阅读说明：本技术 改性铜片及其制备方法、用于电催化还原二氧化碳的催化电极及其应用 (Modified copper sheet and preparation method thereof, catalytic electrode for electrocatalytic reduction of carbon dioxide and application of catalytic electrode ) 是由 宁汇 鲁佩芳 焦振梅 胡涵 赵青山 吴文婷 李忠涛 吴明铂 于 2021-09-17 设计创作，主要内容包括：本发明提供了一种改性铜片及其制备方法、用于电催化还原二氧化碳的催化电极及其应用,涉及催化还原二氧化碳技术领域。该改性铜片的制备方法通过将预处理后的铜片先进行电抛光后再进行氧化处理,将得到的氧化铜片进行紫外光还原处理,得到改性铜片；该制备方法可实现对铜片的表面改性,经过上述方法制得的改性铜片具有均匀分布的相互交叉的纳米片状结构,与初始铜片的光滑结构相比,增加了许多活跃的不饱和位点,当将该改性铜片应用于电催化还原CO-(2)反应时,可为CO-(2)和中间产物的吸附和反应提供了很好的场所,并使得反应的比表面积极大地增加,更大程度的暴露了活性位点,有利于电催化还原CO-(2)反应的进行。(The invention provides a modified copper sheet, a preparation method thereof, a catalytic electrode for electrocatalytic reduction of carbon dioxide and application thereof, and relates to the technical field of catalytic reduction of carbon dioxide. The preparation method of the modified copper sheet comprises the steps of performing electropolishing on a pretreated copper sheet, then performing oxidation treatment, and performing ultraviolet light reduction treatment on the obtained copper oxide sheet to obtain the modified copper sheet; the preparation method can realize surface modification of the copper sheet, the modified copper sheet prepared by the method has uniformly distributed intercrossed nano flaky structures, and compared with the smooth structure of the initial copper sheet, a plurality of active unsaturated sites are increased, and when the modified copper sheet is applied to electrocatalytic reduction of CO 2 In the reaction, it may be CO 2 And provides good place for adsorption and reaction of intermediate products, and makes the specific surface area of reaction greatly increased, and exposes active site to a greater extent, and is favorable for electrocatalytic reduction of CO 2 And (3) carrying out the reaction.)

1. The preparation method of the modified copper sheet is characterized by comprising the following steps of:

(a) performing electric polishing on the pretreated copper sheet to obtain a polished copper sheet;

(b) carrying out oxidation treatment on the polished copper sheet to obtain a copper oxide sheet;

(c) and (3) placing the copper oxide sheet in a reducing solution and irradiating by adopting ultraviolet light to obtain the modified copper sheet.

2. The method of claim 1, wherein in the step (a), the pretreatment step comprises:

and (3) carrying out ultrasonic treatment on the initial copper sheet in acetone, ethanol and water respectively, then soaking in an acid solution, and separating to obtain the pretreated copper sheet.

3. The preparation method according to claim 1, wherein in the step (a), the copper sheet after pretreatment is used as a working electrode, the platinum sheet is used as a counter electrode, and Ag/AgCl is used as a reference electrode, and electropolishing is carried out in a three-electrode system using phosphoric acid as an electrolyte;

preferably, constant potential electrolysis is adopted in the electropolishing process, and the voltage is 2-10V;

preferably, the electropolishing time is 50-300 seconds.

4. The method according to claim 1, wherein in the step (b), the oxidizing solution used for the oxidation treatment comprises the following raw materials: hydrochloric acid, hydrogen peroxide and water;

preferably, the concentration of the hydrochloric acid is 1-10 mol/L;

preferably, the concentration of the hydrogen peroxide is 20-35%;

preferably, the volume ratio of the hydrochloric acid to the hydrogen peroxide to the water is (1-10): (20-35): 100, respectively;

preferably, the time of the oxidation treatment is 5-15 min.

5. The method according to any one of claims 1 to 4, wherein in the step (c), the reducing solution comprises the following raw materials: hydrogen peroxide, C1-C4 low carbon alcohol and water.

6. The preparation method of claim 5, wherein the concentration of the hydrogen peroxide is 20-35%;

preferably, the mass ratio of the hydrogen peroxide to the C1-C4 low-carbon alcohol to the water is (1-10): (20-35): 100, respectively;

preferably, the C1-C4 lower alcohol comprises any one of methanol, ethanol, n-propanol or isopropanol or the combination of at least two of the above.

7. The method as claimed in claim 5, wherein in the step (c), the power of the light source used for the UV irradiation is 300- & 600W;

preferably, the time of ultraviolet irradiation is 5-15 min.

8. A modified copper sheet, characterized in that it is produced by the process for the preparation of a modified copper sheet according to any one of claims 1 to 7.

9. A catalytic electrode for the electrocatalytic reduction of carbon dioxide, characterized in that it is made of a modified copper sheet according to claim 8.

10. Use of the modified copper sheet of claim 8 or the catalytic electrode for electrocatalytic reduction of carbon dioxide of claim 9 in the field of catalytic reduction of carbon dioxide.

Technical Field

The invention relates to the technical field of catalytic reduction of carbon dioxide, in particular to a modified copper sheet, a preparation method thereof, a catalytic electrode for electrocatalytic reduction of carbon dioxide and application thereof.

