CN113136597B - Copper-tin composite material and preparation method and application thereof - Google Patents

Abstract

The invention discloses a copper-tin composite material and a preparation method and application thereof. The copper-tin composite material comprises a copper base and copper-tin alloy nanowires supported on the copper base. The copper-tin composite material of the present invention uses copper-tin alloy as a catalytic active material, which can be used as a catalyst, and the copper-tin alloy has a one-dimensional nanowire structure, which increases the specific surface area of the catalyst; in addition, the one-dimensional nanowire structure can accelerate The charge transfer between the catalyst and the electrolyte is beneficial to increase the current density during electrocatalysis. The present invention, through in-situ synthesis combined with high temperature heat treatment and other steps, is beneficial to enhance the binding force between the catalytic active material and the substrate, reduce the contact resistance, further improve the electrocatalytic current density, and can more effectively catalyze the reduction of carbon dioxide and the oxidation of methanol.

Description

A kind of copper-tin composite material and its preparation method and application

technical field

The invention relates to the technical field of catalytic materials, in particular to a copper-tin composite material and a preparation method and application thereof.

Background technique

During the last century, fossil fuels have been the main source of energy for power generation and transportation. With the improvement of people's living standards, the increased demand for energy has led to an increase in the consumption of fossil fuels, which has led to two key issues: (1) the gradual depletion of non-renewable fossil energy; (2) the production of fossil fuels during combustion of greenhouse gases contribute to air pollution and climate change.

To address the twin problems of the energy crisis and greenhouse gas emissions, converting carbon dioxide into useful chemicals and fuels is a sustainable development strategy. The methods of catalytic carbon dioxide reduction include: photocatalytic carbon dioxide reduction, electrocatalytic carbon dioxide reduction, thermocatalytic carbon dioxide reduction, etc. Among them, electrocatalytic carbon dioxide reduction can use solar energy, tidal energy, wind energy and other renewable energy sources as the energy source of the system, and at room temperature, Under normal pressure reaction conditions, inert carbon dioxide molecules can be catalyzed into high value-added chemicals such as formic acid and ethanol. Therefore, electrocatalytic CO2 reduction has a promising development prospect.

In a conventional electrocatalytic CO2 reduction system, the electrocatalytic CO2 reduction reaction occurs at the cathode and the kinetically slow oxygen evolution reaction occurs at the anode, resulting in excessively high overpotential and overall energy input. In addition, the added value of the oxygen product obtained by the oxygen evolution reaction is low, and reactive oxygen species will be generated in the process of generating oxygen. Studies have shown that the reactive oxygen species will shorten the life of the proton exchange membrane in the electrolytic cell.

Therefore, it is of great significance to replace the oxygen evolution reaction of the anode with a thermodynamically more favorable oxidation reaction, which can catalyze the generation of high value-added chemicals even at low potentials.

In recent years, studies have shown that adding oxidizable substances to the anolyte, such as methanol, ethanol, urea, etc., can significantly reduce the anode potential during the electrocatalytic water hydrogen production reaction. More importantly, these small organic molecules can Valuable chemicals are obtained in anodizing. At the same time, the study found that this strategy is also applicable to the electrocatalytic carbon dioxide reduction reaction at the cathode. For example, Sumit Verma et al. replaced the oxygen evolution reaction of the anode with glycerol oxidation during electrocatalytic carbon dioxide reduction, which can save 53% of the However, this study only reduced the potential of the anode and did not analyze the products after anodization; Xinfa Wei et al. used mesoporous tin dioxide grown on carbon cloth and copper oxide nanosheets grown on foamed copper, respectively As cathode and anode catalysts, it can electrocatalyze carbon dioxide reduction and methanol oxidation to formic acid under low cell pressure, respectively. However, there are still problems such as low current density and complicated catalyst preparation. Therefore, attempts have been made to develop a catalyst that can be used for both electrocatalytic CO2 reduction and anode oxidation, and can generate high value-added chemicals with high selectivity and low energy consumption.

SUMMARY OF THE INVENTION

The present invention aims to solve at least one of the technical problems existing in the prior art. Therefore, the present invention proposes a copper-tin composite material, which has good selectivity and catalytic activity for electrocatalytic carbon dioxide.

Meanwhile, the present invention also provides the preparation method and application of the copper-tin composite material.

Specifically, the technical scheme adopted in the present invention is as follows:

A first aspect of the present invention is to provide a copper-tin composite material, including a copper substrate and copper-tin alloy nanowires supported on the copper substrate.

