Preparation method and application of Cu micron wire with low length-diameter ratio

Abstract

The invention discloses a preparation method and application of a Cu micron wire with a low length-diameter ratio, and belongs to the technical field of low-dimensional functional materials. The invention aims to solve the problem that a Cu micron wire with a low length-diameter ratio cannot be prepared in the prior art. 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 gas diffusion electrode for electrocatalytic reduction of CO2. The method is used for preparation and application of the Cu micron wire with the low length-diameter ratio.

Description

Technical Field

[0001] The present invention belongs to the technical field of low-dimensional functional materials. Background Art

[0002] Due to its high reserves, good electrical conductivity, thermal conductivity and ductility, copper metal plays an important role in commercial applications. When copper and copper-based structures are reduced to the low-dimensional field, they exhibit optical, electrical, magnetic and other properties different from those of bulk or large-sized particles, enabling them to be widely used in multiple fields such as electronics, catalysis, sensing and biomedicine. Their main properties often depend on the regulation of the size and morphological structure of the Cu material.

[0003] In recent years, one-dimensional copper materials (copper nanowires, copper microwires) have received increasing attention due to their high electrical conductivity, low cost and other advantages. Their excellent electrical conductivity makes them potential substitutes for indium tin oxide (ITO) and important candidate materials for manufacturing transparent and flexible electrodes. In addition, due to their special morphology and exposed crystal planes, copper nanowires / microwires often exhibit different activities and catalytic selectivities from those of structures such as nanoparticles and nanosheets during the catalytic process. As important research objects, they are used in thermal catalysis, electrocatalysis, photocatalysis and photothermal catalysis, etc., involving important chemical processes such as 2 CO conversion, hydrogenation reaction, coupling reaction, etc.

[0004] At present, researchers have developed various synthesis methods for one-dimensional copper nanomaterials, including but not limited to oil-phase thermal reduction method, hydrothermal synthesis method and one-step reduction method, etc. However, the Cu nanowires obtained by most of the disclosed methods have a small diameter (mostly below 100 nm) and a large aspect ratio. Copper microwires can be applied to conductive coatings / high-temperature power components, transparent / flexible electrodes, optoelectronic devices and catalytic materials. However, the existing technology has relatively little research on copper microwires and cannot prepare copper microwires with a low aspect ratio. Therefore, to a certain extent, it limits the selection range of the market demand side. Summary of the Invention

[0005] The present invention aims to solve the problem that the prior art cannot prepare copper microwires with a low aspect ratio, and further provides a preparation method and application of copper microwires with a low aspect ratio.

[0006] A preparation method of copper microwires with a low aspect ratio is carried out according to the following steps:

[0007] I. Prepare a precursor salt solution:

[0008] Dissolve sodium halide salt in an alcohol-containing organic solution, and then add copper salt and stir to mix evenly to obtain a precursor salt solution;

[0009] II. Prepare a reducing agent solution:

[0010] Dissolve a reducing agent and a surfactant in an alcohol-containing organic solution to obtain a reducing agent solution;

[0011] III. Reduction:

[0012] Heat the precursor salt solution to 100°C - 150°C, then add the reducing agent solution and mix evenly. Under the condition of a temperature of 100°C - 150°C, react for 0.5 h - 1 h. After the reaction, cool to room temperature, and finally centrifuge, wash, and vacuum dry to obtain low aspect ratio Cu micro-wires.

[0013] Application of the low aspect ratio Cu micro-wires. They are used as raw materials to prepare gas diffusion electrodes for electrocatalytic reduction of CO 2 .

[0014] The beneficial effects of the present invention are:

[0015] The present invention relates to a synthesis method of copper micro-wires, using a surfactant, a reducing agent, a reaction solvent (complexing agent), and adding a certain amount of sodium halide to adjust the product morphology and structure to obtain Cu micro-wires.

[0016] I. The diameter of the Cu micro-wires prepared by the present invention is about 1 - 3 microns, and the length is about 90 - 150 microns. The preparation method is simple and the reaction conditions are mild.