Background

Electrocatalytic reduction of CO₂As a high-efficiency convenient CO conversion₂The approach (a) has been developed vigorously in recent years, and has attracted much attention. Electrocatalytic reduction of CO₂The product is rich in carbon monoxide (CO) and methane (CH)₄) Formic acid (HCOOH) and ethylene (C)₂H₄) Ethanol (C)₂H₅OH), and the like. C1 products such as CO, methane and formic acid have less electrons, short reaction path and high Faraday efficiency up to 90%And above, even close to 100%. The C2 product needs to be hydrogenated continuously on the basis of the C1 intermediate product, the reaction path is long, the intermediate product is complex, and a multi-electron process often needs higher overpotential, so that the Faraday efficiency of the C2 product is strong. Unlike other metal catalysts, copper has unique moderate adsorption to CO, and can not generate CO and CH through premature desorption₄And the C1 products such as HCOOH and the like can not be deactivated by contacting reactants due to too strong adsorption, and the moderate adsorption of CO can make the C-C coupling easier, so that the copper-produced C2 product has incomparable advantages of other metal catalysts.

Directly takes the blocky polycrystalline copper as a working electrode to participate in the electrocatalytic reduction of CO₂The performance of the reaction is poor, the yield of the hydrogen byproduct is high, and the carbon-containing product has only a small amount of C1 products such as methane and carbon monoxide. Researchers have carried out a series of modifications on the copper catalytic material, including methods of controlling the shape and structure of the copper catalytic material, oxidation treatment, compounding with other materials and the like, wherein the modification of the surface of the bulk polycrystalline copper to make the bulk polycrystalline copper have better shape and structure is a simple scheme.

In view of the above, the present invention is particularly proposed.

Disclosure of Invention

The first objective of the present invention is to provide a method for preparing a modified copper sheet, so as to improve the technical problems existing in the prior art.

The second purpose of the invention is to provide a modified copper sheet prepared by the preparation method.

It is a third object of the present invention to provide a method for electrocatalytic reduction of CO₂The catalytic electrode is prepared from the modified copper sheet.

The fourth purpose of the invention is to provide the modified copper sheet or the modified copper sheet for the electro-catalytic reduction of CO₂The use of a catalytic electrode according to (1).

In order to achieve the purpose, the technical scheme of the invention is as follows:

the invention provides a preparation method of a modified copper sheet, which comprises the following steps:

(a) performing electric polishing on the pretreated copper sheet to obtain a polished copper sheet;

(b) carrying out oxidation treatment on the polished copper sheet to obtain a copper oxide sheet;

(c) and (3) placing the copper oxide sheet in a reducing solution and irradiating by adopting ultraviolet light to obtain the modified copper sheet.

Further, on the basis of the above technical solution of the present invention, in the step (a), the pretreatment step includes:

and (3) carrying out ultrasonic treatment on the initial copper sheet in acetone, ethanol and water respectively, then soaking in an acid solution, and separating to obtain the pretreated copper sheet.

Further, on the basis of the above technical scheme of the present invention, in the step (a), the copper sheet after pretreatment is used as a working electrode, the platinum sheet is used as a counter electrode, and Ag/AgCl is used as a reference electrode, and electropolishing is performed in a three-electrode system using phosphoric acid as an electrolyte;

preferably, constant potential electrolysis is adopted in the electropolishing process, and the voltage is 2-10V;

preferably, the electropolishing time is 50-300 seconds.

Further, on the basis of the above technical solution of the present invention, in the step (b), the oxidizing solution used in the oxidation treatment comprises the following raw materials: hydrochloric acid, hydrogen peroxide and water;

preferably, the concentration of the hydrochloric acid is 1-10 mol/L;

preferably, the concentration of the hydrogen peroxide is 20-35%;

preferably, the volume ratio of the hydrochloric acid to the hydrogen peroxide to the water is (1-10): (20-35): 100, respectively;

preferably, the time of the oxidation treatment is 5-15 min.

Further, on the basis of the above technical solution of the present invention, in the step (c), the reducing solution comprises the following raw materials: hydrogen peroxide, absolute ethyl alcohol and water.

Further, on the basis of the technical scheme of the invention, the concentration of the hydrogen peroxide is 20-35%;

preferably, the mass ratio of the hydrogen peroxide to the C1-C4 low-carbon alcohol to the water is (1-10): (20-35): 100, respectively;

preferably, the C1-C4 lower alcohol comprises any one of methanol, ethanol, n-propanol or isopropanol or the combination of at least two of the above.

Further, on the basis of the above technical solution of the present invention, in the step (c), the power of the light source used for the ultraviolet light irradiation is 300-;

preferably, the time of ultraviolet irradiation is 5-15 min.

The invention also provides a modified copper sheet prepared by the preparation method of the modified copper sheet.

The invention also provides a method for electrocatalytic reduction of CO₂The catalytic electrode is prepared from the modified copper sheet.

The invention also provides the modified copper sheet or the modified copper sheet for electro-catalytic reduction of CO₂In the catalytic reduction of CO₂Application in the field.

