Preparation method of Cu foil loaded nano Cu2O electrode and application of Cu foil loaded nano Cu2O electrode in pulse carbon dioxide electrocatalytic reduction

Abstract

The invention belongs to the field of electro-catalysis, and particularly relates to a preparation method of a Cu foil loaded nano Cu2O electrode and application of the Cu foil loaded nano Cu2O electrode in pulse carbon dioxide electro-catalytic reduction. The surface of the Cu foil is modified by the Cu2O nano coating, the Cu2O nano coating is used for pulse carbon dioxide electroreduction reaction, and high methane selectivity and high current density are realized in carbon dioxide electroreduction by regulating and controlling pulse potential. The Faraday efficiency of the methane reaches 92% at-1.15 V vs.RHE, the partial current density of the methane is 111mA. Cm <-2 > at the moment, the stable operation time exceeds 110 hours and is not obviously attenuated, and the Faraday efficiency of the methane with the selectivity being 82% of an unmodified copper electrode is remarkably improved.

Description

Technical Field

[0001] The present invention belongs to the field of electrocatalysis, and particularly relates to a preparation method of a Cu foil-supported nano-Cu2O electrode and its application in pulsed carbon dioxide electrocatalytic reduction. Background Art

[0002] With the acceleration of the industrialization process, the concentration of CO2 in the atmosphere has been continuously increasing, leading to increasingly serious environmental problems such as global warming. Converting CO2 into high-value-added chemicals and fuels can not only reduce greenhouse gas emissions but also achieve the recycling of carbon resources, which has important economic and environmental benefits. CO2RR is a technology that uses electrical energy to reduce CO2 to products such as carbon monoxide, formic acid, methanol, and ethylene, and has the advantages of mild reaction conditions and adjustable product selectivity. CH4 has attracted much attention due to its high calorific value and mature transmission and distribution system. However, the high dissociation energy of the C=O bond in the CO2 molecule and the complex reaction path of the multi-electron transfer process lead to the bottleneck problems of low product selectivity and high overpotential commonly existing in traditional catalysts.

[0003] Among many CO2RR catalysts, copper-based materials have become a research hotspot in the field of carbon dioxide electroreduction due to their unique catalytic performance and product selectivity. Copper-based materials have a moderate CO* intermediate adsorption energy and a unique C-C coupling ability, and are the most potential catalyst types in the CO2RR catalyst system. Copper is the key active center for methane formation in the carbon dioxide electroreduction reaction. The crystal plane orientation of copper-based catalysts has a significant impact on their electrocatalytic activity. The Cu(111) crystal plane has been confirmed to be one of the active sites for carbon dioxide to methane on Cu. Xiao et al. used commercial copper foil as the main body and carried out potentiostatic etching in an acidic electrolyte to obtain the active site Cu(111) crystal plane, which can achieve highly active electrocatalytic CO2 reduction to prepare methane with high selectivity. (Xiao Rui, Xu Weicong, Liu Chao, etc. Etched copper catalyst for electroreduction of CO2 to methane and its preparation and application: CN115216792A[P]. 2022-10-21.)

