Method for co-producing formate through coupling of cathode and anode by using bismuth-based electrode synthesized by one-step galvanic couple replacement

Abstract

The invention relates to a method for co-producing formate through cathode and anode coupling by using a bismuth-based electrode synthesized by one-step galvanic couple replacement, and belongs to the field of electrochemical materials. According to the method, a bismuth / foamy copper electrode and a bismuth / foamed nickel electrode are respectively prepared on a foamy copper substrate and a foamed nickel substrate through a one-step galvanic couple replacement reaction, and are respectively used as a cathode and an anode to synergistically realize carbon dioxide reduction and methanol oxidation reaction and co-production of formate. According to the electrode preparation process, efficient electrode materials can be constructed on different substrates only through one-step reaction, and good expansibility is achieved. The whole process is simple and efficient, complex equipment or subsequent treatment is not needed, and the obtained electrode material is uniform in morphology and rich in active sites. In a coupled electrolysis system, the electrode catalyzes reduction of carbon dioxide at the cathode to generate formate, meanwhile, the formate is co-produced at the anode through methanol oxidation, the system shows formate Faraday efficiency higher than 180% and can stably run for more than 50 hours, and efficient collaborative production of formate at the two ends of the cathode and the anode is achieved.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of electrocatalytic materials, and particularly relates to a simple and efficient preparation method of a bismuth-based self-supporting electrode and application thereof in cathodic carbon dioxide reduction coupled with anodic methanol oxidation to prepare formate. BACKGROUND

[0002] The rapid increase in carbon dioxide emissions has disrupted the natural carbon cycle, leading to a series of environmental problems such as the greenhouse effect and extreme weather. Electrocatalytic reduction of carbon dioxide can reduce carbon dioxide into a variety of high-value fine chemicals, which not only alleviates environmental problems but also helps to cope with energy crises. However, in the traditional electrocatalytic carbon dioxide reduction system, the anode side water oxidation reaction accounts for about 80% of the energy consumption. Replacing the anode reaction with methanol oxidation reaction not only reduces the energy consumption of the reaction, but also has a higher value of oxidation product formate, achieving the simultaneous production of high-value chemicals on the cathode and anode.

[0003] Currently, electrode preparation techniques such as solvothermal method, high-temperature calcination and electrodeposition have been relatively mature. The solvothermal method is usually carried out in a high-temperature and high-pressure reactor, which has harsh reaction conditions and is time-consuming; high-temperature calcination requires long-time heat treatment at hundreds or even thousands of degrees Celsius, which consumes a large amount of energy; and electrodeposition relies on precisely controlled current density, electrolyte composition and other parameters, which requires high equipment and operation. Although these methods can prepare high-performance electrodes, they generally have high energy consumption, strong equipment dependence and long preparation cycle. In addition, the complex process flow and harsh preparation conditions (such as high temperature, high pressure, oxygen-free environment, etc.) seriously restrict the large-scale production and application of electrodes, making cost control and technology popularization face great challenges.

[0004] Under this background, the galvanic displacement technology shows its unique potential and application value. Galvanic displacement reaction is a redox process, in which metal ions with high oxidation-reduction potential in the solution are reduced by another metal. This technology has the following outstanding advantages: first, it is simple and efficient, and does not require external power supply, high-temperature or high-pressure equipment, and can be quickly completed at room temperature and atmospheric pressure, greatly simplifying the preparation process; second, it has low cost, which not only significantly reduces equipment investment and energy consumption, but also has high raw material utilization, which is conducive to large-scale production; third, the prepared electrode catalyst layer often has special microstructures such as porosity and three-dimensionality, which helps to increase the number of active sites and promote mass transfer, thereby improving the catalytic performance.

