Indium-cerium alloy catalytic electrode for CO2 reduction and preparation method of indium-cerium alloy catalytic electrode

Abstract

The invention relates to the technical field of electrocatalytic CO2 reduction, in particular to an indium-cerium alloy catalytic electrode for CO2 reduction and a preparation method of the indium-cerium alloy catalytic electrode. Pure indium metal is used as an electrocatalyst for carbon dioxide reduction, and the selectivity of formic acid is difficult to reach 85% or above. In order to solve the technical problems, the invention provides the indium-cerium alloy catalytic electrode for CO2 reduction, an electrochemical deposition method is adopted to enable In < 3 + > and Ce < 3 + > to be subjected to a reduction precipitation reaction on the surface of a copper foil to obtain the InCe alloy catalytic electrode, an InCe alloy on the surface of the InCe alloy catalytic electrode is In < 0.919 > Ce < 0.081 >, the HER path is remarkably inhibited by the high doping amount of Ce, the intermediate adsorption energy of CO2RR is optimized, and the catalytic performance of CO2 is improved. Under the potential of-1.0937 V, the selectivity of the In < 0.919 > Ce < 0.081 > alloy to formic acid can reach 85% or above, and the selectivity is far higher than that of pure In metal (80%) and that of low-Ce-doped indium cerium alloy (less than 50%).

Description

Technical Field

[0001] This invention relates to the field of electrocatalytic CO2 reduction technology, specifically to an indium-cerium alloy catalytic electrode for CO2 reduction and its preparation method. Background Technology

[0002] Carbon dioxide (CO2) electroreduction technology is one of the key pathways to achieve carbon resource recycling and carbon neutrality. Formic acid (HCOOH) has become an important target product for CO2 reduction due to its high added value and broad application prospects (such as fuel cells and chemical raw materials). However, existing electrocatalysts generally face problems such as low selectivity and severe competitive hydrogen evolution reaction (HER) in the process of CO2 reduction to formic acid, which restricts their industrial application.

[0003] Research on indium (In) metal as a CO2 electroreduction catalyst is relatively mature, but its selectivity for formic acid is low (typically only 40%–60%). This shortcoming mainly stems from the fact that at high overpotentials, the CO2 reduction reaction (CO2RR) and the hydrogen evolution reaction (HER) compete fiercely, causing some current to be used to generate byproducts such as H2, which significantly reduces the Faradaic efficiency of formic acid.

[0004] Similarly, while bismuth (Bi) metal exhibits some activity in the reduction of formic acid by CO2, it also faces interference from HER at high potentials, resulting in limited selectivity. To address this issue, existing technologies (such as Chinese invention patent CN 119859821 A) propose introducing cerium (Ce) into Bi metal to form Bi... 0.958-0.989 Ce 0.011-0.042 The alloy. Studies have shown that this bismuth-cerium alloy can achieve 100% formic acid selectivity at a potential of -1.5V (vs. Ag / AgCl). The mechanism is that the dendritic morphology exposes more active sites, and Ce doping accelerates the electron transfer rate on the catalyst surface, thereby suppressing HER and improving CO2RR efficiency at a lower potential.

[0005] Based on the successful experience with bismuth-cerium alloys, this invention attempts to apply a similar method to indium-cerium alloy systems, specifically by preparing In through small-scale Ce doping (Ce atoms accounting for 1.1%-4.2%). 0.958-0.989 Ce 0.011-0.042 Alloy. However, experimental results show that this strategy has limited effect on improving the performance of indium-cerium alloys: at potentials from -1.04V to -1.20V, In 0.958-0.989 Ce 0.011-0.042The selectivity of the alloy for formic acid remained below 50%, even lower than that of pure In metal (>60%). Further research revealed that the morphological difference between the indium-cerium alloy and the bismuth-cerium alloy was the key limiting factor—the dendritic structure of the bismuth-cerium alloy exposed a large number of active sites, while the indium-cerium alloy tended to form an aggregated blocky structure, resulting in a significant reduction in the number of active sites. In this case, a small amount of Ce doping could not effectively modulate the electronic structure or suppress HER; instead, the morphological limitation led to a decrease in catalytic efficiency.

[0006] To address the aforementioned issues, this invention systematically studies the composition-morphology-property correlation mechanism of indium-cerium alloys, discovering that increasing the Ce atom content to 8.1% significantly suppresses the HER pathway and optimizes the intermediate adsorption energy of CO2RR. Experiments confirm that at a potential of -1.0937V, In... 91.9 Ce 8.1 The alloy exhibits a selectivity for formic acid exceeding 85%, far surpassing that of pure In metal (80%) and low-Ce-doped indium-cerium alloys (<50%). This discovery breaks through the conventional understanding that "a small amount of Ce doping can improve performance," providing a completely new approach for the design of indium-based CO2 reduction catalysts.