[0017] II. When the Cu micro-wires prepared by the present invention are applied to the electrocatalytic reduction of CO 2 reaction, they show good catalytic performance, and the main product is ethylene. Description of the Drawings

[0018] Figure 1 Scanning electron microscope image of the Cu micro-wires prepared in Example 1;

[0019] Figure 2 X-ray diffraction spectrum of the Cu micro-wires prepared in Example 1;

[0020] Figure 3 Scanning electron microscope image of the Cu micro-particles prepared in the comparative experiment;

[0021] Figure 4 Catalytic product distribution map of the electrocatalytic CO 2 by the Cu micro-wires prepared in Example 1;

[0022] Figure 5 Catalytic product distribution map of the electrocatalytic CO 2 by the Cu micro-particles prepared in the comparative experiment. Detailed Embodiments

[0023] Detailed Embodiment 1: A preparation method of low aspect ratio Cu micro-wires in this embodiment is carried out according to the following steps:

[0024] I. Preparation of precursor salt solution:

[0025] Dissolve sodium halide salt in an alcohol-containing organic solution, and then add copper salt and stir to mix evenly to obtain a precursor salt solution;

[0026] II. Preparation of reducing agent solution:

[0027] Dissolve the reducing agent and the surfactant in an alcohol-containing organic solution to obtain a reducing agent solution;

[0028] III. Reduction:

[0029] Heat the precursor salt solution to 100°C - 150°C, then add the reducing agent solution and mix evenly. Under the condition of a temperature of 100°C - 150°C, react for 0.5 h - 1 h. After the reaction, cool to room temperature, and finally centrifuge, wash, and vacuum dry to obtain Cu micro-wires with a low aspect ratio.

[0030] The beneficial effects of this embodiment are as follows:

[0031] This embodiment relates to a synthesis method of Cu micro-wires, using a surfactant, a reducing agent, a reaction solvent (complexing agent), and adding a certain amount of sodium halide to adjust the morphology and structure of the product to obtain Cu micro-wires.

[0032] I. The diameter of the Cu micro-wires prepared in this embodiment is about 1 - 3 microns, and the length is about 90 - 150 microns. The preparation method is simple and the reaction conditions are mild.

[0033] II. When the Cu micro-wires prepared in this embodiment are applied to the electrocatalytic reduction of CO 2 reaction, they exhibit good catalytic performance, and the main product is ethylene.

[0034] Specific Embodiment 2: The difference between this embodiment and Specific Embodiment 1 is that the sodium halide salt described in Step I is sodium chloride or sodium bromide; the copper salt described in Step I is copper nitrate, copper acetate, copper chloride, or copper sulfate. Others are the same as Specific Embodiment 1.

[0035] Specific Embodiment 3: The difference between this embodiment and one of Specific Embodiments 1 or 2 is that the alcohol-containing organic solvent described in Steps I and II is ethylene glycol or triethylene glycol. Others are the same as Specific Embodiment 1 or 2.

[0036] Specific Embodiment 4: The difference between this embodiment and one of Specific Embodiments 1 to 3 is that the molar ratio of the sodium halide salt described in Step I to the volume of the alcohol-containing organic solution is (0.02 - 0.2) mmol:20 mL; the molar ratio of the sodium halide salt to the copper salt described in Step I is 1:(1 - 10). Others are the same as Specific Embodiment 3.

[0037] Specific Embodiment 5: The difference between this embodiment and any one of Embodiments 1 to 4 is that: the reducing agent described in Step 2 is ascorbic acid or sodium borohydride; the surfactant described in Step 2 is PVP K30. Others are the same as those in Embodiments 1 to 4.

[0038] Specific Embodiment 6: The difference between this embodiment and any one of Embodiments 1 to 5 is that: the molar ratio of the reducing agent described in Step 2 to the volume of the alcohol-containing organic solution is (0.5 - 1) mmol: 5 mL; the molar ratio of the surfactant described in Step 2 to the volume of the alcohol-containing organic solution is (1 - 2) mmol: 5 mL. Others are the same as those in Embodiments 1 to 5.

[0039] Specific Embodiment 7: The difference between this embodiment and any one of Embodiments 1 to 6 is that: in Step 3, the reducing agent solution is added at a rate of 0.25 mL / min to 1 mL / min; the volume ratio of the reducing agent solution to the precursor salt solution is 1: (2 - 3). Others are the same as those in Embodiments 1 to 6.

[0040] Specific Embodiment 8: The difference between this embodiment and any one of Embodiments 1 to 7 is that: in Step 3, the centrifugation, washing, and vacuum drying are specifically carried out under the condition of a rotation speed of 5000 rpm to 12000 rpm, centrifuging for 3 min to 10 min to separate the solid, then washing the solid 3 to 5 times with absolute ethanol or n-hexane, and finally vacuum drying for 10 h to 12 h under the condition of a temperature of 40°C to 60°C. Others are the same as those in Embodiments 1 to 7.

[0041] Specific Embodiment 9: The difference between this embodiment and any one of Embodiments 1 to 8 is that: the diameter of the low aspect ratio Cu micro-wires prepared in Step 3 is 1 μm to 3 μm, and the length is 90 μm to 150 μm. Others are the same as those in Embodiments 1 to 8.

