Preparation method and application of Cu-based monatomic alloy nanocube

Abstract

The invention discloses a preparation method and application of a Cu-based monatomic alloy nanocube, and relates to a preparation method and application of a Cu-based monatomic alloy nanocube. The invention aims to solve the problems of low single product selectivity and low reaction activity of the existing pure Cu catalyst. The method comprises the following steps: 1, preparing a precursor salt solution; 2, preparing a reducing agent solution; and 3, reduction. According to the application, the material is used as a raw material for preparing a working electrode for electrocatalytic reduction of CO2. The method is used for preparation and application of the Cu-based monatomic alloy nanocube.

Description

Technical Field

[0001] The invention relates to a preparation method and application of a Cu-based single atom. Background Art

[0003] The technology of electrocatalytic reduction of CO2 to synthesize clean energy materials or chemical raw materials provides a promising technical option for the efficient use of low-carbon electricity, CO2 resource utilization and carbon emission reduction. Cu-based catalysts are the only ones that can electrocatalyze the reduction of CO2 into high value-added products such as methane, ethylene, and ethanol, making it a research hotspot in the field of CO2 resource utilization. However, pure Cu catalysts have problems such as low selectivity and low reaction activity, and have not yet reached the technical standards for industrial application. Summary of the invention

[0004] The present invention aims to solve the problems of low single product selectivity and low reaction activity of existing pure Cu catalysts, and further provides a preparation method and application of Cu-based single-atom alloy nanocubes.

[0005] A method for preparing Cu-based single-atom alloy nanocubes is carried out according to the following steps:

[0006] 1. Preparation of precursor salt solution:

[0007] Dissolving copper salt and nickel salt in a solvent, then adding an amine-containing surfactant and stirring to mix evenly to obtain a precursor salt solution;

[0008] 2. Preparation of reducing agent solution:

[0009] dissolving a reducing agent in a solvent to obtain a reducing agent solution;

[0010] 3. Restore:

[0011] The precursor salt solution is heated to 80°C to 140°C, and then the reducing agent solution is added and mixed evenly. The reaction is carried out at a temperature of 80°C to 140°C for 1h to 4h. After the reaction, the solution is cooled to room temperature, and finally centrifuged, washed and vacuum dried to obtain Cu-based single-atom alloy nanocubes.

[0012] An application of Cu-based single-atom alloy nanocubes, which are used as raw materials to prepare gas diffusion electrodes for electrocatalytic reduction of CO2.

[0013] The beneficial effects of the present invention are:

[0014] 1. The Cu-based single-atom alloy nanocubes prepared by the present invention have a size of about 150nm to 200nm, a relatively simple preparation method, mild reaction conditions, and a relatively uniform distribution of product size and morphology.

[0015] 2. When the Cu-based single-atom alloy nanocubes prepared by the present invention are applied to the electrocatalytic reduction of CO2 reaction, they show a strengthening effect on the CC coupling process. At a certain Cu / Ni ratio, the selectivity of ethylene products is significantly improved, and the catalyst activity is improved to a certain extent. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The Cu prepared in Example 1 19 Scanning electron micrograph of Ni1;

[0017] Figure 2 The Cu prepared in Example 1 19 X-ray diffraction spectra of Ni1 and Cu prepared in comparative experiments;

[0018] Figure 3 The Cu prepared in Example 1 19 Ni1, Cu prepared in Example 2 99 Linear scanning curves of Ni1, Cu4Ni1 prepared in comparative experiment 2, Cu9Ni1 prepared in comparative experiment 3, and Cu prepared in comparative experiment 1 in the applied potential range of 0V to -0.7V (vs RHE);

[0019] Figure 4 The Cu prepared in Example 1 19 Electrochemical impedance spectra of Ni1, Cu4Ni1 prepared in comparative experiment 2, and Cu prepared in comparative experiment 1;

[0020] Figure 5 This is a comparison chart of the electrocatalytic selectivity of single-atom alloy nanocubes with different Cu / Ni ratios in Examples 1 to 2 and Comparative Experiments 1 to 3. DETAILED DESCRIPTION

[0021] Specific implementation method 1: This implementation method is a method for preparing a Cu-based single-atom alloy nanocube, which is carried out according to the following steps:

