Electrode for co2 electrolysis to syngas and method of making same

Abstract

The application relates to a CO2 electrolysis synthesis gas electrode and a preparation method thereof. A precursor solution is prepared through a polymer and a metal salt, the precursor solution is carbonized on a three-dimensional conductive substrate to form an integrated catalytic electrode, the adhesion of a catalytic layer and the three-dimensional conductive substrate is improved, and therefore the stability of the catalytic layer is improved. Calcination makes the polymer play a pore-forming role, and makes the metal catalyst uniformly dispersed on the pore wall. The obtained porous catalyst layer has a high specific surface area and catalytic activity. Nitrogen sites are introduced after carbonization by adding a nitrogen-containing precursor in the precursor solution, a metal-nitrogen-carbon catalyst layer is formed, the adsorption capacity for CO2 is increased, and therefore the conversion rate of CO2 is improved. The CO2 electrolysis synthesis gas electrode prepared by the application has a larger specific surface area, higher metal dispersity and stability than the catalytic electrode prepared by an adhesion method in the prior art, and therefore has higher electrolysis CO2 activity and a longer service life.

Description

Technical Field

[0001] This invention belongs to the field of gas diffusion electrode technology, specifically relating to a CO2 electrolysis syngas production electrode and its preparation method. Background Technology

[0002] Converting CO2 into value-added carbon-containing chemicals can not only solve environmental problems but also create economic benefits. Utilizing green energy sources such as solar and wind power to electrolyze CO2 and water to produce syngas (CO and H2), important chemical raw materials, is a promising emerging technology that has been the subject of much research in recent years and is considered an important method for achieving carbon emission reduction and resource utilization. As a promising new technology, CO2 electrolysis to syngas technology still requires further development and improvement in many aspects. Electroreduction catalysts and catalytic electrodes are key research areas because the electrolysis effect largely depends on the performance of the CO2 electroreduction catalyst and the preparation method of the catalytic electrode.

[0003] Most existing CO2 electrolysis catalysts have short operating times, which cannot meet industrial requirements. For example, the nickel-based catalyst prepared in the literature (Large-scale and highly selective CO2 electrocatalytic reduction on nickel single-atom catalyst, Joule, 2019, 3 265-278) and loaded onto carbon paper with conductive agents and binders only operated for 24 hours for CO2 electroreduction. The flexible silver nanowire electrode prepared in the literature (Ultrathin Ag nanowires electrode for electrochemical syngas production from carbon dioxide, ACS Sustainable Chemistry & Engineering, 2018, 6, 7687-7694) only operated for a dozen hours for CO2 electrolysis to syngas. The main preparation process of the existing CO2 electrolysis catalytic electrode is as follows: first, the CO2 electrolysis catalyst is synthesized; then, the catalyst, binder, and solvent are made into a slurry; the catalyst is then adhered to a conductive substrate by the binder. The preparation process is complex, and the catalyst layer is prone to detachment from the conductive substrate, leading to changes in the catalyst layer structure and thus reducing the catalyst's lifespan. Especially in liquid-phase electrolysis systems, not only is hydrogen evolution significant, but the catalyst layer is also more prone to detachment under water scouring conditions, further reducing catalyst lifespan. For example, patent CN 112609207A (a method for preparing a porous electrocatalyst for efficient carbon dioxide reduction) discloses preparing an electrode dispersion using a porous tin-based catalyst, a conductive agent, and a Nafion solution, then dropwise adding it onto a carbon paper electrode. After drying, the resulting catalytic electrode can operate for 100 hours in CO2 electrolysis. Patent CN111672505 A (a silver-based carbon dioxide reduction catalyst and its preparation method) uses a drop-coating method to prepare a silver-based catalytic electrode that can operate for over 120 hours in CO2 electrolysis. Catalytic electrodes formed by adhering the catalyst to a conductive substrate with a binder are structurally unstable during electrolysis, and the catalyst layer is prone to detachment and deactivation, leading to reduced catalyst lifespan and failing to meet commercial requirements. Therefore, it is necessary to develop catalytic electrodes with stable structures and long lifespans to meet the needs of industrial applications.

[0004] For the reasons stated above, this invention is proposed. Summary of the Invention

[0005] To address the problems of unstable catalyst layer structure and short lifespan in electrodes prepared by existing technologies, this invention provides a CO2 electrolysis syngas production electrode and its preparation method. The electrode prepared by the method of this invention is a three-dimensional porous metal-nitrogen-carbon integrated catalytic electrode. During the CO2 electrolysis process, the catalyst layer structure is stable, exhibiting high CO2 electrolysis activity and a long service life.