The copper-tin composite material according to the first aspect of the present invention at least includes the following beneficial effects:

In the present invention, copper-tin alloy nanowires are loaded on the surface of the copper substrate, and the copper-tin alloy can be used as a catalytic active site, and has good catalytic activity for electrocatalytic carbon dioxide reduction; at the same time, the copper-tin alloy increases the material ratio in the form of nanowires. The surface area can accelerate the charge transfer between the copper-tin composite material and the electrolyte during the electrocatalytic carbon dioxide reduction process, improve the current density, and then improve the catalytic efficiency.

In some embodiments of the present invention, in the copper-tin alloy nanowires, the mass content of tin is 0.7% to 13%.

In some embodiments of the present invention, the copper-tin alloy nanowires contain Cu ₃ Sn and Cu ₆ Sn ₅ .

In some embodiments of the present invention, the copper-tin alloy nanowires have a diameter of 200-300 nm.

In some embodiments of the present invention, the copper substrate is any one of copper sheet and foamed copper, preferably foamed copper.

A second aspect of the present invention provides a method for preparing the above-mentioned copper-tin composite material, comprising the following steps:

(1) In-situ growth of copper hydroxide nanowires on a copper substrate;

(2) heating the copper hydroxide nanowires to obtain copper oxide nanowires;

(3) reducing the copper oxide nanowires to copper nanowires by an electrochemical reduction method;

(4) depositing tin on the copper nanowires;

(5) calcining the sample obtained in step (4) to obtain a copper-tin composite material.

According to the preparation method of the copper-tin composite material of the second aspect of the present invention, at least the following beneficial effects are included:

The inventors found that if the copper hydroxide nanowires are directly reduced to copper, the obtained copper will not be able to maintain the nanowire morphology; at the same time, if a reducing agent is used to chemically reduce the copper hydroxide nanowires or copper oxide nanowires, the copper hydroxide nanowires or copper oxide nanowires will also be reduced. Destructing the nanowire structure, the resulting material has limited electrocatalytic performance for carbon dioxide reduction. In the present invention, the nanowires of copper hydroxide are converted into nanowires of copper oxide and then electrolytically reduced to copper, so that the material can maintain the nanowire structure, and calcination is carried out after depositing tin to form a copper-tin alloy as a catalytic active material, so that the The copper-tin composite material has good catalytic activity.

In some embodiments of the present invention, in step (1), the preparation method of the copper hydroxide nanowires is as follows: immersing the copper substrate in an alkaline solution, then in-situ growth of hydroxide on the copper substrate copper nanowires.

In some embodiments of the present invention, the alkaline solution contains a base and an oxidizing agent.

In some embodiments of the present invention, the alkali includes at least one of sodium hydroxide and potassium hydroxide; the oxidant is persulfate, including at least one of sodium persulfate and ammonium persulfate, preferably persulfate Ammonium sulfate.

When the copper substrate is immersed in the alkaline solution, the copper on the surface of the copper substrate is rapidly oxidized to Cu ²⁺ by the oxidant, and the Cu ²⁺ reacts rapidly with the OH ^- in the alkaline solution to form monoclinic Cu(OH) ₂ crystals which are deposited on the copper. substrate surface. The nucleation shape of monoclinic Cu(OH) ₂ crystals is usually a rod-like structure with a tip. Under mild oxidizing conditions, most of the copper ions are transferred to the tip, causing the crystal to grow rapidly in the vertical direction, while only a small Part of the crystals grow in the diameter direction, and therefore, nanowire-like structures are easily formed. Persulfate oxidants such as ammonium persulfate exist in the solution as peroxodisulfate ions and ammonium ions, among which peroxodisulfate contains peroxy groups, which have strong oxidizing properties and can promote copper to be rapidly oxidized by oxidants to Cu ²⁺ . For example, when ammonium persulfate is used as the oxidant and sodium hydroxide is used as the base, the following reaction occurs during the preparation of copper hydroxide nanowires: Cu+4NaOH+(NH ₄ ) ₂ S ₂ O ₈ →Cu(OH) ₂ +2Na _{2 SO4 + 2NH3} +2H2O.

In some embodiments of the present invention, in the alkaline solution, the concentration of the base is 3-6 mol/L, preferably 6 mol/L; the mass ratio of the oxidant to the base is 1:(3-5).

The amount of alkaline solution can be adjusted according to actual needs, and it is advisable to completely immerse the copper substrate.

In some embodiments of the present invention, the soaking time of the copper substrate in the alkaline solution is 10-40 minutes.

