A method for preparing a high-efficiency electrocatalytic carbon reduction electrode by high-frequency oscillation assisted surface bonding

Abstract

The application relates to a method for preparing a high-efficiency electrocatalytic carbon reduction electrode by high-frequency oscillation assisted surface bonding, and relates to a method for preparing a high-efficiency electrocatalytic carbon reduction electrode. The method solves the problem of low Faraday efficiency of existing silver-based electrocatalytic electrodes in producing carbon monoxide. The method comprises the following steps: one, preparing a precursor dispersion liquid by high-frequency oscillation; two, preparing a silver-based electrode by a self-spreading method. The application is used for preparing a high-efficiency electrocatalytic carbon reduction electrode by high-frequency oscillation assisted surface bonding.

Description

TECHNICAL FIELD

[0001] The present application relates to a method for preparing a high-efficiency electrocatalytic carbon reduction electrode. BACKGROUND

[0002] The increasing content of carbon dioxide has caused energy crisis and greenhouse effect, which has become one of the main problems faced by human society in the 21st century. Carbon dioxide can be converted into various high-value chemical fuels such as carbon monoxide, methane, ethanol, etc. through reduction reaction. The electrocatalytic reduction reaction has mild conditions, and with the decreasing cost of wind and solar energy conversion into electricity year by year, it is possible to convert carbon dioxide into high-value chemical fuels by using electricity. However, the low efficiency of carbon reduction reaction, the diversity of products, and the instability of catalysts greatly limit its application value. Therefore, developing a high-efficiency, single-product, and stable carbon reduction electrode has become the research focus in the field of electrocatalytic carbon reduction.

[0003] Silver, as a noble metal electrocatalyst, has been widely studied for its high carbon monoxide selectivity, low overpotential, and relatively low cost in the process of carbon reduction. However, like other carbon reduction catalysts, the main problem faced by silver-based catalysts is still how to suppress the HER side reaction caused by water electrolysis during the reaction. The increase in hydrogen production caused by the HER reaction will inevitably lead to a decrease in the yield of carbon-containing products. Therefore, reducing hydrogen production and improving the faradaic efficiency (electron utilization efficiency) of carbon monoxide has become a top priority. SUMMARY

[0004] The present application aims to solve the problem of low faradaic efficiency of silver-based electrocatalytic electrodes for producing carbon monoxide, and further provides a method for preparing a high-efficiency electrocatalytic carbon reduction electrode by high-frequency oscillation assisted surface bonding.

[0005] A method for preparing a high-efficiency electrocatalytic carbon reduction electrode by high-frequency oscillation assisted surface bonding, which is carried out according to the following steps:

[0006] I. Preparation of precursor dispersion liquid by high-frequency oscillation:

[0007] Mix micron-sized silver powder, Nafion solution, and anhydrous ethanol to obtain a suspension, then high-frequency oscillate the suspension under the condition of a power of 10 kHz to 40 kHz to obtain a dispersion liquid;

[0008] The volume ratio of Nafion solution to anhydrous ethanol is (3-27):50; the concentration of micron-sized silver powder in the suspension is 0.13 g / mL to 0.19 g / mL;

[0009] II. Preparation of silver-based electrode by self-spreading method:

[0010] A layer of hydrophobic and air-permeable film is attached to the back of the conductive substrate and heated to preheat, then at the preheating temperature, the dispersion droplets are coated on the surface of the conductive substrate on the side without the hydrophobic and air-permeable film, after the dispersion is completely spread and wetted and dried, the silver-based electrode fixed on the substrate is obtained by cooling to room temperature.

[0011] The beneficial effects of the present application are:

[0012] Firstly, the raw materials used in the present application are abundant in nature and easy to obtain. At the same time, the preparation process is simple and efficient, which can effectively reduce the preparation cost of carbon reduction catalytic electrodes.

[0013] Secondly, the preparation process of the present application is simple and controllable, and the reaction conditions are mild. The surface energy of the substrate is reduced through the preheating process, and the self-spreading effect of the solution on the material surface is utilized, without the need for additional energy input. Since this method is not limited by the type of catalyst particles, it has strong universality and can be applied to other catalyst powders used in the field of carbon reduction.

[0014] Thirdly, the powder electrode obtained in the present application is fixed on the conductive substrate. Due to the polarity of Nafion molecules, during ultrasonic oscillation, the polar end of the Nafion molecule is close to the metal side under the external vibration field, and the non-polar end tends to the outside, so that the entire Nafion molecule has orientation, and the electrode surface after drying has strong hydrophobic effect, without the need for additional hydrophobic treatment, which can effectively inhibit the HER reaction and improve the faradic efficiency of carbon monoxide, reaching a maximum of 81.5% at a current density of-15mA / cm2. In addition, uniform silver powder and Nafion molecules are obtained during ultrasonic treatment, which improves the stability of the electrode during catalytic process. The micron-sized silver powder has a large specific surface area, which can increase the active sites and improve the catalytic reaction efficiency.