[0006] The first objective of this invention is to provide a method for preparing an electrode for CO2 electrolysis to syngas, the method comprising the following steps:

[0007] (1) Preparation of precursor solution: Dissolve phenolic resin or polypropylene resin in ethanol to obtain solution A. Dissolve polyether or polyepoxide with dicyandiamide or melamine in a mixed solution of ethanol and water to obtain solution B. Mix solution A and solution B evenly and add metal salt at a temperature of 20-100℃ to obtain precursor solution.

[0008] (2) Loading: The three-dimensional conductive substrate is impregnated or coated with the precursor solution and dried to obtain the electrode precursor;

[0009] (3) Calcination: The electrode precursor is calcined in stages under a protective atmosphere to obtain the calcined electrode.

[0010] (4) Acid washing: The calcined electrode is acid washed to obtain the CO2 electrolysis syngas electrode.

[0011] The polyepoxide in this invention has 80-20000 carbon atoms.

[0012] Furthermore, in step (1), the mass concentration of phenolic resin or polypropylene resin in ethanol is 0.01-0.2 g / mL;

[0013] The mass concentration of polyether or polyepoxide in a mixed solution of dicyandiamide or melamine in ethanol-water is 0.01-0.3 g / mL, the mass ratio of polyether or polyepoxide to dicyandiamide or melamine is 10:1-1:20, and the volume ratio of ethanol to water in the mixed solution is 1:4-5:1.

[0014] Preferably, in step (1), the mass concentration of phenolic resin or polypropylene resin in ethanol is 0.05-0.1 g / mL;

[0015] The mass concentration of polyether or polyepoxide in a mixed solution of dicyandiamide or melamine in ethanol-water is 0.05-0.15 g / mL, and the volume ratio of ethanol to water in the mixed solution is 3:5-5:3.

[0016] Furthermore, the volume ratio of solution A to solution B is 1-60:5-100.

[0017] Furthermore, the metal salt mentioned in step (1) is one or more of nickel acetate, nickel nitrate, nickel sulfate, nickel chloride, copper acetate, copper nitrate, copper sulfate, copper chloride, silver nitrate, silver acetate, silver methanesulfonate, chloroauric acid, zinc acetate, zinc nitrate and zinc sulfate.

[0018] The concentration of metal ions in the metal salt in the precursor solution is 0.002-0.8 mol / L.

[0019] Preferably, the metal salt mentioned in step (1) is a mixture of two or more of the following: nickel acetate, nickel nitrate, nickel sulfate, nickel chloride, copper acetate, copper nitrate, copper sulfate, copper chloride, silver nitrate, silver acetate, silver methanesulfonate, chloroauric acid, zinc acetate, zinc nitrate, and zinc sulfate.

[0020] The concentration of metal ions in the metal salt in the precursor solution is 0.05-0.2 mol / L.

[0021] Through extensive experimentation, the inventors discovered that when two or more metal salts are mixed, the prepared electrode exhibits a more stable total current density and higher CO selectivity.

[0022] Furthermore, the concentration of the metal ions in the metal salt in the precursor solution is 0.05-0.2 mol / L.

[0023] Furthermore, in step (1), a metal salt is added at a temperature of 40-60°C.

[0024] Furthermore, in step (2), the three-dimensional conductive substrate is made of one of the following: carbon cloth, carbon paper, nickel foam, copper foam, stainless steel mesh, and titanium mesh.

[0025] Furthermore, in step (2), the drying process involves first drying at 20-80℃ for 1-6 hours, and then drying at 100-140℃ for 1-48 hours.

[0026] Preferably, in step (2), the drying process involves first drying at 40-60℃ for 3-4 hours, and then drying at 100-120℃ for 20-24 hours.

[0027] Furthermore, in step (3), the protective atmosphere is any one of nitrogen, argon, helium and hydrogen mixture;

[0028] The staged heating and calcination involves heating at a rate of 1-10℃ / min to 200-400℃ for 1-6 hours, followed by heating at a rate of 1-20℃ / min to 600-1200℃ for 1-100 hours.

[0029] Preferably, in step (3), the staged heating and calcination is carried out at a heating rate of 5℃ / min, heating to 300-400℃ for 2-4 hours, and then heating to 700-1000℃ for 6-20 hours at a heating rate of 10℃ / min.

