Preparation and Application of an r-Cu2(OH)3X Electrocatalyst

Abstract

The application relates to the preparation of an r-Cu2(OH)3X electrocatalyst and application thereof, and belongs to the technical field of electrocatalyst preparation. The preparation method adopts an improved sol-gel method, and after washing and drying, carbon dioxide electrolysis is carried out under alkaline conditions to obtain the catalyst r-Cu2(OH)3X by doping halogen into a copper-based material. Due to the electron regulation effect of halogen on copper, the copper has high reaction activity and selectivity to multi-carbon products in an alkaline electrolyte, and can be used as a catalyst for electrocatalytic carbon dioxide reduction to produce multi-carbon products in an alkaline environment. The catalyst for alkaline electrocatalytic carbon dioxide reduction to produce multi-carbon products has high activity and obvious stability advantages, and has a broad development prospect.

Description

Technical Field

[0001] This invention relates to the field of electrocatalytic carbon dioxide reduction reaction technology under alkaline conditions, specifically to a method for preparing a halogen-doped copper-based catalyst and its application in the efficient and stable electrocatalytic reduction of carbon dioxide to produce multi-carbon products under alkaline conditions. Background Technology

[0002] With the intensification of global climate change and the gradual depletion of fossil fuel resources, the development of sustainable clean energy technologies has become an important topic in scientific research. Carbon dioxide (CO2) is a major component of greenhouse gases, and its continuous rise in concentration has led to rising global temperatures and more frequent extreme weather events. Therefore, effectively converting CO2 into valuable chemicals and fuels can not only reduce environmental pollution but also alleviate the energy crisis to some extent. Finding efficient and safe CO2 conversion technologies is crucial. Electrocatalytic CO2 reduction (CO2RR) is an effective method for converting greenhouse gases into valuable chemicals. However, current catalysts in CO2 reduction reactions often suffer from poor selectivity for multi-carbon products, insufficient activity, and poor stability, limiting their industrial application. Therefore, the development of new, highly efficient catalysts has become a current research hotspot.

[0003] In recent years, research on non-metallic copper-doped catalysts has been increasing in order to improve catalytic activity and selectivity while reducing catalyst costs. For example, boron-doped graphene-anchored copper clusters have significantly improved the C2 product formation efficiency in electrocatalytic carbon dioxide reduction; nitrogen-doped carbon-confined copper-silver bimetallic catalysts have efficiently generated high-value-added products in electrocatalytic carbon dioxide reduction; and high selectivity for multi-carbon products has been achieved by utilizing special proton transport and phosphorus electronic structure modification through in-situ electrodeposition at different potentials to prepare phosphorus-containing Cu catalysts (CuP-xV). Although these catalysts are significantly superior to elemental copper catalysts in terms of selectivity and activity for multi-carbon production in carbon dioxide reduction, their selectivity still needs improvement, and the catalyst synthesis methods are complex, ultimately failing to meet the practical requirements of carbon dioxide reduction. Summary of the Invention

[0004] The purpose of this invention is to develop a method for preparing an r-Cu2(OH)3X catalyst that continuously operates in an alkaline electrocatalytic carbon dioxide reduction process. This catalyst operates at a total current density of −250 mA cm⁻¹. −2 The Faraday efficiency for producing multi-carbon products can reach approximately 78%, which is 2.5 times that of copper hydroxide and twice that of metallic copper. Under constant potential electrolysis stability testing at −1.9 V vs. Ag / AgCl, it can maintain a long-term stability of −90 mA cm⁻¹. –2The catalyst exhibits high local carbon production current density and nearly 45% ethylene selectivity without significant deactivation. Furthermore, the synthesis method is simple and efficient.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows: A method for preparing an r-Cu2(OH)3X electrocatalyst includes the following steps: (1) Dissolve copper halide in propanol to prepare a solution with a concentration of 0.15-6 mol / L; add propylene oxide and deionized water under continuous stirring to obtain a mixed solution; (2) Seal and age the mixed solution for 1-5 days. After aging, centrifuge the solution to obtain a precipitate, wash and vacuum dry it. (3) Electroreconstruction: The dried product is made into an electrode sheet and electrolyzed in an electrolyte for 10-30 min.

