CN114774987B - Iron-based bipolar membrane and preparation method and application thereof - Google Patents
Iron-based bipolar membrane and preparation method and application thereof Download PDFInfo
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- 239000012528 membrane Substances 0.000 title claims abstract description 128
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 title claims abstract description 68
- 229910052742 iron Inorganic materials 0.000 title claims abstract description 29
- 238000002360 preparation method Methods 0.000 title claims abstract description 16
- 229920000557 Nafion® Polymers 0.000 claims abstract description 33
- CWYNVVGOOAEACU-UHFFFAOYSA-N Fe2+ Chemical compound [Fe+2] CWYNVVGOOAEACU-UHFFFAOYSA-N 0.000 claims abstract description 20
- 229910001448 ferrous ion Inorganic materials 0.000 claims abstract description 16
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 16
- 230000002378 acidificating effect Effects 0.000 claims abstract description 15
- 230000009467 reduction Effects 0.000 claims abstract description 13
- 238000003825 pressing Methods 0.000 claims abstract description 12
- 239000002131 composite material Substances 0.000 claims abstract description 7
- 238000007605 air drying Methods 0.000 claims abstract description 6
- 238000005507 spraying Methods 0.000 claims abstract description 6
- 238000000034 method Methods 0.000 claims abstract description 5
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 51
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 claims description 38
- 239000000243 solution Substances 0.000 claims description 36
- 239000010410 layer Substances 0.000 claims description 27
- 239000011550 stock solution Substances 0.000 claims description 7
- MCDLETWIOVSGJT-UHFFFAOYSA-N acetic acid;iron Chemical compound [Fe].CC(O)=O.CC(O)=O MCDLETWIOVSGJT-UHFFFAOYSA-N 0.000 claims description 6
- 239000011229 interlayer Substances 0.000 claims description 6
- BAUYGSIQEAFULO-UHFFFAOYSA-L iron(2+) sulfate (anhydrous) Chemical compound [Fe+2].[O-]S([O-])(=O)=O BAUYGSIQEAFULO-UHFFFAOYSA-L 0.000 claims description 6
- 238000005266 casting Methods 0.000 claims description 3
- LFKXWKGYHQXRQA-FDGPNNRMSA-N (z)-4-hydroxypent-3-en-2-one;iron Chemical compound [Fe].C\C(O)=C\C(C)=O.C\C(O)=C\C(C)=O LFKXWKGYHQXRQA-FDGPNNRMSA-N 0.000 claims description 2
- 229910002651 NO3 Inorganic materials 0.000 claims description 2
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 claims description 2
- 239000008367 deionised water Substances 0.000 claims description 2
- 229910021641 deionized water Inorganic materials 0.000 claims description 2
- 238000001035 drying Methods 0.000 claims description 2
- 229960002089 ferrous chloride Drugs 0.000 claims description 2
- 235000003891 ferrous sulphate Nutrition 0.000 claims description 2
- 239000011790 ferrous sulphate Substances 0.000 claims description 2
- NMCUIPGRVMDVDB-UHFFFAOYSA-L iron dichloride Chemical compound Cl[Fe]Cl NMCUIPGRVMDVDB-UHFFFAOYSA-L 0.000 claims description 2
- 229910000359 iron(II) sulfate Inorganic materials 0.000 claims description 2
- 239000011259 mixed solution Substances 0.000 claims description 2
- 239000002253 acid Substances 0.000 abstract description 13
- 230000003197 catalytic effect Effects 0.000 abstract description 6
- 230000000694 effects Effects 0.000 abstract description 6
- 238000006243 chemical reaction Methods 0.000 abstract description 5
- 125000002091 cationic group Chemical group 0.000 abstract description 3
- 238000006460 hydrolysis reaction Methods 0.000 abstract description 2
- -1 iron ions Chemical class 0.000 abstract description 2
- BDAGIHXWWSANSR-UHFFFAOYSA-N methanoic acid Natural products OC=O BDAGIHXWWSANSR-UHFFFAOYSA-N 0.000 description 40
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 description 24
- OSWFIVFLDKOXQC-UHFFFAOYSA-N 4-(3-methoxyphenyl)aniline Chemical compound COC1=CC=CC(C=2C=CC(N)=CC=2)=C1 OSWFIVFLDKOXQC-UHFFFAOYSA-N 0.000 description 20
- 235000019253 formic acid Nutrition 0.000 description 20
- 235000019441 ethanol Nutrition 0.000 description 17
- 239000003792 electrolyte Substances 0.000 description 13
- 238000010586 diagram Methods 0.000 description 5