[0005] Electrode displacement technology exhibits unique process advantages in the anode-cathode coupling system for the preparation of formate. In traditional coupling systems, different catalytic materials are typically used for the anode and cathode, each relying on its own complex preparation process, which is cumbersome and costly. Electrode displacement technology, however, can construct highly efficient catalytic electrodes on different substrates in a single reaction step, significantly simplifying the entire preparation process from the outset. This method not only greatly improves the efficiency of electrode preparation but also provides a new approach for constructing highly active and stable catalytic electrodes. This simple, efficient, and scalable material preparation process lays a solid foundation for the synergistic co-production of formate at both anode and cathode, and is of great value in promoting the practical application of this coupling system in energy conversion and green chemical engineering. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a one-step method for preparing bismuth-based electrodes via electrode displacement. This method is simple, highly efficient, and easily scalable. In this method, a self-supporting electrode (including copper foam and nickel foam) serves as both a supporting substrate and a sacrificial template, undergoing a displacement reaction with trivalent bismuth ions as an oxidant, thereby in-situ loading of bismuth active material onto the surface of copper foam or nickel foam in one step. The prepared electrodes are used as the cathode and anode of an electrolytic cell, respectively: the bismuth / copper foam electrode serves as the cathode for the electrocatalytic reduction of carbon dioxide to prepare formate, and the bismuth / nickel foam electrode serves as the anode for the electrocatalytic oxidation of methanol to prepare formate, thus achieving a co-production process of formate by the synergistic production of anode and cathode.

[0007] The purpose of this invention is to provide a process for preparing bismuth-based electrodes using a coupling substitution method, and to apply it to a catalytic system of carbon dioxide reduction coupled to methanol oxidation at the anode. This method requires no external energy input and has advantages such as simple process flow, low cost for large-scale scalability, and abundant active sites in the prepared catalyst. It can effectively improve the selectivity of formate and the reaction current density, while significantly reducing the overall energy consumption of the system.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a bismuth-based electrode is prepared by a one-step electrode replacement method; the cathode for the electrocatalytic reduction of carbon dioxide to formate is selected as a bismuth / copper foam electrode or a platinum mesh electrode, and the anode is selected as a bismuth / nickel foam electrode or a platinum mesh electrode, and the cathode and anode are not used simultaneously as platinum mesh electrodes;

[0009] The method for preparing the bismuth / foamed copper electrode includes the following steps:

[0010] (S1) Place 2cm A 3cm thick copper foam electrode was immersed in an acetonitrile solution containing a certain amount of sodium bismuthate dihydrate and concentrated hydrochloric acid for 10-40 minutes at room temperature. The volume of acetonitrile in the solution was 15-35 mL, the mass of sodium bismuthate dihydrate was 0.158-0.316 g, and the volume of 12 mol / L concentrated hydrochloric acid was 200-400 μL. The bismuth loading on the copper foam electrode was adjusted by controlling the immersion time, with optimal performance observed at an immersion time of 20 minutes.

[0011] (S2) Take out the soaked copper foam electrode, rinse the electrode surface with a large amount of ultrapure water, and dry it at room temperature. At this time, the electrode surface changes from brownish-red before the reaction to brownish-black, and the bismuth / copper foam electrode is obtained.

[0012] The method for preparing the bismuth / nickel foam electrode includes the following steps:

[0013] (S1) Place 2cm A 2cm thick nickel foam electrode was immersed in a solution of N,N-dimethylformamide containing bismuth nitrate pentahydrate and concentrated nitric acid for 10-40 minutes at room temperature. The volume of N,N-dimethylformamide in the solution was 10-30 mL, the mass of bismuth nitrate pentahydrate was 0.097-0.194 g, and the volume of 16 mol / L concentrated nitric acid was 200-400 μL. The bismuth loading on the nickel foam electrode was adjusted by controlling the immersion time, with optimal performance observed at an immersion time of 20 minutes.

[0014] (S2) Take out the soaked nickel foam electrode, rinse the electrode surface with a large amount of ultrapure water, and dry it at room temperature. At this time, the electrode surface changes from gray before the reaction to gray-black, and the bismuth / nickel foam electrode is obtained.

