Gas diffusion electrode and preparation method thereof

Abstract

A gas diffusion electrode and a method of making the same, the gas diffusion electrode comprising a gas diffusion layer and a catalyst layer coupled to the gas diffusion layer wherein the catalyst layer comprises copper nanorods or copper nanowires having a matchstick-like array structure, the gas diffusion electrode being arranged to electrocatalytically reduce carbon dioxide under acidic conditions. The preparation method of the gas diffusion electrode comprises the following steps: (1) sputtering a copper target material on a gas diffusion layer of a substrate to prepare a copper plating layer, and (2) growing a copper hydroxide nanowire on the copper plating layer through chemical oxidation in-situ growth, and (3) converting the copper hydroxide nanowire into a nano-copper electrode with a match-shaped array structure through impregnation.

Description

Technical Field

[0001] This disclosure relates to the field of electrocatalysis, specifically to a gas diffusion electrode and its preparation method. Background Technology

[0002] Electrocatalytic carbon dioxide reduction technology driven by clean energy can convert greenhouse gases into high-value-added small-molecule products, such as carbon monoxide (CO), methane (CH4), formic acid (HCCOH), acetic acid (CH3COOH), ethylene (C2H4), and ethanol (C2H5OH), thereby achieving energy conversion while reducing carbon dioxide emissions into the atmosphere. Therefore, electrocatalytic carbon dioxide reduction technology is of great significance in reducing carbon emissions and improving energy efficiency. Metal catalysts are widely used in electrocatalytic carbon dioxide reduction technology, especially copper-based catalysts, which are the only ones capable of efficiently converting carbon dioxide into multi-carbon products. Currently, the electrolytes for copper-based catalyst / electrode electrocatalytic carbon dioxide reduction are mostly neutral and alkaline electrolytes, such as potassium bicarbonate and potassium hydroxide. Due to their relatively high pH value, alkaline and neutral electrolytes can effectively improve the selectivity of copper-based catalysts for multi-carbon products. However, due to the interaction between carbon dioxide and hydroxide ions (OH-) in alkaline electrolytes... - ) and OH produced in situ - The reaction produces carbonates (bicarbonates) as a byproduct, with only a small amount of carbon dioxide being converted into the high-value-added target product. Therefore, neutral and alkaline electrolytes significantly reduce the utilization rate of carbon dioxide. Taking ethylene as an example, the highest single-pass conversion rate of carbon dioxide in a neutral electrolyte is 25%, while in an alkaline electrolyte it is far below 5%, resulting in extremely low carbon dioxide utilization and a significant waste of carbon resources.

[0003] To address the aforementioned issues, electrocatalytic carbon dioxide reduction in an acidic electrolyte can avoid carbonate formation. On one hand, protons can directly serve as a hydrogen source, thereby reducing the OH- produced by the hydrolysis reaction. - Ions thus reduce carbon dioxide and OH- - The reaction reduces the amount of carbonate (bicarbonate) formed; on the other hand, the carbonate (bicarbonate) formed in situ is consumed by the proton reaction in the bulk phase and thus converted back into carbon dioxide, avoiding the accumulation of carbonate (bicarbonate). Theoretically, electrocatalytic carbon dioxide reduction in acidic electrolytes can achieve 100% single-pass carbon conversion. Despite the extremely high single-pass conversion, the high proton concentration in acidic systems leads to intense competition between the hydrogen evolution reaction and the carbon dioxide reduction reaction, making hydrogen the main product; furthermore, the activity, selectivity, and stability of copper-based catalysts in acidic systems urgently need improvement. Therefore, developing catalysts with high catalytic activity, high selectivity, and stability is key to the large-scale application of electrocatalytic carbon dioxide reduction technology in acidic systems. Summary of the Invention

[0004] According to a first aspect of the present invention, a gas diffusion electrode is provided, comprising a gas diffusion layer and a catalyst layer coupled to the gas diffusion layer, wherein the catalyst layer comprises a nano-copper material having a matchstick-like array structure, and the gas diffusion electrode is arranged to electrocatalytically reduce carbon dioxide under acidic conditions.

[0005] Preferably, the nano-copper material includes one of copper nanorods and copper nanowires.

[0006] Preferably, the match-shaped array structure includes a head and a handle extending from the head, wherein the head is composed of spherical copper nanoparticles and the handle is composed of copper nanowires.