[0042] Specific Embodiment 10: The application of a low aspect ratio Cu micro-wire in this embodiment, which is used as a raw material to prepare a gas diffusion electrode for electrocatalytic reduction of CO 2 。

[0043] The following examples are used to verify the beneficial effects of the present invention:

[0044] Example 1:

[0045] A preparation method of low aspect ratio Cu micro-wires, which is carried out according to the following steps:

[0046] I. Preparation of the precursor salt solution:

[0047] Dissolve sodium halide salt in an alcohol-containing organic solution, then add copper salt and stir to mix evenly to obtain a precursor salt solution;

[0048] The sodium halide salt is sodium chloride; the alcohol-containing organic solvent is ethylene glycol; the copper salt is copper nitrate;

[0049] The molar ratio of the sodium halide salt to the volume of the alcohol-containing organic solution is 0.2 mmol:20 mL; the molar ratio of the sodium halide salt to the copper salt is 1:10;

[0050] II. Preparation of reducing agent solution:

[0051] Dissolve a reducing agent and a surfactant in an alcohol-containing organic solution to obtain a reducing agent solution;

[0052] The reducing agent is ascorbic acid; the surfactant is PVP K30; the alcohol-containing organic solvent is ethylene glycol;

[0053] The molar ratio of the reducing agent to the volume of the alcohol-containing organic solution is 0.75 mmol:5 mL; the molar ratio of the surfactant to the volume of the alcohol-containing organic solution is 1.5 mmol:5 mL;

[0054] III. Reduction:

[0055] Heat the precursor salt solution to 140 °C, then add the reducing agent solution at a rate of 0.25 mL / min and mix evenly. Under the condition of a temperature of 140 °C, react for 1 h. After the reaction, cool to room temperature, and finally centrifuge, wash, and vacuum dry to obtain Cu micro-wires;

[0056] The volume ratio of the reducing agent solution to the precursor salt solution is 1:2.

[0057] The centrifugation, washing, and vacuum drying in step III are specifically carried out under the condition of a rotation speed of 8000 rpm for 5 min to separate the solid, then wash the solid with anhydrous ethanol 3 times, and finally vacuum dry at a temperature of 60 °C for 12 h.

[0058] The diameter of the Cu micro-wires prepared in step III is 1 μm - 3 μm, and the length is 90 μm - 150 μm.

[0059] Application of the above-prepared Cu micro-wires, the Cu micro-wires are used as raw materials to prepare a gas diffusion electrode for electrocatalytic CO 2 reduction;

[0060] The gas diffusion electrode is specifically prepared according to the following steps:

[0061] ① Add Cu micro-wires to the mixed solution of Nafion and isopropanol, and under the condition of a power of 100 W, ultrasonically mix for 30 min to obtain a catalyst ink;

[0062] In the mixed solution of Nafion and isopropanol, the volume ratio of the Nafion solution to isopropanol is 1:30; the concentration of Cu micro-wires in the catalyst ink is 8 mg / mL;

[0063] ② According to the loading amount of Cu micro-wires being 1 mg / cm 2 , at room temperature, spray the catalyst ink onto the carbon paper, and finally dry it to obtain a gas diffusion electrode;

[0064] The carbon paper is Sigracet 28BC;

[0065] The electrocatalytic CO 2 reduction is specifically carried out according to the following steps:

[0066] ① Assembly: Using a flow-through electrolytic cell, set a gas diffusion electrode between the CO 2 gas flow chamber and the cathode chamber, and set an anion exchange membrane between the cathode chamber and the anode chamber; place the counter electrode in the anode chamber, place the reference electrode in the cathode chamber, and connect the cathode liquid flow cell to the cathode chamber through a conduit, and connect the anode liquid flow cell to the anode chamber through a conduit. Pour the electrolyte into the cathode liquid flow cell and the anode liquid flow cell, and finally connect the positive pole of the power supply to the counter electrode and the negative pole of the power supply to the gas diffusion electrode;

[0067] The electrolyte is a 1 M KOH electrolyte, and the flow rate of the electrolyte is 5 mL / min; the CO 2 gas flow chamber is made of polyether ether ketone (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;

[0068] ② Electrocatalytic CO 2 reduction: At a flow rate of 30 sccm, introduce CO 2 gas into the CO 2 gas flow chamber, keep the CO 2 continuously introduced, and under the condition that the current density of the gas diffusion electrode is 50 mA·cm -2 ~ 500 mA·cm -2 electrocatalytically reduce CO 2 to collect the gas product, separate and purify the electrolyte after the reaction, and thus complete the electrocatalytic CO 2 reduction.

[0069] Comparative experiment: The difference between this comparative experiment and Example 1 is as follows: In step one, the use of sodium halide salt is cancelled; Cu micron particles are obtained in step three. Others are the same as in Example 1.

