A copper-bismuth bimetallic catalyst, a preparation method and application thereof

Abstract

The application discloses a copper-bismuth bimetallic catalyst and a preparation method and application thereof. The copper-bismuth bimetallic catalyst comprises a copper substrate and copper-bismuth nanowires grown on the copper substrate, the copper-bismuth nanowires comprise copper nanowires and a metal bismuth layer loaded on the copper nanowires, and the mass fraction of bismuth in the copper-bismuth nanowires is 40% to 60%. The preparation method of the catalyst comprises the following steps: after in-situ growth of copper hydroxide nanowires on the copper substrate, the copper-bismuth bimetallic catalyst is prepared through heat treatment, electrochemical reduction treatment and bismuth deposition. Meanwhile, the copper-bismuth bimetallic catalyst can not only make full use of the copper and bismuth bimetallic effect, effectively improve the activity, stability and selectivity of electrocatalytic reduction of carbon dioxide, but also has the advantages of simple and controllable preparation, wide application potential window and wide application environment.

Description

Technical Field

[0001] This invention relates to the technical field of catalyst materials, specifically to a copper-bismuth bimetallic catalyst, its preparation method, and its application. Background Technology

[0002] With industrial development and the growth of social activities, the environmental impact of carbon dioxide greenhouse gas emissions needs to be taken seriously.

[0003] Electrochemical reduction of carbon dioxide (CO2) technology utilizes renewable energy sources to convert CO2 gas into high-value-added fuels and chemicals (e.g., formic acid). It effectively reduces atmospheric CO2 concentration and addresses the long-term storage challenges of renewable energy sources. A crucial aspect of this technology is the research on electrocatalysts. Therefore, catalysts for the electrochemical reduction of CO2 to formic acid are of significant research importance.

[0004] Currently, existing technologies demonstrate that copper can electrochemically reduce carbon dioxide to hydrocarbons at high current densities. However, pure copper exhibits poor selectivity for the electrocatalytic reduction of carbon dioxide to formic acid and possesses an extremely high overpotential, hindering practical applications. Furthermore, although researchers have attempted to improve the catalytic activity of copper for carbon dioxide reduction by doping or introducing other metals, it remains difficult to overcome problems such as low single-pass carbon dioxide conversion efficiency, narrow application potential window, limited applicable environments, and poor catalytic performance in acidic environments.

[0005] Therefore, there is an urgent need to develop a catalyst for carbon dioxide reduction that has good electrocatalytic activity, good stability, wide potential window, wide applicability to various environments, and can maintain high carbon dioxide conversion efficiency in acidic environments. Summary of the Invention

[0006] In order to overcome the problems of narrow application range, poor stability, low carbon dioxide conversion efficiency and low selectivity for formate in existing electrocatalysts, the present invention aims to provide a copper-bismuth bimetallic catalyst, its preparation method and application.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] In a first aspect, the present invention provides a copper-bismuth bimetallic catalyst comprising a copper substrate and copper-bismuth nanowires grown on the copper substrate, wherein the copper-bismuth nanowires comprise copper nanowires and a metallic bismuth layer supported on the copper nanowires.

[0009] Preferably, the copper base is one of copper sheet, copper foam, copper plate, and copper rod.

[0010] More preferably, the copper base is copper foam.

[0011] Preferably, the mass fraction of bismuth in the copper-bismuth nanowires is 40% to 60%.

[0012] More preferably, the mass fraction of bismuth in the copper-bismuth nanowires is 50% to 55%.

[0013] Preferably, the length of the copper-bismuth nanowire is on the micrometer scale.

[0014] More preferably, the length of the copper-bismuth nanowire is 2 μm to 10 μm.

[0015] Preferably, the diameter of the copper-bismuth nanowire is 210 nm to 600 nm.

[0016] More preferably, the diameter of the copper bismuth nanowire is 220 nm to 450 nm.

[0017] Preferably, the diameter of the copper nanowire is 200 nm to 300 nm.

[0018] Preferably, the bismuth layer comprises a plurality of bismuth nanoparticles.

[0019] Preferably, the bismuth nanoparticles have a particle size of 10–20 nm.

[0020] In a second aspect, the present invention provides a method for preparing the copper-bismuth bimetallic catalyst described in the first aspect, comprising the following steps:

[0021] After in-situ growth of copper hydroxide nanowires on a copper substrate, copper-bismuth bimetallic catalysts were prepared by heat treatment, electrochemical reduction treatment, and bismuth deposition.

[0022] Specifically, the preparation method of the copper-bismuth bimetallic catalyst includes: growing copper hydroxide nanowires in situ on a copper substrate to obtain a copper substrate with grown copper hydroxide nanowires; placing the copper substrate with grown copper hydroxide nanowires in an oxygen-containing atmosphere for heat treatment to obtain a copper substrate with grown copper oxide nanowires; then electrochemically reducing the copper substrate with grown copper oxide nanowires to obtain a copper substrate with grown copper nanowires; finally, using the copper substrate with grown copper nanowires as a cathode, and depositing bismuth using a constant voltage to obtain the copper-bismuth bimetallic catalyst.

[0023] Preferably, the preparation method of the copper-bismuth bimetallic catalyst further includes a pretreatment step.

