A CO₂ electrocatalytic material with an optimized interface by a reducing atmosphere, its preparation method and application

Abstract

The present invention discloses a carbon dioxide electrocatalytic material with an optimized interface by a reducing atmosphere, its preparation method and application. The preparation method of the electrocatalytic material is as follows: during the hydrothermal synthesis of cuprous oxide, the flow rate of the introduced reducing atmosphere (one or more of CO, H₂, and NH₃ gases) is regulated to obtain a copper-based electrocatalytic material with an optimized interface. The copper-based electrocatalyst with an optimized interface by the reducing atmosphere provided by the present invention exhibits excellent performance in the selectivity of electrocatalytically converting CO₂ to C₂H₄, can inhibit the C₁ pathway and HER of CO₂RR, and is beneficial to the production of C₂⁺ products, while improving the selectivity and Faraday efficiency of C₂H₄.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalyst preparation, and particularly relates to a carbon dioxide electrocatalytic material for optimizing an interface through a reducing atmosphere, a preparation method thereof, and an application thereof. Background Art

[0002] The utilization of carbon dioxide helps to complete the anthropogenic carbon cycle. Electrochemical reduction is a promising strategy that uses renewable electricity to convert CO2 into fuels and value-added raw materials. Among these products, C 2+ Hydrocarbons and oxides, such as high-value-added chemicals or fuels like ethylene (C2H4), ethanol (EtOH), and n-propanol (n-PrOH), can not only "turn waste into treasure" but also mitigate the greenhouse effect caused by carbon emissions. The research on the electrochemical reduction of CO2 is a current research hotspot worldwide, which conforms to the theory of human sustainable development and has important practical significance. However, it is still challenging to catalytically form these multi-carbon compounds with high selectivity through the carbon dioxide reduction reaction (CO2RR); the relatively low Faradaic efficiencies (FEs) and C 2+ The high overpotentials in production still keep the electroreduction of CO2 far from practical application technologies; the multi-step nature of the reaction and multiple competitive pathways make it a challenging problem to design catalysts for the desired C 2+ products.

[0003] So far, copper-based materials are the most effective in the electrocatalytic conversion of CO2 into C 2+ Hydrocarbons and oxides. Using materials chemistry to control the copper surface, aiming to guide the binding of intermediates in each reaction step, provides a way to further improve the selectivity for the desired multi-carbon products. Among them, the focus of improving the FEC2H4 of copper-based catalysts is to optimize the size, morphology, and exposed crystal planes of metal CuNPs. The reconstructed Cu surface caused by the electrochemical reduction of the original Cu2O is beneficial to C-C coupling to C 2+ products and inhibits the competitive hydrogen evolution reaction (HER) during CO2RR. Therefore, Cu2O NPs are more effective than metal Cu NPs in producing highly selective C2H4. The research on Cu2O NPs shows that NPs with different crystal planes exhibit different stabilities and different catalytic activities. However, cuprous oxide cannot well complete the growth of the desired crystal planes during the synthesis process.

[0004] Therefore, an invention is made for optimizing the interface of cuprous oxide, which can effectively improve C 2+A novel method for preparing an electrocatalytic material for the selectivity and conversion rate of products. Through a reducing atmosphere, the present invention increases the density of active sites, optimizes the exposed crystal planes, increases the surface roughness, promotes the electron transfer rate, and reduces the formation barrier of key intermediates, greatly improving the activity and selectivity of the catalyst. Summary of the Invention

[0005] The object of the present invention is to propose an electrocatalytic material for carbon dioxide with an optimized interface through a reducing atmosphere, its preparation method and application, aiming at the technical problems of low catalytic activity, high potential, poor Faraday efficiency and low current efficiency of existing copper-based catalysts.

[0006] To solve the above technical problems, the technical solutions adopted by the present invention are as follows:

[0007] The preparation method of an electrocatalytic material for carbon dioxide with an optimized interface through a reducing atmosphere is as follows: During the hydrothermal synthesis of cuprous oxide, the flow rate of a mixed gas containing a reducing atmosphere (one or more of CO, H2, and NH3 gases) is regulated to obtain a copper-based electrocatalytic material with an optimized interface.

