Application of Ag-doped CuS material in electrocatalytic reduction of carbon dioxide to methanol
By optimizing the electronic structure and active sites of the Ag-doped CuS catalyst, the problems of low selectivity and poor stability of Cu-based catalysts in electrocatalytic CO2 reduction were solved, achieving efficient methanol production, which is suitable for renewable energy-driven electrochemical CO2 reduction systems.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- HYDROGEN BOAT GREEN ENERGY TECHNOLOGY (WUXI) CO LTD
- Filing Date
- 2026-05-08
- Publication Date
- 2026-06-05
AI Technical Summary
Existing Cu-based catalysts exhibit low selectivity in the electrocatalytic reduction of CO2 to methanol, are prone to hydrogen evolution reaction, have poor stability, a limited number of active sites, and insufficient electron transfer efficiency, making it difficult to achieve efficient methanol production.
Ag-doped CuS material was used to synthesize an Ag-doped CuS catalyst via a solvothermal method. Pre-reduction and electrocatalytic reduction were then carried out in a three-electrode system to optimize the electronic structure and active sites of the catalyst, suppress the hydrogen evolution reaction, and promote the hydrogenation of CO intermediates to methanol.
It achieves methanol generation with high selectivity, high stability and high partial current density, and is suitable for flow electrolyzers and membrane electrode electrolyzers. It improves the current density to the level of industrial applications and is suitable for electrochemical CO2 reduction systems driven by renewable energy.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of catalyst preparation technology, specifically relating to the application of an Ag-doped CuS material in the electrocatalytic reduction of CO2 to methanol. Background Technology
[0002] Electrochemical reduction of CO2 is an effective way to achieve carbon resource recycling. Methanol (CH3OH), as an important liquid fuel and chemical raw material, is one of the ideal target products for CO2 reduction. Cu-based catalysts have shown potential in the reduction of CO2 to methanol due to their suitable adsorption energy for CO intermediates. However, pure Cu-based catalysts have problems such as low methanol selectivity, intense competition in the hydrogen evolution reaction, and poor stability.
[0003] In the prior art, Cu-based catalysts can be improved by modifying them with sulfides, but CuS is easily deactivated during electrocatalysis, which limits its application. Heteroatom doping is an effective strategy to regulate the electronic structure of catalysts and enhance the stability of active sites, but how to accurately control the doping ratio to achieve high selectivity and high stability of methanol is still a technical challenge in this field. At present, existing Cu-based catalysts have the following problems: (1) When existing Cu-based catalysts are used to electrocatalyze the reduction of CO2 to methanol, the selectivity is low and side reactions such as hydrogen evolution reaction (HER) are easy to occur, making it difficult for the methanol Faraday efficiency to exceed 60%, for example, Cu@Cu2O (methanol FE=45.0%), Cu3P@C (FE=59.2%). (2) CuS catalysts are easily deeply reduced during electrocatalysis, the structure is easily reconstructed and deactivated, the stability is poor, and it is difficult to meet the requirements of continuous operation for more than 10 hours. (3) The number of active sites of the catalyst is limited and the electron transfer efficiency is insufficient, resulting in low methanol partial current density and slow reaction kinetics. (4) Existing heteroatom doping strategies are difficult to accurately regulate the electronic structure of the catalyst and cannot be efficiently optimized. The adsorption and hydrogenation processes of CO intermediates limit the selectivity and activity of methanol production. Summary of the Invention
[0004] In view of this, the present invention provides an application of Ag-doped CuS material in the electrocatalytic reduction of CO2 to methanol. The Ag-doped material provided by the present invention exhibits good catalytic activity, high methanol selectivity, high CH3OH partial current density, and high structural stability during long-term operation in the electrocatalytic reduction of CO2 to methanol.
[0005] This invention provides an application of Ag-doped CuS material in the electrocatalytic reduction of CO2 to methanol, wherein the Ag-doped CuS material comprises CuS and Ag embedded in the CuS lattice; the molar amount of Ag is 0.5 to 2.5% of the molar amount of copper.
[0006] Preferably, the molar amount of Ag is 0.5% of the molar amount of copper.
[0007] Preferably, the preparation method of the Ag-doped CuS material includes the following steps: Copper salt, sulfur source, surfactant and silver nitrate were dissolved in a mixture of alcohol and water and subjected to a solvothermal reaction to obtain Ag-doped CuS material.