[0015] The present application is used for a method for preparing a high-efficiency electrocatalytic carbon reduction electrode by high-frequency oscillation assisted surface bonding. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 The scanning electron microscope and energy spectrum scanning diagram of the silver-based electrode fixed on the substrate prepared in Example 1;

[0017] Figure 2 The X-ray diffraction spectrum, 1 is the original micron-sized silver powder, and 2 is the silver-based electrode fixed on the substrate prepared in Example 1;

[0018] Figure 3 The X-ray photoelectron spectroscopy analysis of the silver-based electrode fixed on the substrate prepared in Example 1;

[0019] Figure 4 The carbon reduction reaction Faraday efficiency of the silver-based electrode prepared in Example 1 and fixed on the substrate under different current densities, 1 is H2, and 2 is CO;

[0020] Figure 5 The carbon reduction reaction Faraday efficiency of the silver-based electrode prepared in the comparative experiment and fixed on the substrate under different current densities, 1 is H2, and 2 is CO. DETAILED DESCRIPTION

[0021] Specific embodiment one: a method for preparing an efficient electrocatalytic carbon reduction electrode by high-frequency oscillation assisted surface bonding, which is carried out according to the following steps:

[0022] I. Preparation of precursor dispersion liquid by high-frequency oscillation:

[0023] Mix micron-sized silver powder, Nafion solution and anhydrous ethanol to obtain a suspension liquid, then high-frequency oscillate the suspension liquid under the condition of a power of 10 kHz-40 kHz to obtain a dispersion liquid;

[0024] The volume ratio of the Nafion solution to anhydrous ethanol is (3-27): 50; the concentration of micron-sized silver powder in the suspension liquid is 0.13 g / mL-0.19 g / mL;

[0025] II. Preparation of silver-based electrode by self-spreading method:

[0026] Attach a layer of hydrophobic and breathable film to the back of the conductive substrate and heat it to preheat, then at the preheating temperature, drop coat the dispersion liquid on the surface of the conductive substrate on which no hydrophobic and breathable film is arranged, wait for the dispersion liquid to completely spread and wet and dry, and then cool to room temperature to obtain a silver-based electrode fixed on the substrate.

[0027] The electrode prepared in this specific embodiment has uniform silver-based catalyst distribution on the surface and good hydrophobicity, and can be used as an electrocatalytic carbon reduction reaction electrode to achieve efficient and selective reduction of carbon monoxide.

[0028] The beneficial effects of this specific embodiment are:

[0029] Firstly, the raw materials used in this specific embodiment are abundant in nature and easy to obtain. At the same time, the preparation process is simple and efficient, which can effectively reduce the preparation cost of carbon reduction catalyst electrodes.

[0030] Secondly, the preparation process of the embodiment is simple and controllable, and the reaction condition is mild. The surface energy of the substrate is reduced through a preheating process, and the self-spreading effect of the solution on the material surface is utilized without additional energy input. Since the method is not limited by the type of catalyst particles, the preparation method has strong universality and can be applied to other catalyst powders used in carbon reduction.

[0031] Thirdly, the embodiment obtains a powder electrode fixed on a conductive substrate. Due to the polarity of the Nafion molecules, during ultrasonic oscillation, the polar end of the Nafion molecules is close to the metal side, and the non-polar end tends to the outside, so that the entire Nafion molecule has orientation, and the electrode surface after drying has strong hydrophobic effect, without additional hydrophobic treatment, the HER reaction can be effectively inhibited, and the faradic efficiency of carbon monoxide is improved, which can reach 81.5% at a current density of-15 mA / cm 2 In addition, uniform silver powder and Nafion molecules are obtained during ultrasonic treatment, which improves the stability of the electrode in the catalytic process. The micron-sized silver powder has a large specific surface area, which can increase the active sites and improve the catalytic reaction efficiency.

[0032] Embodiment Two: The difference between this embodiment and Embodiment One is that the particle size of the micron-sized silver powder in Step One is <10 μm. The others are the same as Embodiment One.

[0033] Embodiment Three: The difference between this embodiment and Embodiment One or Two is that the suspension is high-frequency oscillated for 10 min to 40 min in Step One. The others are the same as Embodiment One or Two.