[0007] In summary, while existing technologies have improved the performance of bismuth-cerium alloys through Ce doping, indium-cerium alloys require a higher Ce doping ratio to achieve selectivity enhancement due to fundamental differences in morphology and electronic structure. This invention addresses this unmet technical need by proposing a solution based on indium-cerium alloys with high Ce content. Summary of the Invention

[0008] A problem with existing technologies is that when pure indium metal is used as an electrocatalyst for carbon dioxide reduction, it is difficult to achieve a selectivity of formic acid above 85%. To address this problem, this invention provides an indium-cerium alloy catalytic electrode for CO2 reduction, which is produced by electrochemical deposition of Indium... 3+ Ce 3+ A reduction precipitation reaction occurs on the surface of the copper foil to obtain In. 1-x Ce x Alloy catalytic electrode, x=0.081, where x represents the atomic percentage of Ce in the cerium alloy.

[0009] Preferably, the indium-cerium alloy catalytic electrode for CO2 reduction is prepared by the following steps: (1) Dissolve indium salt and cerium salt in a mixed solution formed by acetamide and dimethyl sulfone, stir and mix evenly to make an electrolyte; (2) Place the electrolyte obtained in step (1) in an electrolytic cell, use copper foil as the working electrode, and carry out electrochemical deposition reaction using a three-electrode system; (3) After the electrochemical deposition is completed, the copper foil with deposits on its surface is washed with alcohol and water and then dried to obtain an indium cerium alloy catalytic electrode.

[0010] Preferably, the indium salt is indium hydrate.

[0011] Preferably, the cerium salt is hydrated cerium nitrate.

[0012] Preferably, the counter electrode of the three-electrode system is a platinum mesh or a platinum sheet.

[0013] Preferably, the reference electrode of the three-electrode system is an Ag / AgCl electrode or a saturated calomel electrode.

[0014] Preferably, the molar ratio of acetamide to dimethyl sulfone in step (1) is 4:1.

[0015] The present invention has the following beneficial effects: The indium-cerium alloy catalytic electrode for CO2 reduction provided by this invention (In 1-X Ce X The method of electrocatalysis (x=0.064-0.098) has the following significant advantages: (1) In this invention, at the optimal potential of -1.0937V, indium-cerium alloys (such as In...) 0.919 Ce 0.081 The selectivity for formic acid (HCOOH) is over 85%, which is significantly better than that of pure indium electrode (about 80%) and traditional indium-based catalyst (40-60%). For the first time, indium-based catalysts have achieved high selectivity for formic acid conversion at low overpotential, which solves the technical bottleneck of low selectivity of indium catalytic system due to competitive hydrogen evolution reaction. (2) Through experiments, this invention has found that the atomic percentage of cerium needs to be strictly controlled at 8.1%, which is much higher than that of bismuth-cerium alloys (Ce 1.1-4.2%). This directly overturns the technical prejudice of "the universality of low cerium doping". The research confirms that low cerium doping (such as In) 0.969 Ce 0.031 Due to the bulk structure defects of indium-cerium alloys, the active sites are not exposed enough, and the selectivity is even lower than that of pure indium (<50% vs>60%). However, the high cerium content (x=0.081) of the present invention effectively suppresses the hydrogen evolution side reaction by regulating the electronic structure of the alloy, thereby achieving a leap in selectivity. (3) The present invention can achieve more than 85% formic acid selectivity at a moderate reduction potential of -1.0937 V, which is far superior to the -1.5 V required by the bismuth-cerium alloy system (such as CN 119859821 A), significantly reducing the reaction overpotential, reducing energy consumption, and improving the reaction economy; (4) The present invention uses electrochemical deposition to synthesize alloy electrodes on copper foil in one step. The process is simple and low-cost. The electrolyte system (acetamide / dimethyl sulfone mixed solvent) and electrode structure (copper substrate) have the potential for industrial scale-up. (5) By directional doping of cerium, this invention overcomes the pain points of severe hydrogen evolution side reaction and rapid selective decay of pure indium catalysts at high overpotential, and provides a high-performance indium-based solution for the resource utilization of CO2. Attached Figure Description

[0016] Figure 1 : This is a SEM image of the indium-cerium alloy catalytic electrode obtained in Example 1.

[0017] Figure 2 : This is a Faraday efficiency graph of the catalytic electrode obtained in Example 1 and Comparative Examples 1-6 for reducing CO2 to formic acid.

[0018] Figure 3 : This is a schematic diagram of the H-type electrolytic cell used in this invention. Detailed Implementation

[0019] The present invention will be described in detail below with reference to embodiments. However, it should be understood that the following embodiments are merely illustrative examples of implementation of the present invention and are not intended to limit the scope of the present invention.