[0030] Furthermore, the acid used in the pickling process described in step (4) is one of hydrochloric acid, nitric acid, sulfuric acid and acetic acid, with an acid concentration of 0.1-2 mol / L, a pickling time of 1-60 h and a pickling temperature of 20-60 °C.

[0031] Preferably, the acid concentration is 0.5-1 mol / L, and the pickling time is 6-24 h.

[0032] A second objective of this invention is to provide an electrode for producing syngas by CO2 electrolysis.

[0033] The CO2 electrolysis syngas production electrode prepared by this invention consists of a porous metal-nitrogen-carbon catalyst layer and its supported conductive substrate.

[0034] The metal content in the catalyst layer is 0.2-90%, and the loading is 0.1-500 mg / cm³. 2 .

[0035] Preferably, the metal content in the catalyst layer is 1-20%, and the loading is 0.5-20 mg / cm³. 2 .

[0036] Through extensive experimentation, the inventors determined the concentration of the metal salt and the type of three-dimensional conductive substrate. Only electrodes prepared within the scope of this invention exhibit good catalytic performance.

[0037] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0038] (1) The method of the present invention prepares a precursor solution by polymer and metal salt, and carbonizes it on a three-dimensional conductive substrate to form an integrated catalytic electrode, thereby improving the adhesion between the catalytic layer and the three-dimensional conductive substrate and thus improving the stability of the catalytic layer.

[0039] (2) The calcination method of the present invention enables the polymer to play a pore-forming role, so that the metal catalyst is uniformly dispersed on the pore wall, and the obtained porous catalyst layer has a high specific surface area and catalytic activity.

[0040] (3) The precursor solution of the present invention contains a nitrogen-containing precursor, which introduces nitrogen sites after carbonization, forming a metal-nitrogen-carbon catalyst layer, which increases the adsorption capacity of CO2 and thus improves the conversion rate of CO2.

[0041] (4) The CO2 electrolysis syngas production electrode prepared by the present invention has a more stable electrolysis current density and a more stable CO selectivity than the catalytic electrode prepared by the adhesion method in the prior art. Under the condition of flowing potassium bicarbonate electrolyte, the integrated catalytic electrode can maintain the stability of the catalytic layer structure and the volume ratio of CO / H2 in the syngas can also remain stable for a long time, with an operating life of more than 1000h. The electrode prepared by the present invention has a large specific surface area, high metal dispersion and stability, thus exhibiting high CO2 electrolysis activity and long service life. Attached Figure Description

[0042] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0043] Figure 1 This is a surface photograph of the three-dimensional carbon cloth nickel-nitrogen-carbon integrated electrode prepared in Example 1 of the present invention;

[0044] Figure 2 This is the XRD pattern of the three-dimensional carbon cloth nickel-nitrogen-carbon integrated electrode prepared in Example 1 of this invention;

[0045] Figure 3 This is a schematic diagram of electrolysis in Embodiment 1 of the present invention;

[0046] Figure 4 This is a graph showing the change in total current density of the electrodes prepared in Example 1 and Comparative Example 1 of the present invention as a function of electrolysis voltage;

[0047] Figure 5 This is a graph showing the CO selectivity of the electrodes prepared in Example 1 and Comparative Example 1 as a function of voltage.

[0048] Figure 6 This is a graph showing the change in total current density of the electrodes prepared in Example 1 and Comparative Example 1 of the present invention as a function of reaction time;

[0049] Figure 7 This is a graph showing the change in CO selectivity of the electrodes prepared in Example 1 and Comparative Example 1 of the present invention as a function of reaction time;

[0050] Figure 8 This is a graph showing the change of CO / H2 ratio of the electrodes prepared in Examples 1 and 2 of this invention as a function of reaction time;

[0051] Figure 9 This is a graph showing the change of the synthesis gas integral number as a function of reaction time for the electrodes prepared in Examples 1 and 2 of this invention;

[0052] Figure 10 This is a photograph of the foamed nickel-silver-nitrogen-carbon integrated catalytic electrode prepared in Example 2 of this invention;

[0053] Figure 11 This is a photograph of the titanium mesh-nitrogen-carbon integrated catalytic electrode prepared in Example 3 of this invention. Detailed Implementation

[0054] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0055] Example 1

[0056] This embodiment describes a method for preparing a CO2 electrolysis syngas production electrode, the method comprising the following steps:

[0057] (1) 2g of phenolic resin was dissolved in 50mL of ethanol to obtain solution A. 3g of polyether and 3g of dicyandiamide were dissolved in a mixed solution of 60mL of ethanol and 40mL of water to obtain solution B. Solutions A and B were mixed evenly, and 7g of nickel acetate was added at 30℃ and stirred evenly to obtain the precursor solution.

