Disclosure of Invention
In order to solve the technical problems, the invention provides an electrode for electrochemical reduction of carbon dioxide and application thereof2O, wherein Cu-vacancy copper is the shell, Cu2O is a nucleus body, and the catalyst comprises the following components: 50-90 wt% of Cu, 5-30 wt% of vacancy copper and Cu2O5-20 wt%, and the preparation method of the electrode for electrochemical reduction of carbon dioxide comprises the following steps:
s1: cleaning the copper net, the foamed nickel and the copper foil basal layer with water, ethanol or acetone, and then adding H with the mass concentration of 50-95%3PO4Leveling for 5-1200 s under the condition that the voltage of the constant potential is 3-5V, and then washing and drying for later use;
s2: immersing the substrate layer into a certain amount of mixture of sodium hydroxide and an oxidant, carrying out chemical oxidation reaction for 30 s-120 min, cleaning, and drying at 40-150 ℃ to obtain CuOxA nanowire/Cu base layer;
s3: mixing copper salt, sulfuric acid and a stabilizer, magnetically stirring for 30-120 min to form a precursor copper salt solution, and under the protection of inert atmosphere, changing the current density to CuO at normal temperaturexAnd electrodepositing a catalyst on the surface of the nanowire/Cu base layer to prepare the electrode.
S4: placing the prepared electrode in CO2Reducing the saturated electrolyte for 20-10000 s at constant current density, washing, and drying by using inert gas to prepare a gas diffusion electrode;
s5: and soaking the prepared gas diffusion electrode in a concentrated hydrochloric acid solution with the concentration of 36-38% for 10-30 min, cleaning and drying to obtain the copper electrode.
Preferably, the oxidant is one or two of ammonium persulfate, potassium persulfate, sodium persulfate, hydrogen peroxide and potassium dichromate, the concentration of the oxidant is 0.01-0.2M, the preferred concentration is 0.015-0.12M, and the concentration of the sodium hydroxide is 0.5-4M, the preferred concentration is 0.5-2M; the ratio of the sodium hydroxide to the oxidant is 5-80: 1, and the preferable ratio is 10-40: 1.
Preferably, the precursor copper salt solution is Cu (NO)3)2·3H2O、CuCl2·2H2O、CuSO4·5H2O, wherein the concentration of copper ions is 1 mM-1.4M, preferably 300 mM-1.0M, the pH of a copper salt solution is adjusted to 0.5-2.0 by using sulfuric acid, the stabilizer is one of polyvinylpyrrolidone, trisodium citrate and disodium ethylene diamine tetraacetate, and the concentration ratio of the stabilizer to Cu in the copper salt is 20: 1-1: 30, preferably 10: 1-1: 15;
preferably, in the variable-current electrodeposition, the deposition current density of the first step is-100 to-200 mAcm-2The time of electrodeposition is 5 to 120s, and the preferred condition is-100 to-150 mAcm-2Depositing for 20-60 s; the second step is to deposit a current with a density of-5 to-100 mAcm-2The deposition time is 60-2000 s; the preferable condition is-30 to-70 mAcm-2Depositing for 300-1000 s;
preferably, the CO is2The saturated electrolyte is KHCO3、NaHCO3One or more of NaOH, KOH, NaCl, KCl, KBr and NaBr, and the CO2The concentration of the saturated electrolyte is 0.02-2M, the preferable concentration is 0.1-0.5M, and the current density of the constant current is-5 mAcm-2~-150mAcm-2Preferably, the constant current has a current density of-40 mAcm-2~-80mAcm-2The reduction time is 10-5000 s, and the preferable time is 120-2400 s.
Preferably, the electrode can be used as a cathode for the electrochemical reduction reaction of carbon dioxide.
The invention has the beneficial effects that:
1. by oxidationThe agent directly oxidizes the surface of the substrate, metal hydroxide nanowires can grow on the surface of the substrate in situ under the condition of no template agent, and CuO is obtained by dryingxA nanowire/Cu base layer; the size of the nanowire can be regulated and controlled by regulating and controlling the concentration of the solution; the preparation process is simple and easy to control, and avoids the application of a template agent or a surfactant, so that the preparation cost is reduced;
2. compared with the traditional current deposition technology, the method of variable current deposition is adopted, the gradient catalyst layer can be obtained through deposition, the catalyst layer with the gradient distribution structure is prepared, not only can active centers be provided as much as possible, but also a 'gas-liquid-solid' three-phase reaction interface is favorably constructed, meanwhile, the characteristics of a smooth proton channel and a product/reactant mass transfer channel are achieved, the utilization rate and the electrochemical circulation stability of the catalytic active centers are improved, and the diffusion of reaction raw materials and products is promoted.