[0006] Furthermore, the copper halide is copper fluoride, copper chloride, or copper bromide.

[0007] Further, the molar ratio of propylene oxide to copper halide is (8-12):1. Preferably, the molar ratio of propylene oxide to copper halide is 10:1. Furthermore, the electrolyte is a 1 M KOH solution.

[0008] An r-Cu2(OH)3X electrocatalyst was prepared using the method described above.

[0009] Furthermore, the electrocatalyst exists in two crystalline phases: copper and cuprous oxide.

[0010] Furthermore, the electrocatalyst is applied to the electrocatalytic reduction of carbon dioxide under alkaline conditions.

[0011] Furthermore, the electrocatalyst is applied to the electrocatalytic preparation of multi-carbon products from carbon dioxide under alkaline conditions.

[0012] Preferably, bromine is introduced into metallic copper to first obtain the catalyst precursor. Halogen-doped Cu₂(OH)₃X (X = F, Cl, Br) nanomaterials are used as the working electrode, a platinum sheet electrode as the counter electrode, and an Ag / AgCl electrode as the reference electrode. Using 1 M KOH solution as the electrolyte, constant voltage activation is performed to obtain the Cu-based electrocatalytic CO₂RR catalyst r-Cu₂(OH)₃X. After electrochemical reconstruction, the surface of the r-Cu₂(OH)₃Br catalyst is rich in Cu. 0 / Cu + The presence of sites and residual Br ions significantly increases the lattice spacing, altering the surface electronic structure and local environment of the catalyst, thereby further enhancing the electrocatalytic CO2RR response to C. 2+ Product selectivity.

[0013] A Br-doped Cu-based electrocatalytic CO2RR catalyst was prepared using the method described above.

[0014] Application of a Br-doped Cu-based electrocatalytic CO2RR catalyst, said catalyst for the electrocatalytic CO2RR preparation of C 2+ product.

[0015] The atomic ratio of Br:Cu in the aforementioned bromine-doped copper catalyst precursor should be 1:1.

[0016] The preparation process of the bromine-doped copper catalyst (r-Cu2(OH)3Br) is as follows: 0.3-3 mmol of copper bromide (CuBr2) is dissolved in 0.2-2 mL of 2-propanol to form a dark green transparent solution A. Under continuous stirring, 0.2-2 mL of propylene oxide and 0.02-0.2 mL of deionized water are gradually added to solution A, eventually yielding a blue-green solution B. The resulting mixed solution B is sealed and aged. The precipitate is then washed to remove any possible organic matter. After vacuum drying for 8-12 h, it is ground uniformly to obtain the bromine-doped copper precursor catalyst. The precursor powder is used to prepare the working electrode, and electrolysis is performed for 10-30 min to obtain the catalyst.

[0017] In the above-mentioned method for preparing the catalyst r-Cu2(OH)3Br, the reaction is carried out at room temperature except for vacuum drying.

[0018] The aging process of the catalyst r-Cu2(OH)3Br described above requires 1 to 3 days under sealed conditions.

[0019] In the above-mentioned method for preparing the catalyst r-Cu2(OH)3Br, the washing process uses the organic solvent acetone.

[0020] In the above-mentioned method for preparing the catalyst r-Cu2(OH)3Br, the drying temperature is 60~70℃.

[0021] The preparation method of the above-mentioned catalyst r-Cu2(OH)3Br involves an electrolysis process in a 1 M KOH solution under a CO2 atmosphere.

[0022] Compared with the prior art, the present invention has the following beneficial effects: 1. The synthesis process is simple, the yield is high, and the experimental process is controllable. The obtained catalyst r-Cu2(OH)3X has high crystallinity, exhibits a mixed structure of nanoparticles and dendrites, and has a higher active surface area.