[0058] (2) Loading: The three-dimensional carbon cloth conductive substrate is impregnated with the precursor solution described above, dried at 80°C for 6 hours, and then dried at 120°C for 24 hours to obtain the electrode precursor.

[0059] (3) Calcination: The electrode precursor is placed in a tube furnace under a nitrogen atmosphere and heated to 300°C for 2 hours at a heating rate of 5°C / min. Then, it is heated to 1000°C for 6 hours at a heating rate of 10°C / min to obtain the calcined electrode.

[0060] (4) Pickling: The calcined electrode was immersed in a 1 mol / L hydrochloric acid solution for 24 h at a temperature of 20 °C to obtain a three-dimensional carbon cloth nickel-nitrogen-carbon integrated electrode.

[0061] A surface photograph of the electrode prepared in this embodiment is shown below. Figure 1 As shown, XRD is as follows Figure 2 As shown, the electrode prepared in this embodiment serves as the cathode for CO2 electrolysis to produce syngas, wherein the nickel loading is 0.4 mg / cm³. 2 The anode is an iridium catalyst, the diaphragm is a Nafion cation exchange membrane, and the electrode working area of ​​both the anode and cathode is 200 cm². 2The electrolysis diagram is shown below. Figure 3 As shown, during the test, a circulating pump was used to introduce electrolyte into the electrolytic cell. A 1 mol / L KHCO3 aqueous solution was introduced at the cathode at a flow rate of 2000 mL / min, while CO2 gas was introduced simultaneously at a flow rate of 200 mL / min. A 1 mol / L KHCO3 aqueous solution was introduced at the anode at a flow rate of 2000 mL / min. The test temperature was 30℃, the test voltage was 2.4V-3.6V, and the current density was 10 mA / cm². 2 -47mA / cm 2 The CO selectivity is 46%-52%, and the syngas integral is 43%-48%. Under 2.8V voltage conditions, after 1080 hours of cycle life testing, the total current density can be maintained at 30 mA / cm². 2 The CO selectivity can be maintained at around 50%, the CO / H2 volume ratio at around 100%, and the syngas integral at around 45%, with catalytic performance as follows: Figure 4-9 As shown.

[0062] Example 2

[0063] This embodiment describes a method for preparing a CO2 electrolysis syngas production electrode, the method comprising the following steps:

[0064] (1) Dissolve 1g of phenolic resin in 40mL of ethanol to obtain solution A. Dissolve 2g of polyether and 2g of dicyandiamide in a mixed solution of 50mL of ethanol and 30mL of water to obtain solution B. Mix solutions A and B evenly, add 4g of silver nitrate at 30℃ and stir to mix evenly to obtain the precursor solution.

[0065] (2) Loading: The three-dimensional foamed nickel conductive substrate is impregnated with the precursor solution described above, dried at 60°C for 4 hours, and then dried at 100°C for 24 hours to obtain the electrode precursor.

[0066] (3) Calcination: The electrode precursor is placed in a tube furnace under a nitrogen / hydrogen atmosphere and heated to 300°C for 2 hours at a heating rate of 5°C / min. Then, it is heated to 800°C for 6 hours at a heating rate of 10°C / min to obtain the calcined electrode.

[0067] (4) Acid washing: The calcined electrode was immersed in a 1 mol / L nitric acid solution for 1 hour at a temperature of 40°C to obtain a three-dimensional foamed nickel-silver-nitrogen-carbon integrated electrode. A photograph of the electrode surface is shown below. Figure 10 As shown.

[0068] The electrolytic capacitor prepared in this embodiment is used as the cathode for CO2 electrolysis to produce syngas, wherein the silver loading is 6 mg / cm³. 2The anode is an iridium catalyst, the membrane is a Nafion cation exchange membrane, and the electrode working area of ​​both the anode and cathode is 25 cm². 2 During the test, a circulating pump was used to introduce electrolyte into the electrolytic cell. A 1 mol / L KHCO3 aqueous solution was introduced at a flow rate of 300 mL / min at the cathode, while CO2 gas was introduced at a flow rate of 60 mL / min. A 1 mol / L KHCO3 aqueous solution was introduced at a flow rate of 300 mL / min at the anode. The test temperature was 60℃, and under a voltage of 2.8V, the cycle life test lasted 1080 hours, with the total current density maintained at 56 mA / cm². 2 The CO selectivity can be maintained above 44%, the syngas integral number can be maintained at around 42%, and the catalytic performance is as follows: Figure 8 and 9 As shown.