Compared with the prior art, the technical scheme of the invention has the following technical effects:

(1) the invention provides a preparation method of a modified copper sheet, which comprises the steps of performing electropolishing on a pretreated copper sheet, then performing oxidation treatment, and performing ultraviolet light reduction treatment on the obtained copper oxide sheet to obtain the modified copper sheet; the preparation method can realize surface modification of the copper sheet, the copper sheet prepared by the method has uniformly distributed intercrossed nano flaky structures, and compared with the smooth structure of the initial copper sheet, a plurality of active unsaturated sites are increased, and when the modified copper sheet is applied to electrocatalytic reduction of CO₂In the reaction, it may be CO₂And provides good place for adsorption and reaction of intermediate products, and makes the specific surface area of reaction greatly increased, and exposes active site to a greater extent, and is favorable for electrocatalytic reduction of CO₂And (3) carrying out the reaction.

(2) The invention also provides a modified copper sheet prepared by the preparation method. In view of the advantages of the preparation method, the modified copper sheet has uniformly distributed intercrossed nano flaky structures, and is applied to the electrocatalytic reduction of CO₂Field providesA good foundation.

(3) The invention also provides a method for electrocatalytic reduction of CO₂The catalytic electrode is prepared from the modified copper sheet. In view of the advantages of the modified copper sheet, the modified copper sheet can be used for electrocatalytic reduction of CO₂The use of a catalytic electrode for the electrocatalytic reduction of CO₂The catalytic electrode has the same advantages as the modified copper sheet.

(4) The invention also provides the modified copper sheet or the modified copper sheet for electro-catalytic reduction of CO₂In the catalytic reduction of CO₂Applications in the field of modified copper sheets or for the electrocatalytic reduction of CO as described above₂Has the advantages that the catalytic electrode can be used for catalyzing and reducing CO₂Has good application in the field.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.

FIG. 1 is an X-ray diffraction pattern of a modified copper sheet or an unmodified copper sheet provided in example 1, comparative example 1 and comparative example 2 of the present invention;

FIG. 2 is a scanning electron micrograph of a modified copper sheet or an unmodified copper sheet provided in example 1, comparative example 1 and comparative example 2 of the present invention, wherein (a) is comparative example 1, (b) is comparative example 2, and (c) is example 1;

FIG. 3 is an X-ray photoelectron spectrum of a modified copper sheet or an unmodified copper sheet provided in example 1 and comparative example 1 of the present invention, wherein (a) is the X-ray photoelectron spectrum of the unmodified copper sheet in comparative example 1, (b) is the Cu 2p X ray photoelectron spectrum of the unmodified copper sheet in comparative example 1, (c) is the X-ray photoelectron spectrum of the modified copper sheet in example 1, and (b) is the Cu 2p X ray photoelectron spectrum of the modified copper sheet in example 1;

fig. 4 is an X-ray photoelectron spectrum of a modified copper sheet or an unmodified copper sheet provided in example 1 and comparative example 1 of the present invention, wherein (a) is a C1s X-ray photoelectron spectrum of the unmodified copper sheet in comparative example 1, (b) is an O1s X-ray photoelectron spectrum of the unmodified copper sheet in comparative example 1, (C) is a C1s X-ray photoelectron spectrum of the modified copper sheet in example 1, and (b) is an O1sX X-ray photoelectron spectrum of the modified copper sheet in example 1.

Detailed Description

Embodiments of the present invention will be described in detail below with reference to embodiments and examples, but those skilled in the art will understand that the following embodiments and examples are only illustrative of the present invention and should not be construed as limiting the scope of the present invention. Those who do not specify the conditions are performed according to the conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.

According to a first aspect of the invention, a preparation method of a modified copper sheet is provided, which comprises the following steps:

(a) performing electric polishing on the pretreated copper sheet to obtain a polished copper sheet;

(b) carrying out oxidation treatment on the polished copper sheet to obtain a copper oxide sheet;

(c) and (3) placing the copper oxide sheet in a reducing solution and irradiating by adopting ultraviolet light to obtain the modified copper sheet.

Specifically, in the step (a), the initial copper sheet needs to be pretreated because some oil stains, impurities or oxide layers may exist on the surface of the initial copper sheet. The pretreatment step is not particularly limited herein, as long as oil stains, impurities and an oxide layer on the surface of the initial copper sheet can be sufficiently removed.

The pretreated copper sheet is electropolished to remove surface oxides.

In the step (b), the polished copper sheet is subjected to oxidation treatment to make the surface rough.

In the step (c), the copper oxide sheet is subjected to ultraviolet irradiation and reduction treatment, and the copper oxide can be partially reduced by the process.

The invention provides a preparation method of a modified copper sheet, which is characterized in that pretreated copper is usedCarrying out electropolishing and then oxidation treatment on the copper sheet, and carrying out ultraviolet light reduction treatment on the obtained copper oxide sheet to obtain a modified copper sheet; the preparation method can realize surface modification of the copper sheet, the copper sheet prepared by the method has uniformly distributed intercrossed nano flaky structures, and compared with the smooth structure of the initial copper sheet, a plurality of active unsaturated sites are increased, and when the copper sheet is applied to electrocatalytic reduction of CO₂In the reaction, it may be CO₂And provides good place for adsorption and reaction of intermediate products, and makes the specific surface area of reaction greatly increased, and exposes active site to a greater extent, and is favorable for electrocatalytic reduction of CO₂And (3) carrying out the reaction.