[0023] 2. Copper is the only substance that can simultaneously catalyze the reduction of carbon monoxide, formic acid, and multiple carbon atoms (C2) in CO2. 2+ The product, a metal, has promising applications. This invention improves the selectivity and stability of copper catalysts by introducing halogen elements to modulate their electronic properties, which is crucial for CO2 reduction. The electronic structure of copper in the resulting catalyst r-Cu2(OH)3X is regulated by halogens, optimizing the inherent activity of copper metal and overcoming the inability to simultaneously achieve optimal selectivity for multi-carbon products. Specifically, the r-Cu2(OH)3Br catalyst exhibits the highest selectivity for multi-carbon products at -1.0 V, reaching 78%, with a selectivity of 53.2% for ethylene. This results in excellent activity and stability for CO2 reduction in alkaline media, significantly superior to traditional copper hydroxide and metallic copper catalysts, while also reducing material costs to some extent, making it a viable alternative.

[0024] 3. The obtained catalyst r-Cu2(OH)3X has broad application prospects in electrocatalytic CO2RR, new energy, and other fields. The catalyst described in this invention successfully incorporates non-metallic halogen elements into copper catalysts, successfully adjusting the lattice spacing and internal electronic structure of copper, significantly improving the reactivity and selectivity of copper, and perfectly enhancing catalytic performance while reducing costs. The synthesis process of this invention is simple, the experimental process is easy to control, and it has great potential in the field of electrocatalytic CO2RR. Attached Figure Description

[0025] Figure 1 The images show the SEM images of the catalysts Cu2(OH)3Br and r-Cu2(OH)3Br.

[0026] Figure 2 The XRD patterns of the catalysts Cu2(OH)3Br and r-Cu2(OH)3Br are shown.

[0027] Figure 3 The images show the relevant TEM and HRTEM images of the catalyst r-Cu2(OH)3Br.

[0028] Figure 4 Linear sweep voltammetry curves of catalyst r-Cu2(OH)3X in alkaline medium (1 M KOH).

[0029] Figure 5 The image shows a comparison of the selectivity of the catalyst r-Cu2(OH)3X and its control sample for the electrocatalytic CO2RR to multi-carbon products.

[0030] Figure 6 HRTEM images of the catalyst r-Cu2(OH)3X and control samples (Examples 2-3 and commercial copper hydroxide). Detailed Implementation

[0031] The present invention will be further described in detail below with reference to the accompanying drawings and specific examples. In the present invention, unless otherwise specified, M representing concentration represents mol / L. For example, 1 M KOH represents a 1 mol / L KOH solution.

[0032] (1) Preparation of the precursor: 0.3-3 mmol of copper halide was dissolved in 0.2-2 mL of 2-propanol to form a dark green transparent solution A. Under continuous stirring, 0.2-2 mL of propylene oxide and 0.02-0.2 mL of deionized water were gradually added to solution A to obtain a blue-green solution B. The mixed solution B was sealed and aged for 1-3 days to obtain a blue-green precipitate. The precipitate was then washed with acetone to remove any possible organic matter. After drying in a vacuum oven at 60°C overnight, it was ground uniformly to obtain the halogen-doped copper precursor catalyst (Cu2(OH)3X).

[0033] (2) Preparation of catalyst r-Cu2(OH)3X: The precursor powder Cu2(OH)3X was prepared as the working electrode, the platinum sheet electrode was used as the counter electrode, the Ag / AgCl electrode was used as the reference electrode, and the Cu-based electrocatalytic CO2RR catalyst r-Cu2(OH)3X was obtained by constant voltage activation with 1 M KOH solution as the electrolyte.

[0034] Example 1: r-Cu2(OH)3Br (1) Preparation of the precursor: 3 mmol of copper bromide (CuBr2) was dissolved in 2 mL of 2-propanol to form a dark green transparent solution A. Under continuous stirring, 2 mL of propylene oxide and 0.2 mL of deionized water were gradually added to solution A to obtain a blue-green solution B. The resulting mixed solution B was sealed and aged for 1 day to obtain a blue-green precipitate. The precipitate was then washed with acetone to remove any possible organic matter. After drying in a vacuum oven at 60°C overnight, it was ground uniformly to obtain a bromine-doped copper precursor catalyst (Cu2(OH)3Br).