[0007] Preferably, the diameter of the spherical copper nanoparticles is 50-500 nanometers.

[0008] Preferably, the copper nanowires are copper hydroxide nanowires, which are vertically grown on the gas diffusion layer and have a diameter of 20-100 nanometers and a length of 200-1000 nanometers.

[0009] According to a second aspect of the present invention, a method for preparing a gas diffusion electrode is provided, comprising the following steps: (1) sputtering a copper target onto a gas diffusion layer of a substrate to prepare a copper plating; (2) growing copper hydroxide nanowires on the copper plating by in-situ chemical oxidation; and (3) converting the copper hydroxide nanowires into a catalytic layer of nano-copper having a matchstick-like array structure by impregnation.

[0010] Preferably, the substrate is selected from carbon paper, copper foam, or other copper-plated porous substrates.

[0011] Preferably, the copper nanorods with the matchstick-like array structure are copper nanorods or copper nanowires.

[0012] Preferably, step 1 uses magnetron sputtering to sputter the copper target onto the substrate, and after sputtering is completed, it also includes a step of filling with high-purity nitrogen gas to prevent the material from being oxidized.

[0013] Preferably, the copper target is a 99.99% pure copper target, wherein the magnetron sputtering power is 50-100 watts and the time is 30-300 minutes.

[0014] Preferably, the chemical oxidation in-situ growth in step 2 includes contacting the copper plating with a solution comprising sulfate and a strong alkali to form the copper hydroxide nanowires, and further includes rinsing the copper hydroxide nanowires with ethanol and deionized water.

[0015] Preferably, the sulfate is selected from any one of potassium persulfate, sodium persulfate, ammonium persulfate, or combinations thereof, and the concentration of the sulfate is 0.1 to 2.0 mol / L; wherein the strong base is selected from any one of lithium hydroxide, sodium hydroxide, potassium hydroxide, cesium hydroxide, or combinations thereof, and the concentration of the strong base is 1.0 to 3.0 mol / L.

[0016] Preferably, the impregnation in step 3 includes immersing the copper hydroxide nanowires in a solution comprising triazole organic compound, ammonia and organic solvent to form the nano-copper electrode with a match-shaped array structure, wherein after impregnation, the step further includes rinsing the catalytic layer of the nano-copper with the match-shaped array structure with ethanol and deionized water.

[0017] Preferably, the triazole organic compound is a benzotriazole or its derivative selected from any one of benzotriazole, 5-carboxybenzotriazole, 5-chlorobenzotriazole, 5-bromobenzotriazole, 5-iodobenzotriazole, or combinations thereof, wherein the concentration of the triazole organic compound is 0.2 to 2 mol / L.

[0018] Preferably, the organic solvent is selected from any one of methanol, N,N-dimethylformamide, acetonitrile, benzyl alcohol, toluene, cyclohexane, or combinations thereof.

[0019] According to a third aspect of the present invention, a composite electrode for electrocatalytic carbon dioxide reduction under acidic conditions is characterized in that: the electrode is a gas diffusion electrode, the substrate of which is porous carbon paper with a gas diffusion layer, and the catalyst layer is a composite material with a copper nano-match" / nanowire structure.

[0020] Preferably, the copper nanocatalyst with the nano "match" array structure is characterized in that: the array structure is composed of two parts: copper hydroxide nanowires and nanoparticles, with spherical particles at the top and nanowires in the middle forming a "match"-like structure; the diameter of the spherical nanoparticles is 50-500 nanometers.

[0021] Preferably, the obtained copper nanowires are copper hydroxide nanowires, characterized in that: the copper hydroxide nanowires are vertically grown on the gas diffusion layer, with a diameter of 20-100 nanometers and a length of 200-1000 nanometers.