[0015] The surface of the bismuth / foamed copper electrode is uniformly distributed with bismuth nanobulbs with a diameter of approximately 500 nm.

[0016] The surface of the bismuth / nickel foam electrode is composed of a uniform microporous structure with a consistent morphology and abundant active sites.

[0017] The specific method for testing the cathode electrode performance is as follows: In an H-type electrolytic cell, a bismuth / copper foam electrode is used as the cathode, a silver / silver chloride electrode as the reference electrode, and a platinum mesh electrode as the anode. The electrolyte is a 0.5 mol / L potassium bicarbonate solution saturated with carbon dioxide. The anode and cathode are separated by a proton exchange membrane, and the electroreduction potential range is -0.8 to -1.2 V (vs. RHE).

[0018] The specific method for testing the anolyte performance is as follows: In a single-chamber electrolytic cell, a bismuth / nickel foam electrode is used as the anode, a mercury / mercury oxide electrode as the reference electrode, and a platinum mesh electrode as the cathode. The electrolyte is a mixed solution of 1 mol / L methanol and 1 mol / L potassium hydroxide. The electro-oxidation potential range is 1.4 to 1.6 (vs. RHE).

[0019] The specific anode-cathode coupling test method is as follows: In an H-type electrolytic cell, a bismuth / copper foam electrode is used as the cathode, and a bismuth / nickel foam electrode is used as the anode, forming a dual-electrode system. The cathode electrolyte is a 0.5 mol / L potassium bicarbonate solution saturated with carbon dioxide, and the anode electrolyte is a mixed solution of 1 mol / L methanol and 1 mol / L potassium hydroxide. The anode and cathode are separated by a bipolar membrane, and the cell voltage is set in the range of 2.4-3.2V.

[0020] This invention prepares bismuth / copper foam electrodes and bismuth / nickel foam electrodes via a one-step electrocoupling substitution method, which are then used for cathode carbon dioxide reduction and anolyte methanol oxidation, respectively. In the bismuth / copper foam electrode, bismuth nanobulbs are uniformly loaded onto the copper foam electrode surface, with each nanobulb having a diameter of approximately 500 nm. The bismuth / nickel foam electrode surface consists of a microporous structure with uniform morphology and abundant active sites. In an H-type electrolytic cell, the bismuth / copper foam electrode is used as the cathode for the electrocatalytic reduction of carbon dioxide to formate, achieving a Faraday efficiency of 86% at -1.1 V (vs. RHE) and a current density of up to 40 mA / cm². 2 In a single-chamber electrolytic cell, the formate Faraday efficiency of the bismuth / nickel foam electrode consistently exceeds 95% within the potential range of 1.4–1.6 V (vs. RHE) at 100 mA / cm². 2 It can operate stably for at least 44 hours at a current density. Using bismuth / copper foam and bismuth / nickel foam electrodes in a two-electrode coupling system, at 16 mA / cm²... 2 It can operate stably for 50 hours at a current density, and the sum of the anode and cathode Faraday efficiencies is always greater than 180%, realizing efficient and highly selective anode-cathode co-production of formate.

[0021] Compared with existing technologies, the core advantage of this invention lies in the extremely simple electrode fabrication process:

[0022] (1) The bismuth / copper foam cathode and the bismuth / nickel foam anode are synthesized simultaneously through a single-step galvanic displacement reaction, without the need for multi-step modification or complex post-processing. The process is greatly simplified, and the reaction can be carried out under mild conditions without additional energy input, which effectively reduces the preparation cost and time consumption.

[0023] (2) Thanks to the galvanic displacement technology, the prepared bismuth / foamed copper cathode can maintain high formate selectivity (Faraday efficiency 86%) and high current density (40mA / cm²), while the bismuth loading can be flexibly controlled by a single reaction time parameter, avoiding the complex optimization process commonly found in traditional electrodeposition or hydrothermal methods.