[0020] The copper foil used in the following embodiments of the present invention was purchased from Qinghe County Bodun Hard Alloy Co., Ltd., and the type is T2 purple copper.

[0021] The platinum mesh used in the following embodiments of the present invention was purchased from Shanghai Yueci Electronic Technology Co., Ltd., and the model is 10mm×10mm (L-type). In the following embodiments of the present invention, the electrolyte solution of the Ag / AgCl reference electrode used for electrodeposition is a solution formed by dissolving 200 mM LiCl in 25 mL N,N-dimethylformamide (DMF).

[0022] In the following embodiments of the present invention, the Ag / AgCl reference electrode used for the electrochemical reduction of carbon dioxide was purchased from Shanghai Yueci Electronic Technology Co., Ltd., and the filling solution was a 3 M KCl aqueous solution, model SHI111.

[0023] The structural schematic diagram of the H-type electrolytic cell used in the following embodiments of the present invention is shown in the appendix to the specification. Figure 3 As shown.

[0024] The ion exchange membranes used in the following embodiments of the present invention were purchased from Shanghai Chuxi Industrial Co., Ltd., with a thickness of 25.4 μm and model number N17. Example

[0025] An indium-cerium alloy catalytic electrode for CO2 reduction is prepared as follows: (1) Add acetamide and dimethyl sulfone to a beaker at a molar ratio of 4:1 and heat in a water bath at 65°C until they are mixed evenly. Then, at 65°C, add 50 mM In(NO3)3•3H2O and 12.5 mM Ce(NO3)3•6H2O to 6 mL of the mixed solution to obtain an indium-cerium mixed solution. (2) The indium-cerium mixture obtained in step (1) is placed in a single electrolytic cell as an electrolyte. A copper foil with a thickness of 0.02 mm is used as the working electrode and placed in the cathode chamber of the electrolytic cell. The copper foil has a size of 0.5 cm × 0.5 cm. A platinum mesh is used as the counter electrode and placed in the anode chamber of the electrolytic cell. Ag / AgCl is used as the reference electrode and placed in the cathode chamber of the electrolytic cell. The working electrode, counter electrode, and reference electrode are connected to the corresponding wires of the CHI660E electrochemical workstation. Electrochemical deposition is carried out at atmospheric pressure and 65°C. The electrochemical deposition potential is −1.55 V (vs. Ag / AgCl), and the charge is controlled at 1.5 C. (3) After electrochemical deposition, the working electrode was rinsed three times with anhydrous ethanol and ultrapure water, and dried to obtain an indium-cerium alloy catalytic electrode. The obtained indium-cerium alloy catalytic electrode was placed in a 68% nitric acid solution to dissolve the indium-cerium alloy on the electrode surface. The solution was then diluted to 0.8 mol / L with pure water. Finally, the composition of the indium-cerium alloy on the electrode surface was determined by inductively coupled plasma atomic emission spectrometry (ICP). The indium-cerium alloy on the surface of the indium-cerium alloy catalytic electrode obtained in Example 1 was In 0.919 Ce 0.081 .

[0026] The surface morphology of the indium-cerium alloy catalytic electrode obtained in Example 1 was characterized by SEM, as shown in the attached specification. Figure 1 As shown.

[0027] Comparative Example 1 is the same as Example 1, except that the electrochemical deposition potential in step (2) of Comparative Example 1 is −1.45 V (vs. Ag / AgCl). The indium-cerium alloy on the surface of the indium-cerium alloy catalytic electrode obtained in Comparative Example 1 is In 0.969 Ce 0.031 .

[0028] Comparative Example 2 is the same as Example 1, except that the electrochemical deposition potential in step (2) of Comparative Example 2 is −1.5 V (vs. Ag / AgCl). The indium-cerium alloy on the surface of the indium-cerium alloy catalytic electrode obtained in Comparative Example 2 is In 0.936 Ce 0.064 .

[0029] Comparative Example 3 is the same as Example 1, except that the electrochemical deposition potential in step (2) of Comparative Example 3 is −1.6 V (vs. Ag / AgCl). The indium-cerium alloy on the surface of the indium-cerium alloy catalytic electrode obtained in Comparative Example 3 is In 0.902 Ce 0.098 .

[0030] Comparative Example 4 is the same as Example 1, except that the electrochemical deposition potential in step (2) of Comparative Example 4 is −1.65 V (vs. Ag / AgCl). The indium-cerium alloy on the surface of the indium-cerium alloy catalytic electrode obtained in Comparative Example 4 is In 0.882 Ce 0.0118 .