[0022] According to a fourth aspect of the present invention, a method for preparing a composite electrode is characterized by comprising the following steps: S1) placing carbon paper (10cm × 10cm) with a gas diffusion layer in a magnetron sputtering chamber, then evacuating the chamber and setting the emission power and sputtering time; after sputtering, filling with high-purity nitrogen to prevent the material from being oxidized. S2) weighing a certain amount of persulfate and a strong alkali, dissolving them separately and mixing them evenly to form solution A, and transferring it to a petri dish for later use. S3) placing the material containing the copper plating layer obtained in step S1 in the petri dish of step S2, with the copper plating layer facing down and in contact with the solution; after a blue film forms on the surface, transferring it to a clean petri dish; rinsing three times with ethanol and deionized water respectively, for later use. S4) Weigh a certain amount of triazole organic matter and a certain volume of ammonia water into two different beakers. After the organic matter is fully dispersed, mix the two to form solution B. Then, immerse the material with the blue film obtained in step S3) into solution B. After a green film forms on the surface, take it out and rinse it three times with ethanol and deionized water respectively to obtain the copper nano "match" / nanowire array electrode.

[0023] Preferably, the target material in step S1 is a pure copper target (99.99%), the magnetron sputtering power is 50-100 watts, and the deposition time is 30-300 minutes.

[0024] Preferably, the persulfate in step S2 is one or a combination of potassium persulfate, sodium persulfate, and ammonium persulfate, with a concentration of 0.1 to 2.0 mol / L; the strong base is one or a combination of lithium hydroxide, sodium hydroxide, potassium hydroxide, and cesium hydroxide, with a concentration of 1.0 to 3.0 mol / L.

[0025] Preferably, the triazole organic compound in step S4 is benzotriazole and its derivatives, including but not limited to benzotriazole, 5-carboxybenzotriazole, 5-chlorobenzotriazole, 5-bromobenzotriazole, and 5-iodobenzotriazole, with a concentration of 0.2 to 2 mol / L.

[0026] Preferably, the organic solvent in step S4 is one or a combination of methanol, N,N-dimethylformamide, acetonitrile, benzyl alcohol, toluene, and cyclohexane.

[0027] Preferably, the preparation method can also use foamed copper or other copper-plated porous substrates to prepare electrodes with the same copper nano-match / nanowire array.

[0028] Compared with the prior art, the specific beneficial effects of the present invention include: providing a high-efficiency electrode based on a novel nano-matching array structure, and providing a high-efficiency preparation method for a gas diffusion electrode with a nano-matching array structure, which is prepared by magnetron sputtering, chemical oxidation and wet chemical conversion, and has extremely high catalytic performance in acidic electrolyte (pH 3). Attached Figure Description

[0029] This invention will be described with reference to the accompanying drawings, which are as follows:

[0030] Figure 1 This is a schematic diagram of an embodiment of the gas diffusion electrode according to the present invention;

[0031] Figure 2 This is a transmission electron microscope (TEM) image of copper nano-matches obtained through an embodiment of the gas diffusion electrode preparation method of the present invention;

[0032] Figure 3 yes Figure 2 XRD images of copper nano-match arrays;

[0033] Figure 4 This is a scanning electron microscope (SEM) image of a magnified portion of a copper coating obtained through magnetron sputtering;

[0034] Figure 5 The image shows an X-ray diffraction (XRD) image of copper hydroxide obtained by wet chemical oxidation.

[0035] Figure 6 This is a magnified SEM image of copper hydroxide nanowires obtained by chemical oxidation.

[0036] Figure 7 The image shows a magnified SEM image of the copper nano-matches obtained through wet chemical conversion; and

[0037] Figure 8 This is a graph showing the performance of a copper nano-match array for electrocatalytic carbon dioxide reduction under acidic conditions, obtained through an embodiment of the gas diffusion electrode preparation method of the present invention. Detailed Implementation

[0038] To address the problem of insufficient electrocatalytic performance of copper-based catalysts in acidic electrolyte systems, the present invention aims to provide a composite electrode for the preparation of multi-carbon products by electrocatalytic carbon dioxide reduction under acidic conditions; another objective of the present invention is to provide a method for preparing the composite electrode for the preparation of multi-carbon products by electrocatalytic carbon dioxide reduction under acidic conditions.

[0039] One embodiment of the present invention discloses an electrode with a copper-based nano-"match" array, which can be used for the electrocatalytic reduction of carbon dioxide under acidic conditions to prepare multi-carbon products.

[0040] Reference Figure 1 , Figure 1An embodiment of a gas diffusion electrode 100 according to the present invention is shown. The gas diffusion electrode 100 includes a gas diffusion layer 110 and a catalyst layer 120. The gas diffusion layer 110 is exposed to a gas supply 140, which is carbon dioxide, to achieve carbon dioxide reduction. The gas diffusion layer 110 is composed of a porous substrate such as carbon paper, copper foam, or other copper-plated material. The catalyst layer 120 is in contact with an acidic liquid electrolyte 130. The gas diffusion electrode 100 has optimal conductivity, enabling low-resistance electron transfer.