[0024] Preferably, the pretreatment specifically involves: first soaking the copper substrate in acetone and acid, then rinsing the copper substrate with deionized water and ethanol, and then drying and purging it under a nitrogen atmosphere to obtain a cleaned copper substrate.

[0025] Preferably, the acid solution includes one of hydrochloric acid, sulfuric acid, and nitric acid.

[0026] More preferably, the acid solution is hydrochloric acid with a concentration of 0.5–3.5 mol / L.

[0027] Preferably, the specific operation of the in-situ growth of copper hydroxide nanowires includes: immersing a copper substrate in an alkaline solution to obtain a copper substrate on which copper hydroxide nanowires are grown.

[0028] Preferably, the alkaline solution comprises an alkali and an oxidizing agent.

[0029] Preferably, the alkali includes at least one of sodium hydroxide and potassium hydroxide.

[0030] Preferably, the oxidant is a persulfate, including at least one of sodium persulfate and ammonium persulfate.

[0031] Preferably, the concentration of alkali in the alkaline solution is 3 to 8 mol / L.

[0032] More preferably, the concentration of alkali in the alkaline solution is 6 mol / L.

[0033] Preferably, the mass ratio of the oxidant to the alkali is 1:(3-5).

[0034] Specifically, the amount of alkaline solution can be adjusted according to actual needs, ideally to completely immerse the copper substrate.

[0035] Preferably, the copper substrate is immersed in the alkaline solution for 15 to 40 minutes.

[0036] Preferably, the heat treatment specifically involves heating a copper substrate with grown copper hydroxide nanowires to 150–350°C in an oxygen-containing atmosphere and holding it at that temperature for 1–3 hours to obtain a copper substrate with grown copper oxide nanowires.

[0037] Preferably, the oxygen-containing atmosphere is air.

[0038] Preferably, the electrochemical reduction treatment specifically involves: using a copper substrate with grown copper oxide nanowires as the working electrode in an electrolyte, and performing electroreduction with a constant current to obtain a copper substrate with grown copper oxide nanowires.

[0039] Preferably, the electrolyte includes one or more of sodium bicarbonate solution and potassium bicarbonate solution.

[0040] More preferably, the electrolyte is a potassium bicarbonate solution of 0.05 mol / L to 0.5 mol / L.

[0041] Preferably, the current density of the constant current is 4 mA / cm². 2~7mA / cm 2 .

[0042] Preferably, the electroreduction time is 3000s to 7200s.

[0043] Preferably, the specific method for depositing bismuth is as follows: in a solution containing bismuth ions, using a copper substrate with grown copper nanowires as the working electrode, bismuth is electrodeposited using a constant voltage to obtain a copper-bismuth bimetallic catalyst.

[0044] Preferably, the bismuth-containing solution comprises a soluble bismuth salt and an ethylene glycol solution.

[0045] Preferably, the soluble bismuth salt includes at least one of bismuth nitrate and bismuth nitrate pentahydrate.

[0046] Preferably, the ethylene glycol solution is a 99 wt% ethylene glycol solution.

[0047] Preferably, the bismuth-containing solution comprises 8 g / L to 10 g / L bismuth nitrate pentahydrate.

[0048] Preferably, the electrodeposited bismuth uses an Ag / AgCl electrode as a reference electrode, and the E of the electrodeposited bismuth is... Ag / AgCl The voltage range is -1.5V to -2.5V.

[0049] More preferably, the electrodeposited bismuth uses an Ag / AgCl electrode as a reference electrode, and the E of the electrodeposited bismuth... Ag / AgCl The voltage range is -1.6V to -2.0V.

[0050] Preferably, the electrodeposited bismuth further includes a graphite carbon rod as the counter electrode.

[0051] Preferably, the electrodeposition time of bismuth is 3500s to 6000s.

[0052] More preferably, the electrodeposition time of bismuth is 3800s to 4800s.

[0053] Thirdly, the present invention provides an electrode comprising the copper-bismuth bimetallic catalyst.

[0054] Fourthly, the present invention provides an application of the above-mentioned copper-bismuth bimetallic catalyst in the electrocatalytic reduction of carbon dioxide.

[0055] Preferably, the electrocatalytic reduction of carbon dioxide is carried out in a neutral or acidic environment.

[0056] Preferably, the pH value of the electrolyte for the electrocatalytic reduction of carbon dioxide is ≤7.0.

[0057] More preferably, the pH value of the electrolyte for the electrocatalytic reduction of carbon dioxide is 7.0 or 3.0 to 5.0.

[0058] Fifthly, the present invention provides a method for electrocatalytic reduction of carbon dioxide, comprising the following steps:

[0059] The copper-bismuth bimetallic catalyst was used as the cathode, and carbon dioxide was introduced into the reaction electrolyte to carry out electrolysis.

[0060] The reaction electrolyte includes at least one of potassium bicarbonate and potassium sulfate; and the pH value of the reaction electrolyte is 3.0 to 7.2.

[0061] Preferably, the electrolyte for the reaction includes one of potassium bicarbonate and potassium sulfate.

[0062] More preferably, the reaction electrolyte comprises a 0.1–1.0 mol / L potassium bicarbonate solution.