3. The oxygen vacancy of the present invention is CO2Provide a large amount of electrons, is beneficial to the adsorption of-CO, -COH intermediate products and-CH2To promote the coupling of C-C, thereby improving the C-C coupling of the Cu catalystxHySelectivity of (a); vacancy copper has more active area, defect sites and coupling synergistic effect among components, so that the selectivity and activity of hydrocarbon products are improved;
4. the invention utilizes Cu+Interacts with each metal to convert CO2The electro-reduction is limited in a 'functional domain', so that the catalyst is prevented from being in CO2Loss in the reduction process and improvement of the stability of the catalyst.
5. According to the invention, the Cu nano structure with a special morphology is grown on the substrate layer, so that the specific surface area, the edge active sites and the corner active sites of the copper electrode are obviously increased, the activity of the copper electrode on the electrocatalytic reduction reaction of carbon dioxide is improved, and the selectivity on hydrocarbon is also improved.
6. The preparation method is simple and easy to operate, the production equipment is conventional, and the prepared electrode has large active specific surface area and higher carbon dioxide catalytic activity.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention is further described below:
an electrode for electrochemical reduction of carbon dioxide and application thereof comprise a catalyst, wherein the catalyst is an ordered core-shell catalyst, and the catalyst is Cu-vacancy copper/Cu2O, wherein Cu-vacancy copper is the shell, Cu2O is a nucleus body, and the catalyst comprises the following components: 50-90 wt% of Cu, 5-30 wt% of vacancy copper and Cu2O5-20 wt%, and the preparation method of the electrode for electrochemical reduction of carbon dioxide comprises the following steps:
s1: cleaning the copper net, the foamed nickel and the copper foil basal layer with water, ethanol or acetone, and then adding H with the mass concentration of 50-95%3PO4Leveling for 5-1200 s under the condition that the voltage of the constant potential is 3-5V, and then washing and drying for later use;
s2: immersing the substrate layer in a quantity of sodium hydroxide and an oxidizing agentThe mixture of (1) and (2) is characterized in that the oxidant is one or two of ammonium persulfate, potassium persulfate, sodium persulfate, hydrogen peroxide and potassium dichromate, the concentration of the oxidant is 0.01-0.2M, the preferable concentration is 0.015-0.12M, and the concentration of the sodium hydroxide is 0.5-4M, the preferable concentration is 0.5-2M; the ratio of sodium hydroxide to oxidant is 5-80: 1, the preferred ratio is 10-40: 1, the reaction is continued for 30 s-120 min, and CuO is obtained after cleaningxA nanowire/Cu base layer;
s3: mixing copper salt, sulfuric acid and a stabilizer, and magnetically stirring for 30-120 min to form a precursor copper salt solution, wherein the precursor copper salt solution is Cu (NO)3)2·3H2O、CuCl2·2H2O、CuSO4·5H2O, wherein the concentration of copper ions is 1 mM-1.4M, preferably 300 mM-1.0M, the pH of a copper salt solution is adjusted to 0.5-2.0 by using sulfuric acid, the stabilizer is one of polyvinylpyrrolidone, trisodium citrate and disodium ethylene diamine tetraacetate, and the concentration ratio of the stabilizer to Cu in the copper salt is 20: 1-1: 30, preferably 10: 1-1: 15; under the protection of inert atmosphere and at normal temperature, the current density is changed to be CuOxThe catalyst is electrodeposited on the surface of the nanowire/Cu substrate layer, and in the variable-current electrodeposition, the deposition current density of the first step is-100 to-200 mAcm-2The time of electrodeposition is 5 to 120s, and the preferred condition is-100 to-150 mAcm-2Depositing for 20-60 s; the second step is to deposit a current with a density of-5 to-100 mAcm-2The deposition time is 60-2000 s; the preferable condition is-30 to-70 mAcm-2Depositing for 300-1000 s;
s4: placing the prepared electrode in CO2Reducing for 20-10000 s in saturated electrolyte at constant current density, washing, drying with inert gas, and preparing to obtain gas diffusion electrode, wherein the CO is2The saturated electrolyte is KHCO3、NaHCO3One or more of NaOH, KOH, NaCl, KCl, KBr and NaBr, and the CO2The concentration of the saturated electrolyte is 0.02-2M, the preferable concentration is 0.1-0.5M, and the current density of the constant current is-5 mAcm-2~-150mAcm-2Preferably constant currentThe current density of (A) was-40 mAcm-2~-80mAcm-2The reduction time is 10-5000 s, and the preferable time is 120-2400 s;
s5: and soaking the prepared gas diffusion electrode in a concentrated hydrochloric acid solution with the concentration of 36-38% for 10-30 min, cleaning and drying to obtain the copper electrode.