In some embodiments of the present invention, the step of cleaning the copper substrate is also included before step (1). For example, the copper substrate can be immersed in an acetone solution to remove impurities such as grease on the surface, and dilute hydrochloric acid is used to clean the oxidized surface of the copper substrate. thing.

In some embodiments of the present invention, in step (2), heating the copper hydroxide nanowires to obtain copper oxide nanowires is specifically, heating the copper hydroxide nanowires in an oxygen-containing atmosphere at 150-350° C. The wire is heat-treated to obtain copper oxide nanowires.

In some embodiments of the present invention, the oxygen-containing atmosphere is an air atmosphere.

In some embodiments of the present invention, in the process of preparing the copper oxide nanowires, the heat treatment time is 1-2 hours.

In some embodiments of the present invention, in the process of preparing the copper oxide nanowires, the heating rate of the heat treatment process is 5-10° C./min.

In some embodiments of the present invention, in step (3), the electrochemical reduction process is specifically, in the electrochemical reduction electrolyte, the copper substrate on which the copper oxide nanowires are grown is used as a working electrode, and constant Current recovery.

Compared with the reducing agent reduction method, the electrochemical reduction of copper oxide to metallic copper is faster, and the rapid loss of oxygen atoms causes the nanowire surface to restructure, resulting in more grain boundaries, and the surface of copper nanowires is rougher. One-step electrodeposition of tin provides more attachment sites.

In some embodiments of the present invention, the electrochemical reduction electrolyte can be a strong base weak acid salt solution, such as sodium bicarbonate solution, potassium bicarbonate solution, etc., and the concentration can be set to 0.1-0.5mol/L.

In some embodiments of the present invention, the electrochemical reduction electrolyte is free of dissolved oxygen.

In some embodiments of the present invention, the current magnitude of the galvanostatic reduction is 3-6 mA/cm ² .

In some embodiments of the present invention, the galvanostatic reduction time is 1-2 hours.

In some embodiments of the present invention, the galvanostatic reduction is carried out in a three-electrode system, and the reference electrode and the counter electrode can use general electrodes, for example, silver/silver chloride can be used as the reference electrode, and platinum plate can be used as the counter electrode .

In some embodiments of the present invention, in step (4), the method for depositing tin adopts an electrodeposition method.

In some embodiments of the present invention, the electrodeposition method is as follows: a solution containing tin (II) ions is used as the electrodeposition electrolyte, and the copper substrate on which the copper nanowires are grown is used as a working electrode, and a constant current is performed. Electrodeposited tin. Here, tin (II) ions refer to Sn ²⁺ . Sn ²⁺ is easier to electrodeposit to form elemental tin than Sn ⁴⁺ .

In some embodiments of the present invention, the electrodeposition electrolyte contains alkaline substances such as sodium hydroxide, potassium hydroxide, etc., so that the electrodeposition electrolyte is a strong alkaline solution, so as to avoid the hydrolysis of tin (II) ions to form precipitation . The concentration of alkaline substances such as sodium hydroxide and potassium hydroxide is 1 to 5 mol/L, preferably 2 mol/L.

In some embodiments of the present invention, the concentration of tin(II) ions in the electrodeposition electrolyte is 1˜50 mmol/mL.

In some embodiments of the present invention, the current magnitude of the galvanostatic electrodeposition is 3-10 mA/cm ² .

In some embodiments of the present invention, the time of the constant current electrodeposition is 500-3000s, preferably 1000-2500s.

In some embodiments of the present invention, the galvanostatic electrodeposition is carried out in a three-electrode system, and the reference electrode and the counter electrode can use common electrodes, for example, silver/silver chloride can be used as the reference electrode, and platinum plate can be used as the counter electrode. electrode.

In some embodiments of the present invention, in step (5), the calcination temperature is 260-340°C.

Before calcination, the tin obtained by electrodeposition on the copper nanowires mainly exists in the form of metallic tin, and after calcination, it is transformed into a copper-tin alloy, which is beneficial to enhance the bonding force between the active material and the copper substrate and reduce the contact resistance. . And the inventors found in experiments that the current density during electrocatalysis after calcination is higher, the current density is kept stable for a longer time, and the Faradaic efficiency of anodization is higher.

In some embodiments of the present invention, in the calcination process, the holding time at 260-340° C. is 2-5 h.

In some embodiments of the present invention, after the calcination is completed, it is cooled to room temperature at a cooling rate of 1-3°C/min. In the cooling stage of calcination, by controlling the cooling rate, the problem of low catalyst repeatability caused by different cooling times caused by room temperature changes is avoided.