[0063] More preferably, the reaction electrolyte comprises a potassium sulfate solution of 0.1 mol / L to 1.0 mol / L.

[0064] Preferably, the reaction electrolyte is one of a neutral electrolyte or an acidic electrolyte;

[0065] The neutral electrolyte is prepared as follows: Carbon dioxide is bubbled into a potassium bicarbonate solution until the pH value reaches 7.0, thus obtaining the neutral electrolyte.

[0066] The acidic electrolyte is prepared as follows: Carbon dioxide is bubbled into a potassium sulfate solution until saturation, and then the pH is adjusted to 3.0-5.0 with acid to obtain the acidic electrolyte.

[0067] Specifically, compared to a neutral environment, in an acidic electrolyte environment, hydrated hydrogen ions can serve as a proton source for the carbon dioxide reduction reaction, thereby inhibiting OH-. - This avoids the formation of carbonates and prevents carbonate buildup. Furthermore, in an acidic electrolyte environment, even if water in the electrolyte provides protons for CO2 reduction, the locally generated CO3... 2- It can also diffuse from the cathode surface into the acidic electrolyte, where it is acidified into carbon dioxide, thereby improving carbon utilization efficiency.

[0068] Preferably, the method for electrocatalytic reduction of carbon dioxide further includes using Ag / AgCl as a reference electrode and a platinum sheet as a counter electrode; and the electrolysis potential is -1.0V vs. RHE to -1.9V vs. RHE.

[0069] Specifically, within the electrolysis potential range, the main product of the electrocatalytic carbon dioxide reduction reaction is formate.

[0070] The beneficial effects of this invention are: the copper-bismuth bimetallic catalyst of this invention not only fully utilizes the bimetallic effect of copper and bismuth to effectively improve the activity, stability, and selectivity of electrocatalytic reduction of carbon dioxide, but also has the advantages of simple and controllable preparation, a large application potential window, and applicability to various environments. Specifically:

[0071] (1) The copper-bismuth bimetallic catalyst of the present invention can effectively improve the selectivity of electrochemical reduction of carbon dioxide through the bimetallic synergistic effect, effectively improve the Faraday efficiency of electrochemical reduction of formate in carbon dioxide, and improve the current density of carbon dioxide to formate conversion, thereby promoting the conversion of carbon dioxide into high value-added chemicals (i.e. formate).

[0072] (2) The copper-bismuth bimetallic catalyst of the present invention has copper-bismuth nanowires uniformly loaded on its surface, which can not only effectively reduce the contact with the substrate and lower the contact potential of the catalyst, but also increase the specific surface area of ​​the catalyst, which is conducive to exposing more active sites and thus improving the catalytic performance of electrocatalytic reduction of carbon dioxide.

[0073] (3) The preparation method of the copper-bismuth bimetallic catalyst of the present invention has the advantages of simple operation, low cost and strong operability.

[0074] (4) When the copper-bismuth bimetallic catalyst of the present invention is used for electrocatalytic carbon dioxide reduction, it can achieve high selectivity in the electrocatalytic generation of formate from carbon dioxide at a high current density.

[0075] (5) The copper-bismuth bimetallic catalyst of the present invention can be used for electrocatalytic carbon dioxide reduction in acidic environments, and in acidic environments, it also utilizes the alkali metal K in the electrolyte. + The existence of H3O + Competition forms chemically inert hydrated K + The layer inhibits the hydrogen evolution reaction to a certain extent and promotes the adsorption of carbon dioxide, thereby realizing the electrocatalytic reduction of carbon dioxide under acidic conditions.

[0076] (6) The copper-bismuth bimetallic catalyst of the present invention can achieve a maximum Faraday efficiency of 94.5% for the reduction of formate by carbon dioxide under neutral conditions (pH=7.0) and a maximum Faraday efficiency of 96.2% for the reduction of formate by carbon dioxide under acidic conditions (pH=3.6);

[0077] (7) When the copper-bismuth bimetallic catalyst of the present invention is used for electrocatalytic reduction of carbon dioxide, it can effectively promote the conversion of carbon dioxide to formate and improve carbon utilization efficiency. Attached Figure Description

[0078] Figure 1The XRD patterns are of Cu(OH)2NWs, CuO NWs, Cu NWs and CuBi-1 in Example 1.

[0079] Figure 2 This is a scanning electron microscope image of Cu(OH)2NWs from Example 1.

[0080] Figure 3 This is a scanning electron microscope image of CuO NWs from Example 1.

[0081] Figure 4 This is a scanning electron microscope image of Cu NWs from Example 1.

[0082] Figure 5 This is a scanning electron microscope image of CuBi-1 from Example 1.

[0083] Figure 6 This is a linear scan voltammetric curve of CuBi-1 in Example 1 under neutral conditions.

[0084] Figure 7 The diagram shows the Faraday efficiency of the copper-bismuth bimetallic catalysts in Examples 1 and Comparative Examples 1-3 in a neutral environment for the reduction of carbon dioxide to formate.

[0085] Figure 8 Partial current density diagrams for the reduction of carbon dioxide to formate using the copper-bismuth bimetallic catalysts in Examples 1 and Comparative Examples 1-3 in a neutral environment.