As an alternative embodiment of the present invention, in the step (a), the pretreatment step comprises: and (3) carrying out ultrasonic treatment on the initial copper sheet in acetone, ethanol and water respectively, then soaking in an acid solution, and separating to obtain the pretreated copper sheet.

The initial copper sheet is respectively subjected to ultrasonic washing in acetone, ethanol and water, mainly to remove oil stains and impurities, and then soaked and washed in an acid solution, mainly to remove an oxidation layer. Before the next operation, the pretreated copper sheet is temporarily stored in dilute hydrochloric acid and washed before use, so that secondary oxidation in air is avoided.

The specification of the initial copper sheet selected is not particularly limited. In an alternative embodiment of the present invention, the copper sheet has a thickness of 0.1mm and a length and width of 10mm by 10 mm.

As an alternative embodiment of the present invention, in step (a), electropolishing is performed in a three-electrode system using phosphoric acid as an electrolyte, with the pretreated copper sheet as a working electrode, the platinum sheet as a counter electrode, and the Ag/AgCl as a reference electrode.

As an alternative embodiment of the invention, the mass fraction of phosphoric acid is between 85 and 90%.

As an optional embodiment of the invention, the electropolishing process is carried out by constant potential electrolysis at a voltage of 2-10V;

as an alternative embodiment of the invention, the electropolishing time is in the range of 50-300 seconds.

The surface appearance and the composition of the material are controllable through the definition of a three-electrode system adopted in the electropolishing process and the further definition of polishing parameters.

As an alternative embodiment of the present invention, in the step (b), the oxidation solution used in the oxidation treatment comprises the following raw materials: hydrochloric acid, hydrogen peroxide and water;

preferably, the concentration of the hydrochloric acid is 1-10 mol/L; typical, but non-limiting, concentrations of hydrochloric acid are 1mol/L, 2mol/L, 3mol/L, 5mol/L, 7mol/L, 8mol/L, 9mol/L, or 10 mol/L.

Preferably, the concentration of the hydrogen peroxide is 20-35%;

preferably, the volume ratio of the hydrochloric acid to the hydrogen peroxide to the water is (1-10): (20-35): 100. the typical, but non-limiting, volume ratio of hydrochloric acid, hydrogen peroxide and water is 1: 20: 100. 2: 20: 100. 4: 20: 100. 5: 20: 100. 8: 20: 100. 10: 20: 100. 1: 25: 100. 2: 25: 100. 4: 25: 100. 5: 25: 100. 8: 25: 100. 10: 25: 100. 1: 30: 100. 2: 30: 100. 4: 30: 100. 5: 30: 100. 8: 30: 100. 10: 30: 100. 1: 35: 100. 2: 35: 100. 4: 35: 100. 5: 35: 100. 8: 35: 100 or 10: 35: 100.

the oxidation degree can be controlled by further limiting the raw materials and the dosage of the oxidation liquid.

The hydrochloric acid in the oxidizing solution may be replaced with sulfuric acid.

As an alternative embodiment of the present invention, in the step (c), the copper oxide sheet is placed in a reducing solution, and ultraviolet light irradiation is adopted to perform ultraviolet light reduction treatment.

In the step (c), the copper oxide sheet is placed in a reducing solution to reduce the oxide on the surface of the copper, and ultraviolet light is adopted for irradiation to induce the reduction reaction.

As an alternative embodiment of the present invention, the reducing liquid comprises the following raw materials: hydrogen peroxide, C1-C4 low carbon alcohol and water.

The reducing solution prepared by adopting the raw materials has the advantages of good reducing capability on copper oxide sheets, low price, safety, environmental protection and no toxicity.

As an optional embodiment of the invention, the concentration of hydrogen peroxide is 20-35%. Typical but non-limiting concentrations of hydrogen peroxide are 20%, 22%, 25%, 28%, 30%, 32%, or 35%.

As an optional embodiment of the invention, the mass ratio of hydrogen peroxide, C1-C4 low carbon alcohol and water is (1-10): (20-35): 100.

the volume ratio of hydrogen peroxide to C1-C4 lower alcohol to water is typically but not limited to 1: 20: 100. 2: 20: 100. 4: 20: 100. 5: 20: 100. 8: 20: 100. 10: 20: 100. 1: 25: 100. 2: 25: 100. 4: 25: 100. 5: 25: 100. 8: 25: 100. 10: 25: 100. 1: 30: 100. 2: 30: 100. 4: 30: 100. 5: 30: 100. 8: 30: 100. 10: 30: 100. 1: 35: 100. 2: 35: 100. 4: 35: 100. 5: 35: 100. 8: 35: 100 or 10: 35: 100.

as an alternative embodiment of the present invention, the C1-C4 lower alcohol comprises any one of methanol, ethanol, n-propanol or isopropanol or a combination of at least two of the same.

The reduction degree can be controlled by further limiting the raw materials and the use amount of the reduction solution.

As an alternative embodiment of the present invention, the power of the light source used for the ultraviolet light irradiation is 300-600W. Typical but non-limiting light source powers are 300W, 400W, 500W or 600W.

As an alternative embodiment of the invention, the time of the ultraviolet irradiation is 5-15 min. Typical but non-limiting times for UV irradiation are 5min, 8min, 10min, 12min or 15 min.