In some embodiments of the present invention, the calcination process is carried out in a mixture of hydrogen and inert gas. Calcination in a hydrogen-containing gas mixture is more conducive to maintaining the zero valence state of copper and tin metals to form alloys.

In some embodiments of the present invention, the volume ratio of the hydrogen gas to the inert gas is 1:(10-20).

The third aspect of the present invention is to provide the application of the above-mentioned copper-tin composite material in the preparation of electrodes.

The fourth aspect of the present invention is to provide the application of the above-mentioned copper-tin composite material in electrocatalytic carbon dioxide reduction and/or electrocatalytic methanol oxidation.

More specifically, a method for electrocatalytic reduction of carbon dioxide includes the following steps: using the above-mentioned copper-tin composite material as a cathode, electrolyzing an electrolyte into which carbon dioxide is introduced.

In some embodiments of the present invention, in the electrocatalytic carbon dioxide reduction process, the potential of electrolysis is -0.8 to -1.5 V (vs. RHE). In this potential range, the main products of the electrocatalytic carbon dioxide reduction reaction are formic acid, carbon monoxide and hydrogen.

A method for electrocatalytic methanol oxidation, comprising the following steps: using the above-mentioned copper-tin composite material as an anode, electrolyzing an electrolyte solution containing methanol.

In some embodiments of the present invention, in the electrocatalytic methanol oxidation process, the potential of electrolysis is 1.4-2.0 V (vs. RHE). In this potential range, the main product of electrocatalytic methanol oxidation is formic acid.

A method for simultaneous electrocatalytic carbon dioxide reduction and electrocatalytic methanol oxidation, comprising the steps of: using the above-mentioned copper-tin composite material as a cathode in an electrolytic solution fed with carbon dioxide; at the same time, in an electrolytic solution containing methanol, using another copper The tin composite material is used as an anode, the cathode is used as a working electrode, and the anode is used as a reference electrode and a counter electrode, and electrolysis is performed by electrification.

Compared with the prior art, the present invention has the following beneficial effects:

The copper-tin composite material of the present invention uses copper-tin alloy as a catalytic active material, which can be used as a catalyst, and the copper-tin alloy has a one-dimensional nanowire structure, which increases the specific surface area of the catalyst; in addition, the one-dimensional nanowire structure can accelerate The charge transfer between the catalyst and the electrolyte is beneficial to increase the current density during electrocatalysis. The present invention, through in-situ synthesis combined with high temperature heat treatment and other steps, is beneficial to enhance the binding force between the catalytic active material and the substrate, reduce the contact resistance, further increase the electrocatalytic current density, and can more effectively catalyze the reduction of carbon dioxide and the oxidation of methanol.

Description of drawings

1 is the XRD patterns of copper hydroxide nanowires [Cu(OH) ₂ NWs], copper oxide nanowires (CuO NWs) and copper nanowires (Cu NWs) of Example 1;

Figure 2 shows the XRD patterns of CuSn-1, CuSn-2 and CuSn-3;

Figure 3 is a high-resolution scanning electron microscope image of CuSn-1, CuSn-2 and CuSn-3;

Figure 4 shows the performance test results of CuSn-1, CuSn-2, CuSn-3 and copper nanowires (Cu NWs) electrocatalytic carbon dioxide reduction;

Fig. 5 is the stability test result of CuSn-1 electrocatalytic carbon dioxide reduction;

Fig. 6 is the linear sweep voltammogram of CuSn-1 electrocatalytic methanol oxidation;

Fig. 7 is the performance test result of CuSn-1 electrocatalytic methanol oxidation to produce formic acid;

Figure 8 shows the performance test results of CuSn-1 for simultaneous electrocatalytic carbon dioxide reduction and methanol oxidation;

Figure 9 is a high-resolution scanning electron microscope image of CuSn-4, CuSn-5 and CuSn-6;

Fig. 10 is the performance test result of CuSn-4 electrocatalytic carbon dioxide reduction;

Figure 11 is the performance test result of CuSn-5 electrocatalytic carbon dioxide reduction;

Fig. 12 is the performance test result of CuSn-6 electrocatalytic carbon dioxide reduction;

Figure 13 is a high-resolution scanning electron microscope image of CuSn-7;

Figure 14 is the XRD pattern of CuSn-7;

Figure 15 is the performance test result of CuSn-7 electrocatalytic carbon dioxide reduction;

Figure 16 shows the performance test results of CuSn-8 electrocatalytic carbon dioxide reduction.