[0041] When powered, the gas diffusion electrode 100 uses electrical energy to convert carbon dioxide into reducing chemicals that are less harmful to the environment, including formic acid (HCOO). - ), carbon monoxide (CO), methane (CH4), ethylene (C2H4), and ethanol (C2H5OH).

[0042] The catalyst layer 130 comprises nano-copper materials with a matchstick-like array structure, such as nano-copper rods and nano-copper wires. These materials are simple to prepare, using inexpensive and readily available raw materials, and require short preparation times. More importantly, the nano-copper materials with a matchstick-like array structure exhibit high catalytic activity and high selectivity, enabling the catalyst layer 130 to remain stable even in acidic electrolytes with high proton concentrations, thereby achieving higher carbon dioxide reduction efficiency.

[0043] Figure 2 The structure of a nano-copper 200 with a matchstick-like array structure is shown. The matchstick array structure 200 comprises a head 210 and a stem 220 extending from the head 210. The head 210 is composed of spherical nano-copper particles, while the stem 220 is composed of copper nanowires. In one embodiment, the diameter of the spherical nano-copper particles in the head 210 is 50-500 nanometers.

[0044] Figure 3 The X-ray diffraction (XRD) pattern of nano-copper 200 with a matchstick-like array structure is shown.

[0045] In one embodiment, the copper nanowires are copper hydroxide nanowires, which are vertically grown on the gas diffusion layer. The copper hydroxide nanowires have a diameter of 20-100 nanometers and a length of 200-1000 nanometers.

[0046] The present invention also provides a method for preparing a gas diffusion electrode. The steps include: (1) sputtering a copper target onto a gas diffusion layer of a substrate to prepare a copper coating, the substrate being selected from carbon paper, copper foam or other copper-plated porous substrates; (2) growing copper hydroxide nanowires on the copper coating by in-situ chemical oxidation; and (3) converting the copper hydroxide nanowires into a nano-copper electrode with a matchstick-like array structure by impregnation.

[0047] Specifically, the method for preparing the gas diffusion electrode is embodied in the following manner: First, carbon paper (10cm×10cm) with a gas diffusion layer is placed in a magnetron sputtering chamber, and then a vacuum is drawn and the emission power setting and sputtering time are set. Figure 4 This is a scanning electron microscope (SEM) image showing a magnified portion of the copper plating obtained by magnetron sputtering. High-purity nitrogen gas was introduced after sputtering to prevent oxidation of the material. The magnetron sputtering power was 50-100 watts, and the deposition time was 30-300 minutes.

[0048] 2. Weigh out a certain amount of persulfate and strong base, dissolve them separately, mix them thoroughly to form solution A, and transfer it to a petri dish for later use. The persulfate is one or a combination of potassium persulfate, sodium persulfate, and ammonium persulfate, with a concentration of 0.1 to 2.0 mol / L; the strong base is one or a combination of lithium hydroxide, sodium hydroxide, potassium hydroxide, and cesium hydroxide, with a concentration of 1.0 to 3.0 mol / L.

[0049] 3. Place the copper-plated material obtained in step 1 into the petri dish from step 2, with the copper plating facing down and in contact with the solution; after a blue film forms on the surface, transfer it to a clean petri dish to form copper hydroxide. Rinse three times with ethanol and deionized water respectively, and set aside for later use. Figure 5 The image shows an X-ray diffraction (XRD) image of copper hydroxide obtained by wet chemical oxidation. Figure 6 This displays an SEM image of copper hydroxide nanowires.

[0050] IV. Weigh a certain amount of triazole organic compound and a certain volume of ammonia water into two different beakers. After the organic compound is fully dispersed, mix them with an organic solvent to form solution B. The triazole organic compound is benzotriazole and its derivatives, including but not limited to benzotriazole, 5-carboxybenzotriazole, 5-chlorobenzotriazole, 5-bromobenzotriazole, and 5-iodobenzotriazole, with a concentration of 0.2 to 2 mol / L. The organic solvent is one or a combination of methanol, N,N-dimethylformamide, acetonitrile, benzyl alcohol, toluene, and cyclohexane.