[0070] Figure 1 Scanning electron microscope image of the Cu micro-wires prepared in Example 1; It can be seen from the figure that the obtained Cu micro-wires have a diameter of about 1 - 3 microns and a length of about 90 - 150 microns, and are relatively evenly distributed.

[0071] Figure 2 X-ray diffraction pattern of the Cu micro-wires prepared in Example 1; It can be seen from the figure that the obtained material is mainly pure Cu and has good crystallinity.

[0072] Figure 3 Scanning electron microscope image of the Cu micron particles prepared in the comparative experiment; It can be seen from the figure that the main product is Cu micron particles with a size of about 0.5 - 2 microns, and the size distribution is relatively uniform.

[0073] Figure 4 Catalytic product distribution map of the Cu micro-wires prepared in Example 1 for electrocatalytic CO 2 ; It can be seen from the figure that during the electrocatalytic CO 2 reduction process, the main catalytic product of Cu micro-wires is CO at low current density. As the reaction current density increases, the main catalytic product is C 2 H 4 . At a current density of 250 mA cm -2 , the highest Faraday efficiency of C 2 H 4 is 33.4%, and it shows a good inhibitory effect on H 2 products. The Faraday efficiency of hydrogen is below 20% at a current density below 400 mA cm -2 .

[0074] Figure 5 Catalytic product distribution map of the Cu micron particles prepared in the comparative experiment for electrocatalytic CO 2 ; It can be seen from the figure that during the electrocatalytic CO 2 reduction process, the main catalytic products of Cu micron particles are similar to those of Cu micro-wires at low current density, both being CO. However, at high reaction rates, the selectivity of H 2 and CH 4 is relatively high. At a current density of 400 mA cm -2 , the highest Faraday efficiency of CH 4 is 23.3%, significantly higher than 11.5% of Cu micro-wires. And the selectivity of the C-C coupling product ethylene is relatively low.

Claims

1. A method for preparing a low aspect ratio Cu microwire, characterized in that It is carried out in the following steps:

1. Preparation of precursor salt solution: Dissolving a sodium halide salt in an alcohol-containing organic solution, then adding a copper salt and stirring to mix evenly to obtain a precursor salt solution; 2. Preparation of reducing agent solution: dissolving a reducing agent and a surfactant in an alcohol-containing organic solution to obtain a reducing agent solution; 3. Restore: The precursor salt solution is heated to 100°C to 150°C, and then the reducing agent solution is added and mixed evenly. The reaction is carried out at a temperature of 100°C to 150°C for 0.5h to 1h. After the reaction, the solution is cooled to room temperature, and finally centrifuged, washed and vacuum dried to obtain low aspect ratio Cu microwires.

2. The method for preparing a low aspect ratio Cu microwire according to claim 1, characterized in that The sodium halide salt described in step 1 is sodium chloride or sodium bromide; the copper salt described in step 1 is copper nitrate, copper acetate, copper chloride or copper sulfate.

3. The method for preparing a low aspect ratio Cu microwire according to claim 1, characterized in that The alcohol-containing organic solvent described in step 1 and step 2 is ethylene glycol or triethylene glycol.

4. The method for preparing a low aspect ratio Cu microwire according to claim 1, characterized in that The volume ratio of the amount of the sodium halide salt described in step 1 to the alcohol-containing organic solution is (0.02-0.2) mmol:20 mL; the molar ratio of the sodium halide salt described in step 1 to the copper salt is 1:(1-10).

5. The method for preparing a low aspect ratio Cu microwire according to claim 1, characterized in that The reducing agent described in step 2 is ascorbic acid or sodium borohydride; the surfactant described in step 2 is PVPK30.

6. The method for preparing a low aspect ratio Cu microwire according to claim 1, characterized in that The volume ratio of the amount of the reducing agent described in step 2 to the alcohol-containing organic solution is (0.5-1) mmol:5 mL; the volume ratio of the amount of the surfactant described in step 2 to the alcohol-containing organic solution is (1-2) mmol:5 mL.

7. The method for preparing a low aspect ratio Cu microwire 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 1 mL / min; the volume ratio of the reducing agent solution to the precursor salt solution in step 3 is 1:(2 to 3).

8. The method for preparing a low aspect ratio Cu microwire 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 or n-hexane 3 to 5 times, and finally vacuum drying at a temperature of 40°C to 60°C for 10h to 12h.

9. The method for preparing a low aspect ratio Cu microwire according to claim 1, characterized in that The low aspect ratio Cu microwire prepared in step 3 has a diameter of 1 μm to 3 μm and a length of 90 μm to 150 μm.

10. Application of a low aspect ratio Cu microwire 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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