Detailed ways

The technical effects of the present invention are further described below in conjunction with specific embodiments.

Example 1

A preparation method of a copper-tin composite material, comprising the following steps:

(1) Preparation of copper hydroxide nanowires

The commercial copper foam with an area of 1 × 2 cm ² was sonicated in an acetone solution for fifteen minutes to remove impurities such as grease on the surface. Prepare 40ml of dilute hydrochloric acid solution with a concentration of 1mol/L, put the copper foam after cleaning in the acetone solution into the prepared dilute hydrochloric acid solution for 15 minutes and ultrasonically remove the oxides on its surface.

Weigh 1.8g of solid sodium hydroxide particles (6M) and dissolve it in 7.5ml of deionized water to prepare a sodium hydroxide solution; weigh 0.4g of solid ammonium persulfate (0.24M) and dissolve it in deionized water to prepare a solution. The sodium hydroxide solution is poured into the ammonium persulfate solution while stirring to obtain a mixed solution, and then the cleaned copper foam is put into the mixed solution, and allowed to stand for 15 minutes at room temperature, then the hydroxide can be grown in situ on the copper foam. copper nanowires.

(2) Preparation of copper oxide nanowires

The copper hydroxide nanowires obtained in step (1) are calcined in a tube furnace, heated to 300° C. in an air atmosphere (the heating rate is 5° C./min), and kept for 3 hours to naturally cool down to room temperature to obtain copper oxide nanowires.

(3) Preparation of copper nanowires

The copper oxide nanowires obtained in step ( ₂ ) are reduced by constant current in the H-type electrolytic cell of three electrodes, and the potassium bicarbonate solution saturated with N is used as electrolyte, the concentration of potassium bicarbonate is 0.1mol/L, and the constant current It was set to 5 mA/cm ² and the reduction time was 5000 s. The foamed copper with copper oxide nanowires grown in step (2) is used as the working electrode, the silver/silver chloride is used as the reference electrode, and the platinum sheet is used as the counter electrode. After the galvanostatic reduction is completed, copper nanowires are obtained on the foamed copper.

(4) Electrodeposition of tin

Weigh 11.2g of solid potassium hydroxide into 100ml of deionized water, stir to dissolve, then add 1128mg of stannous chloride dihydrate for ultrasonic dissolution, and use the foamed copper grown with copper nanowires obtained in step (3) as the working electrode, The area of the working electrode was fixed at 2cm ² , silver/silver chloride was the reference electrode, the platinum sheet was the counter electrode, the galvanostatic current was set to 5mA/cm ² , and the electrodeposition time was 2000s.

(5) Calcination

The sample obtained in step (4) is heat-treated in a hydrogen-argon mixture (hydrogen:argon=6:94, v/v), heated to 300°C, kept for 3h, and the cooling rate is controlled to be 1°C/min and cooled to room temperature , to obtain a copper-tin composite material, marked as CuSn-1.

Structure Characterization:

The XRD patterns of the copper hydroxide nanowires [Cu(OH) ₂ NWs], copper oxide nanowires (CuO NWs) and copper nanowires (Cu NWs) prepared in steps (1) to (3) are shown in Figure 1. The XRD pattern of CuSn-1 is shown in Fig. 2, and the high-resolution scanning electron microscope pattern of CuSn-1 is shown in Fig. 3(a), (d). Among them, Figure 2 shows that the diffraction peaks related to Cu ₃ Sn and Cu ₆ Sn ₅ alloy phases appear in CuSn-1, and (a) and (d) of Figure 3 show that CuSn-1 has a nanowire array structure, and the diameter of the nanowires is 200 to 300 nm.

It can be seen from Figures 1 to 3 that copper hydroxide nanowires, copper oxide nanowires, copper nanowires and copper-tin alloy nanowires are successfully prepared on foamed copper in this implementation.

After testing, the copper-tin alloy nanowires in CuSn-1 contain 7.9% tin by mass.

