated through the peak area, the gold content is only 1%, and the element composition of the ultra-fine sub-nano gold composite material electrocatalyst is proved. See FIG. 4 (instrument model: PHI QuanteraSXM).
(5) Pore structure characterization of composite electrocatalyst
The nitrogen adsorption-desorption curve test of the ultra-fine sub-nano gold composite material electrocatalyst shows that the uniform pore size distribution of the material is further calculated by adsorption-desorption data, and the method comprises the following steps of: to be used for
On the ordinate, p/p 0 A straight line was fitted for the abscissa, and the BET specific surface area was 4.36/(intercept+slope). The BET specific surface area of the pure zeolite imidazole framework material (ZIF-8) is 1116m 2 ·g -1 In contrast, the specific surface areas of the porous carbon and the superfine sub-nano gold composite electrocatalyst are respectively reduced to 630m 2 ·g -1 (T＝700)、56m 2 ·g -1 The influence of the sub-nano gold on the pore size distribution of the porous carbon proves the porosity of the porous carbon support and the uniformity of the composite material, and provides a guarantee for the application of the porous carbon support in the electrocatalytic alcohol oxidation reaction. See FIGS. 5 (a) and 5 (b) (instrument model number Micromeritics ASAP 2020).
(6) Characterization of the electrocatalytic performance of alcohol oxidation reactions of composite electrocatalysts
The method adopts a commercial glassy carbon electrode to load an ultrafine sub-nano gold composite material electrocatalyst and comprises the following specific operations: polishing a commercial glassy carbon electrode by using alumina particles, sequentially and ultrasonically cleaning the commercial glassy carbon electrode by using dilute nitric acid, acetone and ethanol respectively, dispersing 10mg of superfine sub-nano gold composite material electrocatalyst or commercial platinum carbon into 0.5mL of absolute ethanol, and performing ultrasonic treatment for 3min to obtain a suspension, and coating the commercial glassy carbon electrode by using 10 mu L of the suspension, wherein the method comprises the following specific operations: 2. Mu.L of each solution was added dropwise, left standing for 5min and naturally air-dried, and then repeatedly added dropwise for 5 times, followed by sealing with 1. Mu.L of a perfluorosulfonic acid type polymer solution, and drying at 30℃for 1 hour in a desiccator to obtain a modified glassy carbon electrode (the modified glassy carbon electrode obtained with commercial platinum carbon was designated as Pt/C).
The modified glassy carbon electrode prepared by taking the ultra-fine sub-nano gold composite material electrocatalyst obtained in the examples 1 to 4 and commercial platinum carbon as a catalyst is tested by the following test method: the electrochemical workstation is used for testing the electrocatalytic performance of the alcohol oxidation reaction by adopting a traditional three-electrode system with an Ag/AgCl (saturated KCl) electrode as a reference electrode, an improved glassy carbon electrode as a working electrode and a platinum wire as a counter electrode. First at 0.5. 0.5M H 2 SO 4 Electrochemical activation of the modified glassy carbon electrode with a potential cycling window from-0.2 to 1.2V (vs Ag/AgCl) for an electrolyte at a scan rate of 5mVs -1 The cyclic voltammetry test was performed for current-voltage relationship as shown in FIG. 6 (a), and the electrochemically active area was calculated therefrom as shown in FIG. 6 (b) (instrument model: pine Bipotentiostat Basic WaveDriver 20 Bundle). The method for calculating the electrochemical active area (ECSA) comprises the following steps: stripping with measured gold oxidePeak charge (Q) Au -O, i.e. the cathodic peak area between 0.3V and 0.8V) and the mass of gold (m Au ) And based on the use of 450. Mu.C/cm 2 The ECSA of the catalyst can be calculated as the relative charge of the monolayer oxygen adsorbed on gold as follows: ecsa=q Au -O/(450μC/cm 2 *m Au ). The specific numerical values are as follows: the electrochemically active area obtained in example 3 was 147m 2 ·g Au -1 Far exceeding the electrochemically active area (-530 times) of commercial platinum carbon.
In 0.5. 0.5M H containing 1.0M methanol 2 SO 4 Electrolyte and 0.5. 0.5M H containing 1.0M ethanol 2 SO 4 Respectively performing electrocatalytic test of methanol oxidation and ethanol oxidation in electrolyte, and testing current density with cyclic voltammetry at scanning speed of 50mVs -1 Referring to FIGS. 7 (a) and 7 (c), a clear cathodic peak from the reduction of the Au-O intermediate was scanned in the reverse direction around 0.5V, and a cathodic peak near 0.7V was scanned in the forward direction due to oxidation of the alcohol molecule. By redox peak ratio I f /I b To compare the size of the electrocatalyst with the poisoning resistance (I) f : forward scan peak current, I b : reverse scan peak current), the higher the ratio indicates a stronger resistance to CO-based poisoning substances, thereby oxidizing and converting alcohol to CO during anodic scan 2 The ability of CO poisoning substances to accumulate on the catalyst surface is slower, so the electrocatalyst has stronger poisoning resistance, see fig. 7 (a) and (c); the stability was tested by chronoamperometry, see fig. 7 (b) and (d); wherein FIGS. 7 (a) and (b) are electrocatalytic characterization of a methanol oxidation reaction and FIGS. 7 (c) and (d) are electrocatalytic characterization of an ethanol oxidation reaction. (instrument model: pine Bipotentiostat Basic WaveDriver 20 Bundle). The specific electrocatalytic performance is as follows: the current density of the Methanol Oxidation Reaction (MOR) obtained in example 3 was 6.62 A.mg Au -1 About 330 times that of commercial platinum carbon, the redox peak ratio I obtained in example 3 f /I b 2.1, which is far more than 0.8 of commercial platinum carbon, proves that the antitoxic capability is stronger; the Ethanol Oxidation Reaction (EOR) current density obtained in example 3 was 1.1 mA.mg Au -1 About 330 times that of commercial platinum carbon, oxygen obtained in example 3Reduction to reduction peak ratio I f /I b 0.5, which is far more than 0.07 of commercial platinum carbon, and the ultra-fine sub-nano gold composite material has stronger anti-poisoning capability; the chronoamperometry shows that the modified glassy carbon electrode obtained in example 3 can still maintain about 80% and 70% of current density after undergoing 50 and 200 cycles of testing, demonstrating the high stability and recycling rate of the ultra-fine sub-nano-gold composite electrocatalyst of the invention.