[0069] Example 3

[0070] This embodiment describes a method for preparing a CO2 electrolysis syngas production electrode, the method comprising the following steps:

[0071] (1) Dissolve 1g of phenolic resin in 40mL of ethanol to obtain solution A. Dissolve 2g of polyether and 2g of dicyandiamide in a mixed solution of 50mL of ethanol and 30mL of water to obtain solution B. Mix solutions A and B evenly, add 1g of chloroauric acid at 100℃ and stir to mix evenly to obtain precursor solution.

[0072] (2) Loading: The three-dimensional titanium mesh conductive substrate is coated with the precursor solution described above, dried at 60°C for 4 hours, and then dried at 100°C for 24 hours to obtain the electrode precursor.

[0073] (3) Calcination: The electrode precursor is placed in a tube furnace under a nitrogen atmosphere and heated to 300°C for 2 hours at a heating rate of 5°C / min. Then, it is heated to 900°C for 6 hours at a heating rate of 10°C / min to obtain the calcined electrode.

[0074] (4) Acid washing: The calcined electrode is immersed in a 2 mol / L nitric acid solution for 2 hours at a temperature of 60°C to obtain a three-dimensional titanium mesh gold-nitrogen-carbon integrated electrode, such as... Figure 11 As shown.

[0075] The electrolytic capacitor prepared in this embodiment is used as the cathode for CO2 electrolysis to produce syngas, wherein the gold loading is 0.2 mg / cm³. 2 The anode is an iridium catalyst, the membrane is a Nafion cation exchange membrane, and the electrode working area of ​​both the anode and cathode is 25 cm². 2During the test, a circulating pump was used to introduce electrolyte into the electrolytic cell. A 2 mol / L KHCO3 aqueous solution was introduced at a flow rate of 300 mL / min to the cathode, while CO2 gas was introduced at a flow rate of 60 mL / min. A 2 mol / L KHCO3 aqueous solution was introduced at a flow rate of 300 mL / min to the anode. The test temperature was 30℃, and under a voltage of 2.8V, the cycle life test lasted 1080 hours, with the total current density maintained at 18 mA / cm². 2 CO selectivity can be maintained above 40%, and the syngas integral can be maintained at around 45%.

[0076] Example 4

[0077] This embodiment describes a method for preparing a CO2 electrolysis syngas production electrode, the method comprising the following steps:

[0078] (1) 2g of polypropylene resin was dissolved in 50mL of ethanol to obtain solution A. 3g of polyethylene oxide and 3g of melamine were dissolved in a mixed solution of 60mL of ethanol and 40mL of water to obtain solution B. Solutions A and B were mixed evenly, and 4g of nickel acetate and 3g of silver nitrate were added at 40℃ and stirred evenly to obtain the precursor solution.

[0079] (2) Loading: The three-dimensional carbon cloth conductive substrate is impregnated with the precursor solution described above, dried at 80°C for 6 hours, and then dried at 120°C for 24 hours to obtain the electrode precursor.

[0080] (3) Calcination: The electrode precursor is placed in a tube furnace under an argon / hydrogen atmosphere and heated to 200°C for 6 hours at a heating rate of 10°C / min. Then, it is heated to 600°C for 20 hours at a heating rate of 20°C / min to obtain the calcined electrode.

[0081] (4) Pickling: The calcined electrode was immersed in 0.5 mol / L hydrochloric acid solution for 24 h at a immersion temperature of 60 °C to obtain a three-dimensional carbon cloth silver nickel-nitrogen-carbon integrated electrode.

[0082] The electrolytic capacitor prepared in this embodiment is used as the cathode for CO2 electrolysis to produce syngas, wherein the silver-nickel alloy loading is 2 mg / cm³. 2 The anode is an iridium catalyst, the diaphragm is an anion exchange membrane, and the electrode working area of ​​both the anode and cathode is 200 cm². 2During the test, a circulating pump was used to introduce electrolyte into the electrolytic cell. A 1 mol / L KHCO3 aqueous solution was introduced at the cathode at a flow rate of 2000 mL / min, while CO2 gas was introduced at a flow rate of 300 mL / min. A 1 mol / L KHCO3 aqueous solution was introduced at the anode at a flow rate of 2000 mL / min. The test temperature was 60℃, and under a voltage of 3.2V, the cycle life exceeded 1080 hours, with the total current density maintained at 120 mA / cm². 2 CO selectivity can be maintained at around 51%, and syngas integral can be maintained at around 49%.