[0051] 5. Immerse the material with the blue film obtained in step 3 into solution B. After a green film forms on the surface, take it out and rinse it three times with ethanol and deionized water respectively to obtain the copper nano "match" / nanowire array electrode. Figure 7 SEM images of magnified portions of the catalytic layer containing copper nano-matches are shown.

[0052] Example 1:

[0053] Place a 10cm x 10cm carbon paper with a gas diffusion layer in the magnetron sputtering apparatus and adjust the vacuum to 10. -6A copper target was sputtered onto carbon paper using a torrent generator with an emission power of 80 watts for 30 minutes, resulting in carbon paper with a copper coating. Then, 2.5 g of sodium hydroxide and 0.7 g of ammonium persulfate were dissolved to form a mixed solution. The resulting copper-coated carbon paper was cut into 1.5 cm × 1.5 cm shapes, and the copper side was immersed in the mixture. After immersion for ten minutes, an electrode with a copper hydroxide nanowire precursor was obtained. 3 g of 5-carboxybenzotriazole was dissolved in 100 mL of acetonitrile solution, and 20 mL of ammonia was added, stirring for 30 minutes. The copper hydroxide nanowire precursor electrode was immersed in a solution containing 5-carboxybenzotriazole for three minutes. After washing, a copper electrode with a nano-matchstick array structure was obtained.

[0054] Example 2:

[0055] Place the carbon paper with the gas diffusion layer into the magnetron sputtering instrument. Adjust the vacuum state to 10. -6 A copper target was sputtered onto carbon paper using a torr (torr) with an emission power of 80 watts, resulting in carbon paper with a copper coating. Then, 2.5 g of sodium hydroxide and 0.7 g of potassium persulfate were dissolved thoroughly to form a mixed solution. The resulting carbon paper with the copper coating was cut into 1.5 cm × 1.5 cm shapes, and the copper side was immersed in the above mixed solution. After immersion for ten minutes, an electrode with a copper hydroxide nanowire precursor was obtained. 3 g of 5-carboxybenzotriazole was dissolved in 100 mL of methanol solution, and 20 mL of ammonia was added, stirring for 30 minutes. The copper hydroxide nanowire precursor electrode was immersed in a solution containing 5-carboxybenzotriazole for three minutes. After washing, it was ready for use, resulting in a copper electrode with a nano-matchstick array structure.

[0056] Example 3:

[0057] Clean copper foam was cut into 1.5cm x 1.5cm shapes and washed twice with acetone and deionized water, respectively. Then, 2.5g of sodium hydroxide and 0.7g of ammonium persulfate were dissolved thoroughly to form a mixed solution. The resulting copper foam was immersed in this mixed solution. Once a blue film formed on the surface, it was removed, yielding a copper foam electrode with a copper hydroxide nanowire precursor. 3g of 5-carboxybenzotriazole was dissolved in 100mL of acetonitrile solution, and 20mL of ammonia was added. The solution was stirred for 30 minutes. The copper foam electrode with the copper hydroxide nanowire precursor was immersed in a solution containing 5-carboxybenzotriazole for three minutes. After washing, it was ready for use, yielding a copper electrode with a nano-matchstick array structure.

[0058] In one embodiment, the gas diffusion electrode of the present invention is applied as follows: 0.5 mol / L sulfuric acid is used as the anolyte, and 3 mol / L KCl and 0.5 mmol / L electrolyte are used as the catholyte, with a total electrolyte volume of 20 mL. A three-chamber flow cell is used as the reactor for testing, wherein the working electrode is a copper electrode with a nano-matchstick array structure, and the effective working distance is 1.0 cm. 2 The counter electrode is a platinum sheet with an effective working area of ​​1.0 cm². 2 The reference electrode was saturated Ag / AgCl, and the diaphragm was a Nafion 117 membrane. High-purity carbon dioxide was introduced into the electrolytic cell at a rate of 20 mL / min, and the electrolyte was circulated using a peristaltic pump at a circulation rate of 10 mL / min. The test was conducted in constant current mode, with a current density set from -100 to -1000 mA / cm². Gas products were analyzed by gas chromatography every 7 minutes; liquid products were collected every 45 minutes and quantitatively analyzed using nuclear magnetic resonance spectroscopy. Figure 8 The performance of copper nano-match arrays obtained by wet chemical conversion under acidic conditions for electrocatalytic carbon dioxide reduction is shown in the figure.