[0004] Regarding the problem of unsatisfactory selectivity and stability in the traditional potentiostatic mode, the introduction of pulse electrocatalysis technology can significantly improve the intrinsic activity of carbon dioxide electrocatalysis. (Mao Qing, Zhou Wei, Gao Yanfei. Preparation method of a crystal plane controllable Ag nanofunctional coating for CO2 electroreduction reaction: CN118461037A[P]. 2024-08-09) The application of pulse technology in copper-based materials for carbon dioxide electrocatalysis has been one of the research hotspots in the field of electrocatalysis in recent years. Cu nanomaterials can undergo dynamic evolution under the action of pulses. By periodically applying pulsed voltage or current, the surface state, reaction path, and product selectivity of copper-based catalysts can be effectively regulated, the passivation of the electrode surface can be alleviated, the adsorption behavior of intermediate products can be optimized, side reactions can be inhibited, and thus the efficiency and stability of carbon dioxide reduction can be improved. (Xi W, Zhou H, Yang P, et al. Pulse Manipulationon Cu-Based Catalysts for Electrochemical Reduction of CO2[J]. ACS Catalysis, 2024, 14(18): 13697-13722.) By precisely regulating the step potential, the surface oxidation state and crystal plane configuration of the material can be effectively regulated, and the copper catalyst can be highly selectively directed to certain desired products. Li et al. reported a strategy for the directional conversion of carbon dioxide electroreduction products by regulating the surface structure of copper-based catalysts through cathodic corrosion. (Li G, Liu H, YangH, et al. Tuning product distributions of CO2electroreduction over copper foilthrough cathodic corrosion[J]. Chemical Engineering Science, 2022, 263: 118142.) Using the electrochemical corrosion method, ultrafine Cu nanoparticles (particle size 50±8nm) mainly with (111) crystal planes were generated on the surface of two-dimensional copper foil, and the Faraday efficiency of methane (CH4) reached 69.6% (-1.2V vs RHE), which was attributed to the stable adsorption of the *COOH intermediate by the close-packed structure of the Cu(111) crystal plane and the reduction of the C-O bond dissociation energy barrier.

[0005] In summary, for the Cu-based electrode materials disclosed in the prior art, the selectivity of methane is not ideal, and the low carbon dioxide adsorption of copper foil is also not conducive to the progress of the catalytic reaction. In this experiment, a Cu foil-supported nano-Cu2O electrode was constructed, and the selection of the Cu(111) crystal plane configuration was achieved through pulse reduction. At the same time, by adjusting the pulse potential and reduction time, the selectivity of methane was significantly improved, providing a new design idea for the development of an efficient and stable carbon dioxide electrocatalytic reduction catalyst system. Summary of the Invention

[0006] The present invention aims to provide a preparation method of a Cu foil supported nano-Cu2O electrode and its application in pulsed carbon dioxide electrocatalytic reduction. The present invention provides a preparation method of a Cu foil supported nano-Cu2O electrode, which has a simple preparation process and controllable operating conditions. When it is used in pulsed carbon dioxide electroreduction experiments, high methane selectivity can be achieved in carbon dioxide electroreduction by regulating the pulsed potential and pulsed time.

[0007] The present invention provides the following technical solutions:

[0008] A preparation method of a Cu foil supported nano-Cu2O electrode comprises the following steps:

[0009] Step (1) Preparation of Cu2O nanoparticles:

[0010] In constant-temperature deionized water, copper chloride solution, sodium hydroxide solution and ascorbic acid solution are sequentially added dropwise for a reduction reaction; after the reaction is complete, solid product particles are obtained by centrifuging alternately with absolute ethanol and deionized water; water-soluble impurities are removed by suction filtration and vacuum drying is carried out to obtain Cu2O nanoparticle powder.

[0011] Step (2) Preparation and loading of the Cu2O nano-coating:

[0012] Ethanol, deionized water, compounded alkaline resin Aemion+ TM and acetone are ultrasonically mixed evenly to obtain a mixed solution; then the Cu2O nanoparticle powder obtained in step (1) is added to the mixed solution and ultrasonically mixed to obtain a catalyst slurry; it is loaded on the copper foil by brushing, and the loading amount is 1-5 mg·cm -2 to obtain a Cu foil supported nano-Cu2O electrode.

[0013] Further, in step (1), the volume ratio of deionized water to the subsequent added copper chloride solution, sodium hydroxide solution and ascorbic acid solution is greater than 7:1 to ensure the dispersion of the materials. The molar concentration ratio of the copper chloride solution, sodium hydroxide solution and reducing agent solution is 1:2:1, and the volume ratio of the added amounts is 1:3:2.

[0014] Further, in step (1), the reduction time ranges from 0.5 to 3 h.