- 239000000047 product Substances 0.000 description 5
- 230000002441 reversible effect Effects 0.000 description 5
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 4
- 229910052799 carbon Inorganic materials 0.000 description 4
- 238000001816 cooling Methods 0.000 description 4
- 239000011521 glass Substances 0.000 description 4
- 238000010438 heat treatment Methods 0.000 description 4
- 239000012263 liquid product Substances 0.000 description 4
- 239000002184 metal Chemical group 0.000 description 4
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- 238000012876 topography Methods 0.000 description 2
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- 150000007513 acids Chemical class 0.000 description 1
- 150000001298 alcohols Chemical class 0.000 description 1
- 239000003513 alkali Substances 0.000 description 1
- 239000003125 aqueous solvent Substances 0.000 description 1
- 239000002585 base Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
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- 229940021013 electrolyte solution Drugs 0.000 description 1
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- 239000000446 fuel Substances 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 238000000227 grinding Methods 0.000 description 1
- ZRALSGWEFCBTJO-UHFFFAOYSA-N guanidine group Chemical group NC(=N)N ZRALSGWEFCBTJO-UHFFFAOYSA-N 0.000 description 1
- 150000002391 heterocyclic compounds Chemical group 0.000 description 1
- 229930195733 hydrocarbon Natural products 0.000 description 1
- 150000002430 hydrocarbons Chemical class 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 150000002460 imidazoles Chemical group 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
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Classifications
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- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
- C25B13/00—Diaphragms; Spacing elements
- C25B13/02—Diaphragms; Spacing elements characterised by shape or form
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- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
- C25B13/00—Diaphragms; Spacing elements
- C25B13/04—Diaphragms; Spacing elements characterised by the material
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- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
- C25B3/00—Electrolytic production of organic compounds
- C25B3/01—Products
- C25B3/07—Oxygen containing compounds
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- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
- C25B3/00—Electrolytic production of organic compounds
- C25B3/20—Processes
- C25B3/25—Reduction
- C25B3/26—Reduction of carbon dioxide
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Electrolytic Production Of Non-Metals, Compounds, Apparatuses Therefor (AREA)
Abstract
The invention discloses an iron-based bipolar membrane and a preparation method and application thereof. The iron-based bipolar membrane provided by the invention is a composite membrane comprising a commercial alkaline membrane layer, a ferrous ion intermediate layer and a Nafion acidic membrane layer. The bipolar membrane is prepared by spraying ferrous ion solution and Nafion membrane solution on a commercial alkaline membrane in sequence, and then air-drying and cold-pressing. Commercial alkaline membranes in the iron-based bipolar membrane prepared by the method have cationic groups, so that the conduction of OH ‑ in the alkaline membranes can be realized; the Nafion series membrane has high proton conductivity, and can realize the conduction of H + in an acid membrane; the iron ions serving as the middle catalytic layer can be subjected to catalytic hydrolysis reaction with water molecules, so that the reaction activity of the water is improved, and the water molecule bonds are weakened; therefore, the iron-based bipolar membrane provided by the invention can realize efficient reduction of CO 2, and has a good application prospect.
Description
Technical Field
The invention relates to an iron-based bipolar membrane, a preparation method and application thereof, and belongs to the technical field of electrochemical reduction of CO 2.