[0083] Example 5

[0084] This embodiment describes a method for preparing a CO2 electrolysis syngas production electrode, the method comprising the following steps:

[0085] (1) Dissolve 3g of phenolic resin in 60mL of ethanol to obtain solution A. Dissolve 2g of polyether and 32g of dicyandiamide in a mixed solution of 40mL of ethanol and 30mL of water to obtain solution B. Mix solutions A and B evenly. Add 2g of nickel nitrate, 1g of zinc nitrate and 1g of silver nitrate at 60℃ and stir to mix evenly to obtain precursor solution.

[0086] (2) Loading: The three-dimensional carbon cloth conductive substrate is impregnated with the precursor solution described above, dried at 80°C for 6 hours, and then dried at 120°C for 24 hours to obtain the electrode precursor.

[0087] (3) Calcination: The electrode precursor is placed in a tube furnace under an argon / hydrogen atmosphere and heated to 400°C for 1 hour at a heating rate of 1°C / min. Then, it is heated to 600°C for 100 hours at a heating rate of 1°C / min to obtain the calcined electrode.

[0088] (4) Pickling: The calcined electrode was immersed in 0.1 mol / L hydrochloric acid solution for 24 h at a immersion temperature of 40 °C to obtain a three-dimensional carbon cloth silver nickel zinc-nitrogen-carbon integrated electrode.

[0089] The electrolytic capacitor prepared in this embodiment is used as the cathode for CO2 electrolysis to produce syngas, wherein the silver-nickel-zinc loading is 3 mg / cm³. 2 The anode is an iridium catalyst, the diaphragm is an anion exchange membrane, and the electrode working area of ​​both the anode and cathode is 200 cm². 2During the test, a circulating pump was used to introduce electrolyte into the electrolytic cell. A 1 mol / L KHCO3 aqueous solution was introduced at the cathode at a flow rate of 2000 mL / min, while CO2 gas was introduced simultaneously at a flow rate of 300 mL / min. A 1 mol / L KHCO3 aqueous solution was introduced at the anode at a flow rate of 2000 mL / min. The test temperature was 80℃, and under a voltage of 3.0V, the cycle life exceeded 1080 hours, with the total current density maintained at 116 mA / cm². 2 CO selectivity can be maintained at around 53%, and syngas integral can be maintained at around 52%.

[0090] Comparative Example 1

[0091] The preparation method of the CO2 electrolysis syngas production electrode in this comparative example includes the following steps:

[0092] 2g of phenolic resin was dissolved in 50mL of ethanol, and 3g of polyether and 3g of dicyandiamide were dissolved in 60mL of ethanol and 40mL of aqueous solution. The two solutions were mixed thoroughly. 7g of nickel acetate was added at 60℃ and stirred until homogeneous. The mixture was dried at 80℃ for 6 hours, and then at 120℃ for 24 hours. The dried solid was then placed in a tube furnace and calcined at 300℃ for 2 hours at a rate of 5℃ / min, followed by calcination at 1000℃ under a nitrogen atmosphere for 6 hours. The solid was then immersed in 1mol / L hydrochloric acid solution for 24 hours to obtain a porous nickel-nitrogen-carbon catalyst. Using a cation exchange resin as a binder, the porous nickel-nitrogen-carbon catalyst was sprayed onto a three-dimensional carbon cloth. After drying, a CO2 electrolysis syngas production electrode was obtained.

[0093] The electrode prepared in this comparative example was used as the cathode for synthesis gas, wherein the nickel loading was approximately 0.4 mg / cm³. 2 The anode is an iridium catalyst, the diaphragm is a Nafion cation exchange membrane, and the electrode working area of ​​both the anode and cathode is 200 cm². 2 During the test, a circulating pump was used to introduce electrolyte into the electrolytic cell. A 1 mol / L KHCO3 aqueous solution was introduced at the cathode at a flow rate of 2000 mL / min, while CO2 gas was introduced at a flow rate of 200 mL / min. A 1 mol / L KHCO3 aqueous solution was introduced at the anode at a flow rate of 2000 mL / min. The test temperature was 30℃, the test voltage was 2.4-3.6V, and the current density was 8-37 mA / cm². 2 The CO selectivity was 41-47%, and the syngas integral was 36-43%. Under 2.8V voltage conditions, the cycle life test lasted 1080 hours, with a total current density of 22 mA / cm². 2 Reduced to 8 mA / cm 2The CO selectivity decreased from 46% to 24%, the CO / H2 volume ratio decreased from 85% to 32%, and the syngas integral decreased from 45% to 15%. Specific catalytic performance details are as follows: Figure 4-7 .