Electrocatalytic performance test:

(1) Electrocatalytic carbon dioxide reduction

CuSn-1 was used as the working electrode (the area of the working electrode was fixed as 2cm ² ) to conduct the performance test of electrocatalytic carbon dioxide reduction in the H-type electrolytic cell, silver/silver chloride was used as the reference electrode, and the platinum sheet was used as the counter electrode; For comparison, the same performance test was carried out with the copper foam with copper nanowires (Cu NWs) grown in step (3) as the working electrode. Specifically, electrolysis at a fixed charge (5 coulombs) in 0.5 mol/L potassium bicarbonate saturated with _CO2 , at a voltage of -1.4V vs. RHE, the Faradaic efficiency of the liquid-phase product formic acid was measured to be 87%, and the gas-phase product The Faradaic efficiency of carbon monoxide was 5% and the rest was hydrogen, while the current density reached 161 mA/cm ² . The performance test results of CuSn-1 electrocatalytic reduction of carbon dioxide to produce formic acid and carbon monoxide are shown in Figure 4.

The stability test of the electrocatalytic carbon dioxide reduction of CuSn-1 was carried out at a current density of about 140 mA/cm ² , and the results are shown in Figure 5. It can be seen from Figure 5 that CuSn-1 has good stability in the electrocatalytic carbon dioxide reduction process, and the Faradaic efficiency of formic acid production does not decrease after a long time test.

(2) Electrocatalytic methanol oxidation

The performance of electrocatalytic methanol oxidation was tested in H-type electrolytic cell with CuSn-1 as the working electrode, silver/silver chloride as the reference electrode, and platinum sheet as the counter electrode. Specifically, in the mixed solution of 1 mol/L KOH and 1 mol/L CH ₃ OH saturated with N ₂ for fixed-charge electrolysis, in the voltage range of 1.4-2.0 V vs. RHE, the Faradaic efficiency of the liquid product formic acid was measured at 95. % or more, a small amount of oxygen is generated, and the geometric current density of electrocatalytic methanol oxidation reaches 510 mA/cm ² at 1.8 V vs. RHE. The linear sweep voltammogram and performance test results of electrocatalytic methanol oxidation are shown in Figure 6 and Figure 7, respectively.

(3) Simultaneous electrocatalytic carbon dioxide reduction and methanol oxidation

Two CuSn-1s were used as cathode and anode, respectively, and the performance of electrocatalytic carbon _dioxide reduction and methanol oxidation were simultaneously tested in H-type electrolysis cell. The solution is a mixed solution of 1 mol/L KOH and 1 mol/L CH ₃ OH saturated with N ₂ , the electrolysis voltage is set to a negative voltage, the working electrode is clamped on the working electrode for carbon dioxide reduction, and the reference electrode clamp and the counter electrode clamp are placed on the On the working electrode of methanol oxidation, the performance test results are shown in Figure 8.

Figure 8 shows that when the two electrodes are electrolyzed at the same time, the Faradaic efficiency FE _CO2/HCOOH of the cathode electrocatalytic carbon dioxide reduction reaches 93.2%, and the faradaic efficiency FE _CH3OH/HCOOH of the anode electrocatalytic methanol oxidation is as high as 99.1%, which can be achieved at high Faradaic efficiency. At the same time, formic acid is generated.

Comparative Example 1

This comparative example provides a copper-tin composite material, the preparation method of which is different from that of Example 1: in step (4), the amount of stannous chloride dihydrate is reduced to 22.6 mg, and the electrodeposition time is set to 22.6 mg. for 50s. Other operations are the same as in Example 1.

The copper-tin composite material obtained in this comparative example is marked as CuSn-2.

Structure Characterization:

The XRD pattern of CuSn-2 is shown in Fig. 2, and the high-resolution scanning electron microscope pattern is shown in Fig. 3(b), (e). It can be seen that CuSn-2 has diffraction peaks related to the Cu ₃ Sn alloy phase, but no diffraction peaks related to the Cu ₆ Sn ₅ alloy phase. The copper-tin alloy nanowire array structure is formed on the foamed copper substrate, and the diameter of the nanowires Larger than 200 to 300 nm.

Electrocatalytic performance test:

(1) Electrocatalytic carbon dioxide reduction

The performance test of electrocatalytic carbon dioxide reduction was carried out in H-type electrolytic cell with CuSn-2 as the working electrode, silver/silver chloride as the reference electrode, and platinum sheet as the counter electrode. Specifically, in _CO2 -saturated 0.5 mol/L potassium bicarbonate for electrolysis, the Faradaic efficiency of the gas-phase product carbon monoxide was measured to be 39% at a voltage of -1.4V vs. RHE, compared with CuSn in Example 1. -1 is improved; the Faradaic efficiency of the liquid product formic acid is 38%, which is lower than that of CuSn-1 in Example 1; the rest is hydrogen, and the current density reaches 177 mA/cm ² , the performance test of electrocatalytic carbon dioxide reduction The results are shown in Figure 4. The test results of CuSn-2 reflect that with the decrease of tin content in the copper-tin alloy, the Faradaic efficiency of electrocatalytic carbon dioxide reduction for formic acid decreases, and the Faradaic efficiency of carbon monoxide increases.