[0031] Comparative Example 5 is the same as Example 1, except that the electrochemical deposition potential in step (2) of Comparative Example 5 is −1.85 V (vs. Ag / AgCl). The indium-cerium alloy on the surface of the indium-cerium alloy catalytic electrode obtained in Comparative Example 5 is In 0.481 Ce 0.519 .

[0032] Comparative Example 6 is the same as Example 1, except that 12.5 mM Ce(NO3)3•6H2O was not added in step (1) of Comparative Example 6.

[0033] The electrocatalysts obtained in Example 1 and Comparative Examples 1-6 of this invention were used as the working electrodes for the CO2 reduction reaction and placed in an H-type electrolytic cell (a schematic diagram of the H-type electrolytic cell is attached to the instruction manual). Figure 3 The cathode chamber (shown) utilizes a three-electrode system. A platinum mesh is used as the counter electrode in the anode chamber of the H-type electrolytic cell, and Ag / AgCl is used as the reference electrode in the cathode chamber. The working electrode, counter electrode, and reference electrode are connected to the corresponding wires of the CHI660E electrochemical workstation. The electrolyte used in the cathode chamber is 50 mL of 0.1 M KHCO3 aqueous solution containing saturated CO2, and the electrolyte used in the anode chamber is 50 mL of 0.1 M KHCO3 aqueous solution. An ion exchange membrane isolates the cathode and anode chambers within the H-type electrolytic cell, and the carbon dioxide reduction reaction is carried out at room temperature. The electrochemical reduction potentials are −1.7 V, −1.75 V, −1.8 V, and −1.85 V (vs. Ag / AgCl). The electrode calculation formula E(vs. RHE) = E(vs. Ag / AgCl) + 0.6563V was used to convert the reversible hydrogen electrode values ​​to -1.0437 V, -1.0937 V, -1.1437 V, and -1.1937 V (vs. RHE), respectively. The electrochemical reduction time was 3600 s for all values. After the electrochemical reduction was completed, the obtained products were characterized by gas chromatography and ion chromatography. The test results are shown in the appendix to the instruction manual. Figure 2 As shown. Figure 2 In the text, In represents comparative example 6, In 0.969 Ce 0.031 In 0.936 Ce 0.064 In 0.919 Ce 0.081 In 0.902 Ce 0.098 In 0.882 Ce 0.118 In 0.481 Ce 0.519 Comparative Examples 1, 2, 1, 3, 4, and 5 were compared. The specific test results are summarized in Table 1.

[0034] Table 1 , Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. An indium-cerium alloy catalytic electrode for CO2 reduction, characterized in that, It is achieved by using electrochemical deposition method to make In 3+ Ce 3+ A reduction precipitation reaction occurs on the surface of the copper foil to obtain In. 1-x Ce x Alloy catalytic electrode, x=0.081, where x represents the atomic percentage of Ce in the cerium alloy.

2. An indium-cerium alloy catalytic electrode for CO2 reduction according to any one of claims 1, characterized in that, The preparation method includes the following steps: (1) Dissolve indium salt and cerium salt in a mixed solution formed by acetamide and dimethyl sulfone, stir and mix evenly to make an electrolyte; (2) Place the electrolyte obtained in step (1) in an electrolytic cell, use copper foil as the working electrode, and carry out electrochemical deposition reaction using a three-electrode system; (3) After the electrochemical deposition is completed, the copper foil with deposits on its surface is washed with alcohol and water and then dried to obtain an indium cerium alloy catalytic electrode.

3. The indium-cerium alloy catalytic electrode for CO2 reduction according to claim 2, characterized in that, The indium salt is indium hydrate nitrate.

4. The indium-cerium alloy catalytic electrode for CO2 reduction according to claim 2, characterized in that, The cerium salt is hydrated cerium nitrate.

5. An indium-cerium alloy catalytic electrode for CO2 reduction according to claim 2, characterized in that, The counter electrode of the three-electrode system is a platinum mesh or platinum sheet.

6. An indium-cerium alloy catalytic electrode for CO2 reduction according to claim 2, characterized in that, The reference electrode for the three-electrode system is an Ag / AgCl electrode or a saturated calomel electrode.

7. An indium-cerium alloy catalytic electrode for CO2 reduction according to claim 2, characterized in that, In step (1), the molar ratio of acetamide to dimethyl sulfone is 4:

1.

8. A method for electrocatalytic CO2 reduction, characterized in that, The indium-cerium alloy catalytic electrode according to any one of claims 1-7 is used as the working electrode to achieve CO2 reduction using a three-electrode system.

9. The electrocatalytic CO2 reduction method according to claim 8, characterized in that, The electrochemical reduction potential is -1.0937 V (vs. RHE).

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