From the above characterization results, it can be seen that the ultra-fine sub-nano gold composite electrocatalyst of the present invention is composed of sub-nano gold and porous carbon support. The porous carbon is formed by calcining ZIF-8 serving as a template and a sacrificial agent at a high temperature, the size is about 200-600 nm, the porous carbon is mainly in a dodecahedron shape, sub-nano gold grows in porous carbon pore channels, the size is-2 nm, and the atomic content ratio of gold is-1%. The ultra-fine sub-nano gold composite material electrocatalyst shows characteristic diffraction peaks of ultra-fine sub-nano gold at 38.2 degrees, 44.3 degrees, 64.6 degrees and 77.8 degrees, and also shows characteristic diffraction peaks of porous carbon at 24.4 degrees and 44.0 degrees, and the crystal structure of the electrocatalyst is proved. The electrochemical active area of the ultra-fine sub-nano gold composite material electrocatalyst is 147m 2 ·g Au -1 In the electrochemical alcohol oxidation reaction, the current density of the Methanol Oxidation Reaction (MOR) is 6.62 A.mg Au -1 Redox peak ratio I f /I b 2.1, an Ethanol Oxidation Reaction (EOR) current density of 0.9mA.mg Au -1 Redox peak ratio I f /I b At 0.5, its excellent electrocatalytic performance was demonstrated.
The porous carbon is used as a material with high specific surface area, so that the stability of the sub-nano gold particles is greatly improved, the agglomeration phenomenon is reduced, the specific surface area and available active sites are increased, and the catalytic activity is greatly improved. And the porous carbon has regular pore structure, high pore rate and high specific surface area, provides a channel which is convenient for rapid diffusion of reactant molecules, is beneficial to reaction and promotes desorption of CO intermediates. By utilizing the synergistic effect of the two, the problem of poisoning of the traditional metal catalyst can be solved, and the stability and the recycling rate of the catalyst can be increased.
The foregoing has described exemplary embodiments of the invention, it being understood that any simple variations, modifications, or other equivalent arrangements which would not unduly obscure the invention may be made by those skilled in the art without departing from the spirit of the invention.
Claims (9)
1. The preparation method of the superfine sub-nano gold composite material electrocatalyst based on porous carbon support is characterized by comprising the following steps:
mixing porous carbon, chloroauric acid serving as a metal salt precursor and water to obtain a first mixture, stirring until the first mixture is uniformly mixed, adding sodium borohydride aqueous solution serving as a reducing agent, stirring uniformly to obtain a second mixture, filtering, and washing to obtain the superfine sub-nano gold composite material electrocatalyst, wherein the ratio of sodium borohydride to chloroauric acid in the sodium borohydride aqueous solution is 1:1, wherein the ratio of the mass parts of the porous carbon to the mass parts of the chloroauric acid is (800-850): 1;
the size of the porous carbon is 150-700 nm, the size of the sub-nano gold is 1.5-2.3 nm, the average number of BET surface areas of the ultra-fine sub-nano gold composite electrocatalyst is 56m < 2 >. G < -1 >, and the BET surface area of the porous carbon is 300-650 m < 2 >. G < -1 >.
2. The production method according to claim 1, wherein when the parts by weight of the substance are in mmol, the parts by weight are in mg; the chloroauric acid is added in the form of an aqueous chloroauric acid solution.
3. The method according to claim 1, wherein the concentration of chloroauric acid in the first mixture is 0.09-0.12 mM, and ethanol is used for the washing.
4. The method of producing according to claim 1, wherein the method of producing the porous carbon comprises: and (3) burning the ZIF-8 crystal for 6-7 hours at 550-800 ℃ in a nitrogen or inert gas environment, cooling to room temperature of 20-25 ℃, soaking in hydrochloric acid for etching, washing with ultrapure water, and drying to obtain black powder which is the porous carbon, wherein the concentration of hydrochloric acid is 5-7M.
5. The method according to claim 1, wherein the aqueous sodium borohydride solution is added at a rate of 5 to 10. Mu.L/s.
6. The method according to claim 1 or 5, wherein the concentration of sodium borohydride in the aqueous sodium borohydride solution is 8 to 12mmol/L.
7. An ultra-fine sub-nano gold composite electrocatalyst obtained by the method according to any one of claims 1 to 6.
8. The ultra-fine sub-nano-gold composite electrocatalyst according to claim 7, comprising porous carbon and sub-nano-gold grown in pores of the porous carbon.
9. The use of the ultra-fine sub-nano gold composite electrocatalyst according to claim 7 for increasing the poisoning resistance of the catalyst.
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