Comparative Example 2

This comparative example provides a copper-tin composite material, the preparation method of which is different from that of Example 1 in that: in step (4), the electrodeposition time is set to 3000s. Other operations are the same as in Example 1.

The copper-tin composite material obtained in this comparative example is marked as CuSn-3.

Structure Characterization:

The XRD pattern of CuSn-3 is shown in Fig. 2, and the high-resolution scanning electron microscope pattern is shown in Fig. 3 (c) and (f). It can be seen that in addition to the diffraction peaks related to Cu ₃ Sn and Cu ₆ Sn ₅ alloy phases in CuSn-3, there are also diffraction peaks related to SnO, and CuSn-3 has a large number of clusters on the surface of the nanowire array, The nanowire array structure is damaged to some extent. This reflects that too long electrodeposition time during the electrodeposition of tin will lead to excessive tin deposition, and excessive tin will lead to the destruction of the nanowire array structure, and the emergence of a new SnO phase, which may lead to the current density decreases.

Electrocatalytic performance test:

(1) Electrocatalytic carbon dioxide reduction

The performance of electrocatalytic carbon dioxide reduction was tested in H-type electrolytic cell with CuSn-3 as the working electrode, silver/silver chloride as the reference electrode, and platinum sheet as the counter electrode. Specifically, in _CO2 -saturated 0.5mol/L potassium bicarbonate electrolysis at a fixed charge, the Faradaic efficiency of the liquid-phase product formic acid was measured to be 74% at the voltage of -1.4V vs. RHE, and the Faradaic efficiency of the gas-phase product carbon monoxide was measured to be 74%. is 7.7%, the hydrogen Faradaic efficiency is increased to 21%, and the current density is reduced to 143 mA/cm ² . The performance test results of electrocatalytic carbon dioxide reduction are shown in Fig. 4 .

The test results of CuSn-3 reflect that excess tin will lead to a decrease in the current density during electrocatalysis and a decrease in the Faradaic efficiency of electrocatalytic carbon dioxide reduction for formic acid.

Comparative Example 3

This comparative example provides a copper-tin composite material, the preparation method of which is different from that of Example 1 mainly in that this comparative example directly electrochemically reduces copper hydroxide nanowires to copper.

Specifically, the preparation method of the copper-tin composite material of this comparative example comprises the following steps:

(1) Preparation of copper hydroxide nanowires

This step is the same as step (1) of Example 1.

(2) Electrochemical reduction of copper hydroxide nanowires

The copper hydroxide nanowires obtained in step (1) are galvanostatic reduction in a three-electrode H-type electrolytic cell, the concentration of potassium bicarbonate in the electrolyte is 0.1 mol/L, and the galvanostatic current is set to 5mA/cm ² , and the reduction time for 5000s. The copper foam with copper hydroxide nanowires grown in step (1) is used as a working electrode, silver/silver chloride is used as a reference electrode, and a platinum sheet is used as a counter electrode.

(3) Electrodeposition of tin

Weigh 11.2g of solid potassium hydroxide into 100ml of deionized water, stir to dissolve, then add 1128mg of stannous chloride dihydrate for ultrasonic dissolution, use the foamed copper obtained in step (2) as the working electrode, and the area of the working electrode is fixed at 2cm ^2. Silver/silver chloride is the reference electrode, platinum sheet is the counter electrode, the constant current is set to 5mA/cm ² , and the electrodeposition time is 2000s.

(4) Calcination

The sample obtained in step (3) was heat-treated in a hydrogen-argon gas mixture (hydrogen:argon=6:94, v/v), heated to 300°C, kept for 3h, and the cooling rate was controlled to be 1°C/min and cooled to room temperature , to obtain a copper-tin composite material, marked as CuSn-4.

Structure Characterization:

The high-resolution scanning electron microscope images of CuSn-4 are shown in (a) and (d) of Figure 9. It can be seen that the nanowire array is destroyed and the nanowires are aggregated, indicating that the electrochemical reduction of copper hydroxide nanowires is directly carried out. Without first being converted into copper oxide nanowires, the nanowire array structure will be destroyed. At the same time, the high-resolution scanning electron microscope image obtained in another area of CuSn-4 is shown in Fig. 9(g), it can also be observed that the nanowires aggregate into clusters, and the morphology is different from that in Fig. 9(a), further It is reflected that the nanowires in CuSn-4 are aggregated, and the aggregated morphology is not uniform, indicating that the direct electrochemical reduction of copper hydroxide nanowires cannot control the morphology of the nanowires.