Background
Electrochemical CO 2 reduction (CO 2 RR) is a widely accepted technology at present that can use CO 2 produced by human production activities as a carbon source to produce high value added fuels and chemicals while effectively mitigating the emissions of CO 2 in the atmosphere [ chem. Soc. Rev.2014,45,631-675]. CO 2 can be converted in electrochemical reactors into a number of products such as acids, alcohols, hydrocarbons and synthesis gas using electricity from renewable energy sources such as wind, solar, tidal and geothermal [ Joule.2018,2,825-832]. The selectivity of different products depends on a number of influencing factors, including: the type of catalyst and its morphology, electrolyte type and concentration and pH, electrolyte flow characteristics, aqueous or non-aqueous solvents, temperature, pressure, potential and current density, and the impurities present in the electrolyte and the design of the electrolytic cell, etc. [ ACS catalyst.2017, 7,4822-4827].
In general, in order to prevent the product of reduction of CO 2 from diffusing to the anode to be oxidized, and the type of electrolyte used is not the same due to the occurrence of different reactions between the anode and cathode. Therefore, a polymer film is often added between the anode and cathode for separating the anode and cathode [ Ind. Eng. Chem. Res.2019,58,1834-1847]. The types of polymer films are three at present, namely: basic anion exchange, acid and bipolar membranes, wherein acid membranes have been demonstrated to increase competing reaction hydrogen evolution due to the conduction of large amounts of protons to the cathode, while basic membranes have been demonstrated to have higher formic acid "penetration" resulting in the loss of CO 2 to reduce liquid products [ adv. Sustein. Syst.2018,2,1700187].
Unlike the two membranes described above, the bipolar membrane composition includes a positively charged Anion Exchange Layer (AEL), an intermediate catalytic layer, and a negatively charged Cation Exchange Layer (CEL) [ chemsuschem 2014,7,3017-3020], which can operate in two modes, (a) forward biased (V > 0) with the CEL of the membrane toward the anode, and (b) reverse biased (V < 0) with the CEL toward the cathode. In the forward bias mode, the electric field causes mobile ions to migrate toward the Interface Region (IR), which ions accumulate at the junction to compensate for the charge in the layer, thereby reducing the selectivity of the film. In contrast, in reverse bias mode, when the applied voltage reaches a certain value, separation of water molecules will occur at the interface of AEL and CEL, and there is an enhanced electric field effect at the interior of the film, onsager's law of the second wien effect [ electrodim. Acta.1986,31,1175-1177], H + will migrate through CEL to the cathode and OH - through AEL to the anode in the presence of the applied electric field. Bipolar membranes have a distinct advantage over single layer alkaline or acidic membranes in electrochemical reduction of CO 2: (a) When the bipolar membrane is used as a diaphragm, the anode and cathode can use two electrolyte solutions with different pH values, and the pH values of the electrolytes at two sides can be maintained in the use process; (b) The "breakthrough" of the liquid product from the cathode to the anode is negligible; (c) When the electrolytes of the anode and the cathode are pure water, the acidification and alkalization of the electrolytes do not need to add extra acid and alkali.
However, in the field of electrochemical reduction of CO 2 in China, both universities and scientific institutions are still focusing on the development of electrocatalysts. Reaction devices and electrolytes have been studied until now, and no one has been involved with bipolar membranes.
Disclosure of Invention
The technical problems to be solved by the invention are as follows: technical problem of how to make bipolar membranes useful for efficient electrochemical reduction of CO 2 using commercial alkaline membranes.
In order to solve the technical problems, the invention provides an iron-based bipolar membrane which is a composite membrane comprising a commercial alkaline membrane layer, a ferrous ion intermediate layer and a Nafion acidic membrane layer which are connected in sequence.
Preferably, the bipolar membrane is prepared by spraying ferrous ion solution and casting Nafion membrane solution on commercial alkaline membrane in sequence, and then air drying and cold pressing.
The invention also provides a preparation method of the iron-based bipolar membrane, which comprises the following steps:
Step 1: preparing Nafion stock solution into Nafion acetone solution;
Step 2: spraying a ferrous ion solution on the commercial alkaline membrane to obtain a ferrous ion salt intermediate layer;
step 3: casting the Nafion acetone solution prepared in the step 1 on the ferrous ion interlayer, and then sequentially carrying out air drying and cold pressing to obtain the iron-based bipolar membrane.