[0008] The preparation method of an electrocatalytic material for carbon dioxide with an optimized interface through a reducing atmosphere specifically includes the following steps: Prepare an aqueous solution of divalent copper salt, and while continuously introducing a reducing gas into it, then dropwise add a sodium hydroxide solution into it, heat it in a water bath and continuously stir for a certain time, and then dropwise add an ascorbic acid solution into it, heat it in a water bath and continuously stir for a certain time, and after centrifugal separation, wash it with water and alcohol several times to obtain a copper-based electrocatalytic material with an optimized interface.

[0009] Further, the reducing gas is one or more of CO, H2, and NH3, nitrogen is used as the diluent gas of the mixed gas, and the volume fraction of the reducing gas in the mixed gas is 5-15%.

[0010] Further, the concentration of the aqueous solution of divalent copper salt is 0.001-0.1 mol / L, preferably 0.005-0.01 mol / L; based on the volume of the aqueous solution of divalent copper salt being 100 ml, the flow rate of the introduced reducing gas is 0.2-2 mL / min, preferably 0.4-0.6 mL / min.

[0011] Further, the concentration of the sodium hydroxide solution is 1-3 mol / L, the dropping rate is 1-5 mL / min, the molar ratio of sodium hydroxide to divalent copper salt in the feed is 10-30:1, preferably 20:1, the stirring time after dropping is 0.5-3 h, and the hydrothermal temperature is 40-60 °C.

[0012] Further, the concentration of the ascorbic acid solution is 0.2 - 1 mol / L, the dropping rate is 1 - 5 mL / min, the molar ratio of ascorbic acid to divalent copper salt in the feed is 4 - 8:1, preferably 6:1, then the stirring time is 0.5 - 3 h, and the hydrothermal temperature is 40 - 60°C.

[0013] Further, the number of water washing times is 1 - 3 times, and the number of alcohol washing times is 1 - 3 times. The alcohol is one or more of ethanol, methanol, and isopropanol.

[0014] The carbon dioxide electrocatalytic material that optimizes the interface through a reducing atmosphere provided by the present invention can be well applied to electrocatalytically convert CO2 into C 2+ in the product. The application method is as follows: The carbon dioxide electrocatalytic material is coated on carbon paper as the working electrode, nickel foam is used as the anode, a saturated Ag / AgCl electrode is used as the reference electrode, and a 0.1 - 1 mol / L KHCO3 aqueous solution is used as the electrolyte. The electrolyte is aerated with CO2 to make it saturated, and the reaction is carried out in a gas diffusion electrode GDE of a three - electrode system. The cathode and anode electrolytes are separated by an anion - exchange membrane, and the cathode and anode electrolytes flow in and out continuously, and the electrolytic reaction converts CO2 into C 2+ in the product.

[0015] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: The present invention proposes a carbon dioxide electrocatalytic material that optimizes the interface through a reducing atmosphere, which can inhibit the C1 pathway and HER of CO2RR, and is beneficial to the formation of C 2+ in the product. At the same time, it improves the selectivity and Faraday efficiency of C2H4. The experimental results show that the CO2 electrocatalytic reduction material prepared by the present invention can be stably tested for 2 h, and the Faraday efficiency of CO2 reduction to C2H4 reaches about 35.8%. The Faraday efficiency of the optimized material for reducing C2H4 is about 11.8% higher than that of pure cuprous oxide. Description of the Drawings

[0016] Figure 1a It is the SEM scanning electron microscope image of the electrocatalytic material sample prepared in the control example.

[0017] Figure 1b It is the SEM scanning electron microscope image of the electrocatalytic material sample prepared in Example 1.

[0018] Figure 2 It is the comparison result of the XRD diagrams of the electrocatalytic material samples prepared in the control example and Example 1. Detailed Embodiments

[0019] The following further illustrates the present invention with specific embodiments, but the protection scope of the present invention is not limited thereto.