[0008] Preferably, the copper salt includes one or more of anhydrous copper nitrate, copper chloride, and copper acetate; the sulfur source includes thiourea; and the surfactant includes one or more of sodium dodecyl sulfate, polyethylene glycol, and hexadecyltrimethylammonium chloride.
[0009] Preferably, the alcohol is one or more of ethanol, glycerol, and polyethylene glycol; the volume ratio of alcohol to water in the mixture of alcohol and water is 1:3.
[0010] This invention also provides a method for electrocatalytically reducing CO2 to methanol, comprising the following steps: In a three-electrode system, CO2 gas is introduced into the electrolyte until saturation, followed by pre-reduction and electrocatalytic reduction to obtain methanol. The three-electrode system includes a working electrode, a reference electrode, and a counter electrode. The working electrode is made of Ag-doped CuS material.
[0011] Preferably, the electrolyte is a KHCO3 solution; the concentration of the KHCO3 solution is 0.3~0.7 mol / L.
[0012] Preferably, after CO2 gas is introduced into the electrolyte until saturation is reached for 25-35 minutes, pre-reduction and electrocatalytic reduction are carried out sequentially.
[0013] Preferably, the pre-reduction potential is -1.5V vs Ag / AgCl; the pre-reduction time is 15~25min.
[0014] Preferably, the electrocatalytic reduction is a constant potential reduction; the potential of the electrocatalytic reduction is -0.8 to -1.2 V vs. RHE; and the time of the electrocatalytic reduction is 9.5 to 10.5 h.
[0015] The Ag-doped CuS material provided by this invention enriches CO intermediates through Ag doping, promoting a key pathway for CO hydrogenation to methanol. CO→ CHO→ OCH3) suppresses side reactions such as CC coupling and hydrogen evolution, while optimizing the electronic structure through the synergistic effect of Ag and Cu, thereby improving catalytic activity and methanol selectivity. Data from the examples show that the Ag-doped CuS material provided by this invention can achieve highly selective methanol preparation in a neutral electrolyte (KHCO3 solution), exhibits stable performance over a wide potential window, is compatible with conventional H-type electrolytic cells, and has flexible application scenarios. Attached Figure Description
[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the embodiments will be briefly described below.
[0017] Figure 1 Tafel graphs for Example 1 and Comparative Example 1; Figure 2 The following data are presented for four catalysts, CuS, Ag-CuS-0.5%, Ag-CuS-1.5%, and Ag-CuS-2.5%, at different potentials: (a) the Faradaic efficiency of CH3OH; (b) the partial current density of CH3OH; (c) the half-cathode energy efficiency; and (d) the production rate of CH3OH. Figure 3 SEM image of Ag-CuS-0.5% catalyst; Figure 4 The XRD patterns are of four catalysts: CuS, Ag-CuS-0.5%, Ag-CuS-1.5%, and Ag-CuS-2.5% after pre-reduction. Figure 5 Stability test curves for Ag-CuS-0.5% catalyst; Figure 6 XRD patterns of CuS and Ag-CuS-0.5%; Figure 7 Cu2p spectra of CuS and Ag-CuS-0.5% XPS; Figure 8 The in-situ Raman spectra of Ag-CuS-0.5% at different potentials are shown. Detailed Implementation
[0018] This invention provides an application of Ag-doped CuS material in the electrocatalytic reduction of CO2 to methanol, wherein the Ag-doped CuS material comprises CuS and Ag embedded in the CuS lattice; the molar amount of Ag is 0.5 to 2.5% of the molar amount of copper.
[0019] In this invention, the molar amount of Ag is 0.5%, 1.5%, or 2.5% of the molar amount of copper.
[0020] The Ag-doped CuS material provided by this invention can also be extended to flow electrolyzers and membrane electrode electrolyzer systems, further increasing the current density to industrial application levels (>200 mA·cm). -2 It is applicable to renewable energy-driven electrochemical CO2 reduction systems to achieve carbon resource recycling.
[0021] This invention also provides a method for preparing Ag-doped CuS materials, comprising the following steps: Copper salt, sulfur source, surfactant and silver nitrate are dissolved in a mixture of alcohol and water and subjected to a solvothermal reaction to obtain Ag-doped CuS material; the molar amount of Ag is 0.5 to 2.5% of the molar amount of copper.