[0094] Comparative Example 2

[0095] The preparation method of the CO2 electrolysis syngas production electrode in this comparative example includes the following steps:

[0096] 1 g of phenolic resin was dissolved in 40 mL of ethanol, and 2 g of polyether and 2 g of dicyandiamide were dissolved in 50 mL of ethanol and 30 mL of aqueous solution. The two solutions were mixed thoroughly. 4 g of silver nitrate was added at 30 °C and stirred until homogeneous. The mixture was then dried at 60 °C for 4 h, followed by drying at 100 °C for 24 h. After drying, the mixture was placed in a tube furnace and calcined at 300 °C at a rate of 5 °C / min for 2 h, followed by calcination at 800 °C at a rate of 10 °C / min under a nitrogen / hydrogen atmosphere for 6 h. The mixture was then soaked in 1 mol / L nitric acid solution for 1 h to obtain a porous silver-nitrogen-carbon catalyst. Using a cation exchange resin as a binder, the porous silver-nitrogen-carbon catalyst was sprayed onto nickel foam. After drying, a CO2 electrolysis syngas production electrode was obtained.

[0097] The electrode prepared in this comparative example was used as the cathode for CO2 electrolysis to produce syngas, with a silver loading of approximately 6 mg / cm³. 2 The anode is an iridium catalyst, the membrane is a Nafion cation exchange membrane, and the electrode working area of ​​both the anode and cathode is 25 cm². 2 During the test, a circulating pump was used to introduce electrolyte into the electrolytic cell. A 1 mol / L KHCO3 aqueous solution was introduced at a flow rate of 300 mL / min at the cathode, while CO2 gas was introduced at a flow rate of 60 mL / min. A 1 mol / L KHCO3 aqueous solution was introduced at a flow rate of 300 mL / min at the anode. The test temperature was 60℃, and the cycle life was tested for 1080 hours at 2.8V, with the total current density starting at 54 mA / cm². 2 Reduced to 16 mA / cm 2 CO selectivity decreased from 43% to 19%, CO / H2 volume ratio decreased from 80% to 28%, and syngas integral decreased from 42% to 13%.

[0098] Comparative Example 3

[0099] The preparation method of the CO2 electrolysis syngas production electrode in this comparative example includes the following steps:

[0100] (1) 2g of phenolic resin was dissolved in 50mL of ethanol to obtain solution A, and 3g of polyether was dissolved in a mixed solution of 60mL of ethanol and 40mL of water to obtain solution B. Solutions A and B were mixed evenly, and 7g of nickel acetate was added at 30℃ and stirred evenly to obtain the precursor solution.

[0101] (2) The three-dimensional carbon cloth conductive substrate is impregnated with the precursor solution described above, dried at 80°C for 6 hours, and then dried at 120°C for 24 hours to obtain the electrode precursor.

[0102] (3) The electrode precursor was placed in a tube furnace under a nitrogen atmosphere and heated to 300°C for 2 hours at a heating rate of 5°C / min. Then it was heated to 1000°C for 6 hours at a heating rate of 10°C / min to obtain the calcined electrode.

[0103] (4) The calcined electrode was soaked in 1 mol / L hydrochloric acid solution for 24 h at a soaking temperature of 20 °C to obtain a CO2 electrolysis synthesis gas electrode.

[0104] The electrode prepared in this comparative example was used as the cathode for CO2 electrolysis to produce syngas, wherein the nickel loading was approximately 0.02 mg / cm³. 2 The anode is an iridium catalyst, the diaphragm is a Nafion cation exchange membrane, and the electrode working area of ​​both the anode and cathode is 200 cm². 2 During the test, a circulating pump was used to introduce electrolyte into the electrolytic cell. A 1 mol / L KHCO3 aqueous solution was introduced at a flow rate of 2000 mL / min at the cathode, while CO2 gas was introduced at a flow rate of 200 mL / min. A 1 mol / L KHCO3 aqueous solution was introduced at a flow rate of 2000 mL / min at the anode. The test temperature was 30℃, and the cycle life was tested for 336 hours at 2.8V, with the total current density starting at 1.3 mA / cm². 2 Reduced to 0.4 mA / cm 2 CO selectivity decreased from 1% to 0.02%, and the syngas integral decreased from 4% to 1.2%.