[0086] Figure 9 The figure shows the stability test results of the CuBi-1 carbon dioxide reduction reaction in a neutral environment.

[0087] Figure 10 This is a linear scan voltammetric curve of CuBi-1 in Example 1 under neutral conditions.

[0088] Figure 11 The Faraday efficiency diagram shows the reduction of carbon dioxide to formate in CuBi-1 of Example 1 and CuSn of Comparative Example 4 in an acidic environment.

[0089] Figure 12 The diagram shows the partial current density of CuBi-1 in Example 1 and CuSn in Comparative Example 4 as carbon dioxide reduced to formate in an acidic environment. Detailed Implementation

[0090] The present invention will be further described in detail below through specific embodiments.

[0091] Example 1

[0092] This embodiment provides a method for preparing a copper-bismuth bimetallic catalyst, including the following steps:

[0093] (1) Pretreatment: The area is 3cm 2 The foamed copper (size: 1cm×3cm) was first soaked in acetone and ultrasonically treated for 10-15min; the foamed copper was then transferred to 1mol / L HCl and ultrasonically treated for 15min; the foamed copper was then rinsed three times with deionized water and three times with ethanol, and dried and purged under nitrogen atmosphere at 10-35℃ to obtain cleaned foamed copper.

[0094] (2) Preparation of copper hydroxide nanowires: 2.71 g of solid sodium hydroxide particles were dissolved in 11.3 mL of deionized water and stirred for 5 min to prepare a 6 M sodium hydroxide solution; 0.62 g of solid ammonium persulfate was dissolved in 11.3 mL of deionized water and stirred for 5 min to prepare a 0.24 M ammonium persulfate solution.

[0095] While stirring, the above 6M sodium hydroxide solution was poured into 0.24M ammonium persulfate solution. Then, the cleaned copper foam was placed into the mixed solution and left to stand at room temperature for 20 minutes. Copper hydroxide nanowires were grown in situ on the copper foam, resulting in copper foam with copper hydroxide nanowires (denoted as Cu(OH)2NWs).

[0096] (3) Preparation of copper oxide nanowires: The copper foam with copper hydroxide nanowires grown in step (2) is placed in a tube furnace and heated to 200°C at a heating rate of 5°C / min. The temperature is held for 2 hours and then cooled naturally to obtain copper foam with copper oxide nanowires grown on it (denoted as CuO NWs).

[0097] (4) Preparation of copper nanowires: The copper foam with copper oxide nanowires grown in step (3) was used as the working electrode, the Ag / AgCl electrode as the reference electrode, and the platinum sheet electrode as the counter electrode. A 0.1 mol / L potassium bicarbonate solution was selected as the electrolyte, and the electrode was prepared at 5 mA / cm². 2 At a current density of 6000s, constant current reduction was performed to obtain copper foam (denoted as Cu NWs) with copper nanowires grown on it.

[0098] (5) Electrodeposition of bismuth: Weigh 776 mg of bismuth nitrate pentahydrate and add it to 80 mL of 99 wt% ethylene glycol solution. Dissolve by sonication to obtain the electrolyte.

[0099] The copper foam with copper nanowires grown in step (4) was used as the working electrode, and the working electrode area was fixed at 2 cm². 2 Using an Ag / AgCl electrode as the reference electrode and a graphite carbon rod as the counter electrode, at E Ag / AgCl A copper-bismuth bimetallic catalyst, labeled CuBi-1, was obtained by electrodeposition at -1.8V for 4000s.

[0100] Structural characterization:

[0101] X-ray diffraction (XRD) tests were performed on the surfaces of Cu(OH)₂NWs, CuO NWs, Cu NWs, and CuBi⁻¹ samples from Example 1. The test results are as follows: Figure 1 As shown.

[0102] The surfaces of Cu(OH)₂NWs, CuO NWs, Cu NWs, and CuBi₁ in Example 1 were tested using scanning electron microscopy (SEM). The obtained SEM images are shown below. Figure 2 , Figure 3 , Figure 4 and Figure 5 As shown.

[0103] Depend on Figure 1 , Figures 2-5 It can be seen that in the preparation process of the copper-bismuth bimetallic catalyst in Example 1, copper nanowires are first grown in situ on the surface of copper foam; then, the copper nanowires grown in situ on the surface of copper foam can be transformed into copper oxide nanowires by heat treatment; then, under the action of an applied current, the copper oxide nanowires grown in situ on the surface of copper foam are reduced to copper nanowires; finally, the copper-bismuth bimetallic catalyst is obtained by electrodepositing bismuth nanoparticles on the copper nanowires grown in situ on the surface of copper foam.