[0022] In this invention, the copper salt may include one or more of anhydrous copper nitrate, copper chloride, and copper acetate; the sulfur source may include thiourea; and the surfactant may include one or more of sodium dodecyl sulfate (SDS), polyethylene glycol (PEG-6000), and hexadecyltrimethylammonium chloride (CTAC). In this invention, the alcohol may be one or more of ethanol, glycerol, and polyethylene glycol (PEG-400). In this invention, the volume ratio of alcohol to water in the mixture may be 1:3. In this invention, the molar ratio of the copper salt to the sulfur source may be 1:2 to 3, specifically 1:2.5.
[0023] In this invention, the temperature of the solvothermal reaction can be 80~120℃, specifically 100℃, and the reaction time can be 12~24h, specifically 18h. In this invention, after the solvothermal reaction, the solvothermal reaction system is further subjected to sequential cooling, separation, washing, and drying.
[0024] In this invention, Ag-doped CuS material is synthesized by a one-step solvothermal method. The performance can be precisely optimized by adjusting the Ag doping ratio (0.5% is optimal). It does not require complex equipment, has low cost, and is easy to scale up for production.
[0025] This invention also provides a method for the electrocatalytic reduction of CO2 to methanol, comprising the following steps: In a three-electrode system, CO2 gas is introduced into the electrolyte until saturation, followed by pre-reduction and electrocatalytic reduction to obtain methanol. The three-electrode system includes a working electrode, a reference electrode, and a counter electrode. The working electrode is made of Ag-doped CuS material.
[0026] In this invention, the electrolyte can be a KHCO3 solution; the concentration of the KHCO3 solution can be 0.3~0.7 mol / L, specifically 0.5 mol / L. In this invention, it is preferable to perform electrocatalysis after bubbling CO2 gas into the electrolyte until saturation for 30 minutes.
[0027] In this invention, the pre-reduction potential can be -1.5V vs Ag / AgCl; the pre-reduction time can be 15~25min, specifically 20min.
[0028] In this invention, the electrocatalytic reduction is a constant potential reduction; the potential of the electrocatalytic reduction can be -0.8 to -1.2 V vs. RHE, preferably -1.0 V vs. RHE; the time of the electrocatalytic reduction can be 9.5-10.5 h, specifically 10 h.
[0029] To further illustrate the present invention, the technical solutions provided by the present invention will be described in detail below with reference to the accompanying drawings and embodiments, but these should not be construed as limiting the scope of protection of the present invention.
[0030] The specifications of the experimental reagents used in the examples are as follows: silver nitrate (99%), thiourea (analytical grade), hexadecyltrimethylammonium bromide (analytical grade), ethylene glycol (analytical grade), potassium bicarbonate (analytical grade), anhydrous ethanol (analytical grade), isopropanol (analytical grade), deionized water (18.25Ω), and Nafion solution (5wt%).
[0031] Experimental instruments: electronic analytical balance, intelligent magnetic stirrer, CNC ultrasonic cleaner, benchtop high-speed centrifuge, vacuum drying oven, electrochemical workstation, H-type electrochemical reaction cell, gas chromatograph, X-ray diffractometer, field emission scanning electron microscope, X-ray photoelectron spectrometer, Raman spectrometer.
[0032] Example 1 Weigh out 0.483g of copper nitrate trihydrate, 0.38g of thiourea, and 0.2g of CTAB and dissolve them in a mixed solution of 10mL of ethylene glycol and 30mL of deionized water. Stir magnetically for 30min. Then add 1.7mg of silver nitrate and continue stirring until homogeneous. Transfer the mixed solution to a polytetrafluoroethylene liner and heat at 100℃ for 18h. After the reaction was completed, the product was cooled to room temperature, centrifuged to separate the product, washed several times with deionized water and ethanol, and dried under vacuum at 60°C for 12 h to obtain Ag-CuS-0.5% catalyst.
[0033] Working electrode preparation: 5 mg Ag-CuS-0.5% catalyst was dispersed in a mixture of 490 μL deionized water, 490 μL isopropanol, and 20 μL Nafion solution (5 wt%), and sonicated for 1 h to obtain catalyst ink; 100 μL of the ink was drop-coated onto carbon paper and allowed to dry naturally to obtain a loading of 0.5 mg·cm³. -2 Carbon paper.