[0034] Embodiment Four: The difference between this embodiment and any one of Embodiments One to Three is that the mass percentage of the Nafion solution in Step One is 1% to 5%. The others are the same as Embodiments One to Three.

[0035] Embodiment Five: The difference between this embodiment and any one of Embodiments One to Four is that the conductive substrate in Step Two is carbon paper. The others are the same as Embodiments One to Four.

[0036] Embodiment Six: The difference between this embodiment and any one of Embodiments One to Five is that the hydrophobic and breathable film is bonded to the back of the conductive substrate in Step Two. The others are the same as Embodiments One to Five.

[0037] Seventh embodiment: the difference between this embodiment and one of the first to sixth embodiments is that the heating and preheating in step two is specifically preheating for 10-40 minutes at a temperature of 70-120°C. The rest is the same as the first to sixth embodiments.

[0038] Eighth embodiment: the difference between this embodiment and one of the first to seventh embodiments is that in step two, the droplet of the dispersion liquid is coated on the surface of the conductive substrate without a hydrophobic and air-permeable film on one side at a preheating temperature of 70-120°C. The rest is the same as the first to seventh embodiments.

[0039] Ninth embodiment: the difference between this embodiment and one of the first to eighth embodiments is that the drying in step two is specifically drying for 10-40 minutes in an air atmosphere and at a temperature of 70-120°C. The rest is the same as the first to eighth embodiments.

[0040] Tenth embodiment: the difference between this embodiment and one of the first to ninth embodiments is that the amount of the droplet of the dispersion liquid in step two is 50-200 mL / cm 2 2 . The rest is the same as the first to ninth embodiments.

[0041] The following examples are used to verify the beneficial effects of the present application:

[0042] Example 1:

[0043] A method for preparing a high-efficiency electrocatalytic carbon reduction electrode by high-frequency oscillation assisted surface bonding, which is carried out according to the following steps:

[0044] I. Preparation of a precursor dispersion liquid by high-frequency oscillation:

[0045] Mix micron-sized silver powder, Nafion solution and anhydrous ethanol to obtain a suspension liquid, then high-frequency oscillate the suspension liquid at a power of 40 kHz for 30 minutes to obtain a dispersion liquid;

[0046] The mass percentage of the Nafion solution is 5%; the volume ratio of the Nafion solution to anhydrous ethanol is 3:10; the concentration of micron-sized silver powder in the suspension liquid is 0.15 g / mL;

[0047] II. Preparation of a silver-based electrode by a self-spreading method:

[0048] Bond a layer of hydrophobic and air-permeable film on the back of the conductive substrate, preheat for 30 minutes at a temperature of 90°C, then coat the droplet of the dispersion liquid on the surface of the conductive substrate at a preheating temperature of 90°C and a droplet amount of 200 mL / cm 2 ​The dispersion droplets were coated on the surface of the conductive substrate without the hydrophobic and air-permeable film on one side under the condition that the dispersion was completely spread and wetted, and then dried for 20 min in air at 90℃, and finally cooled to room temperature to obtain the silver-based electrode fixed on the substrate.

[0049] The particle size of the micron-sized silver powder in step one was about 5 μm.

[0050] The conductive substrate in step two was a carbon paper with a size of 1×3 cm 2 .

[0051] The hydrophobic and air-permeable film in step two was a commercial hydrophobic and air-permeable film produced by Hebei Xindongsheng Sealing Material Co., Ltd., and the main components were non-woven fabric, polyethylene and polypropylene.

[0052] Figure 1 The scanning electron microscope and energy spectrum scanning diagram of the silver-based electrode fixed on the substrate prepared in Example One; as shown in the diagram, the particle size of the Ag-based catalyst was about 5 microns, which was uniformly distributed on the surface of the electrode and was the main component. The Nafion component was uniformly distributed around the catalyst and had a small amount, which was difficult to be observed under the energy spectrum.

[0053] Figure 2 The X-ray diffraction spectrum, 1 was the original micron-sized silver powder, and 2 was the silver-based electrode fixed on the substrate prepared in Example One; as shown in the diagram, the Ag-based catalyst did not change in phase before and after the preparation of the electrode, and the crystal structure remained unchanged.

[0054] Figure 3 The X-ray photoelectron spectroscopy analysis of the silver-based electrode fixed on the substrate prepared in Example One; as shown in the diagram, only two peak values of Ag3d3 / 2 and Ag3d5 / 2 were observed on the Ag3d orbital, indicating that the catalyst still existed in the form of zero-valent silver atoms and was not oxidized.