[0104] Further analysis shows that... Figure 1 It can be seen that the XRD diffraction pattern of the copper-bismuth bimetallic catalyst in Example 1 shows obvious diffraction peaks of Cu and Bi elements, confirming that copper-bismuth bimetallic nanowires were grown in situ on the surface of copper foam. Combined with... Figure 1 ,from Figure 2 It can be clearly observed that copper hydroxide nanowires are uniformly distributed on the surface of the copper foam substrate, and the surface of the copper hydroxide nanowires is relatively smooth; from Figure 3 It was clearly observed that the copper oxide nanowires obtained after heat treatment exhibited a slightly bent state; from Figure 4 It can be observed that the surface of the copper nanowires obtained after electrochemical reduction is relatively rough; from Figure 5 It can be seen that bismuth is uniformly deposited on the surface of copper nanowires in the form of nanoparticles, forming copper-bismuth nanowires (diameter of 200-300 nm). The diameter of the copper-bismuth nanowires is 220 nm-500 nm (mainly 220 nm-450 nm). Bismuth nanoparticles with a particle size of 10-20 nm and a length of at least 2 μm are deposited on the copper-bismuth nanowires.

[0105] According to high-resolution scanning mapping tests, the mass fraction of bismuth in the copper-bismuth bimetallic nanowires on the surface of the copper-bismuth bimetallic catalyst in Example 1 was 54.3%.

[0106] Comparative Example 1

[0107] This comparative example provides a method for preparing a foam copper catalyst (i.e., Cu NWs) with copper nanowires grown on it. The only difference between this example and Example 1 is that it does not include the step of electrodepositing bismuth (5).

[0108] Comparative Example 2

[0109] This comparative example provides a method for preparing a copper-bismuth bimetallic catalyst (i.e., CuBi-2), which differs from Example 1 only in that the electrodeposition time in step (5) of electrodepositing bismuth is replaced with 1000 s. Specifically, it includes the following steps:

[0110] (1) Pretreatment: The area is 3cm 2 The foamed copper (size: 1cm×3cm) was first soaked in acetone and ultrasonically treated for 10-15min; the foamed copper was then transferred to 1mol / L HCl and ultrasonically treated for 15min; the foamed copper was then rinsed three times with deionized water and three times with ethanol, and dried and purged under nitrogen atmosphere at 10-35℃ to obtain cleaned foamed copper.

[0111] (2) Preparation of copper hydroxide nanowires: 2.71 g of solid sodium hydroxide particles were dissolved in 11.3 mL of deionized water and stirred for 5 min to prepare a 6 M sodium hydroxide solution; 0.62 g of solid ammonium persulfate was dissolved in 11.3 mL of deionized water and stirred for 5 min to prepare a 0.24 M ammonium persulfate solution.

[0112] While stirring, the above 6M sodium hydroxide solution was poured into 0.24M ammonium persulfate solution. Then, the cleaned copper foam was placed into the mixed solution and left to stand at room temperature for 20 minutes. Copper hydroxide nanowires were grown in situ on the copper foam, resulting in copper foam with copper hydroxide nanowires (denoted as Cu(OH)2NWs).

[0113] (3) Preparation of copper oxide nanowires: The copper foam with copper hydroxide nanowires grown in step (2) is placed in a tube furnace and heated to 200°C at a heating rate of 5°C / min. The temperature is held for 2 hours and then cooled naturally to obtain copper foam with copper oxide nanowires grown on it (denoted as CuO NWs).

[0114] (4) Preparation of copper nanowires: The copper foam with copper oxide nanowires grown in step (3) was used as the working electrode, the Ag / AgCl electrode as the reference electrode, and the platinum sheet electrode as the counter electrode. A 0.1 mol / L potassium bicarbonate solution was selected as the electrolyte, and the electrode was prepared at 5 mA / cm². 2 At a current density of 6000s, constant current reduction was performed to obtain copper foam (denoted as Cu NWs) with copper nanowires grown on it.

[0115] (5) Electrodeposition of bismuth: Weigh 776 mg of bismuth nitrate pentahydrate and add it to 80 mL of 99 wt% ethylene glycol solution. Dissolve by sonication to obtain the electrolyte.

[0116] The copper foam with copper nanowires grown in step (4) was used as the working electrode, and the working electrode area was fixed at 2 cm². 2 Using an Ag / AgCl electrode as the reference electrode and a graphite carbon rod as the counter electrode, in E Ag / AgCl Electrodeposition at -1.8V for 1000s yielded a copper-bismuth bimetallic catalyst, labeled CuBi-2.

[0117] High-resolution scanning mapping tests showed that the mass fraction of bismuth in the copper-bismuth bimetallic nanowires on the surface of the copper-bismuth bimetallic catalyst in Comparative Example 2 was 11.36%; the morphology of the copper-bismuth bimetallic nanowires was interlaced.

[0118] Comparative Example 3

[0119] This comparative example provides a method for preparing a copper-bismuth bimetallic catalyst (CuBi-3), which differs from Example 1 only in that the electrodeposition time in step (5) of electrodepositing bismuth is replaced with 3000 s. Specifically, it includes the following steps:

[0120] (1) Pretreatment: The area is 3cm 2 The foamed copper (size: 1cm×3cm) was first soaked in acetone and ultrasonically treated for 10-15min; the foamed copper was then transferred to 1mol / L HCl and ultrasonically treated for 15min; the foamed copper was then rinsed three times with deionized water and three times with ethanol, and dried and purged under nitrogen atmosphere at 10-35℃ to obtain cleaned foamed copper.