[0015] Further, in step (2), in the mixed solution, the mass ratio of ethanol, deionized water, compounded alkaline resin Aemion+ TM , acetone is 240:240:1:15, and the mass ratio of the mixed solution to the Cu2O nanoparticles is 100:1.

[0016] The Cu foil-supported nano-Cu2O electrode prepared by the above preparation method is applied to pulsed carbon dioxide electrocatalytic reduction to convert CO2 into CH4, specifically as follows: The reduction reaction is carried out in an H-type electrolytic cell, and the test system is a three-electrode system, where the counter electrode is a platinum sheet electrode, the reference electrode is a saturated calomel electrode, and the Cu foil-supported nano-Cu2O electrode is the working electrode; 0.5 mol·L -1 of potassium bicarbonate solution is used as the electrolyte. Before the reaction, carbon dioxide gas is introduced to saturate the solution; circulating water is used to maintain a constant temperature, and the temperature is set to 0-25 °C; then the anodic potential and cathodic potential are alternately applied, and the pulse time is controlled to generate CH4.

[0017] Furthermore, the anodic potential range is 0-1 V (vs. RHE), and the cathodic potential range is -1 to -1.3 V (vs. RHE).

[0018] Furthermore, the range of the time ratio of alternately applying the potential is 3:7 to 7:3. The preferred pulse period for each cycle is 10 s.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] (1) The synthesis process of the Cu foil-supported nano-Cu2O electrode prepared by this method is simple, easy to operate, suitable for large-scale industrial production, and the design of the coating has a wide application range.

[0021] (2) The Cu foil-supported nano-Cu2O electrode prepared by this method has high selectivity and high partial current density for methane. In the H-type electrolytic cell test, a Cu2O nanoparticle coating was constructed on the surface of a commercial copper foil substrate. When the catalyst was at -1.15 V vs. RHE, the Faraday efficiency of methane reached 92%, and at this time, the partial current density of methane was 111 mA·cm -2 , and the stable operation time exceeded 110 hours without obvious attenuation, and the selectivity was significantly improved compared with 82% of the unmodified copper electrode. Brief Description of the Drawings

[0022] Figure 1 is the SEM picture of the Cu2O nanoparticle catalyst with different reduction times in Example 1 of the present invention.

[0023] Figure 2 is the TEM picture of the Cu2O nanoparticle catalyst corresponding to the reduction time of 1 h in Example 1 of the present invention.

[0024] Figure 3 is the TEM picture of the crystal phase of the Cu2O nanoparticle catalyst corresponding to the reduction time of 1 h in Example 1 of the present invention after being pulsed.

[0025] Figure 4It is the Faraday efficiency diagram of the copper foil and the copper foil-supported nano-Cu2O electrode of the present invention at -1.0 to -1.3 V (vs. RHE).

[0026] Figure 5 It is the Faraday efficiency diagram of the copper foil-supported nano-Cu2O electrode in Example 1 of the present invention at different anodic potentials of +0.17 V or +0.47 V or +0.78 V or +0.88 V or +0.98 V at a cathodic potential of -0.5 to -1.0 V (vs. RHE).

[0027] Figure 6 It is the partial current density diagram of methane of the copper foil-supported nano-Cu2O electrode in Example 1 of the present invention at different anodic potentials of +0.17 V or +0.47 V or +0.78 V or +0.88 V or +0.98 V at a cathodic potential of -0.5 to -1.0 V (vs. RHE).

[0028] Figure 7 It is the stability test diagram of 110 hours of the copper foil-supported nano-Cu2O electrode in Example 1 of the present invention at an anodic potential of +0.78 V.

[0029] Figure 8 It is the methane Faraday efficiency diagram of the copper foil-supported nano-Cu2O electrode in Example 1 of the present invention at different ratios of the applied time of the pulsed anodic potential to the cathodic potential. Detailed implementation mode

[0030] To further illustrate the present invention, the preparation method of the copper foil-supported nano-Cu2O electrode provided by the present invention and its application in pulsed carbon dioxide electrocatalytic reduction are described in detail below in conjunction with embodiments.