[0034] Electrocatalytic testing conditions: In an H-type electrolytic cell, using 0.5 mol / L KHCO3 solution as the electrolyte, CO2 gas was introduced for 30 min to saturate the electrolyte (pH=7.2). Ag / AgCl was used as the reference electrode, Pt sheet as the counter electrode, and the above-mentioned loaded carbon paper as the working electrode. Pre-reduction was first performed at -1.5V Ag / AgCl for 20 min. Then, electrolysis was performed at -1.0V (vs. RHE) as the electrolysis potential for 10 h under constant potential.
[0035] Product detection: Gas phase products were analyzed by gas chromatography (TCD detector for H2, FID detector for CO and CH4), and liquid phase products (methanol) were detected by nuclear magnetic resonance spectroscopy (DMSO as internal standard).
[0036] Test results: At -1.0V vs. RHE potential, the H2 Faradaic efficiency is 28.5%, the CO2RR / H2 reaction selectivity ratio is 2.27, the methanol Faradaic efficiency FE(CH3OH) is 64.8%, and the methanol partial current density is 13.6 mA·cm⁻¹. -2 Methanol production rate: 84.38 μmol·h⁻¹ -1 ·cm -2 Half-cell cathode energy efficiency: 34.84% No significant performance degradation was observed after 10 hours of continuous operation.
[0037] Example 2 The only difference from Example 1 is that the amount of silver nitrate added was changed to 5.1 mg, resulting in an Ag-CuS-1.5% catalyst. The remaining preparation steps, electrode preparation, and electrocatalytic testing conditions were exactly the same.
[0038] Test results: H2 Faradaic efficiency: 42.3%; CO2RR / H2 selectivity ratio: 1.36; Methanol Faradaic efficiency (FE): 50.7%; Methanol partial current density: 10.2 mA·cm⁻¹ -2 Semi-cathode energy efficiency: 26.52%.
[0039] Example 3 The only difference from Example 1 is that the amount of silver nitrate added was changed to 8.4 mg, resulting in an Ag-CuS-2.5% catalyst. The remaining preparation steps, electrode preparation, and electrocatalytic testing conditions were exactly the same.
[0040] Test results: H2 Faraday efficiency: 58.6%; CO2RR / H2 selectivity ratio: 0.71; methanol Faraday efficiency (FE): 31.5%; methanol partial current density: 6.8 mA·cm⁻¹ -2 Semi-cathode energy efficiency: 15.92%.
[0041] Comparative Example 1 The only difference from Example 1 is that silver nitrate is not added; all other raw materials, proportions, preparation, and testing are exactly the same.
[0042] result: At a potential of -1.0 V vs RHE: methanol Faraday efficiency: 20.0%; methanol partial current density: 4.25 mA·cm⁻¹ -2 CO2RR / H2 selectivity ratio: 0.34; Tafel slope: 272 mV·dec -1 .
[0043] The CO2RR / H2 reaction selectivity ratio in Example 1 was 2.27, while the CO2RR / H2 reaction selectivity ratio in Comparative Example 1 was 0.34, demonstrating that Ag-doped CuS can effectively regulate the electronic structure of the catalyst and suppress the hydrogen evolution reaction.
[0044] Figure 1 The Tafel graphs for Example 1 and Comparative Example 1 (CuS) are shown below. Figure 1 It can be seen that the Tafel slope of the Ag-CuS-0.5% catalyst is 138 mVdec. -1 The Tafel slope of CuS is 272 mVdec. -1 This proves that the electron transfer resistance (Rct) is smaller. CO intermediate hydrogenation process ( CO→ CHO→ OCH3) has faster kinetics.
[0045] Figure 2 The following data are presented for four catalysts at different potentials: (a) the Faradaic efficiency of CH3OH; (b) the partial current density of CH3OH; (c) the half-cathode energy efficiency; and (d) the production rate of CH3OH. Figure 2 It can be seen that within the wide potential window of -0.8 to -1.2 V vs. RHE, the methanol Faradaic efficiency of Example 1 consistently exceeds 40%. When the doping concentration increases from 0.5% to 2.5%, the Faradaic efficiency of CH3OH decreases, but it remains higher than that of pure CuS-based CH3OH, indicating that Ag-doped CuS significantly improves the Faradaic efficiency of CH3OH. The partial current density of Ag-CuS-0.5% CH3OH is consistently higher than that of CuS, Ag-CuS-1.5%, and Ag-CuS-2.5% across the entire voltage range, reaching 13.6 mA cm⁻¹ at -1.0 V vs. RHE. -2The methanol Faraday efficiency reached 64.8%, and after 10 hours of continuous operation, the methanol Faraday efficiency remained above 60%, with no significant decrease in current density, demonstrating its superior catalytic activity. The Ag-CuS-0.5% catalyst achieved a CH3OH energy efficiency of 34.84% at a potential of -1.0V vs. RHE, showing a significant advantage over CuS, Ag-CuS-1.5%, and Ag-CuS-2.5% catalysts. The Ag-CuS-0.5% catalyst achieved a CH3OH production rate of 84.38 μmol / h at a potential of -1.0V vs. RHE. -1 cm -2 The pure CuS catalyst exhibits a methanol Faradaic efficiency of 20% and a partial current density of 4.25 mA·cm⁻¹ at -1.0 V vs. RHE potential. -2 .