[0022] 1. Preparation of precursor salt solution:

[0023] Dissolving copper salt and nickel salt in a solvent, then adding an amine-containing surfactant and stirring to mix evenly to obtain a precursor salt solution;

[0024] 2. Preparation of reducing agent solution:

[0025] dissolving a reducing agent in a solvent to obtain a reducing agent solution;

[0026] 3. Restore:

[0027] The precursor salt solution is heated to 80°C to 140°C, and then the reducing agent solution is added and mixed evenly. The reaction is carried out at a temperature of 80°C to 140°C for 1h to 4h. After the reaction, the solution is cooled to room temperature, and finally centrifuged, washed and vacuum dried to obtain Cu-based single-atom alloy nanocubes.

[0028] The beneficial effects of this embodiment are:

[0029] 1. The Cu-based single-atom alloy nanocubes prepared in this embodiment have a size of about 150 nm to 200 nm, the preparation method is relatively simple, the reaction conditions are mild, and the product size and morphology are relatively uniformly distributed.

[0030] 2. The Cu-based single-atom alloy nanocubes prepared in this embodiment, when applied to the electrocatalytic reduction of CO2 reaction, show a strengthening effect on the CC coupling process. The selectivity of ethylene products is significantly improved at a certain Cu / Ni ratio, and the catalyst activity is improved to a certain extent.

[0031] Specific embodiment 2: This embodiment is different from specific embodiment 1 in that: the copper salt described in step 1 is copper chloride, copper bromide or copper sulfate; the nickel salt described in step 1 is nickel chloride or nickel acetate; the solvent described in step 1 and step 2 is water, ethylene glycol or 2-ethoxyethanol; the amine-containing surfactant described in step 1 is hexadecylamine, octadecylamine or oleylamine. The rest is the same as specific embodiment 1.

[0032] Specific embodiment 3: This embodiment differs from specific embodiment 1 or 2 in that: the molar ratio of the copper element in the copper salt to the nickel element in the nickel salt in step 1 is (19-99):1; the volume ratio of the amount of the copper salt in step 1 to the solvent is (0.03-0.3) mmol:20 mL; the molar ratio of the copper salt to the amine-containing surfactant in step 1 is 1:(2-4). Others are the same as specific embodiment 1 or 2.

[0033] Specific embodiment 4: This embodiment is different from one of specific embodiments 1 to 3 in that the reducing agent in step 2 is ascorbic acid or glucose. The rest is the same as specific embodiment 3.

[0034] Specific embodiment 5: This embodiment differs from Specific embodiments 1 to 4 in that the volume ratio of the amount of the reducing agent in step 2 to the solvent is (0.1-1) mmol:20 mL. The rest is the same as Specific embodiments 1 to 4.

[0035] Specific embodiment 6: This embodiment is different from specific embodiments 1 to 5 in that the volume ratio of the reducing agent solution to the precursor salt solution in step 3 is 1:(5-10). Other aspects are the same as specific embodiments 1 to 5.

[0036] Specific embodiment 7: This embodiment differs from Specific embodiments 1 to 6 in that: in step 3, the reducing agent solution is added at a rate of 0.25 mL / min to 0.75 mL / min. The rest is the same as Specific embodiments 1 to 6.

[0037] Specific embodiment eight: This embodiment differs from specific embodiments one to seven in that the centrifugation, washing and vacuum drying described in step three are specifically centrifuged at a rotation speed of 5000 rpm to 12000 rpm for 3 min to 10 min to separate the solid, then wash the solid with anhydrous ethanol and n-hexane for 3 to 5 times, and finally vacuum dry it at room temperature for 10 h to 12 h. The rest is the same as specific embodiments one to seven.

[0038] Specific embodiment 9: This embodiment is different from specific embodiments 1 to 8 in that the particle size of the Cu-based single-atom alloy nanocubes described in step 3 is 150nm to 200nm. The rest is the same as specific embodiments 1 to 8.

[0039] Specific embodiment 10: This embodiment uses a Cu-based single-atom alloy nanocube as a raw material to prepare a gas diffusion electrode for electrocatalytic reduction of CO2.