[0035] (2) Preparation of catalyst r-Cu2(OH)3Br: The precursor powder Cu2(OH)3Br was prepared as the working electrode, the platinum sheet electrode was used as the counter electrode, the Ag / AgCl electrode was used as the reference electrode, and 1 M KOH solution was used as the electrolyte. The Cu-based electrocatalytic CO2RR catalyst r-Cu2(OH)3Br was obtained by constant voltage activation.

[0036] Example 2: r-Cu2(OH)3Cl (1) Preparation of the precursor Cu2(OH)3Cl: 3 mmol of copper chloride (CuCl2) was dissolved in 2 mL of 2-propanol to form a dark green transparent solution A. Under continuous stirring, 2 mL of propylene oxide and 0.2 mL of deionized water were gradually added to solution A to obtain a blue-green solution B. The resulting mixed solution B was sealed and aged for 1 day to obtain a blue-green precipitate. The precipitate was then washed with acetone to remove any possible organic matter. After drying in a vacuum oven at 60°C overnight, it was ground uniformly to obtain a bromine-doped copper precursor catalyst (Cu2(OH)3Cl).

[0037] (2) Preparation of catalyst r-Cu2(OH)3Cl: The precursor powder was prepared into a working electrode, a platinum sheet electrode was used as the counter electrode, an Ag / AgCl electrode was used as the reference electrode, and 1 M KOH solution was used as the electrolyte. The Cu-based electrocatalytic CO2RR catalyst r-Cu2(OH)3Cl was obtained by constant voltage activation.

[0038] Example 3: r-Cu2(OH)3F (1) Preparation of the precursor Cu2(OH)3F: 3 mmol of copper fluoride (CuF2) was dissolved in 2 mL of 2-propanol to form a dark green transparent solution A. Under continuous stirring, 2 mL of propylene oxide and 0.2 mL of deionized water were gradually added to solution A to obtain a blue-green solution B. The resulting mixed solution B was sealed and aged for 1 day to obtain a blue-green precipitate. The precipitate was then washed with acetone to remove any possible organic matter. After drying in a vacuum oven at 60°C overnight, it was ground uniformly to obtain the bromine-doped copper precursor catalyst (Cu2(OH)3F).

[0039] (2) Preparation of catalyst r-Cu2(OH)3F: The precursor powder was prepared into a working electrode, a platinum sheet electrode was used as the counter electrode, an Ag / AgCl electrode was used as the reference electrode, and 1 M KOH solution was used as the electrolyte. The Cu-based electrocatalytic CO2RR catalyst r-Cu2(OH)3F was obtained by constant voltage activation.

[0040] Example 4: r-Cu(OH)2 Commercial copper hydroxide powder was used to prepare the working electrode, a platinum sheet electrode was used as the counter electrode, an Ag / AgCl electrode was used as the reference electrode, and 1 M KOH solution was used as the electrolyte. The Cu-based electrocatalytic CO2RR catalyst r-Cu(OH)2 was obtained by constant voltage activation.

[0041] Example 5: r-Cu

[0042] Commercial copper powder was used to prepare the working electrode, a platinum sheet electrode was used as the counter electrode, and an Ag / AgCl electrode was used as the reference electrode. A 1 M KOH solution was used as the electrolyte, and the Cu-based electrocatalytic CO2RR catalyst r-Cu was obtained by constant voltage activation. Example 6