[0031] Example 1: Preparation of Cu foil-supported nano-Cu2O electrode

[0032] (1) Preparation of Cu2O nanoparticles: Bath in deionized water at a constant temperature of 15 - 25 °C, ensuring that the volume ratio of deionized water to the volume of the subsequent added solution is greater than 7:1. The concentration ratio of the copper chloride solution, sodium hydroxide solution, and ascorbic acid solution is 1:2:1, and the volume ratio of the added amounts is 1:3:2. Reduce for 0.5 h, 1 h, and 3 h respectively. Centrifuge three times alternately with absolute ethanol and deionized water, and filter to wash away water-soluble impurities, and vacuum dry at 60 °C for 12 h to obtain Cu2O powder. The SEM images of Cu2O nanoparticles with different reduction times are as Figure 1 shown. For 0.5 h, the corresponding particles are not completely nucleated. For 1 h, the corresponding particles are in a uniform cubic morphology. For 3 h, the corresponding particles show an agglomeration phenomenon. Therefore, the Cu2O nano-cubic particles synthesized at a reduction time of 1 h are preferably selected for subsequent loading tests, and their morphology on TEM is as Figure 2 shown.

[0033] (2) Preparation and loading of the Cu2O nanocoating: Ethanol, deionized water, the compounded alkaline resin Aemion+ TM , and acetone were mixed in a test tube according to the mass ratio of 240:240:1:15 and mixed evenly by ultrasonic. Finally, the Cu2O powder was mixed with the above solution at a mass ratio of 1:100, and the catalyst slurry was obtained after ultrasonic mixing. The copper foil substrate was fixed on a constant-temperature heating table, and the heating table was maintained at a constant temperature of 60 °C. The coating stock solution was brush-coated on the surface of the copper foil substrate, brush-coated on both sides, and three sets of loading amounts were made, which were 1, 3, and 5 mg·cm -2 , and Cu foil-supported nano-Cu2O electrodes with three different loading amounts were obtained.

[0034] The electrodes prepared by the above method and the pure copper foil were tested for pulsed carbon dioxide electroreduction, and the test results are as follows.

[0035] Example 2: Influence of copper foil electrodes and Cu foil-supported nano-Cu2O electrodes on the electrocatalytic reduction activity of pulsed carbon dioxide

[0036] A copper foil with a purity of 99.99% and a thickness of 0.2 mm was used as the substrate material, and the catalytic performance of pulsed carbon dioxide electroreduction reaction was tested using the copper foil and the Cu foil-supported nano-Cu2O electrode obtained in Example 1, respectively.

[0037] Pulsed carbon dioxide electroreduction test: The tests involved in this experiment were carried out in an H-type electrolytic cell. The test system was a three-electrode system, in which the counter electrode was a platinum sheet electrode, the reference electrode was a saturated calomel electrode, and the copper foil and the Cu foil-supported nano-Cu2O electrode obtained in Example 1 were used as the working electrodes. A 0.5 mol·L -1 potassium bicarbonate solution was used as the electrolyte. Before the test, carbon dioxide gas was introduced to saturate the solution. The constant temperature was maintained using circulating water, and the temperature was set to 0 - 25 °C. The cathodic potential range during the test was -1 to -1.3 V (vs. RHE). Under the condition that the pulsed anodic potential was +0.78 V, the pulsed carbon dioxide electroreduction test was carried out, and the gas products were introduced into a gas chromatograph for detection.

[0038] Results of the pulsed carbon dioxide electroreduction test: The selectivity distribution of the products is as Figure 4 shown. When the Cu foil electrode was at -1.15 V vs. RHE, the Faraday efficiency of methane reached 82%. When the Cu foil-supported nano-Cu2O electrode was at -1.15 V vs. RHE, the Faraday efficiency of methane reached 92%, and the partial current density of methane was 111 mA·cm -2 , with a stability of 110 hours. The stability test is as Figure 7As shown. The Cu(111) crystal plane configuration appeared after the pulse, and the results are as Figure 3 shown.