Preferably, the concentration of the Nafion acetone solution in the step 1 is 20-40 wt%.
Preferably, the spraying amount of the ferrous ion solution in the step 2 is 3-10 mL; the ferrous ion solution is a mixed solution obtained by dispersing soluble ferrous salt in absolute ethyl alcohol and deionized water in a volume ratio of 1:1; the concentration of the ferrous ion solution is 0.005-0.02M.
Preferably, the ferrous salt is at least one of ferrous nitrate, ferrous chloride, ferrous sulfate, ferrous acetate and ferrous acetylacetonate.
Preferably, the air-drying conditions in the step 3 are as follows: drying for 1-3 h in flowing air atmosphere at 30-60 ℃; the cold pressing conditions are as follows: cold pressing at room temperature and 1-10 MPa for 5-30 s.
The invention also provides application of the iron-based bipolar membrane in electrochemical reduction of CO 2.
Compared with the prior art, the invention has the beneficial effects that:
(1) The iron-based bipolar membrane prepared by the invention comprises a commercial alkaline membrane layer, an intermediate ferrous ion layer and a Nafion acidic membrane layer; wherein the commercial alkaline membrane carries cationic groups such as quaternary ammonium salt, heterocyclic compound, imidazoles, guanidine groups, metal groups and the like, so that the conduction of OH-in the alkaline membrane can be realized under the action of the cationic groups; the Nafion series membrane has high proton conductivity, and can realize the conduction of H + in an acid membrane; iron ions serving as an intermediate catalytic layer can be subjected to catalytic hydrolysis reaction with water molecules, so that the reaction activity of the water is improved, and the water molecule bonds are weakened; therefore, in the CO 2 reduction process, the iron-based bipolar membrane can accelerate the intermediate layer to be hydrolyzed into H + and OH -, and transfer the H + and OH - to the cathode and the anode respectively under the action of reverse bias voltage, so that CO 2 can be reduced efficiently;
(2) The bipolar membrane prepared by the invention can effectively inhibit the penetration of ions between the cathode and the anode, can effectively inhibit the conduction of CO 2 reduction liquid products on the cathode side to the anode to be oxidized, reduces the loss of the cathode products, and has good application prospect.
Drawings
FIG. 1 is a scanning electron microscope image of the bipolar membrane prepared in example 1, wherein (a) and (b) are respectively surface topography images of the acidic membrane side and the alkaline membrane side of the bipolar membrane; (c) (d) are cross-sectional views of the acidic and basic membrane sides of the bipolar membrane, respectively;
FIG. 2 is a graph of the Faraday efficiencies of formic acid at different potentials using a Cu-doped-Bi electrode as the working electrode, with the middle separator being commercial alkaline membrane A201, commercial acidic membrane Nafion 212, and bipolar membrane prepared in example 1, respectively;
FIG. 3 shows the "breakthrough" rate of CO 2 reduction product (formic acid) from cathode to anode using a Cu-doped-Bi electrode as the working electrode, with the middle separator being commercial alkaline membrane A201, commercial acidic membrane Nafion 212, and bipolar membrane prepared in example 1, respectively;
FIG. 4 shows the contents of formic acid, methanol and ethanol in the anode chamber in sequence tested using a commercial alkaline membrane A201, a commercial acidic membrane Nafion 212 and the bipolar membrane prepared in example 1, respectively, using carbon paper as the working electrode and the counter electrode, a 0.5M KHCO 3 solution as the anode side electrolyte, and a 0.5M KHCO 3 solution containing formic acid, methanol and ethanol (0.02M) in sequence, respectively, for one hour at a current density of 50mA/cm 2;
FIG. 5 is a physical view of the bipolar membrane prepared in example 1;
Fig. 6 is a diagram of the operating mechanism of the bipolar membrane prepared in example 1, wherein under reverse bias, the iron in the middle layer will promote dissociation of water, resulting in H + passing through the acidic membrane to the cathode compartment and OH - passing through the alkaline membrane to the anode compartment.
Detailed Description
In order to make the invention more comprehensible, preferred embodiments accompanied with figures are described in detail below.