[0043] Structural characterization of Cu2(OH)3Br and r-Cu2(OH)3Br catalysts: The structures of the catalyst precursors Cu₂(OH)₃Br and r-Cu₂(OH)₃Br prepared in Example 1 were characterized. The microstructure of the catalyst surface was observed using field emission scanning electron microscopy (SEM). Sample preparation: Conductive adhesive was adhered to the sample tray on the sample stage. The sample to be tested was then cut to an appropriate size and adhered to the conductive adhesive. Loose powder was gently removed by blowing with a nitrogen gun. The sample stage was then placed in a gold sputtering machine for gold sputtering to enhance the conductivity of the sample. After gold sputtering, the sample was ready for testing. Figure 1 It can be observed that the precursor catalyst prepared in Example 1 has a relatively smooth and regular nanosheet structure, while the r-Cu2(OH)3Br catalyst becomes sharper and rougher after electrochemical reconstruction, transforming into a mixed structure of nanoparticles and dendrites. This is beneficial for the contact between the electrode material and the electrolyte, providing a larger active surface area for the electrocatalytic CO2RR reaction.

[0044] The crystal structure and phase composition of the catalyst precursors Cu2(OH)3Br and r-Cu2(OH)3Br from Example 1 were analyzed using powder X-ray diffraction (XRD). The sample powder or carbon paper was placed in a groove in a quartz plate, the surface was flattened, and then the plate was placed in the XRD machine. The scanning range was 5°–80°, and the scanning speed was 10° / min. -1 The diffraction pattern was obtained. The diffraction peaks of the catalyst precursor are clearly visible, corresponding to those on the standard card Cu2(OH)3Br (PDF#45-1309). Figure 2 (a) After reconstruction, the catalyst mainly consists of two crystalline phases: Cu (PDF#04-0836) and Cu2O (PDF#05-0667). Figure 2 (b) In summary, the XRD pattern shows that bromine was successfully introduced into the copper-based catalyst, and the remodeling altered the catalyst's configuration and electronic structure.

[0045] The structural features of the catalyst surface prepared in Example 1 were further observed using a FEI TF300 transmission electron microscope (TEM). Before testing, a small amount of catalyst loaded on carbon paper was scraped off with a file, thoroughly ground, and then poured into a vial filled with ethanol. The sample was ultrasonically sonicated for at least 15 minutes in an ultrasonic oscillator to ensure uniform dispersion of the catalyst in the solvent. A small amount of solution was then dropped onto a molybdenum grid for sample injection and testing. Figure 3 The nanoparticles and dendritic hybrid structure can be clearly observed. Figure 3 (a) is consistent with the SEM test results. Furthermore, lattice fringes belonging to Cu(111) and Cu2O(111) can be measured. Figure 3 (b)

[0046] Electrochemical testing of r-Cu2(OH)3X catalyst: All electrochemical tests in this embodiment were performed at room temperature (25°C) using a CHI760E electrochemical workstation. The tests employed a gas diffusion flow cell apparatus in a 1 M KOH alkaline medium (pH=13.6), with the electrode of the material under test serving as the working electrode (catalyst contact area with electrolyte of 1 cm²). 2 A platinum sheet electrode was used as the counter electrode, and an Ag / AgCl electrode was used as the reference electrode (0.197 V). vs The electrochemical performance of the prepared catalyst was tested using a reversible hydrogen electrode (RHE).

[0047] Linear voltammetric scans (LSV) were performed on the catalysts r-Cu2(OH)3Br, r-Cu2(OH)3Cl, r-Cu2(OH)3F, r-Cu(OH)2, and r-Cu prepared in Examples 1-5: at 5 mV s -1 The scan rate is between 0 and −2.0 V. vs. Linear voltammetric scanning tests were performed within the Ag / AgCl voltage range. For example... Figure 4 As shown, r-Cu2(OH)3Br exhibits a significant advantage in current density compared to r-Cu2(OH)3Cl, r-Cu2(OH)3F, r-Cu(OH)2, and r-Cu, especially at a voltage of -2.0 V. vs At Ag / AgCl, the current density reaches as high as −280 mA cm⁻¹. -2 It has better catalytic activity.