[0121] (2) Preparation of copper hydroxide nanowires: 2.71 g of solid sodium hydroxide particles were dissolved in 11.3 mL of deionized water and stirred for 5 min to prepare a 6 M sodium hydroxide solution; 0.62 g of solid ammonium persulfate was dissolved in 11.3 mL of deionized water and stirred for 5 min to prepare a 0.24 M ammonium persulfate solution.

[0122] While stirring, the above 6M sodium hydroxide solution was poured into 0.24M ammonium persulfate solution. Then, the cleaned copper foam was placed into the mixed solution and left to stand at room temperature for 20 minutes. Copper hydroxide nanowires were grown in situ on the copper foam, resulting in copper foam with copper hydroxide nanowires (denoted as Cu(OH)2NWs).

[0123] (3) Preparation of copper oxide nanowires: The copper foam with copper hydroxide nanowires grown in step (2) is placed in a tube furnace and heated to 200°C at a heating rate of 5°C / min. The temperature is held for 2 hours and then cooled naturally to obtain copper foam with copper oxide nanowires grown on it (denoted as CuO NWs).

[0124] (4) Preparation of copper nanowires: The copper foam with copper oxide nanowires grown in step (3) was used as the working electrode, the Ag / AgCl electrode as the reference electrode, and the platinum sheet electrode as the counter electrode. A 0.1 mol / L potassium bicarbonate solution was selected as the electrolyte, and the electrode was prepared at 5 mA / cm². 2 At a current density of 6000s, constant current reduction was performed to obtain copper foam (denoted as Cu NWs) with copper nanowires grown on it.

[0125] (5) Electrodeposition of bismuth: Weigh 776 mg of bismuth nitrate pentahydrate and add it to 80 mL of 99 wt% ethylene glycol solution. Dissolve by sonication to obtain the electrolyte.

[0126] The copper foam with copper nanowires grown in step (4) was used as the working electrode, and the working electrode area was fixed at 2 cm². 2 Using an Ag / AgCl electrode as the reference electrode and a graphite carbon rod as the counter electrode, at E Ag / AgCl A copper-bismuth bimetallic catalyst, labeled CuBi-3, was obtained by electrodeposition at -1.8V for 3000s.

[0127] High-resolution scanning mapping tests showed that the mass fraction of bismuth in the copper-bismuth bimetallic nanowires on the surface of Comparative Example 3 was 31.78%. The morphology of the copper-bismuth bimetallic nanowires was interlaced and staggered. Compared with CuBi-1, the bismuth nanoparticles on the surface of the copper-bismuth bimetallic catalyst in Comparative Example 3 had uneven distribution.

[0128] Comparative Example 4

[0129] This comparative example provides a method for preparing a copper-tin alloy nanowire catalyst (CuSn), which differs from Example 1 only in that "electrodeposited bismuth" is replaced with "electrodeposited tin and calcination". Specifically, it includes the following steps:

[0130] (1) Pretreatment: The area is 3cm 2The foamed copper (size: 1cm×3cm) was first soaked in acetone and ultrasonically treated for 10-15min; the foamed copper was then transferred to 1mol / L HCl and ultrasonically treated for 15min; the foamed copper was then rinsed three times with deionized water and three times with ethanol, and dried and purged under nitrogen atmosphere at 10-35℃ to obtain cleaned foamed copper.

[0131] (2) Preparation of copper hydroxide nanowires: 2.71 g of solid sodium hydroxide particles were dissolved in 11.3 mL of deionized water and stirred for 5 min to prepare a 6 M sodium hydroxide solution; 0.62 g of solid ammonium persulfate was dissolved in 11.3 mL of deionized water and stirred for 5 min to prepare a 0.24 M ammonium persulfate solution.

[0132] While stirring, the above 6M sodium hydroxide solution was poured into 0.24M ammonium persulfate solution. Then, the cleaned copper foam was placed into the mixed solution and left to stand at room temperature for 20 minutes. Copper hydroxide nanowires were grown in situ on the copper foam, resulting in copper foam with copper hydroxide nanowires (denoted as Cu(OH)2NWs).

[0133] (3) Preparation of copper oxide nanowires: The copper foam with copper hydroxide nanowires grown in step (2) is placed in a tube furnace and heated to 200°C at a heating rate of 5°C / min. The temperature is held for 2 hours and then cooled naturally to obtain copper foam with copper oxide nanowires grown on it (denoted as CuO NWs).

[0134] (4) Preparation of copper nanowires: The copper foam with copper oxide nanowires grown in step (3) was used as the working electrode, the Ag / AgCl electrode as the reference electrode, and the platinum sheet electrode as the counter electrode. A 0.1 mol / L potassium bicarbonate solution was selected as the electrolyte, and the electrode was prepared at 5 mA / cm². 2 At a current density of 6000s, constant current reduction was performed to obtain copper foam (denoted as Cu NWs) with copper nanowires grown on it.

[0135] (5) Electrodeposition of tin and calcination: Weigh 11.2g of potassium hydroxide solid into 100mL of deionized water, stir to dissolve, and then add 1128mg of stannous chloride dihydrate to dissolve by ultrasonication to obtain the electrolyte for electrodeposition of tin.