The commercial alkaline membranes used in the following examples were purchased from Tokuyama, japan, iron compounds, absolute ethanol, acetone from Shanghai Ala Biotechnology Co., ltd, and Nafion solution (stock solution) from Sigma-Aldrich.
Example 1
The embodiment provides a preparation method of an iron-based bipolar membrane, which comprises the following specific preparation processes:
Heating 50mLNafion stock solution (30 wt%) in water bath at 85 ℃ for 5h, cooling to room temperature, and fixing volume to 50mL by using acetone, and repeating for three times to obtain 30wt% Nafion acetone solution. A commercial alkaline film was fixed between two glass plates to achieve an effective area of 2x 2cm 2, placed on a 45 ℃ hot plate, and 5ml of 0.01m aqueous ethanol solution of Fe (II) (iron acetate) (ethanol: H 2 o=1:1 volume ratio) was sprayed uniformly onto the commercial alkaline film using a spray gun. 2.5mL of the 30wt% Nafion acetone solution was cast on the Fe (II) -containing interlayer film, and the film was dried in an air-flow atmosphere at 30℃for 2 hours. Then cold pressing the commercial alkaline membrane, the Fe (II) intermediate layer and the acid membrane composite layer for 10s at room temperature of 3MPa to obtain the bipolar membrane.
Example 2
The embodiment provides a preparation method of an iron-based bipolar membrane, which comprises the following specific preparation processes:
Heating 50mLNafion stock solution (30 wt%) in water bath at 85 ℃ for 5h, cooling to room temperature, and fixing volume to 50mL by using acetone, and repeating for three times to obtain 30wt% Nafion acetone solution. A commercial alkaline film was fixed between two glass plates to achieve an effective area of 2 x 2cm 2, placed on a 45 ℃ hot plate, and 5ml of 0.01m aqueous ethanol solution of Fe (II) (iron acetate) (ethanol: H 2 o=1:1 volume ratio) was sprayed uniformly onto the commercial alkaline film using a spray gun. 5mL of the 30wt% Nafion acetone solution was cast on the Fe (II) -containing interlayer film, and the film was dried in an air-flow atmosphere at 30℃for 2 hours. Then cold pressing the commercial alkaline membrane, the Fe (II) intermediate layer and the acid membrane composite layer for 10s at room temperature of 3MPa to obtain the bipolar membrane.
Example 3
The embodiment provides a preparation method of an iron-based bipolar membrane, which comprises the following specific preparation processes:
Heating 50mLNafion stock solution (30 wt%) in water bath at 85 ℃ for 5h, cooling to room temperature, and fixing volume to 50mL by using acetone, and repeating for three times to obtain 30wt% Nafion acetone solution. A commercial alkaline film was fixed between two glass plates to achieve an effective area of 2x 2cm 2, placed on a 45 ℃ hot plate, and 5ml of 0.01m aqueous ethanol solution of Fe (II) (iron acetate) (ethanol: H 2 o=1:1 volume ratio) was sprayed uniformly onto the commercial alkaline film using a spray gun. 7.5mL of the above 30wt% Nafion acetone solution was cast on the Fe (II) -containing interlayer film, and dried in an air-flowing atmosphere at 30℃for 2 hours. Then cold pressing the commercial alkaline membrane, the Fe (II) intermediate layer and the acid membrane composite layer for 10s at room temperature of 3MPa to obtain the bipolar membrane.
Example 4
The embodiment provides a preparation method of an iron-based bipolar membrane, which comprises the following specific preparation processes:
Heating 50mLNafion stock solution (30 wt%) in water bath at 85 ℃ for 5h, cooling to room temperature, and fixing volume to 50mL by using acetone, and repeating for three times to obtain 30wt% Nafion acetone solution. A commercial alkaline film was fixed between two glass plates to achieve an effective area of 2 x 2cm 2, placed on a 45 ℃ hot plate, and 5ml of 0.01m aqueous ethanol solution of Fe (II) (iron acetate) (ethanol: H 2 o=1:1 volume ratio) was sprayed uniformly onto the commercial alkaline film using a spray gun. 10mL of the 30wt% Nafion acetone solution was cast on the Fe (II) -containing interlayer film, and the film was dried in an air-flow atmosphere at 30℃for 2 hours. Then cold pressing the commercial alkaline membrane, the Fe (II) intermediate layer and the acid membrane composite layer for 10s at room temperature of 3MPa to obtain the bipolar membrane.