[0105] The experimental results of this comparative example show that without the addition of a dinitrile ammonia nitrogen source, after calcination and acid washing, most of the nickel is washed away, the amount of catalyst becomes very small, the activity is very low, it can form a carbon-nitrogen-metal catalyst with the metal when there are nitrogen sites, but it is difficult to form when there are no nitrogen sites, the activity is very low, and mainly hydrogen is generated, with very little CO.

[0106] Experimental Example 1

[0107] This study investigates the effect of metal salt type on the total current density and CO selectivity when the prepared electrode is used as the cathode for CO2 electrolysis to produce syngas.

[0108] The CO2 electrolysis synthesis gas electrode was prepared by changing only the type of metal salt and keeping the amount added the same, while all other methods were the same as in Example 1. The total current density and CO selectivity were tested using the same methods as in Example 1. The results are shown in Table 1.

[0109] Table 1

[0110]

[0111] As can be seen from Table 1, when two or more metal salts are selected and mixed, the prepared electrode has a more stable total current density and higher CO selectivity.

[0112] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing an electrode for CO2 electrolysis to produce syngas, characterized in that, The preparation method includes the following steps: (1) Preparation of precursor solution: Dissolve phenolic resin or polypropylene resin in ethanol to obtain solution A, the mass concentration of phenolic resin or polypropylene resin in ethanol is 0.01-0.2 g / mL; dissolve polyether or polyepoxide and dicyandiamide or melamine in a mixed solution of ethanol and water to obtain solution B, the mass concentration of polyether or polyepoxide and dicyandiamide or melamine in the mixed solution of ethanol and water is 0.01-0.3 g / mL, the mass ratio of polyether or polyepoxide to dicyandiamide or melamine is 10:1-1:20, and the mass ratio of ethanol to water is... The volume ratio of ethanol to water in the mixed solution is 1:4-5:1; the volume ratio of solution A to solution B is 1-60:5-100. Solution A and solution B are mixed thoroughly, and a metal salt is added at a temperature of 20-100℃ to obtain a precursor solution. The metal salt is at least two of the following: nickel acetate, nickel nitrate, nickel sulfate, nickel chloride, copper acetate, copper nitrate, copper sulfate, copper chloride, silver nitrate, silver acetate, silver methanesulfonate, chloroauric acid, zinc acetate, zinc nitrate, and zinc sulfate. The concentration of the metal ion in the metal salt in the precursor solution is 0.05-0.2 mol / L. (2) Loading: The three-dimensional conductive substrate is impregnated or coated with the precursor solution and dried to obtain the electrode precursor; (3) Calcination: The electrode precursor is calcined in stages under a protective atmosphere to obtain the calcined electrode; (4) Acid washing: The calcined electrode is acid washed to obtain the CO2 electrolysis syngas production electrode. In step (2), the drying process involves first drying at 20-80℃ for 1-6 hours, and then drying at 100-140℃ for 1-48 hours. In step (3), the protective atmosphere is any one of nitrogen, argon, helium and hydrogen mixture; the staged heating and calcination is to heat to 200-400℃ for 1-6h at a heating rate of 1-10℃ / min, and then heat to 600-1200℃ for 1-100h at a heating rate of 1-20℃ / min. The acid used in the pickling process described in step (4) is one of hydrochloric acid, nitric acid, sulfuric acid and acetic acid. The concentration of the acid is 0.1-2 mol / L, the pickling time is 1-60 h, and the pickling temperature is 20-60℃.

2. The method for preparing a CO2 electrolysis syngas electrode according to claim 1, characterized in that, In step (2), the three-dimensional conductive substrate is made of one of the following: carbon cloth, carbon paper, nickel foam, copper foam, stainless steel mesh, and titanium mesh.

3. A CO2 electrolysis syngas production electrode prepared by the preparation method according to claim 1 or 2, characterized in that, The CO2 electrolysis syngas production electrode is composed of a porous metal-nitrogen-carbon catalyst layer and its supporting conductive substrate.

4. The CO2 electrolysis syngas production electrode according to claim 3, characterized in that, The mass fraction of metal in the catalyst layer is 0.2-90%, and the loading is 0.1-500 mg / cm³. 2 .

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