[0020] Control Example

[0021] The control example is pure cuprous oxide. Weigh 171.5 mg of copper chloride dihydrate and prepare it into a 100 mL 0.01 mol / L copper chloride solution, and heat it in a 55 °C water bath with continuous stirring. Weigh 8.0 g of sodium hydroxide and prepare it into a 100 mL 2.0 mol / L aqueous sodium hydroxide solution. Take 10 ml and slowly add it drop by drop to the above solution at a dropping rate of 3 mL / min. After continuously stirring for 0.5 h, weigh 10.56 g of ascorbic acid and prepare it into a 100 mL 0.6 mol / L solution. Take 10 ml and slowly add it drop by drop to the above solution at a dropping rate of 3 mL / min, and then continue to stir and reduce it in a 55 °C water bath for 3 h. After centrifugally washing it 3 times with distilled water and 3 times with ethanol, a dark red precipitate is obtained, and it is dried in a vacuum drying oven at 55 °C for 5 h to obtain the electrocatalytic material.

[0022] The material prepared in the control example was analyzed by SEM. As Figure 1a shown, the cuprous oxide has a uniform cubic structure, a smooth surface, and a particle size of about 1 μm. Then, the sample was analyzed by XRD. As Figure 2 can be seen, the diffraction peaks of the prepared product correspond to the standard diffraction peaks of cuprous oxide, and no impurity peaks of other products are found.

[0023] The electrocatalytic performance of the material prepared in the control example was tested as follows:

[0024] Weigh 10 mg of the electrocatalytic material and put it into a vial, add 960 uL of isopropanol and 40 uL of nafion solution (5%wt) and mix them, and ultrasonicate for 2 hours until the catalyst is completely dispersed to obtain a uniform catalyst ink.

[0025] Take 300 uL of the prepared catalyst ink and evenly coat it on a 1 cm * 3 cm carbon paper. After drying, it is used as the working electrode, with a nickel foam as the anode and a saturated Ag / AgCl electrode as the reference electrode. The catalytic performance test was carried out using a CS2350H electrochemical workstation from Wuhan Koster in a gas diffusion electrode (GDE) of a three-electrode system. The electrolyte continuously flows in and out, and the cathode and anode electrolytes are separated by an anion exchange membrane. The flow rate of the cathode solution is 2 ml / min, and the flow rate of the anode solution is 5 ml / min. The electrolyte is a 0.5 mol / L aqueous KHCO3 solution, and the electrolyte is saturated with CO2 by aeration before the test. The electrochemical workstation was polarized at a potential of -1.84 V (vs Ag / AgCl) and the products were detected. The total current density of the electrocatalytic performance is 130 mA, the Faraday efficiency of ethylene is 24%, and the partial current density is 31.2 mA; C 2+The product Faraday efficiency is 38.4%, the partial current density is 49.9 mA, and it can be stably tested for 2 h.

[0026] Example 1

[0027] Weigh 171.5 mg of copper chloride dihydrate and prepare a 100 mL 0.01 mol / L copper chloride solution. Heat it in a water bath at 55 °C with continuous stirring and introduce a CO-N2 mixed gas (CO volume fraction 10%) with a flow rate of 3 mL / min. Weigh 8.0 g of sodium hydroxide and prepare a 100 mL 2.0 mol / L sodium hydroxide aqueous solution. Take 10 ml and slowly add it drop by drop to the above solution at a dropping rate of 3 mL / min. After continuous stirring for 0.5 h, weigh 10.56 g of ascorbic acid and prepare a 100 mL 0.6 mol / L solution. Take 10 ml and slowly add it drop by drop to the above solution at a dropping rate of 3 mL / min. Then continue to stir and reduce it in a water bath at 55 °C for 3 h. The dark red precipitate obtained after centrifugal washing 3 times with distilled water and 3 times with ethanol is dried in a vacuum drying oven at 55 °C for 5 h to obtain the electrocatalytic material.

[0028] The material prepared in the control example was analyzed by SEM. As Figure 1b shown, the cuprous oxide has a uniform cubic structure, a smooth surface, and a particle size of about 1 μm. Then the sample was analyzed by XRD. As Figure 2 can be seen, the diffraction peaks of the prepared product correspond to the standard diffraction peaks of cuprous oxide, and no impurity peaks of other products were found.