According to the second aspect of the invention, the modified copper sheet is also provided, and is prepared by adopting the preparation method of the modified copper sheet.

In view of the advantages of the preparation method, the modified copper sheet has a uniformly distributed intercrossed nano sheet structure, compared with the smooth structure of the original copper sheet, a plurality of active unsaturated sites are added, and the modified copper sheet is applied to the electrocatalytic reduction of CO₂The field provides a good foundation.

According to the bookIn a third aspect of the invention, there is also provided a method for electrocatalytic reduction of CO₂The catalytic electrode is prepared from the modified copper sheet.

In view of the advantages of the modified copper sheet, the modified copper sheet can be used for electrocatalytic reduction of CO₂The use of a catalytic electrode for the electrocatalytic reduction of CO₂The catalytic electrode has the same advantages as the modified copper sheet.

According to a fourth aspect of the present invention, there is also provided the above modified copper sheet or the use thereof for the electrocatalytic reduction of CO₂In the catalytic reduction of CO₂Application in the field.

In view of the above-mentioned modified copper sheets or for the electrocatalytic reduction of CO₂Has the advantages that the catalytic electrode can be used for catalyzing and reducing CO₂Has good application in the field.

The present invention will be further described with reference to specific examples and comparative examples.

Example 1

The embodiment provides a preparation method of a modified copper sheet, which comprises the following steps:

(a) flattening and cleaning a sheet-shaped initial copper sheet with the length and width of 10mm x 10mm and the thickness of 0.1mm, ultrasonically washing the sheet-shaped initial copper sheet in acetone, absolute ethyl alcohol and deionized water for 10min respectively, soaking the sheet-shaped initial copper sheet in 3mol/L HCl for 2min, taking out the sheet-shaped initial copper sheet and cleaning the sheet-shaped initial copper sheet with the deionized water, temporarily storing the treated copper sheet in dilute hydrochloric acid before the next operation, and performing pre-washing;

taking an initial copper sheet as a working electrode, a platinum sheet as a counter electrode and Ag/AgCl as a reference electrode, performing electropolishing operation in a three-electrode system taking 85% phosphoric acid as electrolyte, performing constant-potential electrolysis, polishing for 150s at a voltage of 3V, taking out, and washing with deionized water to obtain a polished copper sheet;

(b) putting the polished copper sheet into an oxidizing solution for oxidation treatment, wherein the oxidation treatment time is 5min, and obtaining a copper oxide sheet;

wherein, the preparation of the oxidizing solution comprises the following steps: 1mL of 3mol/L HCl and 305.7. mu.L of 30% H₂O₂Stirring and dispersing in 48.5mL of deionized water;

(c) and (3) washing the copper oxide sheet by using deionized water, immediately placing the copper oxide sheet into a reducing solution, irradiating the copper oxide sheet for 10min by using ultraviolet light under a 300W mercury lamp, taking out the copper oxide sheet, cleaning the copper oxide sheet by using the deionized water, and drying the copper oxide sheet in vacuum to obtain the modified copper sheet.

Wherein, the preparation of reducing solution: 1mL of 30% H₂O₂2mL of absolute ethyl alcohol and 47mL of deionized water are fully mixed to prepare a reducing solution.

Example 2

This example provides a method for preparing a modified copper sheet, which is similar to example 1 except that the uv irradiation time used in step (c) is changed from 10min to 5 min.

Example 3

This example provides a method for preparing a modified copper sheet, which is similar to example 1 except that the uv irradiation time used in step (c) is changed from 10min to 4 min.

Example 4

The embodiment provides a preparation method of a modified copper sheet, which comprises the following steps:

(a) flattening and cleaning a sheet-shaped initial copper sheet with the length and width of 10mm x 10mm and the thickness of 0.1mm, respectively ultrasonically washing the sheet-shaped initial copper sheet in acetone, absolute ethyl alcohol and deionized water for 30min, soaking the sheet-shaped initial copper sheet in 1mol/L HCl for 20min, taking out the sheet-shaped initial copper sheet and cleaning the sheet-shaped initial copper sheet with the deionized water, temporarily storing the treated copper sheet in dilute hydrochloric acid before the next operation, and performing pre-washing;

taking an initial copper sheet as a working electrode, a platinum sheet as a counter electrode and Ag/AgCl as a reference electrode, performing electropolishing operation in a three-electrode system taking 90% phosphoric acid as electrolyte, performing constant-potential electrolysis, polishing for 200s under the voltage of 5V, taking out, and washing with deionized water to obtain a polished copper sheet;

(b) putting the polished copper sheet into an oxidizing solution for oxidation treatment, wherein the oxidation treatment time is 15min, and obtaining a copper oxide sheet;

wherein, the preparation of the oxidizing solution comprises the following steps: 1mL of 1mol/L HCl and 305.7. mu.L of 30% H₂O₂Stirring and dispersing in 48.5mL of deionized water;

(c) and (3) washing the copper oxide sheet by using deionized water, immediately placing the copper oxide sheet into a reducing solution, irradiating the copper oxide sheet for 15min by using ultraviolet light under a 300W mercury lamp, taking out the copper oxide sheet, cleaning the copper oxide sheet by using the deionized water, and drying the copper oxide sheet in vacuum to obtain the modified copper sheet.