[0024] (3) The obtained bismuth / foamed nickel anode still has a rich porous structure and high electrocatalytic activity without the use of precious metals or complex molding processes. The formate Faraday efficiency exceeds 95% within a wide potential window (1.4-1.6V vs. RHE) and has excellent stability at high current densities.

[0025] (4) A formate-producing system was formed by assembling a bismuth / copper foam cathode and a bismuth / nickel foam anode, and the current reached 16 mA / cm at a cell voltage of 3V. 2 The sum of the formate selectivity of the anode and cathode is always greater than 180%, and it can operate stably for 50 hours. Attached Figure Description

[0026] Figure 1 This is a scanning electron microscope image of the bismuth / copper foam electrode from Example 1.

[0027] Figure 2 The image shows the X-ray diffraction pattern of the bismuth / copper foam electrode in Example 1.

[0028] Figure 3 Linear scan voltammetry, potentiostatic electrolysis diagram and Faraday efficiency diagram of the bismuth / foamed copper electrode in Example 1.

[0029] Figure 4 This is a scanning electron microscope image of the bismuth / nickel foam electrode from Example 2.

[0030] Figure 5 The image shows the X-ray diffraction pattern of the bismuth / nickel foam electrode in Example 2.

[0031] Figure 6 Linear scan voltammetry, Faraday efficiency plot, potentiostatic electrolysis plot, and stability test plot of the bismuth / nickel foam electrode in Example 2.

[0032] Figure 7 The figures show the linear sweep voltammetry, Faraday efficiency plot, and stability test plot of the coupled system in Example 3.

[0033] Figure 8 Schematic diagram of a cathode carbon dioxide reduction coupled to an anode methanol oxidation electrolytic cell. Detailed Implementation

[0034] The present invention will now be described in detail through specific embodiments, but the scope of protection of the present invention is not limited to the scope described in the embodiments.

[0035] Example 1

[0036] The preparation of the bismuth / foamed copper electrode involves the following steps: 0.316 g of sodium bismuthate dihydrate and 200 μL of 12 mol / L concentrated hydrochloric acid are added to 25 mL of acetonitrile solution, followed by adding a 2 cm... A 3 cm thick copper foam electrode was immersed in the above solution and allowed to stand at room temperature for 20 minutes. The immersed copper foam electrode was then removed, its surface thoroughly rinsed with a large amount of ultrapure water, and dried at room temperature. The dried electrode surface changed from its original brownish-red color to brownish-black, thus obtaining the bismuth / copper foam electrode.

[0037] like Figure 1 As shown, scanning electron microscopy reveals that the surface of the bismuth / copper foam electrode has a uniformly loaded bulk structure, with the diameter of a single bismuth nanobulb being approximately 500 nm.

[0038] like Figure 2 As shown, the X-ray diffraction pattern reveals diffraction peaks for copper and bismuth, which are consistent with the characteristic cards for elemental bismuth and elemental copper, proving the loading of bismuth on copper foam.

[0039] The carbon dioxide reduction performance test of the bismuth / copper foam electrode was conducted as follows: In an H-type electrolytic cell, a bismuth / copper foam electrode was used as the cathode, a platinum mesh electrode as the anode, and a silver / silver chloride electrode as the reference electrode. The electrolyte was 0.5 mol / L potassium bicarbonate saturated with carbon dioxide. A proton exchange membrane was used to separate the anode and cathode. During the test, carbon dioxide was bubbled into the cathode electrolyte at a flow rate of 20 mL / min.

[0040] like Figure 3 As shown in Figure a, linear sweep voltammetry tests were performed on the electrode, and it was found that the current density of the bismuth / copper foam electrode in a carbon dioxide atmosphere was significantly better than that in an argon atmosphere, which proved the excellent carbon dioxide reduction performance of the bismuth / copper foam electrode.