[0136] The copper foam with copper nanowires grown in step (4) was used as the working electrode, and the working electrode area was fixed at 2 cm². 2 The Ag / AgCl electrode is used as the reference electrode, and the graphite carbon rod is used as the counter electrode. The constant current is set to 5 mA / cm². 2 The electrodeposition time was 2000 s;

[0137] The deposited sample was then placed in a hydrogen-argon mixture (hydrogen:argon = 6:94, v / v), heated to 300℃, held for 3 hours, and cooled to room temperature at a rate of 1℃ / min to obtain a copper-tin alloy nanowire catalyst (denoted as CuSn).

[0138] Performance testing

[0139] 1. Electrocatalytic carbon dioxide reduction performance test in neutral environment

[0140] Test samples: Cu NWs, CuBi-1, CuBi-2 and CuBi-3.

[0141] Test Method: The test sample was used as the working electrode, Ag / AgCl as the reference electrode, and a platinum sheet as the counter electrode. The electrocatalytic carbon dioxide reduction performance was tested in an H-type electrolytic cell containing a 0.5 mol / L potassium bicarbonate solution. During the test, the immersion area of ​​the working electrode was 0.25 cm². 2 The flow rate of carbon dioxide was continuously introduced at 1 to 10 mL / min, and electrolysis was carried out within the potential range of -1.0 to -1.9 V (vs. RHE).

[0142] (1) Argon and carbon dioxide were introduced into two H-type electrolytic cells containing 0.5 mol / L potassium bicarbonate solutions, respectively, so that the electrolyte was saturated with argon and carbon dioxide (pH = 7.0), respectively. The linear voltammetric curves of the copper-bismuth bimetallic catalyst (i.e., the test sample) in Example 1 were tested using the above test methods and conditions. The results are as follows: Figure 6 As shown.

[0143] Depend on Figure 6 It can be seen that the current density of the catalyst is higher in CO2-saturated electrolyte than in Ar-saturated electrolyte, indicating that the copper-bismuth bimetallic catalyst in Example 1 has good carbon dioxide reduction performance in a neutral environment.

[0144] (2) Carbon dioxide was introduced into an H-type electrolytic cell containing 0.5 mol / L potassium bicarbonate solution to saturate the electrolyte with carbon dioxide (pH = 7.0). The electrocatalytic carbon dioxide reduction performance of CuBi-1, CuBi-2, CuBi-3, and Cu NWs in a neutral environment was tested using the above-described test method. The Faradaic efficiency and current density results for formate were measured under different potential conditions (potential: -1.0 to -1.9 V vs. RHE), as shown below. Figure 7 , Figure 8 As shown in Table 1.

[0145] Table 1. Test results of electrocatalytic carbon dioxide reduction performance under neutral environment.

[0146]

[0147] Depend on Figure 7 , Figure 8 As shown in Table 1, the formate exhibits the highest Faradaic efficiency (94.5%) of CuBi-1 at a potential of -1.1 V vs. RHE. Furthermore, the formate shows the highest partial current density (220 mA / cm²) at a potential of -1.8 V vs. RHE. -2 Compared with Cu NWs, CuBi-2 and CuBi-3, CuBi-1 formate has a higher Faradaic efficiency and current density, indicating that CuBi-1 has the best electrocatalytic carbon dioxide reduction performance in a neutral environment.

[0148] According to the test results of electrocatalytic carbon dioxide reduction performance in a neutral environment, Cu NWs mainly undergo hydrogen evolution reaction under the conditions of potential of -1.0 to -1.9V vs. RHE, and the Faradaic efficiency of its formate is below 20.0%.

[0149] Under potentials ranging from -1.0 to -1.9 V vs. RHE, the Faradaic efficiency of CuBi-2 formate is below 60.0%; the highest Faradaic efficiency (54.8%) is observed at a potential of -1.1 V vs. RHE; and the maximum partial current density (82.0 mA cm⁻¹) is reached at a potential of -1.8 V vs. RHE. -2 However, at this point, the hydrogen evolution reaction is dominant, which is reflected in the fact that the Faraday efficiency of formate is only 34.2%.

[0150] The Faradaic efficiency of CuBi-3 formate is below 80.0% under potentials ranging from -1.0 to -1.9 V vs. RHE. The highest Faradaic efficiency (78.5%) is achieved at a potential of -1.6 V vs. RHE. The highest partial current density (168.9 mA cm⁻¹) is also observed at a potential of -1.9 V vs. RHE. -2 However, the Faraday efficiency of its formate is only 64.8%.

[0151] (3) Stability Test: Using CuBi-1 from Example 1 as the test sample, the potential was set to -1.3V vs. RHE, the running time was approximately 12 hours, and a 0.5 mol / L potassium bicarbonate solution saturated with carbon dioxide (pH = 7.0) was used as the electrolyte. Other conditions were handled according to the method for testing the electrocatalytic carbon dioxide reduction performance in a neutral environment. The test results are as follows: Figure 9 As shown.

[0152] Depend on Figure 9 It can be seen that CuBi-1 exhibits good reactivity and stability for the carbon dioxide reduction reaction under neutral conditions, with an initial current density of 145 mA cm⁻¹. -2 After 12 hours of testing, the current density remained at 140 mA cm⁻¹. -2 This indicates that the Faraday efficiency of CuBi-1 formate remains at around 90%.