[0039] Example 3: Influence of Pulse Anodic Potential on the Electrocatalytic Reduction Activity of Pulse Carbon Dioxide

[0040] The catalytic performance test of the Cu foil-supported nano-Cu2O electrode prepared in Example 1 of the present invention was carried out for the pulse carbon dioxide electroreduction reaction at different anodic potentials.

[0041] Pulse carbon dioxide electroreduction test: The test involved in this experiment was carried out in an H-type electrolytic cell. The test system was a three-electrode system, in which the counter electrode was a platinum sheet electrode, the reference electrode was a saturated calomel electrode, and the working electrode was the Cu foil-supported nano-Cu2O electrode obtained in Example 1 of the present invention. Using 0.5 mol·L -1 of potassium bicarbonate solution as the electrolyte, carbon dioxide gas was introduced to saturate the solution before the test. The constant temperature was maintained using circulating water, and the temperature was set to 0 - 25 °C. The cathodic potential range during the test was -1 to -1.3 V (vs. RHE). Pulse carbon dioxide electroreduction tests were carried out at pulse anodic potentials of +0.17 V, +0.47 V, +0.78 V, +0.88 V, and +0.98 V respectively. The pulse anodic potential time was set to 5 s, and the gas products were introduced into a gas chromatograph for detection.

[0042] Results of the pulse carbon dioxide electroreduction test: The selectivity distribution of the products is as Figure 5 shown, and the partial current density curve of methane is as Figure 6 shown. At a pulse anodic potential of +0.17 V, at -1.15 V vs. RHE, the Faraday efficiency of methane reached 73%, and the partial current density of methane was 86 mA·cm -2 ; at a pulse anodic potential of +0.47 V, at -1.15 V vs. RHE, the Faraday efficiency of methane reached 87%, and the partial current density of methane was 104 mA·cm -2 ; at a pulse anodic potential of +0.78 V, at -1.15 V vs. RHE, the Faraday efficiency of methane reached 92%, and the partial current density of methane was 111 mA·cm -2 ; at a pulse anodic potential of +0.88 V, at -1.15 V vs. RHE, the Faraday efficiency of methane reached 89%, and the partial current density of methane was 94 mA·cm -2 ; at a pulse anodic potential of +0.98 V, at -1.08 V vs. RHE, the Faraday efficiency of methane reached 87%, and the partial current density of methane was 98 mA·cm-2 Among them, under the condition that the pulsed anode potential is +0.78V, the selectivity of methane is the best. Taking this potential as the preferred potential, the following pulsed reduction time tests are carried out.

[0043] Example 4: Influence of Pulse Time on the Electrocatalytic Reduction Activity of Pulsed Carbon Dioxide

[0044] The catalytic performance test of the pulsed carbon dioxide electroreduction reaction was carried out on the Cu foil supported nano-Cu2O electrode prepared in Example 1 of the present invention under different pulsed potential application ratios.

[0045] Pulsed carbon dioxide electroreduction test: The test involved in this experiment was carried out in an H-type electrolytic cell. The test system was a three-electrode system, in which the counter electrode was a platinum sheet electrode, the reference electrode was a saturated calomel electrode, and the working electrode was the Cu foil supported nano-Cu2O electrode obtained in Example 1 of the present invention. 0.5mol·L -1 of potassium bicarbonate solution was used as the electrolyte. Before the test, carbon dioxide gas was introduced to saturate the solution. Circulating water was used to maintain a constant temperature, and the temperature was set to 0-25°C. The cathode potential range during the test was -1 to -1.3V (vs. RHE). Under the condition that the pulsed anode potential was +0.78V, the pulsed carbon dioxide electroreduction test was carried out under the conditions that the application time ratio of the pulsed anode potential to the cathode potential was 3:7, 1:1, and 7:3 respectively. The gas products were introduced into a gas chromatograph for detection.