[0041] like Figure 3 As shown in Figure b, constant potential electrolysis tests were performed on the electrodes. The bismuth / copper foam electrode achieved a current density of 30 mA / cm² at a potential of -1V (vs. RHE). 2 Quantitative analysis of the products, such as... Figure 3 As shown in Figure c, the bismuth / copper foam electrode achieves a formate Faraday efficiency of 86% at a potential of -1.1V (vs. RHE).

[0042] Example 2

[0043] The preparation of the bismuth / nickel foam electrode involves the following steps: 0.097 g of bismuth nitrate pentahydrate and 200 μL of 16 mol / L concentrated nitric acid are added to 20 mL of N,N-dimethylformamide solution, followed by adding a 2 cm... A 2 cm thick nickel foam electrode was immersed in the above solution and allowed to stand at room temperature for 20 minutes. The immersed nickel foam electrode was then removed, its surface thoroughly rinsed with plenty of ultrapure water, and dried at room temperature. The dried electrode surface changed from its original silver color to gray, thus obtaining the bismuth / nickel foam electrode.

[0044] like Figure 4 As shown, the surface of the bismuth / nickel foam electrode is composed of a microporous structure with a uniform surface morphology and abundant active sites.

[0045] like Figure 5 As shown, the X-ray diffraction pattern reveals diffraction peaks for nickel and bismuth, which are consistent with the characteristic cards for elemental bismuth and elemental nickel, proving the loading of bismuth on nickel foam.

[0046] The methanol oxidation performance test of the bismuth / nickel foam electrode is performed as follows: in a single-chamber electrolytic cell, a bismuth / nickel foam electrode is used as the anode, a platinum mesh electrode is used as the silver electrode, and a mercury / mercury oxide electrode is used as the reference electrode. The electrolyte is a mixed solution of 1 mol / L methanol and 1 mol / L potassium hydroxide.

[0047] like Figure 6 As shown in Figure a, linear sweep voltammetry tests were performed on the electrode, and it was found that the current density of the bismuth / nickel foam electrode in a potassium hydroxide mixed solution with added methanol was significantly better than that without added methanol, which proves the excellent methanol oxidation performance of the bismuth / nickel foam electrode.

[0048] By performing quantitative analysis on the products, such as Figure 6 As shown in Figure b, the formate faradaic efficiency of the bismuth / nickel foam electrode is greater than 95% at potentials of 1.4–1.6 V (vs. RHE). Figure 6 As shown in Figure c, constant potential electrolysis tests were performed on the electrodes. The bismuth / nickel foam electrode achieved a current density of 120 mA / cm² at a potential of 1.6 V (vs. RHE). 2 .

[0049] like Figure 6 As shown in Figure d, the methanol oxidation stability of the electrode was tested. Electrolysis was performed at 1.55V (vs. RHE) for 44 hours, and the current density remained approximately 100 mA / cm². 2 This demonstrates the excellent stability of the bismuth / nickel foam electrode.

[0050] Example 3

[0051] The performance test of the cathode carbon dioxide reduction coupled to the anodic methanol oxidation to formate production was conducted as follows: A dual-electrode system was constructed in an H-type electrolytic cell, using a bismuth / copper foam electrode as the cathode and a bismuth / nickel foam electrode as the anode. The cathode electrolyte was 0.5 mol / L potassium bicarbonate saturated with carbon dioxide, and the anolyte was a mixed solution of 1 mol / L methanol and 1 mol / L potassium hydroxide. The cathode and anode were separated by a bipolar membrane. During the test, carbon dioxide was bubbled into the cathode electrolyte at a flow rate of 20 mL / min.

[0052] like Figure 7 As shown in Figure a, linear sweep voltammetry tests were performed within the cell voltage range of 1-3.5V. It can be seen that the carbon dioxide-coupled methanol oxidation system requires a lower cell voltage than the coupled water oxidation system at the same current density. At 15mA / cm²... 2 At the current density, the cell voltage decreased by 400mV.