In particular, the electrode can be used as a cathode for the electrochemical reduction reaction of carbon dioxide.
Example 1
Ultrasonic washing copper mesh as substrate in ultrapure water and ethanol for 10min, respectively, and treating with 95% H3PO4Leveling for 900s under the condition that the constant potential voltage is 4V, washing and drying for later use; immersing the substrate layer into a mixture of 2M sodium hydroxide aqueous solution and 0.05M ammonium persulfate, wherein the ratio of sodium hydroxide to oxidant is 15: 1, continuously reacting for 30min, and drying at 100 ℃ to obtain CuOxA nanowire/Cu base layer; 0.4M CuCl with the molar concentration ratio of disodium ethylene diamine tetraacetate dihydrate to Cu in the copper salt being 1:12·2H2O is mixed with disodium edetate dihydrate and H is used2SO4Adjusting the pH of the copper salt solution to 1.0 as an electrolyte, and adopting a deposition current density of-150 mAcm-2Depositing for 60s, and then adopting the deposition current density of-60 mAcm-2Depositing for 1200s, and cleaning, and placing the prepared electrode in CO2Saturated 0.5M NaHCO3Medium constant current density-80 mAcm-2Reducing for 2000s, washing and drying to prepare the gas diffusion electrode; soaking the prepared gas diffusion electrode in 37.5% concentrated hydrochloric acid solution for 15min, cleaning, and drying to obtain 70% Cu-10% vacancy copper/20% Cu2O, and an ordered core-shell catalyst.
Example 2
Ultrasonic washing copper mesh as substrate in ultrapure water and ethanol for 10min, respectively, and treating with 95% H3PO4Leveling for 900s under the condition that the voltage of the constant potential is 4V, washing and drying for later use; immersing the substrate layer in a 1.5M aqueous solution of sodium hydroxideIn the mixture of the solution and 0.05M potassium persulfate, the ratio of sodium hydroxide to oxidant is 10:1, the reaction is continued for 40min, and CuO is obtained by drying at 100 DEG CxA nanowire/Cu base layer; 0.2M of Cu (NO) is added according to the molar concentration ratio of the disodium ethylene diamine tetraacetate dihydrate to the Cu in the copper salt of 1:13)2·3H2O is mixed with disodium edetate dihydrate and H is used2SO4Adjusting the pH of the copper salt solution to 1.0 as an electrolyte, and adopting a deposition current density of-120 mAcm-2Depositing for 80s, and then adopting a deposition current density of-60 mAcm-2Depositing for 1500s, cleaning, and placing the prepared electrode in CO2Saturated 0.2M KHCO3Medium constant current density-60 mAcm-2Reducing for 2000s, washing, and drying with inert gas to prepare a gas diffusion electrode; soaking the prepared gas diffusion electrode in a concentrated hydrochloric acid solution with the concentration of 37.5% for 15min, cleaning and drying to obtain 60% Cu-30% vacancy copper/10% Cu2O, and an ordered core-shell catalyst.