[0040] The following examples are used to verify the beneficial effects of the present invention:

[0041] Embodiment 1:

[0042] A method for preparing Cu-based single-atom alloy nanocubes is carried out according to the following steps:

[0043] 1. Preparation of precursor salt solution:

[0044] Dissolving copper salt and nickel salt in a solvent, then adding an amine-containing surfactant and stirring to mix evenly to obtain a precursor salt solution;

[0045] The copper salt is copper chloride; the nickel salt is nickel chloride; the solvent is water; the amine-containing surfactant is hexadecylamine;

[0046] The molar ratio of the copper element in the copper salt to the nickel element in the nickel salt is 19:1; the volume ratio of the amount of the copper salt to the solvent is 0.25mmol:20mL; the molar ratio of the copper salt to the amine-containing surfactant is 1:3;

[0047] 2. Preparation of reducing agent solution:

[0048] dissolving a reducing agent in a solvent to obtain a reducing agent solution;

[0049] The solvent is water; the reducing agent is glucose;

[0050] The volume ratio of the amount of the reducing agent to the solvent is 0.6mmol:20mL;

[0051] 3. Restore:

[0052] The precursor salt solution was heated to 140°C, and then the reducing agent solution was added at a rate of 0.5 mL / min and mixed evenly. The reaction was carried out at 140°C for 4 h, and then cooled to room temperature. Finally, the solution was centrifuged, washed and vacuum dried to obtain Cu-based single-atom alloy nanocubes, namely Cu 19 Ni1;

[0053] The volume ratio of the reducing agent solution to the precursor salt solution is 1:10.

[0054] The centrifugation, washing and vacuum drying described in step 3 are specifically to centrifuge for 5 minutes at a rotation speed of 7000 rpm to separate the solid, then wash the solid three times with anhydrous ethanol and n-hexane, and finally vacuum dry it at room temperature for 12 hours.

[0055] The particle size of the Cu-based single-atom alloy nanocubes described in step three is 150nm to 200nm.

[0056] Application of the Cu-based single-atom alloy nanocubes prepared as above, the Cu-based single-atom alloy nanocubes are used as raw materials to prepare gas diffusion electrodes for electrocatalytic CO2 reduction;

[0057] The gas diffusion electrode is specifically prepared according to the following steps:

[0058] ① Add Cu-based single-atom alloy nanocubes into a mixed solution of Nafion and isopropanol, and mix them ultrasonically for 30 minutes at a power of 100 W to obtain a catalyst ink;

[0059] The volume ratio of Nafion solution to isopropanol in the mixed solution of Nafion and isopropanol is 1:30; the concentration of Cu-based single-atom alloy nanocubes in the catalyst ink is 8 mg / mL;

[0060] ② According to the loading amount of Cu-based single-atom alloy nanocubes is 1 mg / cm 2 , at room temperature, the catalyst ink is sprayed onto carbon paper and finally dried to obtain a gas diffusion electrode;

[0061] The carbon paper is Sigracet 28BC;

[0062] The electrocatalytic CO2 reduction is specifically carried out according to the following steps:

[0063] ① Assembly: Using a flow-type electrolyzer, a gas diffusion electrode is set between the CO2 gas flow chamber and the cathode chamber, and an anion exchange membrane is set between the cathode chamber and the anode chamber; the counter electrode is set in the anode chamber, the reference electrode is set in the cathode chamber, and the cathode liquid flow cell is connected to the cathode chamber through a conduit, and the anode liquid flow cell is connected to the anode chamber through a conduit, and the electrolyte is poured into the cathode liquid flow cell and the anode liquid flow cell, and finally the positive electrode of the power supply is connected to the counter electrode, and the negative electrode of the power supply is connected to the gas diffusion electrode;

[0064] The electrolyte is a KOH electrolyte with a concentration of 1M, and the flow rate of the electrolyte is 2.5mL / min; the material of the CO2 gas flow chamber is polyetheretherketone (PEEK); the counter electrode is nickel foam; the reference electrode is an Ag / AgCl electrode; the anion exchange membrane is fumasep FAA-3-PK-130;

[0065] ② Electrocatalytic CO2 reduction: CO2 gas was introduced into the CO2 gas flow chamber at a flow rate of 30 sccm. CO2 was continuously introduced at a current density of 100 mA cm at the gas diffusion electrode. -2 ~400mA·cm -2 The electrocatalytic CO2 reduction is completed by electrocatalytically reducing CO2 under the conditions of , collecting the gas product, separating and purifying the electrolyte after the reaction.