[0053] By performing quantitative analysis on the products, such as Figure 7 As shown in Figure b, the sum of the formate Faraday efficiencies of the coupled system is greater than 180% under cell voltages ranging from 2.4V to 3.2V.

[0054] like Figure 7 As shown in Figure c, the stability of the coupled system was tested. After electrolysis at 3V cell voltage for 50 hours, the current density remained at approximately 16mA / cm². 2 Furthermore, the sum of the Faraday efficiencies of the anode and cathode formates is always greater than 180%, demonstrating highly efficient catalytic activity and stability.

[0055] The above embodiments are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any changes made based on the design principles of the present invention, or any non-creative modifications made thereon, shall fall within the scope of protection of the present invention.

Claims

1. A method for the coupled co-production of formate salts by cathode and anode using a bismuth-based electrode synthesized by one-step galvanic displacement, characterized in that: The cathode for electrocatalytic reduction of carbon dioxide to form formate is a bismuth / foam copper electrode or a platinum mesh electrode, the anode for electrocatalytic oxidation of methanol is a bismuth / foam nickel electrode or a platinum mesh electrode, and the platinum mesh electrode is not applied to the cathode and the anode at the same time; The preparation method of the bismuth / foam copper electrode comprises the following steps: S1, soaking the foam copper in a solution of bismuth sodium citrate dihydrate and concentrated hydrochloric acid in acetonitrile; and soaking at room temperature for 10-40 min; the ratio of bismuth sodium citrate dihydrate, concentrated hydrochloric acid and acetonitrile in the solution is (0.158-0.316) g:(200-400) μL:(15-35) mL; the loading amount of bismuth on the foam copper electrode is adjusted by controlling the soaking time; S2, taking out the soaked foam copper electrode, rinsing and drying at room temperature to obtain the bismuth / foam copper electrode; The preparation method of the bismuth / foam nickel electrode comprises the following steps: S1, soaking the foam nickel in a solution of bismuth nitrate pentahydrate and concentrated nitric acid in N,N-dimethylformamide; and soaking at room temperature for 10-40 min; the ratio of bismuth nitrate pentahydrate, concentrated nitric acid and N,N-dimethylformamide in the solution is (0.097-0.194) g:(200-400) μL:(10-30) mL; the loading amount of bismuth on the foam nickel electrode is adjusted by controlling the soaking time; S2, taking out the soaked foam nickel electrode, rinsing and drying at room temperature to obtain the bismuth / foam nickel electrode.

2. The method of claim 1, wherein: In an H-type electrolytic cell, the bismuth / foam copper electrode is used as the cathode, the silver / silver chloride electrode is used as the reference electrode, the platinum mesh electrode is used as the anode, and the electrolyte is a 0.5 mol / L potassium bicarbonate solution saturated with carbon dioxide; the cathode and the anode are separated by a proton exchange membrane, and the electro-reduction potential interval is-0.8 to-1.2 V (vs. RHE).

3. The method of claim 1, wherein: In a single-chamber electrolytic cell, the bismuth / foam nickel electrode is used as the anode, the mercury / mercury oxide electrode is used as the reference electrode, the platinum mesh electrode is used as the cathode, and the electrolyte is a mixed solution of 1 mol / L methanol and 1 mol / L potassium hydroxide; the electro-oxidation potential interval is 1.4 to 1.6 V (vs. RHE).

4. The method of claim 1, wherein: In an H-type electrolytic cell, the bismuth / foam copper electrode is used as the cathode, and the bismuth / foam nickel electrode is used as the anode to form a two-electrode system; the cathode tank electrolyte is a 0.5 mol / L potassium bicarbonate solution saturated with carbon dioxide, and the anode tank electrolyte is a mixed solution of 1 mol / L methanol and 1 mol / L potassium hydroxide; the cathode and the anode are separated by a bipolar membrane, and the tank voltage is set in the interval of 2.4 to 3.2 V.

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