Example 3
Ultrasonically washing copper foil serving as a substrate in ultrapure water and ethanol for 10min respectively, then leveling for 900s in H3PO4 with the mass concentration of 95% under the condition that the voltage of a constant potential is 3V, and washing and drying for later use; immersing the substrate layer in a mixture of 1.0M sodium hydroxide aqueous solution and 0.02M potassium dichromate at a ratio of sodium hydroxide to oxidant of 12: 1, reacting for 40min, and drying at 80 deg.C to obtain CuOxA nanowire/Cu base layer; 0.3M of Cu (NO) with the molar concentration ratio of sodium citrate to Cu in copper salt being 2: 13)2·3H2Mixing O with sodium citrate, and using H2SO4Adjusting the pH of the copper salt solution to 1.0 as an electrolyte, and adopting a deposition current density of-150 mAcm-2Depositing for 60s, and then adopting the deposition current density of-60 mAcm-2Depositing for 1000s, cleaning, placing the prepared electrode in 0.5M KBr saturated with CO2 and constant current density of-60 mAcm-2Reducing for 1500s, washing, and drying with inert gas to prepare a gas diffusion electrode; prepared by the above methodSoaking the gas diffusion electrode in 37.5% concentrated hydrochloric acid solution for 20min, cleaning, and drying to obtain Cu-5% vacancy copper/10% Cu2O, and an ordered core-shell catalyst.
Example 4
Ultrasonic washing copper mesh as substrate in ultrapure water and ethanol for 10min, respectively, and treating with 95% H3PO4Leveling for 700s under the condition that the voltage of the constant potential is 4V, washing and drying for later use; immersing the substrate layer into a mixture of 1.5M sodium hydroxide aqueous solution and 0.05M potassium persulfate, wherein the ratio of sodium hydroxide to oxidant is 10:1, continuously reacting for 40min, and drying at 100 deg.C to obtain CuOxA nanowire/Cu base layer; 0.3M of Cu (NO) with the molar concentration ratio of sodium citrate to Cu in copper salt being 2: 13)2·3H2Mixing O with sodium citrate, and using H2SO4Adjusting the pH of the copper salt solution to 1.0 as an electrolyte, and adopting a deposition current density of-120 mAcm-2Depositing for 80s, and then depositing at a current density of-40 mAcm-2Depositing for 1000s, cleaning, and placing the prepared electrode in CO2Saturated 0.5M KBr medium constant current density-60 mAcm-2Reducing for 1500s, washing, and drying with inert gas to prepare a gas diffusion electrode; soaking the prepared gas diffusion electrode in a concentrated hydrochloric acid solution with the concentration of 37.5% for 20min, cleaning and drying to obtain the copper based on 85% Cu-5% vacancy/10% Cu2O, and an ordered core-shell catalyst.
Example 5
Ultrasonic washing nickel screen as substrate in ultrapure water and ethanol for 20min, respectively, and treating with 95% H3PO4Leveling for 500s under the condition that the voltage of the constant potential is 5V, washing and drying for later use; immersing the substrate layer into a mixture of 1.5M sodium hydroxide aqueous solution and 0.05M potassium persulfate, wherein the ratio of sodium hydroxide to oxidant is 10:1, continuously reacting for 40min, and drying at 100 deg.C to obtain CuOxA nanowire/Cu base layer; 0.2M of Cu (NO) with the molar concentration ratio of sodium citrate to Cu in copper salt being 1: 23)2·3H2Mixing O with sodium citrate, and using H2SO4Adjusting the pH of the copper salt solution to 1.0 as an electrolyte, and adopting a deposition current density of-150 mAcm-2Depositing for 30s, and then adopting a deposition current density of-80 mAcm-2Depositing for 1200s, cleaning, and placing the prepared electrode in CO2Saturated 0.5M KHCO3Medium constant current density-80 mAcm-2Reducing for 1500s, washing, and drying with inert gas to prepare a gas diffusion electrode; soaking the prepared gas diffusion electrode in 37.5% concentrated hydrochloric acid solution for 15min, cleaning, and drying to obtain 70% Cu-20% vacancy copper/10% Cu2O, and an ordered core-shell catalyst.