[0055] The silver-based electrode fixed on the substrate prepared in Example One was tested by using a H-type electrolytic cell three-electrode system with a 0.5 mol / L KHCO3 solution as the electrolyte, and the composition of the gaseous product was determined by a gas chromatograph. Figure 4 The carbon reduction reaction Faraday efficiency of the silver-based electrode fixed on the substrate prepared in Example One under different current densities, 1 was H2, and 2 was CO. As shown in the diagram, under the condition that the current density was -15 mA / cm 2 , the Faraday efficiency of carbon monoxide produced in the reaction was 81.5%.

[0056] At the same time, the partial current density of carbon monoxide was measured to be 12.23 mA / cm 2 under the condition that the current density was -15 mA / cm 2 .The reaction potential is -1.34 V (vs. RHE). The Faraday efficiency of the product remains almost unchanged, only decreasing by 3% under the condition of a current density of -15 mA / cm 2 Compared with the existing silver-based carbon reduction catalytic electrode, the material prepared in Example One has high product selectivity and catalytic stability.

[0057] Comparative Experiment: The difference between this comparative experiment and Example One is that the high-frequency oscillation treatment in Step One is cancelled. The others are the same as Example One.

[0058] The test conditions are the same as Example One, Figure 5 The Faraday efficiency of the carbon reduction reaction of the silver-based electrode prepared in the comparative experiment and fixed on the substrate under different current densities, 1 is H2, and 2 is CO. The results of the comparative experiment show that the Faraday efficiency of carbon monoxide produced by the silver-based electrode prepared in the comparative experiment and fixed on the substrate is only 41.6% under the condition of a current density of -15 mA / cm 2 ​

Claims

1. A method for fabricating high-efficiency electrocatalytic carbon reduction electrodes by high-frequency oscillation-assisted surface bonding, characterized in that It is carried out according to the following steps: I. The precursor dispersion liquid is prepared by high frequency oscillation: The micron silver powder, Nafion solution and anhydrous ethanol are mixed to obtain a suspension liquid, and then the suspension liquid is oscillated under the condition of power of 10 kHz-40 kHz to obtain a dispersion liquid; The volume ratio of the Nafion solution to anhydrous ethanol is (3-27):50; the concentration of the micron silver powder in the suspension liquid is 0.13 g / mL-0.19 g / mL; and the mass percentage of the Nafion solution is 1%-5%; II. The silver-based electrode is prepared by self-spreading method: A hydrophobic and air-permeable film is attached to the back of the conductive substrate and heated for preheating, then the dispersion liquid is drop-coated on the surface of the conductive substrate without the hydrophobic and air-permeable film at the preheating temperature, after the dispersion liquid is completely spread, wetted and dried, the silver-based electrode fixed on the substrate is obtained by cooling to room temperature.

2. The method for preparing a high-efficiency electrocatalytic carbon reduction electrode by high-frequency oscillation auxiliary surface bonding according to claim 1, characterized in that The particle size of the micron silver powder in step I is <10 μm.

3. The method for fabricating a high-efficiency electrocatalytic carbon reduction electrode by high-frequency oscillation-assisted surface bonding according to claim 1, characterized in that The suspension liquid is oscillated for 10 min-40 min in step I.

4. The method for fabricating a high-efficiency electrocatalytic carbon reduction electrode by high-frequency oscillation-assisted surface bonding according to claim 1, characterized in that The conductive substrate in step II is carbon paper.

5. The method for fabricating a high-efficiency electrocatalytic carbon reduction electrode by high-frequency oscillation-assisted surface bonding according to claim 4, characterized in that The hydrophobic and air-permeable film in step II is attached to the back of the conductive substrate.

6. The method for fabricating a high-efficiency electrocatalytic carbon reduction electrode by high-frequency oscillation-assisted surface bonding according to claim 1, characterized in that The preheating in step II is specifically preheated for 10 min-40 min at the temperature of 70℃-120℃.

7. The method for fabricating a high-efficiency electrocatalytic carbon reduction electrode by high-frequency oscillation-assisted surface bonding according to claim 6, characterized in that The dispersion liquid is drop-coated on the surface of the conductive substrate without the hydrophobic and air-permeable film at the preheating temperature of 70℃-120℃ in step II.

8. The method for fabricating a high-efficiency electrocatalytic carbon reduction electrode by high-frequency oscillation-assisted surface bonding according to claim 7, characterized in that The drying in step II is specifically dried for 10 min-40 min under the condition of air atmosphere and the temperature of 70℃-120℃.

9. The method for fabricating a high-efficiency electrocatalytic carbon reduction electrode by high-frequency oscillation-assisted surface bonding according to claim 1, characterized in that The amount of the dispersion solution described in Step two to be added is 50 mL / cm 2 ~ 200 mL / cm 2 .

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