[0153] 2. Electrocatalytic carbon dioxide reduction performance test in acidic environment

[0154] Test samples: CuBi-1, CuSn

[0155] Test Method: The test sample was used as the working electrode, Ag / AgCl as the reference electrode, and a platinum sheet as the counter electrode. The electrocatalytic carbon dioxide reduction performance was tested in an H-type electrolytic cell containing a 0.5 mol / L potassium sulfate solution acidified with dilute sulfuric acid. During the test, the immersion area of ​​the working electrode was 0.25 cm². 2 The flow rate of carbon dioxide was continuously introduced at 1 to 10 mL / min, and electrolysis was carried out within the potential range of -1.0 to -1.9 V (vs. RHE).

[0156] (1) Argon and carbon dioxide were introduced into two H-type electrolytic cells containing 0.5 mol / L potassium sulfate solutions, respectively. Then, the pH of the electrolyte was adjusted to 3.6 using dilute sulfuric acid. The linear voltammetric curve of the copper-bismuth bimetallic catalyst (i.e., the test sample) in Example 1 was then tested using the above-described test methods and conditions. The results are as follows: Figure 10 As shown.

[0157] Depend on Figure 10 It can be seen that the current density of this catalyst is higher in CO2-saturated electrolyte than in Ar-saturated electrolyte, indicating that the copper-bismuth bimetallic catalyst CuBi-1 in Example 1 also has good carbon dioxide reduction performance in acidic environment.

[0158] (2) Carbon dioxide was introduced into an H-type electrolytic cell containing 0.5 mol / L potassium sulfate solution until saturation. The electrolyte was then acidified with dilute sulfuric acid to a pH of 3.6. The electrocatalytic carbon dioxide reduction performance of CuBi-1 and CuSn in an acidic environment was then tested using the methods described above. The Faraday efficiency and current density results for formate were measured under different potential conditions (potential: -1.0 to -1.9 V vs. RHE), as shown below. Figure 11 , Figure 12 As shown in Table 2.

[0159] Table 1. Test results of electrocatalytic carbon dioxide reduction performance under acidic conditions.

[0160]

[0161] Depend on Figure 11 , Figure 12 As shown in Table 2, the formate of CuSn exhibits the highest Faradaic efficiency of 80.7% at a potential of –1.6V vs. RHE; under other potential conditions, the Faradaic efficiency of the formate is below 80%, indicating that hydrogen evolution of CuSn is more severe in acidic environments; and at a potential of –1.7V vs. RHE, the formate exhibits the highest partial current density of 163 mA cm⁻¹. -2 .

[0162] The formate of CuBi-1 exhibits the highest Faradaic efficiency, reaching 96.2%, at a potential of -1.5 V vs. RHE. Simultaneously, the formate of CuBi-1 shows the highest partial current density of 219.3 mA cm⁻¹ at a potential of -1.8 V vs. RHE. -2 Compared to CuSn, CuBi-1 formate exhibits significantly higher Faradaic efficiency and current density, indicating that CuBi-1 demonstrates superior electrocatalytic carbon dioxide reduction performance in acidic environments.

[0163] Compared to CuSn, CuBi-1 formate has a higher Faraday efficiency and a higher partial current density.

[0164] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for electrocatalytic reduction of carbon dioxide, characterized in that, Includes the following steps: Electrolysis is carried out by passing carbon dioxide into the reaction electrolyte using a copper-bismuth bimetallic catalyst as the cathode. The electrolyte is potassium sulfate; and the pH of the electrolyte is 3.0~5.

0. The copper-bismuth bimetallic catalyst comprises a copper substrate and copper-bismuth nanowires grown on the copper substrate. The copper-bismuth nanowires comprise copper nanowires and a metallic bismuth layer supported on the copper nanowires. The metallic bismuth layer comprises a plurality of bismuth nanoparticles with a particle size of 10–20 nm. The mass fraction of bismuth in the copper-bismuth nanowires is 40%~60%; The diameter of the copper-bismuth nanowires is 100 nm to 600 nm.

2. The method for electrocatalytic reduction of carbon dioxide according to claim 1, characterized in that, The preparation method of the copper-bismuth bimetallic catalyst includes the following steps: After in-situ growth of copper hydroxide nanowires on a copper substrate, copper-bismuth bimetallic catalysts were prepared by heat treatment, electrochemical reduction treatment, and bismuth deposition. The specific method for depositing bismuth is as follows: in a solution containing bismuth ions, using a copper substrate with grown copper nanowires as the working electrode, bismuth is electrodeposited at a constant voltage to obtain a copper-bismuth bimetallic catalyst; the electrodeposition of bismuth uses an Ag / AgCl electrode as the reference electrode and a graphite carbon rod as the counter electrode; the Ag / AgCl value for bismuth electrodeposition is -1.5 V to -2.5 V; and the electrodeposition time for bismuth is 3500 s to 6000 s.

3. The method for electrocatalytic reduction of carbon dioxide according to claim 2, characterized in that: The bismuth-containing solution comprises a soluble bismuth salt and an ethylene glycol solution; the soluble bismuth salt comprises at least one of bismuth nitrate and bismuth nitrate pentahydrate.

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