[0066] Example 2: The difference between this example and Example 1 is that the molar ratio of the copper element in the copper salt to the nickel element in the nickel salt in step 1 is 99:1; and the Cu 99 Ni1. Others are the same as those in the first embodiment.

[0067] Comparative Experiment 1: The difference between this comparative experiment and Example 1 is that the nickel salt is not used in step 1, and Cu particles, namely Cu, are prepared in step 3. The rest is the same as Example 1.

[0068] Comparative Experiment 2: The difference between this comparative experiment and Example 1 is that the molar ratio of the copper element in the copper salt to the nickel element in the nickel salt in step 1 is 4:1; and Cu4Ni1 is prepared in step 3. The rest is the same as Example 1.

[0069] Comparative Experiment 3: The difference between this comparative experiment and Example 1 is that the molar ratio of the copper element in the copper salt to the nickel element in the nickel salt in step 1 is 9:1; and Cu9Ni1 is prepared in step 3. The rest is the same as Example 1.

[0070] Figure 1 The Cu prepared in Example 1 19 Scanning electron microscope image of Ni1; As can be seen from the figure, the obtained Cu 19The size of Ni1 nanocubes is about 150nm to 200nm.

[0071] Figure 2 The Cu prepared in Example 1 19 X-ray diffraction spectra of Ni1 and Cu prepared in the comparative experiment; it can be seen from the figure that the obtained material is mainly pure Cu with good crystallinity, and there is no diffraction peak of Ni or Ni oxide in the XRD spectrum, indicating that Ni is uniformly doped into the Cu lattice and there is no Ni agglomeration, which is a Cu-based single-atom alloy.

[0072] Figure 3 The Cu prepared in Example 1 19 Ni1, Cu prepared in Example 2 99 Linear scanning curves of Ni1, Cu4Ni1 prepared in comparative experiment 2, Cu9Ni1 prepared in comparative experiment 3, and Cu prepared in comparative experiment 1 in the applied potential range of 0V to -0.7V (vs RHE); As can be seen from the figure, during the electrocatalytic CO2 reduction process, when a small amount of Ni atoms are introduced into the Cu matrix (Cu 19 Ni1、Cu 99 Ni1), the reaction current density is higher than that of pure Cu at the same applied potential, indicating that the introduction of an appropriate amount of Ni enhances the activity of the Cu catalyst. However, for Cu9Ni1 and Cu4Ni1 catalysts with relatively high Ni content, the electrochemical activity is much lower than that of Cu and CuNi single-atom alloys.

[0073] Figure 4 The Cu prepared in Example 1 19 Electrochemical impedance spectra of Ni1, Cu4Ni1 prepared in comparative experiment 2, and Cu prepared in comparative experiment 1; As can be seen from the figure, Cu 19 Ni1 (4.24Ω) has a smaller charge transfer impedance than Cu (5.70Ω) and Cu4Ni1 (7.25Ω), indicating that single-atom dispersed Ni can accelerate the charge transfer process on the surface of Cu nanocubes and improve the electrocatalytic activity.

[0074] Example 1 Preparation of Cu 19 The molar ratio of the copper element in the copper salt to the nickel element in the nickel salt in the Ni1 process is 19:1, that is, Ni / (Ni+Cu)=1:20=5%; the Cu prepared in Example 2 99The molar ratio of the copper element in the copper salt to the nickel element in the nickel salt described in the Ni1 process is 99:1, that is, Ni / (Ni+Cu)=1:100=1%; the molar ratio of the copper element in the copper salt to the nickel element in the nickel salt described in the Cu4Ni1 process prepared in the comparative experiment 2 is 4:1, that is, Ni / (Ni+Cu)=1:5=20%; the molar ratio of the copper element in the copper salt to the nickel element in the nickel salt described in the Cu9Ni1 process prepared in the comparative experiment 3 is 9:1, that is, Ni / (Ni+Cu)=1:10=10%.