Example 6
Ultrasonic washing copper foil as substrate in ultrapure water and ethanol for 30min, respectively, and treating with 95% H3PO4Leveling for 600s under the condition that the voltage of the constant potential is 4V, washing and drying for later use; immersing the substrate layer into a mixture of 1.5M sodium hydroxide aqueous solution and 0.05M potassium persulfate, wherein the ratio of sodium hydroxide to oxidant is 12: 1, continuously reacting for 60min, and drying at 100 ℃ to obtain CuOxA nanowire/Cu base layer; 0.2M Cu (NO) with molar concentration ratio of polyvinylpyrrolidone to Cu in copper salt of 0.001: 13)2·3H2O is mixed with polyvinylpyrrolidone and H is used2SO4Adjusting the pH of the copper salt solution to 1.0 as an electrolyte, and adopting a deposition current density of-180 mAcm-2Depositing for 30s, and then adopting a deposition current density of-70 mAcm-2Depositing for 1000s, cleaning, and placing the prepared electrode in CO2Saturated 0.5M KHCO3Medium constant current density-60 mAcm-2Reducing for 1200s, washing, and drying with inert gas to prepare a gas diffusion electrode; soaking the prepared gas diffusion electrode in a concentrated hydrochloric acid solution with the concentration of 37.5% for 15min, cleaning and drying to obtain the copper/5% Cu based on 90% Cu-5% vacancy2O, and an ordered core-shell catalyst.
Example 7
Ultrasonically washing copper foil serving as a substrate in ultrapure water and ethanol for 30min respectively, then leveling for 600s in H3PO4 with the mass concentration of 95% under the constant potential voltage of 4V, washing, and drying for later use; immersing the substrate layer into a mixture of 1.8M sodium hydroxide aqueous solution and 0.05M ammonium persulfate, wherein the ratio of sodium hydroxide to oxidant is 10:1, continuously reacting for 40min, and drying at 100 ℃ to obtain CuOxA nanowire/Cu base layer; 0.2M Cu (NO) with molar concentration ratio of polyvinylpyrrolidone to Cu in copper salt of 5: 13)2·3H2O is mixed with polyvinylpyrrolidone and H is used2SO4Adjusting the pH of the copper salt solution to 1.0 as an electrolyte, and adopting a deposition current density of-180 mAcm-2Depositing for 30s, and then adopting a deposition current density of-60 mAcm-2Depositing for 1000s, cleaning, and placing the prepared electrode in 0.5M KHCO saturated with CO23Medium constant current density-60 mA cm-2Reducing for 1200s, washing, and drying with inert gas to prepare a gas diffusion electrode; the gas diffusion electrode prepared above was immersed in a concentrated hydrochloric acid solution of 37.5% concentration for 15min, washed and dried to prepare an electrode based on a 90% Cu-5% vacancy copper (Cu-V) (shell)/5% Cu2O (core) ordered "core-shell" catalyst.
Example 8
Ultrasonic washing copper foil as substrate in ultrapure water and ethanol for 30min, respectively, and treating with 95% H3PO4Leveling for 600s under the condition that the voltage of the constant potential is 4V, washing and drying for later use; immersing the substrate layer into a mixture of 1.5M sodium hydroxide aqueous solution and 0.05M potassium persulfate, wherein the ratio of sodium hydroxide to oxidant is 10:1, continuously reacting for 40min, and drying at 100 deg.C to obtain CuOxA nanowire/Cu base layer; mixing 0.2M CuSO4 & 5H2O and polyvinylpyrrolidone at molar concentration ratio of polyvinylpyrrolidone to Cu in copper salt of 1: 10, and adding H2SO4Adjusting the pH of the copper salt solution to 1.0 as an electrolyte, and adopting a deposition current density of-120 mAcm-2Depositing for 90s, and then adopting a deposition current density of-70 mAcm-2Depositing for 300s, cleaning, and placing the prepared electrode onCO2Saturated 0.5M NaCl constant current density-60 mAcm-2Reducing for 1200s, washing, and drying with inert gas to prepare a gas diffusion electrode; soaking the prepared gas diffusion electrode in 37.5% concentrated hydrochloric acid solution for 15min, cleaning, and drying to obtain 70% Cu-20% vacancy copper/10% Cu2O, and an ordered core-shell catalyst.