Wherein, the preparation of reducing solution: 1mL of 25% H₂O₂2mL of absolute ethyl alcohol and 50mL of deionized water are fully mixed to prepare a reducing solution.

Comparative example 1

The comparative example provides a preparation method of an unmodified copper sheet, comprising the following steps:

flattening and cleaning a sheet-shaped initial copper sheet with the length and width of 10mm x 10mm and the thickness of 0.1mm, respectively ultrasonically washing the sheet-shaped initial copper sheet in acetone, absolute ethyl alcohol and deionized water for 10min, soaking the sheet-shaped initial copper sheet in 3mol/L HCl for 2min, taking out the sheet-shaped initial copper sheet and cleaning the sheet-shaped initial copper sheet with the deionized water, temporarily storing the treated copper sheet in dilute hydrochloric acid before the next operation, and performing pre-washing to obtain an unmodified copper sheet.

Comparative example 2

This comparative example provides a method of preparing a modified copper sheet, except that step (c) was not performed, and the remaining steps (a) and (b) were the same as example 1, i.e., the copper oxide sheet was a modified copper sheet.

Comparative example 3

This comparative example provides a process for the preparation of a modified copper sheet, which was the same as example 1 except that step (b) was not performed, i.e., the polished copper sheet obtained in step (a) was directly subjected to step (c) to obtain a modified copper sheet.

Comparative example 4

The comparative example provides a preparation method of a modified copper sheet, except that in the step (c), the copper oxide sheet is immediately placed in a reducing solution after being washed by deionized water, ultraviolet irradiation is not carried out, the copper oxide sheet is taken out and washed by the deionized water, and vacuum drying is carried out to obtain the modified copper sheet, and the other steps are the same as those in the example 1.

Comparative example 5

The comparative example provides a preparation method of a modified copper sheet, except that in the step (c), the copper oxide sheet is washed by deionized water and then is not placed in a reducing solution, ultraviolet irradiation is directly carried out, the copper oxide sheet is washed by the deionized water after the ultraviolet irradiation, and vacuum drying is carried out to obtain the modified copper sheet, and the other steps are the same as those in the example 1.

Example 5-example 8

Examples 5 to 8 each provide a method for electrocatalytic reduction of CO₂The catalytic electrodes of (3) were prepared using the modified copper sheets provided in examples 1-4, respectively.

Comparative examples 6 to 10

Comparative examples 6 to 10 respectively provide a method for electrocatalytic reduction of CO₂The catalytic electrodes of (1) were made using the modified copper sheets provided in comparative examples 1-5, respectively.

In order to illustrate the technical effects of the above examples and comparative examples, the following experimental examples were specifically set.

Experimental example 1

(1) The modified copper sheets or unmodified copper sheets provided in the above examples and comparative examples were subjected to XRD detection (X-ray diffractometer, netherlands, X' Pert PRO MPD) and electron microscope scanning, as represented by example 1, comparative example 1 and comparative example 2, and the specific results are shown in fig. 1-2.

As shown in fig. 1, it is apparent that the peak positions of the unmodified copper sheet of comparative example 1, which is cleaned by acetone, ethanol and deionized water and the oxide layer is removed by hydrochloric acid, are 43.30 °, 50.43 ° and 74.13 °, corresponding to the crystal planes 111, 200 and 220 of Cu (04-0836). The modified copper sheet (copper oxide sheet) provided in comparative example 2 showed Cu and Cu₂The mixed state of O comprises 29.55 degrees, 36.42 degrees, 42.30 degrees, 52.45 degrees, 61.34 degrees and 73.53 degrees corresponding to Cu (04-0836) in addition to the characteristic peaks of Cu₂O (05-0667) with 110, 111, 200, 211, 220 and 311 crystal planes. The XRD pattern of the modified copper sheet provided in example 1 shows only characteristic peaks of elemental copper, which indicates that the copper oxide sheet is placed in a reducing solution and reduced under the irradiation of ultraviolet light.

As shown in fig. 2(a), the surface of the unmodified copper sheet of comparative example 1 after only pretreatment was smooth. As shown in fig. 2(b), the modified copper sheet (copper oxide sheet) provided in comparative example 2 has a cubic structure, and as shown by the characterization result of an X-ray diffractometer, the modified copper sheet is a typical cuprous oxide cubic structure, and the particle size is about 300nm, as for elemental copper shown in XRD, since XRD can detect the depth of about 10 μm, cuprous oxide on the surface and elemental copper inside are both detected, while a scanning electron microscope can only observe the structure of the surface of the material, which indicates that the copper sheet is only oxidized on the surface. FIG. 2(c) is a scanning electron microscope image of the modified copper sheet of example 1, which shows that the copper oxide sheet treated by UV light changes the original cubic structure to form an intercrossed nano-sheet structure.

(2) In order to further explore the morphological and structural features of the modified copper sheet, the modified copper sheet provided in example 1 was subjected to SEM-EDS mapping test, and two elements, Cu and O, were uniformly dispersed on the surface of the modified copper sheet. The content of the scanning electron microscope elements is shown in table 1.