[0048] Electrocatalytic CO2RR preparation of C using catalysts r-Cu2(OH)3Br, r-Cu2(OH)3Cl, r-Cu2(OH)3F, r-Cu(OH)2, and r-Cu prepared in Examples 1-5. 2+ Product performance testing. The test voltage range is −0.8 V to −1.2 V. vs. RHE, with 1 M KOH solution as the electrolyte, and each test lasted 30 min. Figure 5As shown in Table 1, the r-Cu2(OH)3Br catalyst exhibits the highest selectivity for multi-carbon products, reaching 78%, under the reversible hydrogen electrode condition at –1.0 V. The Faradaic efficiencies for ethylene and ethanol are 53.2% and 20%, respectively. These results demonstrate that r-Cu2(OH)3Br can not only effectively catalyze the CO2 conversion process but also achieve significant performance in the generation of multi-carbon products.

[0049] Table 1 shows the Faraday efficiency of C2H4 and C2H5OH for CO2RR under different potential conditions of catalyst r-Cu2(OH)3Br.

[0050] -1.4 45.81 21.14 -1.3 50.19 16.86 -1.2 47.45 20.00 -1.1 49.64 18.23 -1.0 53.21 20.06 -0.9 43.25 15.34 -0.8 30.30 14.95 -0.7 34.82 11.11 -0.6 20.11 7.68 -0.5 14.73 0.34 HRTEM tests were performed on the catalysts r-Cu₂(OH)₃Br, r-Cu₂(OH)₃Cl, r-Cu₂(OH)₃F, and r-Cu(OH)₂ prepared in Examples 1-5 to obtain more detailed crystal structure characteristics. The Cu₂O(111) lattice spacing of the four catalysts was the same, while the Cu(111) lattice spacing was different. Furthermore, with the introduction of fluorine, chlorine, and bromine, the d-Cu(111) spacing gradually increased, indicating that the Br-doped sample had the largest interplanar spacing. This change may be related to the changes in crystal and electronic structure caused by the introduction of Br ions, thereby exposing more active sites.

[0051] The above embodiments are only used to illustrate the present invention. Any equivalent transformations and improvements made on the basis of the technical solutions of the present invention should not be excluded from the protection scope of the present invention.

Claims

1. A method for preparing an r-Cu2(OH)3X electrocatalyst, characterized in that, The steps include the following: (1) Dissolve copper halide in propanol to prepare a solution with a concentration of 0.15-6 mol / L; add propylene oxide and deionized water under continuous stirring to obtain a mixed solution; (2) Seal and age the mixed solution for 1-5 days. After aging, centrifuge the solution to obtain a precipitate, wash and vacuum dry it. (3) Electroreconstruction: The dried product was made into an electrode sheet and electrolyzed in 1 M KOH electrolyte for 10~30 min. The electrolysis voltage range was −0.8 V to −1.2 V vs. RHE.

2. The method for preparing an r-Cu2(OH)3X electrocatalyst according to claim 1, characterized in that, The copper halides are copper fluoride, copper chloride, and copper bromide.

3. The method for preparing an r-Cu2(OH)3X electrocatalyst according to claim 1, characterized in that, The molar ratio of propylene oxide to copper halide is (8-12):

1.

4. The method for preparing an r-Cu2(OH)3X electrocatalyst according to claim 1, characterized in that, The electrolyte is a 1 M KOH solution.

5. An r-Cu2(OH)3X electrocatalyst, characterized in that: It is prepared by any one of the methods described in claims 1-4.

6. The r-Cu2(OH)3X electrocatalyst according to claim 5, characterized in that: The electrocatalyst exists in two crystalline phases: copper and cuprous oxide.

7. The application of the r-Cu2(OH)3X electrocatalyst according to claim 5, characterized in that: The electrocatalyst is used for the electrocatalytic reduction of carbon dioxide under alkaline conditions.

8. The application of the r-Cu2(OH)3X electrocatalyst according to claim 7, characterized in that: The electrocatalyst is used to electrocatalyze the preparation of multi-carbon products from carbon dioxide under alkaline conditions.

9. The application of the r-Cu2(OH)3X electrocatalyst according to claim 8, characterized in that: The alkaline condition is that 1 M KOH is used as the electrolyte.

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