Comparative example 1
Ultrasonic washing copper mesh as substrate in ultrapure water and ethanol for 10min, respectively, and treating with 95% H3PO4Leveling for 900s under the condition that the constant potential voltage is 4V, washing and drying for later use; 0.4M CuCl with the molar concentration ratio of disodium ethylene diamine tetraacetate dihydrate to Cu in the copper salt being 1:12·2H2O is mixed with disodium edetate dihydrate and H is used2SO4Adjusting the pH of the copper salt solution to 1.0 as an electrolyte, and adopting a deposition current density of-150 mAcm-2Depositing for 60s, and then adopting the deposition current density of-60 mAcm-2Depositing for 1200s, and cleaning, and placing the prepared electrode in CO2Saturated 0.5M NaHCO3Medium constant current density-80 mAcm-2Reducing for 2000s, washing and drying to prepare the gas diffusion electrode; soaking the prepared gas diffusion electrode in 37.5% concentrated hydrochloric acid solution for 15min, cleaning, and drying to obtain 70% Cu-10% vacancy copper/20% Cu2O, and an ordered core-shell catalyst.
Comparative example 2
Ultrasonic washing copper mesh as substrate in ultrapure water and ethanol for 10min, respectively, and treating with 95% H3PO4Leveling for 900s under the condition that the constant potential voltage is 4V, washing and drying for later use; immersing the substrate layer into a mixture of 2M sodium hydroxide aqueous solution and 0.05M ammonium persulfate, wherein the ratio of sodium hydroxide to oxidant is 15: 1, continuously reacting for 30min, and drying at 100 ℃ to obtain CuOxA nanowire/Cu base layer; 0.4M CuCl with the molar concentration ratio of disodium ethylene diamine tetraacetate dihydrate to Cu in the copper salt being 1:12·2H2O is mixed with disodium edetate dihydrate and H is used2SO4Adjusting pH of the copper salt solution to 1.0 to obtain electrolyte with a deposition current density of-60 mAcm-2Depositing for 1200s, and cleaning, and placing the prepared electrode in CO2Saturated 0.5M NaHCO3Medium constant current density-80 mAcm-2Reducing for 2000s, washing and drying to prepare the gas diffusion electrode; soaking the prepared gas diffusion electrode in 37.5% concentrated hydrochloric acid solution for 15min, cleaning, and drying to obtain 70% Cu-10% vacancy copper/20% Cu2O, and an ordered core-shell catalyst.
Comparative example 3
Ultrasonic washing copper mesh as substrate in ultrapure water and ethanol for 10min, respectively, and treating with 95% H3PO4Leveling for 900s under the condition that the constant potential voltage is 4V, washing and drying for later use; immersing the substrate layer into a mixture of 2M sodium hydroxide aqueous solution and 0.05M ammonium persulfate, wherein the ratio of sodium hydroxide to oxidant is 15: 1, continuously reacting for 30min, and drying at 100 ℃ to obtain CuOxA nanowire/Cu base layer; 0.4M CuCl with the molar concentration ratio of disodium ethylene diamine tetraacetate dihydrate to Cu in the copper salt being 1:12·2H2O is mixed with disodium edetate dihydrate and H is used2SO4Adjusting the pH of the copper salt solution to 1.0 as an electrolyte, and adopting a deposition current density of-240 mAcm-2Depositing for 60s, and then adopting the deposition current density of-60 mAcm-2Depositing for 1200s, cleaning, and placing the prepared electrode in CO2Saturated 0.5M NaHCO3Medium constant current density-80 mAcm-2Reducing for 2000s, washing and drying to prepare the gas diffusion electrode; soaking the prepared gas diffusion electrode in 37.5% concentrated hydrochloric acid solution for 15min, cleaning, and drying to obtain 70% Cu-10% vacancy copper/20% Cu2O, and an ordered core-shell catalyst.
Comparative example 4
Using copper net as substrate, adding ultrapure water and pure waterUltrasonic washing in alcohol for 10min, respectively, and treating with 95% H3PO4Leveling for 900s under the condition that the constant potential voltage is 4V, washing and drying for later use; immersing the substrate layer in a mixture of 2M sodium hydroxide aqueous solution and 0.005M ammonium persulfate, the ratio of sodium hydroxide to oxidant is 15: 1, continuously reacting for 30min, and drying at 100 deg.C to obtain CuOxA nanowire/Cu base layer; 0.4M CuCl with the molar concentration ratio of disodium ethylene diamine tetraacetate dihydrate to Cu in the copper salt being 1:12·2H2O is mixed with disodium edetate dihydrate and H is used2SO4Adjusting the pH of the copper salt solution to 1.0 as an electrolyte, and adopting a deposition current density of-150 mAcm-2Depositing for 60s, and then adopting the deposition current density of-120 mAcm-2Depositing for 1200s, and cleaning, and placing the prepared electrode in CO2Saturated 0.5M NaHCO3Medium constant current density-80 mAcm-2Reducing for 2000s, washing and drying to prepare the gas diffusion electrode; soaking the prepared gas diffusion electrode in 37.5% concentrated hydrochloric acid solution for 15min, cleaning, and drying to obtain 70% Cu-10% vacancy copper/20% Cu2O, and an ordered core-shell catalyst.