[0046] Figure 3 SEM image of Ag-CuS-0.5% catalyst; Figure 4 The XRD patterns are of four catalysts: CuS, Ag-CuS-0.5%, Ag-CuS-1.5%, and Ag-CuS-2.5%, after pre-reduction.
[0047] Figure 5 The stability test curves for the Ag-CuS-0.5% catalyst are shown below. Figure 5 It can be seen that after 10 hours of continuous operation in the H-type electrolytic cell, the methanol Faraday efficiency and current density did not decrease significantly, and the average Faraday efficiency remained above 60%, thus solving the problem of CuS easy reduction and deactivation.
[0048] Figure 6 XRD patterns of CuS and Ag-CuS-0.5% are shown. Figure 6 It can be confirmed that Ag successfully doped the CuS lattice, resulting in a low-angle shift of the diffraction peaks; Figure 7 Cu2p spectra of CuS and Ag-CuS-0.5% XPS, from Figure 7 It can be confirmed that Ag interacts with Cu, the Cu 2p binding energy is reduced, and the electronic structure is optimized.
[0049] Figure 8 The in-situ Raman spectra of Ag-CuS-0.5% at different potentials are shown below. Figure 8 It can be confirmed that CO is a key intermediate in methanol formation, and Ag doping promotes CO adsorption and enrichment.
[0050] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. People can obtain other embodiments based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.
Claims
1. The application of an Ag-doped CuS material in the electrocatalytic reduction of CO2 to methanol, wherein the Ag-doped CuS material comprises CuS and Ag embedded in the CuS lattice; the molar amount of Ag is 0.5 to 2.5% of the molar amount of copper.
2. The application as described in claim 1, characterized in that, The molar amount of Ag is 0.5% of the molar amount of copper.
3. The application as described in claim 1, characterized in that, The preparation method of the Ag-doped CuS material includes the following steps: Copper salt, sulfur source, surfactant and silver nitrate were dissolved in a mixture of alcohol and water and subjected to a solvothermal reaction to obtain Ag-doped CuS material.
4. The application as described in claim 1, characterized in that, The copper salt includes one or more of anhydrous copper nitrate, copper chloride, and copper acetate; the sulfur source includes thiourea; and the surfactant includes one or more of sodium dodecyl sulfate, polyethylene glycol, and hexadecyltrimethylammonium chloride.
5. The application as described in claim 1, characterized in that, The alcohol is one or more of ethanol, glycerol, and polyethylene glycol; the volume ratio of alcohol to water in the mixture of alcohol and water is 1:
3.
6. A method for electrocatalytically reducing CO2 to methanol, characterized in that, Includes the following steps: In a three-electrode system, CO2 gas is introduced into the electrolyte until saturation, followed by pre-reduction and electrocatalytic reduction to obtain methanol. The three-electrode system includes a working electrode, a reference electrode, and a counter electrode. The working electrode is made of Ag-doped CuS material.
7. The method as described in claim 6, characterized in that, The reference electrode is Ag / AgCl; the counter electrode is a Pt sheet.
8. The method as described in claim 6, characterized in that, The electrolyte is a KHCO3 solution with a concentration of 0.3-0.7 mol / L. After CO2 gas is introduced into the electrolyte until saturation for 25-30 minutes, pre-reduction and electrocatalytic reduction are carried out sequentially.
9. The method as described in claim 6, characterized in that, The pre-reduction potential is -1.5V vs Ag / AgCl; the pre-reduction time is 15~25min.
10. The method as described in claim 6, characterized in that, The electrocatalytic reduction is a constant potential reduction; the electrocatalytic reduction potential is -0.8 to -1.2 V vs. RHE; the electrocatalytic reduction time is 9.5 to 10.5 h.