TABLE 1 relative contents of the different elements

As can be seen from the data in Table 1, copper is present in a majority of 66.06% with a small amount of 33.94% elemental oxygen. The modified copper sheet samples were freshly prepared prior to testing for scanning electron microscopy and stored in inert gas-tight bags, exposed to only a small amount of air during scanning electron microscopy testing, and it is evident that the oxygen content of 33.94% cannot be completely attributed to the oxidation of air. But the XRD spectrum shows that the modified copper sheet only has a crystalline copper simple substance, so that the oxygen element is required to be present in the amorphous copper oxide or cuprous oxide, and further analysis and characterization are required.

(3) In order to explore the information such as the surface electronic structure, the element content and the like of the modified copper sheet, X-ray photoelectron spectroscopy (XPS) tests are carried out on the unmodified copper sheet and the modified copper sheet. Fig. 3(a) shows the full spectrum of the unmodified copper sheet of comparative example 1, which can be seen to contain C, O and Cu elements. Fig. 3(c) shows the full spectrum of the modified copper sheet of example 1, which can be seen to also contain C, O and Cu elements. Both contain C elements from adsorbed small CH compounds, and C contamination in XPS testing. Comparative example 1O in the unmodified copper sheet was generated by air oxidation. FIGS. 3(b) and (d) are high resolution Cu 2p spectra of the unmodified Cu flake of comparative example 1 and the modified Cu flake of example 1, respectively, and 932.6eV and 952.2eV, respectively, in FIG. 3(b) correspond to Cu⁰2p 3/2 fromSpin orbit peak and 2p 1/2 spin orbit peak, the two peak separation of 19.8eV is also the signature feature of elemental copper. 934.4eV is ascribed to Cu²⁺Possibly due to slight oxidation of the copper sheet by air during storage. In FIG. 3(d), 932.8eV corresponds to Cu⁰Cu 2p 3/2 spin orbit peak of (a). 935.5eV and 954.3eV, respectively for Cu²⁺2p 3/2 spin orbit peak and 2p 1/2 spin orbit peak.

FIGS. 4(b) and (d) are high resolution O1s spectra for the unmodified copper sheet of comparative example 1 and the modified copper sheet of example 1, respectively, and 530.6eV and 531.9eV in FIG. 4(b) correspond to lattice oxygen and chemisorbed oxygen, respectively, for the unmodified copper sheet of comparative example 1, and 533.3eV is the characteristic peak of C-O bond. In FIG. 4(d), 530.0eV and 531.6eV correspond to the lattice oxygen and chemisorbed oxygen, respectively, of the modified copper flake of example 1, and in combination with the high resolution Cu 2p spectrum and XRD pattern of the modified copper flake, it is presumed that the lattice oxygen is CuO at 530.0 eV. Thus, example 1 modified copper sheets consisted of a major portion of elemental copper and a minor amount of copper oxide.

Experimental example 2

For comparison of the electrocatalytic reduction of CO of the modified or unmodified copper sheets provided in the examples and comparative examples₂Performance, represented by the modified or unmodified copper sheets provided in example 1, comparative example 1 and comparative example 2, was subjected to CO₂Experiment of electrocatalytic reduction reaction.

CO₂The electrocatalytic reduction reaction is carried out in an H-shaped electrolytic cell by setting parameters of an electrochemical workstation, a gas product is directly input into a cathode chamber of the electrolytic cell to detect the composition and the concentration of the product through gas chromatography, and a liquid product is taken out after the reaction and transferred to liquid chromatography for analysis. 40mL KHCO with concentration of 0.1mol/L is injected into both the positive and negative chambers of the H-type electrolytic cell₃The electrolyte is separated by a treated proton exchange membrane (Nafion N-117 membrane).

The treatment method of the proton exchange membrane comprises the following steps: putting the proton exchange membrane in a beaker, adding 5% hydrogen peroxide solution which is submerged in the proton exchange membrane, stirring and heating in an oil bath at 80 ℃ for 1 hour, washing with deionized water, and transferring 5% H₂SO₄In solution, the solution is required to be immersed in a proton membrane, and stirred and added in an oil bath at the temperature of 80 DEG CHeating for 1 hr, washing the proton membrane with deionized water for several times to remove residual H₂SO₄And immersed in deionized water for use.

The three-electrode system consists of a working electrode, a reference electrode and a counter electrode. Ag/AgCl (saturated KCl solution) and a platinum net are respectively used as a reference electrode and a counter electrode, and a working electrode is a modified copper sheet.

The electrolyte needs to use high-purity N in a cathode chamber before catalytic reaction₂Air was introduced from the bottom for 30min to exhaust air in the electrolyte. Then introducing high-purity CO₂Gas for 30min to make CO₂Fully saturated, reduced mass transfer resistance, and always maintained the flow rate of 20mL/min (detected at the gas chromatography air inlet) in the electrocatalytic reaction process. Cyclic Voltammetry (CV) measurements were performed on a CHI 760E electrochemical workstation, with a scan rate of 20 mV. multidot.S^-1The scanning window is 2 to-2V; linear Sweep Voltammetry (LSV) testing was performed on a CHI 760E electrochemical workstation at a sweep rate of 20 mV. multidot.S^-1The scanning window is 0.5 to-1.5V. Potentiostatic electrolysis experiments (I-t) were also carried out on the CHI 760E electrochemical workstation, with a voltage setting in the range-1.8 to-2.2V, for a duration of typically 2 h. After the reaction is carried out for 0.5h, sampling once every 15min, introducing gas chromatography, taking an average value of the test concentrations of the products in the previous and next times as a final result, taking liquid in a cathode chamber after the reaction is finished, filtering, and detecting the liquid product by the liquid chromatography.