Comparative example 5
Ultrasonic washing copper mesh as substrate in ultrapure water and ethanol for 10min, respectively, and treating with 95% H3PO4Leveling for 900s under the condition that the constant potential voltage is 4V, washing and drying for later use; immersing the substrate layer into a mixture of 2M sodium hydroxide aqueous solution and 0.25M ammonium persulfate, wherein the ratio of sodium hydroxide to oxidant is 15: 1, continuously reacting for 30min, and drying at 100 ℃ to obtain CuOxA nanowire/Cu base layer; 0.4M CuCl with the molar concentration ratio of disodium ethylene diamine tetraacetate dihydrate to Cu in the copper salt of 2-10: 12·2H2O is mixed with disodium edetate dihydrate and H is used2SO4Adjusting the pH of the copper salt solution to 1.0 as an electrolyte, and adopting a deposition current density of-150 mAcm-2Depositing for 60s, and then adopting the deposition current density of-60 mAcm-2Depositing for 1200s, and cleaning, and placing the prepared electrode in CO2Saturated 0.5M NaHCO3Medium constant current density-80 mAcm-2Reducing for 2000s, washing and drying to prepare the gas diffusion electrode; soaking the prepared gas diffusion electrode in 37.5% concentrated hydrochloric acid solution for 15min, cleaning, and drying to obtain 70% Cu-10% vacancy copper/20% Cu2O, and an ordered core-shell catalyst.
Comparative example 6
Ultrasonic washing copper mesh as substrate in ultrapure water and ethanol for 10min, respectively, and treating with 95% H3PO4Leveling for 900s under the condition that the constant potential voltage is 4V, washing and drying for later use; immersing the substrate layer into a mixture of 2M sodium hydroxide aqueous solution and 0.03M ammonium persulfate, wherein the ratio of sodium hydroxide to oxidant is 15: 1, continuously reacting for 30min, and drying at 100 ℃ to obtain CuOxA nanowire/Cu base layer; 0.4M CuCl with the molar concentration ratio of disodium ethylene diamine tetraacetate dihydrate to Cu in the copper salt of 2-10: 12·2H2O is mixed with disodium edetate dihydrate and H is used2SO4Adjusting the pH of the copper salt solution to 1.0 as an electrolyte, and adopting a deposition current density of-150 mAcm-2Depositing for 60s, and then adopting the deposition current density of-60 mAcm-2Depositing for 1200s, and cleaning, and placing the prepared electrode in CO2Saturated 0.5M NaHCO3Medium constant current density-80 mAcm-2Reducing for 2000s, washing and drying to prepare the gas diffusion electrode; soaking the prepared gas diffusion electrode in 37.5% concentrated hydrochloric acid solution for 15min, cleaning, and drying to obtain 70% Cu-10% vacancy copper/20% Cu2O, and an ordered core-shell catalyst.
The prepared electrode is used as a cathode of a reaction system for electrochemically catalyzing and reducing carbon dioxide, a three-electrode system is adopted for electrochemical test in the experiment, the prepared copper electrode is 1cm multiplied by 1cm and is used as a working electrode, and Hg/HgCl is used as a working electrode2A calomel electrode of saturated KCl as a reference electrode, 3cm2The platinum sheet electrode as the counter electrode and the cathode chamber 180mL of 0.5M NaHCO3Solution in the anode 100mL of 0.1M H2SO4Electrocatalytic reduction of CO2During the reaction, CO2The flow rate is set as 100 mL/min; the catalytic reduction product was detected every 15 min.