[0075] Figure 5 The electrocatalytic selectivity comparison diagram of single-atom alloy nanocubes with different Cu / Ni ratios in Examples 1 to 2 and Comparative Experiments 1 to 3 is shown in the figure. It can be seen from the figure that the introduction of Ni will affect the catalytic selectivity of Cu nanocubes. Compared with pure Cu samples, Cu and Cu 19 The product distribution of Ni1 is similar, and the main catalytic product is ethylene at higher current density. 19 Ni1 exhibits higher ethylene selectivity at higher reaction rates, with a peak at 400 mA cm -2 The peak Faraday efficiency of ethylene at the current density reached 62.6%, showing a promoting effect on CC coupling. In addition, when the Ni content was high, the C2H4 selectivity decreased significantly, accompanied by an increase in H2 and CH4 production, among which C4Ni1 at 400mAcm -2 The highest methane selectivity at the current density is 16.4%, which may be because when a large number of Ni atoms are introduced, it is difficult to form a single-atom alloy structure with Ni atomic-level distribution, but a nano-alloy structure with local Ni enrichment is formed.

Claims

1. A method for preparing Cu-based single-atom alloy nanocubes, characterized in that It is carried out in the following steps:

1. Preparation of precursor salt solution: Dissolving copper salt and nickel salt in a solvent, then adding an amine-containing surfactant and stirring to mix evenly to obtain a precursor salt solution; 2. Preparation of reducing agent solution: dissolving a reducing agent in a solvent to obtain a reducing agent solution; 3. Restore: The precursor salt solution is heated to 80°C to 140°C, and then the reducing agent solution is added and mixed evenly. The reaction is carried out at a temperature of 80°C to 140°C for 1h to 4h. After the reaction, the solution is cooled to room temperature, and finally centrifuged, washed and vacuum dried to obtain Cu-based single-atom alloy nanocubes.

2. The method for preparing a Cu-based single-atom alloy nanocube according to claim 1, characterized in that The copper salt described in step 1 is copper chloride, copper bromide or copper sulfate; the nickel salt described in step 1 is nickel chloride or nickel acetate; the solvent described in step 1 and step 2 is water, ethylene glycol or 2-ethoxyethanol; the amine-containing surfactant described in step 1 is hexadecylamine, octadecylamine or oleylamine.

3. The method for preparing a Cu-based single-atom alloy nanocube according to claim 1, characterized in that The molar ratio of the copper element in the copper salt described in step one to the nickel element in the nickel salt is (19-99):1; the volume ratio of the amount of the copper salt described in step one to the solvent is (0.03-0.3) mmol:20 mL; the molar ratio of the copper salt described in step one to the amine-containing surfactant is 1:(2-4).

4. The method for preparing a Cu-based single-atom alloy nanocube according to claim 1, characterized in that The reducing agent in step 2 is ascorbic acid or glucose.

5. The method for preparing a Cu-based single-atom alloy nanocube according to claim 1, characterized in that The volume ratio of the amount of the reducing agent described in step 2 to the solvent is (0.1-1) mmol:20 mL.

6. The method for preparing a Cu-based single-atom alloy nanocube according to claim 1, characterized in that The volume ratio of the reducing agent solution to the precursor salt solution described in step 3 is 1:(5-10).

7. The method for preparing a Cu-based single-atom alloy nanocube according to claim 1, characterized in that In step 3, the reducing agent solution is added at a rate of 0.25 mL / min to 0.75 mL / min.

8. The method for preparing a Cu-based single-atom alloy nanocube according to claim 1, characterized in that The centrifugation, washing and vacuum drying described in step three are specifically centrifuged at a rotation speed of 5000rpm to 12000rpm for 3min to 10min to separate the solid, then washing the solid with anhydrous ethanol and n-hexane 3 to 5 times, and finally vacuum drying at room temperature for 10h to 12h.

9. The method for preparing a Cu-based single-atom alloy nanocube according to claim 1, characterized in that The particle size of the Cu-based single-atom alloy nanocubes described in step three is 150nm to 200nm.

10. Use of a Cu-based single-atom alloy nanocube prepared as claimed in claim 1, characterized in that It is used as raw material to prepare gas diffusion electrodes for electrocatalytic reduction of CO2.

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