Gas chromatography conditions: the high-purity argon gas is used as carrier gas, the chromatographic column is a PORAPARK Q packed column, and the detectors are a Thermal Conductivity Detector (TCD) and a hydrogen Flame Ionization Detector (FID). The thermal conductivity detector is used for detecting H₂And CO. Hydrogen flame ionization detector for detecting CH₄、C₂H₄And C₂H₆. Wherein, the hydrogen generator and the air compressor are a hydrogen source and an air source of the hydrogen flame ionization detector. The type of the reduction product is determined by the display position of each signal peak in the gas chromatogram, the concentration of each reduction product is determined according to the proportion of the peak area of each signal peak to the concentration, and then the Faraday efficiency of each gas phase product is calculated.

Liquid chromatography conditions: the chromatographic column is SH1011 column and the column temperature is 40 ℃. The mobile phase is a 5mmol/L sulfuric acid solution, and the flow rate is 0.8 mL/min. The type of the reduction product is determined by the display position of each signal peak in the liquid chromatogram, the concentration of each reduction product is determined according to the proportion of the peak area of each signal peak to the concentration, and then the Faraday efficiency of each liquid phase product is calculated.

Example 1, comparative example 1 and comparative example 2 CO₂The data of the electrocatalytic reduction reaction are shown in tables 2 to 4.

Table 2 modified copper sheets provided in example 1

Table 3 unmodified copper sheet provided in comparative example 1

Table 4 modified copper sheet provided in comparative example 2

Compared with the data of the comparative example 1 and the example 1, the current density before and after the modification of the copper sheet is not changed greatly under the same voltage, but the product distribution is changed greatly. Specifically, the unmodified copper sheet of comparative example 1 was subjected to CO₂The products of the electrocatalytic reduction reaction are essentially hydrogen and formic acid, concentrated in the C1 product, producing only about 16% ethanol at higher voltage. The modified copper sheet provided in example 1 was subjected to an electrolysis experiment under-1.0V to-2.2V (vs Ag/AgCl), and CO was added₂Reduction to CO, CH₄、C₂H₄HCOOH and C₂H₅And (5) OH. In comparison withFormic acid has the highest selectivity at low voltages of-1.0V (vs Ag/AgCl), with increasing faradaic efficiencies for ethylene and ethanol. As can be seen from the data in tables 2 and 3, the copper sheet is modified, so that the generation of the byproduct hydrogen is greatly inhibited, namely the hydrogen is obviously reduced at each voltage, and particularly, the Faraday efficiency of the hydrogen is reduced from about 62% to about 13% at a voltage of-2.0V. Meanwhile, the Faraday efficiencies of ethylene and ethanol of the modified copper sheet in example 1 are obviously improved at each voltage compared with that of the unmodified copper sheet in comparative example 1, wherein the improvement is most obvious at-1.8V, the unmodified copper sheet in comparative example 1 does not produce ethylene and ethanol basically, and after modification, the Faraday efficiency of ethylene of the modified copper sheet in example 1 reaches 19.48%, and the Faraday efficiency of ethanol reaches 35.34%.

Comparative example 1 modified copper sheet and comparative example 1 unmodified copper sheet electrocatalytic reduction of CO at different voltages₂C2 product (C)₂H₄、C₂H₅OH) is used. As is apparent from the data in tables 2 and 3, the modified copper sheet of example 1 has a higher product selectivity of C2, reaching a Faraday efficiency of 57.14% at-2.0V (vs Ag/AgCl) which is nearly 5 times the Faraday efficiency (11.58%) of the C2 product of the unmodified copper sheet of comparative example 1 at the same voltage. The comparison is more remarkable at-1.8V (vs Ag/AgCl), the unmodified copper sheet in the comparative example 1 only generates hydrogen, formic acid and carbon monoxide at the voltage, and almost no C2 product exists, while the modified copper sheet in the example 1 has the Faraday efficiency of 54.82% of the C2 product, which fully illustrates the necessity of modifying the copper sheet. The modified copper sheet has abundant dangling bonds, unsaturated bonds and extremely large specific surface area due to the unique crossed nanosheet structure, and is used for electrocatalysis of CO₂Deep reduction offers the possibility of multi-carbon products.

As can be seen from the data in table 4, the modified copper sheet of example 1 has better hydrogen evolution inhibition and higher selectivity of C2 product than the modified copper sheet of comparative example 2 (which was oxidized only and not exposed to the reducing solution and ultraviolet irradiation). Specifically, the modified copper sheet provided in example 1 was able to be used at each test voltageInhibiting nearly half of the hydrogen production; electrocatalytic reduction of CO by the modified copper sheet of comparative example 2₂The faradaic efficiency of the produced ethanol is only below 7 percent, while the faradaic efficiency of the ethanol of the modified copper sheet in the example 1 can reach above 30 percent and reach 35.34 percent at-1.8V (vs Ag/AgCl), which is more than 5 times that of the modified copper sheet in the comparative example 2 under the same voltage. This further illustrates the necessity of modifying the copper sheet using the method provided by the present invention.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.