Specifically, fig. 1 and 2 show the difference in the distribution of the reduction products of example 1 and example 2, respectively, in that: different oxidants are added, and when the ammonium persulfate is selected as the oxidant in example 1, CH is generated at-2.3V4The highest Faraday efficiency of 30.2%, C2H4The Faraday efficiency of (2) is 29%; example 2 formation of CH when Potassium persulfate is used as the oxidizing agent4The highest Faraday efficiency of 28%, C2H4The Faraday efficiency of (2) is 23%; and from the whole reduction potential trend, the faradaic efficiency of the reduction products of ammonium persulfate and potassium persulfate which are both increased along with the increase of the potential is increased firstly and then reduced, the faradaic efficiency has a highest point, and a large amount of C is accompanied by the oxidizing agent2H4However, the catalyst performance is better when the oxidant is ammonium persulfate.
In particular, figure 3 is a product profile for comparative example 1, which, compared to the faradaic efficiency of example 1 of figure 3, gives: electrode without chemical oxidation deposition Cu nanowire layer for catalytic reduction of CH in product after carbon dioxide reduction4And C2H4The faradaic efficiency of (a) is reduced, which indicates that the step of preparing nanowires by the chemical oxidation process is crucial to the performance of the catalyst.
Specifically, the product profile of comparative example 2 in FIG. 4, compared to FIG. 1, gives: comparative example 2 constant current deposition was used to prepare an electrode for catalytic reduction of CH in the product4And C2H4Compared with the traditional current deposition technology, the variable current deposition method is adopted, the gradient catalyst layer can be deposited, the catalyst layer with the gradient distribution structure can be prepared, not only can active centers be provided as much as possible, but also the construction of a gas-liquid-solid three-phase reaction interface is facilitated, and meanwhile, the catalyst layer has smooth qualityThe characteristics of the sub-channel and the product/reactant mass transfer channel improve the utilization rate of the catalytic active center and the electrochemical circulation stability, and promote the diffusion of reaction raw materials and products, thereby improving the current density and showing that the catalytic activity is improved.
Specifically, the product distribution diagram of comparative example 3 in fig. 5, compared with fig. 1, can be obtained: comparative example 3 is an electrode prepared by depositing with variable current density and large current exceeding the protection range and used for reducing CH in products after catalytic reduction4And C2H4The faradaic efficiency of (a) is reduced, which indicates that the selectivity and activity of the catalyst are reduced by too much current. This is mainly due to the fact that the current density is too high, which results in too large particle size of the prepared catalyst, and the specific surface area is reduced, thus reducing the activity, and the electrode structure is changed during the preparation process, which results in reduced selectivity.
Specifically, the product distribution diagram of comparative example 4 in fig. 5, compared with fig. 1, can be obtained: comparative example 4 is an electrode prepared by depositing with variable current density and small current exceeding the protection range, and used for reducing CH in products after catalytic reduction4And C2H4The faradaic efficiency of (a) decreases, which indicates that too little current decreases the selectivity and activity of the catalyst. The main current density is too small, so that the particle size of the surface layer of the prepared catalyst is too small, the particle size of the surface layer of the prepared catalyst is greatly different from that of a large-particle catalyst layer, the surface layer of the prepared catalyst is embedded into holes, the structure is damaged, and the selectivity is reduced.
Specifically, the product distribution diagram of comparative example 5 in fig. 5, compared with fig. 1, can be obtained: cu electrode prepared by oxidizing agent beyond the highest value of the specified range of the invention and used for reducing CH in products after catalytic reduction4And C2H4The faradaic efficiency of (a) is reduced mainly because the oxidant component is too high, resulting in the nanowire being oversized, the specific surface area being reduced, the activity being reduced, the proportion of edge active sites being reduced, and the selectivity also being reduced.
Specifically, the product distribution diagram of comparative example 6 in fig. 5, compared with fig. 1, can be obtained: cu electrode prepared with oxidant beyond the lowest value of the specified range for catalytic reduction of CH in product4And C2H4The faradaic efficiency of (a) is reduced mainly because the oxidizing agent component is too low, resulting in too small nanowire size, too low amount of the oxidizing agent, reduced number of active sites, reduced activity, reduced proportion of edge active sites, and reduced selectivity.
It should be noted that, in this document, moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.
Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.