[0046] Results of the pulsed carbon dioxide electroreduction test: The selectivity distribution of the products is as Figure 8 shown. Under the condition that the application time ratio of the pulsed anode potential to the cathode potential was 3:7, at -1.23V vs. RHE, the Faraday efficiency of methane reached 83%; under the condition that the application time ratio of the pulsed anode potential to the cathode potential was 1:1, at -1.15V vs. RHE, the Faraday efficiency of methane reached 92%; under the condition that the application time ratio of the pulsed anode potential to the cathode potential was 7:3, at -1.15V vs. RHE, the Faraday efficiency of methane reached 88%. Among them, under the condition that the application time ratio of the pulsed anode potential to the cathode potential was 1:1, the selectivity of methane was the best.

Claims

1. A method for preparing a Cu foil-loaded nano-Cu2O electrode, characterized in that: Here are the steps: Step (1) Preparation of Cu2O nanoparticles: In constant temperature deionized water, copper chloride solution, sodium hydroxide solution and ascorbic acid solution are sequentially added dropwise to carry out reduction reaction; after the reaction is complete, anhydrous ethanol and deionized water are alternately centrifuged to obtain solid product particles; water-soluble impurities are washed by suction filtration, and vacuum drying is performed to obtain Cu2O nanoparticle powder; Step (2) Preparation and loading of Cu2O nano-coating: Ethanol, deionized water, and compound alkaline resin Aemion+ TM and acetone to obtain a mixed solution; then, the Cu2O nanoparticle powder obtained in step (1) is added to the mixed solution, and the catalyst slurry is obtained by ultrasonic mixing; and the catalyst slurry is loaded on the copper foil by brush coating, with a loading of 1 to 5 mg cm -2 , and obtain the Cu foil loaded nano-Cu2O electrode.

2. The method for preparing a Cu foil-loaded nano-Cu2O electrode according to claim 1, characterized in that: In the step (1), the volume ratio of deionized water to the subsequently added copper chloride solution, sodium hydroxide solution and ascorbic acid solution is greater than 7:1; the molar concentration ratio of the copper chloride solution, sodium hydroxide solution and reducing agent solution is 1:2:1, and the added volume ratio is 1:3:

2.

3. The method for preparing a Cu foil-loaded nano-Cu2O electrode according to claim 1, characterized in that: In the step (1), the reduction time ranges from 0.5 to 3 hours.

4. The method for preparing a Cu foil-loaded nano-Cu2O electrode according to claim 1, characterized in that: In the step (2), in the mixed solution, ethanol, deionized water, and the composite alkaline resin Aemion+ TM The mass ratio of acetone is 240:240:1:15, and the mass ratio of the mixed solution to Cu2O nanoparticles is 100:

1.

5. The Cu foil-loaded nano-Cu2O electrode prepared by the preparation method according to any one of claims 1 to 4 is used in pulse carbon dioxide electrocatalytic reduction to convert CO2 into CH4.

6. The use according to claim 5, characterized in that: The details are as follows: the reduction reaction was carried out in an H-type electrolytic cell, and the test system was a three-electrode system, in which the counter electrode was a platinum electrode, the reference electrode was a saturated calomel electrode, and the Cu foil-loaded nano-Cu2O electrode was the working electrode; 0.5 mol·L -1 Potassium bicarbonate solution is used as the electrolyte. Carbon dioxide gas is introduced to saturate the solution before the reaction. Circulating water is used to maintain a constant temperature of 0-25°C. Then, the anode potential and the cathode potential are applied alternately, and the pulse time is controlled to generate CH4.

7. The use according to claim 5, characterized in that: The anode potential range is 0 to 1 V (vs. RHE), and the cathode potential range is -1 to -1.3 V (vs. RHE).

8. The use according to claim 5, characterized in that: The ratio of the time of the alternating potential application is in the range of 3:7 to 7:

3.

9. The use according to claim 5, characterized in that: The pulse period of each cycle is 10s.

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