[0029] The electrocatalytic performance of the material prepared in Example 1 was tested as follows:

[0030] Weigh 10 mg of the electrocatalytic material and put it into a vial. Add 960 uL of isopropanol and 40 uL of nafion solution (5%wt) and mix them. Ultrasonic for 2 hours until the catalyst is completely dispersed to obtain a uniform catalyst ink.

[0031] Take 300 μL of the catalyst ink with the above configuration, evenly apply it on a 1 cm * 3 cm carbon paper, and use it as the working electrode after drying. Use nickel foam as the anode and a saturated Ag / AgCl electrode as the reference electrode. The catalytic performance test was carried out using a CS2350H electrochemical workstation from Wuhan Koster in a gas diffusion electrode (GDE) of a three-electrode system. The electrolyte flows continuously in and out. The cathode and anode electrolytes are separated by an anion exchange membrane. The flow rate of the cathode solution is 2 ml / min, and the flow rate of the anode solution is 5 ml / min. The electrolyte is a 0.5 mol / L KHCO3 aqueous solution. Before the test, the electrolyte is saturated by CO2 aeration. The electrochemical workstation is polarized at a potential of -1.84 V (vs Ag / AgCl) and the products are detected. The total current density of the electrocatalytic performance is 200 mA, the Faraday efficiency of ethylene is 26.7%, and the partial current density is 53.4 mA; C 2+ The Faraday efficiency of the product is 47.6%, and the partial current density is 95.2 mA, and it can be stably tested for 2 h.

[0032] Example 2

[0033] Weigh 171.5 mg of copper chloride dihydrate and prepare a 100 mL 0.01 mol / L copper chloride solution. Heat it in a water bath at 55 °C with continuous stirring and introduce a CO-N2 mixed gas (CO volume fraction 10%) with a flow rate of 4 mL / min. Weigh 8.0 g of sodium hydroxide and prepare a 100 mL 2.0 mol / L sodium hydroxide aqueous solution. Take 10 ml and slowly drop it into the above solution drop by drop at a dropping rate of 3 mL / min. After continuously stirring for 0.5 h, weigh 10.56 g of ascorbic acid and prepare a 100 mL 0.6 mol / L solution. Take 10 ml and slowly drop it into the above solution drop by drop at a dropping rate of 3 mL / min, and then continue to stir and reduce it in a water bath at 55 °C for 3 h. After centrifugally washing 3 times with distilled water and 3 times with ethanol, the obtained dark red precipitate is dried in a vacuum drying oven at 55 °C for 5 h to obtain the electrocatalytic material.

[0034] The electrocatalytic performance test of the material prepared in Example 2 is as follows:

[0035] Weigh 10 mg of the electrocatalytic material and put it into a vial, add 960 μL of isopropanol and 40 μL of nafion solution (5%wt), and ultrasonicate for 2 hours until the catalyst is completely dispersed to obtain a uniform catalyst ink.

[0036] Take 300 μL of the catalyst ink with the above configuration, smear it evenly on a 1 cm * 3 cm carbon paper, and use it as the working electrode after drying. Use nickel foam as the anode and a saturated Ag / AgCl electrode as the reference electrode. The catalytic performance test was carried out using a CS2350H electrochemical workstation from Wuhan Koster in a gas diffusion electrode (GDE) of a three-electrode system. The electrolyte flows in and out continuously. The cathode and anode electrolytes are separated by an anion exchange membrane. The flow rate of the cathode liquid is 2 ml / min, and the flow rate of the anode liquid is 5 ml / min. The electrolyte is a 0.5 mol / L KHCO3 aqueous solution. Before the test, the electrolyte was aerated with CO2 to make it saturated. The electrochemical workstation was polarized at a potential of -1.84 V (vs Ag / AgCl) and the products were detected. The total current density of the electrocatalytic performance was 160 mA, the Faraday efficiency of ethylene was 35.8%, and the partial current density was 57.28 mA; C 2+ The Faraday efficiency of the C product was 56.1%, and the partial current density was 89.76 mA, and the test could be stably carried out for 2 h.