[0059] The electrode obtained by this invention can efficiently convert carbon dioxide into multi-carbon small molecule products under acidic conditions, with a multi-carbon product Faradaic efficiency of over 70%. The preparation method of this invention is simple to operate, low in cost, and easy to mass-produce. The electrode made by this invention exhibits high electrocatalytic carbon dioxide reduction performance under acidic conditions and has good application prospects.

Claims

1. A gas diffusion electrode comprising a gas diffusion layer and a catalyst layer coupled to the gas diffusion layer, wherein the catalyst layer comprises a nano-copper material having a matchstick-like array structure, the gas diffusion electrode being arranged to electrocatalytically reduce carbon dioxide under acidic conditions.

2. The gas diffusion electrode according to claim 1, wherein the nano-copper material comprises one of copper nanorods and copper nanowires.

3. The gas diffusion electrode according to claim 2, wherein the match-shaped array structure comprises a head and a stem extending from the head, wherein the head is composed of spherical copper nanoparticles and the stem is composed of copper nanowires.

4. The gas diffusion electrode according to claim 3, wherein the diameter of the spherical copper nanoparticles is 50-500 nanometers.

5. The gas diffusion electrode according to claim 3, wherein the copper nanowire is a copper hydroxide nanowire, and the copper hydroxide nanowire is vertically grown on the gas diffusion layer, with a diameter of 20-100 nanometers and a length of 200-1000 nanometers.

6. A method for preparing a gas diffusion electrode, comprising the following steps: (1) Sputter a copper target onto a gas diffusion layer of a substrate to prepare a copper plating layer; (2) Copper hydroxide nanowires are grown on the copper plating layer by in-situ chemical oxidation; and (3) The copper hydroxide nanowires are transformed into a catalytic layer of copper nanowires with a matchstick-like array structure by impregnation.

7. The method of claim 6, wherein the substrate is selected from carbon paper, copper foam, or other copper-plated porous substrates.

8. The method according to claim 6, wherein the copper nanoparticles having a matchstick-like array structure are copper nanorods or copper nanowires.

9. The method according to claim 6, wherein step 1 uses magnetron sputtering to sputter the copper target onto the substrate, and after sputtering is completed, the method further includes a step of filling with high-purity nitrogen gas to prevent the material from being oxidized.

10. The method according to claim 6, wherein the copper target is a 99.99% pure copper target, and wherein the magnetron sputtering power is 50-100 watts and the time is 30-300 minutes.

11. The method of claim 6, wherein the chemical oxidation in-situ growth in step 2 comprises contacting the copper plating with a solution comprising sulfate and a strong base to form the copper hydroxide nanowires, further comprising rinsing the copper hydroxide nanowires with ethanol and deionized water.

12. The method of claim 11, wherein the sulfate is selected from any one of potassium persulfate, sodium persulfate, ammonium persulfate, or combinations thereof, and the concentration of the sulfate is from 0.1 to 2.0 mol / L; wherein the strong base is selected from any one of lithium hydroxide, sodium hydroxide, potassium hydroxide, cesium hydroxide, or combinations thereof, and the concentration of the strong base is from 1.0 to 3.0 mol / L.

13. The method of claim 6, wherein the impregnation in step 3 comprises immersing the copper hydroxide nanowires in a solution comprising triazole organic compound, ammonia and an organic solvent to form the nanocopper electrode having a match-shaped array structure, wherein after impregnation, the method further comprises rinsing the catalytic layer of the nanocopper having a match-shaped array structure with ethanol and deionized water.

14. The method of claim 13, wherein the triazole organic compound is a benzotriazole or its derivative selected from any one of benzotriazole, 5-carboxybenzotriazole, 5-chlorobenzotriazole, 5-bromobenzotriazole, 5-iodobenzotriazole, or combinations thereof, wherein the concentration of the triazole organic compound is from 0.2 to 2 mol / L.

15. The method of claim 14, wherein the organic solvent is selected from any one of methanol, N,N-dimethylformamide, acetonitrile, benzyl alcohol, toluene, cyclohexane, or combinations thereof.

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