Electrochemical performance testing was performed on the che 760e electrochemical workstation of the Shanghai Chenhua company using a three electrode system. The Cu-doped-Bi metal electrode prepared by electrodeposition is used as a working electrode [ appl.Catal.B.288,120003 (2021) ], the Ag/Agcl electrode is used as a reference electrode, the spectroscopical stone grinding rod is used as a counter electrode, and the electrolyte is 0.5M KHCO 3 solution. Cu-doped-Bi metal electrodes have been demonstrated to be efficient in electrochemical reduction of CO 2 to formic acid, and therefore the catalytic electrode was used to investigate the "breakthrough" effect of the liquid product formic acid from cathode to anode. In the two-electrode test, carbon paper is used as a working electrode and a counter electrode respectively, the anode side electrolyte is 0.5M KHCO 3 solution, and the cathode electrolyte is 0.5M KHCO 3 solution containing formic acid, methanol and ethanol (0.02M) in sequence.
Fig. 1 is a scanning electron microscope image of a bipolar membrane of example 1, in which fig. 1 (a) and 1 (b) are surface topography diagrams of an acidic membrane (Nafion membrane) side and an alkaline membrane side of the bipolar membrane, respectively, and it can be seen that the surfaces of the two are relatively smooth, and contact with a catholyte can be effectively increased. Fig. 1 (c) and 1 (d) are cross-sectional morphology diagrams of the acidic membrane side and the alkaline membrane side of the bipolar membrane, respectively, and it can be seen that the cross section of the acidic membrane side shows a compact microstructure, while the cross section of the alkaline membrane shows a layered porous structure, and the microstructure in the alkaline membrane helps to improve the movement of carriers and accelerate the transmission of OH -.
The Faraday efficiencies of formic acid when using Nafion 212 acid membrane from DuPont, japan A201 alkaline membrane from Tokuyama, and bipolar membrane from example 1, respectively, as working electrodes are shown in FIG. 2. It can be seen that using the bipolar membrane prepared in example 1 as a separator, the formic acid faraday efficiency was significantly higher than using Nafion 212 acid membrane and a201 base membrane, especially at-0.97V, with the highest formic acid faraday efficiency (98%).
The "breakthrough" effect of formic acid from cathode to anode under three membrane operating conditions is shown in fig. 3 when a Cu-doped-Bi metal electrode is used as the working electrode. As can be seen from the figure, the formic acid "penetration" of the alkaline membrane (a 201) is 22.92% which is much higher than that of the Nafion 212 acid membrane in the united states. Whereas the bipolar membrane prepared in example 1 was used, the presence of formic acid was not detected at the anode, indicating that the bipolar membrane prepared in example 1 was effective in inhibiting "breakthrough" of formic acid from the cathode to the anode.
In the two electrode test, carbon paper was used as the working and counter electrodes, as shown in FIG. 4, the anode side electrolyte was a 0.5M KHCO 3 solution, and the catholyte was a 0.5M KHCO 3 solution containing formic acid, methanol, and ethanol (0.02M) in sequence. The contents of formic acid, methanol and ethanol in the anode chamber were measured separately by electrolysis at a current density of 50mA/cm 2 for one hour. The results show that the formic acid, methanol, and ethanol "breakthrough" (cross-over) rates for Nafion 212 membranes are all less than for a201 membranes; whereas the bipolar membrane prepared in example 1 did not detect the presence of formic acid, methanol and ethanol at the anode (and thus is not shown in fig. 4), indicating that the bipolar membrane is effective in inhibiting "breakthrough" of formic acid, methanol and ethanol from the cathode to the anode;
FIG. 5 is a physical diagram showing the bipolar membrane prepared in example 1;
As shown in fig. 6, which is a diagram illustrating the operation mechanism of the bipolar membrane prepared in example 1, the iron in the intermediate layer will promote dissociation of water under the reverse bias, leading to H + passing through the acidic membrane to the cathode compartment and OH - passing through the alkaline membrane to the anode compartment.