[0037] Example 3

[0038] Weigh 171.5 mg of copper chloride dihydrate and prepare a 100 mL 0.01 mol / L copper chloride solution. Heat it in a water bath at 55 °C with continuous stirring, and introduce a CO-N2 mixed gas (CO volume fraction 10%) with a flow rate of 5 mL / min. Weigh 8.0 g of sodium hydroxide and prepare a 100 mL 2.0 mol / L sodium hydroxide aqueous solution. Take 10 ml and slowly add it drop by drop to the above solution at a dropping rate of 3 mL / min. After continuous stirring for 0.5 h, weigh 10.56 g of ascorbic acid and prepare a 100 mL 0.6 mol / L solution. Take 10 ml and slowly add it drop by drop to the above solution at a dropping rate of 3 mL / min, and then continue to stir and reduce it in a water bath at 55 °C for 3 h. The dark red precipitate obtained after centrifugal washing 3 times with distilled water and 3 times with ethanol was dried in a vacuum drying oven at 55 °C for 5 h to obtain the electrocatalytic material.

[0039] The electrocatalytic performance test of the material prepared in Example 3 is as follows:

[0040] Weigh 10 mg of the electrocatalytic material and put it into a vial, add 960 μL of isopropanol and 40 μL of nafion solution (5%wt), and ultrasonicate for 2 hours until the catalyst is completely dispersed to obtain a uniform catalyst ink.

[0041] Take 300 μL of the catalyst ink with the above configuration, smear it evenly on a 1 cm × 3 cm carbon paper, and dry it to be used as the working electrode. Use nickel foam as the anode and a saturated Ag / AgCl electrode as the reference electrode. The catalytic performance test is carried out using a CS2350H electrochemical workstation from Wuhan Koster in a gas diffusion electrode (GDE) of a three-electrode system. The electrolyte flows in and out continuously. The cathode and anode electrolytes are separated by an anion exchange membrane. The flow rate of the cathode liquid is 2 ml / min, and the flow rate of the anode liquid is 5 ml / min. The electrolyte is a 0.5 mol / L KHCO3 aqueous solution. Before the test, the electrolyte is aerated with CO2 to make it saturated. The electrochemical workstation is polarized at a potential of -1.84 V (vs Ag / AgCl) and the products are detected. The total current density of the electrocatalytic performance is 140 mA, the Faraday efficiency of ethylene is 30.8%, and the partial current density is 43.12 mA; C 2+ The Faraday efficiency of the C product is 53.7%, and the partial current density is 75.18 mA, and it can be stably tested for 2 h.

[0042] Example 4

[0043] Weigh 171.5 mg of copper chloride dihydrate and prepare a 100 mL 0.01 mol / L copper chloride solution. Heat it in a 55 °C water bath with continuous stirring and introduce a CO-N2 mixed gas (CO volume fraction 10%) with a flow rate of 6 mL / min. Weigh 8.0 g of sodium hydroxide and prepare a 100 mL 2.0 mol / L sodium hydroxide aqueous solution. Take 10 ml and slowly add it drop by drop to the above solution at a dropping rate of 3 mL / min. After continuously stirring for 0.5 h, weigh 10.56 g of ascorbic acid and prepare a 100 mL 0.6 mol / L solution. Take 10 ml and slowly add it drop by drop to the above solution at a dropping rate of 3 mL / min, and then continue to stir and reduce it in a 55 °C water bath for 3 h. After centrifugally washing 3 times with distilled water and 3 times with ethanol, the dark red precipitate obtained is dried in a vacuum drying oven at 55 °C for 5 h to obtain the electrocatalytic material.

[0044] The electrocatalytic performance test of the material prepared in Example 4 is as follows:

[0045] Weigh 10 mg of the electrocatalytic material and put it into a vial, add 960 μL of isopropanol and 40 μL of nafion solution (5%wt), and ultrasonicate for 2 hours until the catalyst is completely dispersed to obtain a uniform catalyst ink.

[0046] 300 μL of the catalyst ink with the above configuration was evenly applied to a 1 cm × 3 cm carbon paper. After drying, it was used as the working electrode, with nickel foam as the anode and a saturated Ag / AgCl electrode as the reference electrode. The catalytic performance test was carried out using a CS2350H electrochemical workstation from Wuhan Koster in a gas diffusion electrode (GDE) of a three-electrode system. The electrolyte flowed in and out continuously. The cathode and anode electrolytes were separated by an anion exchange membrane. The flow rate of the cathode electrolyte was 2 ml / min, and the flow rate of the anode electrolyte was 5 ml / min. The electrolyte was a 0.5 mol / L KHCO3 aqueous solution. Before the test, the electrolyte was saturated by CO2 aeration. The electrochemical workstation was polarized at a potential of -1.84 V (vs Ag / AgCl) and the products were detected. The total current density of the electrocatalytic performance was 129 mA, the Faraday efficiency of ethylene was 35.5%, and the partial current density was 45.80 mA; 2+ The Faraday efficiency of the C product was 62.8%, and the partial current density was 81.01 mA, and the stable test could be carried out for 2 h.

[0047] The content described in this specification is only a list of the implementation forms of the inventive concept, and the protection scope of the present invention should not be regarded as limited to the specific forms stated in the embodiments.

Claims

1. Application of a carbon dioxide electrocatalytic material with an optimized interface by a reducing atmosphere in electrocatalytic conversion of CO2 to C2H4 products, characterized in that Preparation method of electrocatalytic material, comprising the following steps: preparing an aqueous solution of divalent copper salt, and while continuously introducing a reducing gas thereto, then dropping an aqueous sodium hydroxide solution therein, heating in a water bath and continuously stirring for a certain time, and then dropping an ascorbic acid solution therein, heating in a water bath and continuously stirring for a certain time, centrifuging, washing with water and alcohol several times to obtain a copper-based electrocatalytic material with an optimized interface; The reducing gas is one or more of CO, H2, NH3, and nitrogen is used as a diluent gas for the mixed gas, and the volume fraction of the reducing gas in the mixed gas is 5-15%; The concentration of the divalent copper salt aqueous solution is 0.005-0.01 mol / L; based on the volume of the divalent copper salt aqueous solution being 100 ml, the flow rate of the introduced reducing gas is 0.4-0.6 mL / min; The concentration of the sodium hydroxide solution is 1-3 mol / L, the dropping rate is 1-5 mL / min, the molar ratio of sodium hydroxide to divalent copper salt in the feed is 10-30:1, the stirring time after dropping is 0.5-3 h, and the hydrothermal temperature is 40-60 °C; The concentration of the ascorbic acid solution is 0.2-1 mol / L, the dropping rate is 1-5 mL / min, the molar ratio of ascorbic acid to divalent copper salt in the feed is 4-8:1, and then the stirring time is 0.5-3 h, and the hydrothermal temperature is 40-60 °C.

2. The application according to claim 1, wherein The molar ratio of sodium hydroxide to divalent copper salt in the feed is 20:

1.

3. The application according to claim 1, characterized in that The molar ratio of ascorbic acid to divalent copper salt in the feed is 6:

1.

4. The application according to claim 1, characterized in that The number of water washings is 1-3 times, the number of alcohol washings is 1-3 times, and the alcohol is one or more of ethanol, methanol, and isopropanol.

5. The application according to claim 1, characterized in that The carbon dioxide electrocatalytic material is coated on carbon paper as a working electrode, nickel foam is used as the anode, a saturated Ag / AgCl electrode is used as the reference electrode, a 0.1-1 mol / L KHCO3 aqueous solution is used as the electrolyte, the electrolyte is aerated with CO2 to saturate it, and it is carried out in a gas diffusion electrode GDE of a three-electrode system. The cathode and anode electrolytes are separated by an anion exchange membrane, and the cathode and anode electrolytes flow in and out continuously, and the electrolysis reaction converts CO2 into C2H4 products.

Images