The above-described embodiments are only preferred embodiments of the present invention, and are not intended to be limiting in any way and in nature, and it should be noted that several modifications and additions may be made to those skilled in the art without departing from the invention, which modifications and additions are also intended to be construed as within the scope of the invention.
Claims (6)
1. The preparation method of the iron-based bipolar membrane is characterized by comprising the following steps of:
Step 1: preparing Nafion stock solution into Nafion acetone solution;
Step 2: spraying a ferrous ion solution on the commercial alkaline membrane to obtain a ferrous ion salt intermediate layer;
step 3: casting the Nafion acetone solution prepared in the step 1 on the ferrous ion interlayer, and then sequentially carrying out air drying and cold pressing to obtain the iron-based bipolar membrane;
The ferrous salt is at least one of ferrous nitrate, ferrous chloride, ferrous sulfate, ferrous acetate and ferrous acetylacetonate;
The iron-based bipolar membrane is applied to electrochemical reduction of CO 2.
2. The method for preparing the iron-based bipolar membrane according to claim 1, wherein the concentration of the Nafion acetone solution in the step 1 is 20-40 wt%.
3. The method for preparing the iron-based bipolar membrane according to claim 1, wherein the spraying amount of the ferrous ion solution in the step 2 is 3-10 ml; the ferrous ion solution is a mixed solution obtained by dispersing soluble ferrous salt in absolute ethyl alcohol and deionized water in a volume ratio of 1:1; the concentration of the ferrous ion solution is 0.005-0.02M.
4. The method for preparing an iron-based bipolar membrane according to claim 1, wherein the air-drying conditions in the step 3 are as follows: drying for 1-3 hours in a flowing air atmosphere at 30-60 ℃; the cold pressing conditions are as follows: cold pressing for 5-30 s at room temperature under the condition of 1-10 MPa.
5. The iron-based bipolar membrane prepared by the preparation method according to any one of claims 1 to 4, wherein the bipolar membrane is a composite membrane comprising a commercial alkaline membrane layer, a ferrous ion intermediate layer and a Nafion acidic membrane layer which are sequentially connected.
6. The application of the iron-based bipolar membrane prepared by the preparation method of any one of claims 1-4 in electrochemical reduction of CO 2.
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Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5227040A (en) * | 1987-07-30 | 1993-07-13 | Unisearch Limited | High performance bipolar membranes |
| CN102912374A (en) * | 2012-10-24 | 2013-02-06 | 中国科学院大连化学物理研究所 | Electrochemical reduction CO2 electrolytic tank using bipolar membrane as diaphragm and application of electrochemical reduction CO2 electrolytic tank |
| KR101746591B1 (en) * | 2016-02-29 | 2017-06-14 | 주식회사 이노켐텍 | Bipolar ion exchange composite membrane and method of manufacturing the same |
| KR102062737B1 (en) * | 2019-10-14 | 2020-01-06 | 상명대학교 천안산학협력단 | Bipolar membrane for water dissociation |
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|---|---|---|---|---|
| US5227040A (en) * | 1987-07-30 | 1993-07-13 | Unisearch Limited | High performance bipolar membranes |
| CN102912374A (en) * | 2012-10-24 | 2013-02-06 | 中国科学院大连化学物理研究所 | Electrochemical reduction CO2 electrolytic tank using bipolar membrane as diaphragm and application of electrochemical reduction CO2 electrolytic tank |
| KR101746591B1 (en) * | 2016-02-29 | 2017-06-14 | 주식회사 이노켐텍 | Bipolar ion exchange composite membrane and method of manufacturing the same |
| KR102062737B1 (en) * | 2019-10-14 | 2020-01-06 | 상명대학교 천안산학협력단 | Bipolar membrane for water dissociation |
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