Electrocatalytic performance test:

(1) Electrocatalytic carbon dioxide reduction

The performance of electrocatalytic carbon dioxide reduction was tested in an H-type electrolytic cell with CuSn-4 as the working electrode, silver/silver chloride as the reference electrode, and platinum sheet as the counter electrode. Specifically, fixed-charge electrolysis was performed in 0.5 mol/L potassium bicarbonate saturated with _CO at a voltage of -1.4 V vs. RHE. During the test, it was found that the current density increased from 115 mA/cm 2 at the beginning to 130 mA/cm ² within ² hours, and the current density changed greatly, as shown in Figure 10, which may be related to the instability of the catalyst structure. Compared with the oxidized and re-reduced sample CuSn-1 in Example 1, the current density of CuSn-4 is significantly lower, and the Faradaic efficiency of formic acid is only 32.6%, which further indicates that the nanowire array structure has a structure that increases the current density. Moreover, the nanowire array structure is more conducive to exposing catalytic active sites, which improves the performance of electrocatalytic carbon dioxide to formic acid.

Comparative Example 4

This comparative example provides a copper-tin composite material, the preparation method of which is different from that of Example 1 mainly in that: this comparative example uses sodium borohydride as a reducing agent to reduce copper oxide nanowires.

Specifically, the preparation method of the copper-tin composite material of this comparative example comprises the following steps:

(1) Preparation of copper hydroxide nanowires

This step is the same as step (1) of Example 1.

(2) Preparation of copper oxide nanowires

This step is the same as step (2) of Example 1.

(3) Reduction of copper oxide nanowires

The copper oxide nanowires were reduced by sodium borohydride, a reducing agent. Weigh 2.084g of sodium borohydride (0.5M) and dissolve it in 150ml of ultrapure water, ultrasonically dissolve, put the copper oxide nanowires of step (2) into the sodium borohydride solution and let stand for 2h, rinse with ultrapure water, Blow dry.

(4) Electrodeposition of tin

This step is the same as step (4) of Example 1.

(5) Calcination

This step is the same as step (5) of Example 1.

The copper-tin composite material of this comparative example is designated as CuSn-5.

Structure Characterization:

The high-resolution scanning electron microscope of CuSn-5 is shown in (b) and (e) of Figure 9. It can be seen that the nanowires are not uniformly dispersed, and the phenomenon of staggered fracture occurs, indicating that the reduction of copper oxide nanowires with a reducing agent will damage the nanowires. Nanowire array structure.

Electrocatalytic performance test:

(1) Electrocatalytic carbon dioxide reduction

The performance of electrocatalytic carbon dioxide reduction was tested in an H-type electrolytic cell with CuSn-5 as the working electrode, silver/silver chloride as the reference electrode, and platinum sheet as the counter electrode. Specifically, fixed-charge electrolysis was performed in 0.5 mol/L potassium bicarbonate saturated with _CO at a voltage of -1.4 V vs. RHE. During the test, it was found that the current density increased from 115 mA/cm ² to 157 mA/cm ² within 2 hours, and the current density changed greatly, and the Faradaic efficiency of formic acid was only 33%, as shown in FIG. 11 .

Comparative Example 5

This comparative example provides a copper-tin composite material, the preparation method of which is different from that of Example 1 mainly in that: this comparative example uses sodium borohydride as a reducing agent to reduce copper hydroxide nanowires.

Specifically, the preparation method of the copper-tin composite material of this comparative example comprises the following steps:

(1) Preparation of copper hydroxide nanowires

This step is the same as step (1) of Example 1.

(2) Reduction of copper hydroxide nanowires

The copper oxide nanowires were reduced by sodium borohydride, a reducing agent. Weigh 2.084g of sodium borohydride (0.5M) and dissolve it in 150ml of ultrapure water, ultrasonically dissolve it, put the copper hydroxide nanowires obtained in step (1) into the sodium borohydride solution and let stand for 2h. Rinse, blow dry.

(3) Electrodeposition of tin

This step is the same as step (4) of Example 1.

(4) Calcination

This step is the same as step (5) of Example 1.

The copper-tin composite material of this comparative example is designated as CuSn-6.

Structure Characterization:

The high-resolution scanning electron microscope of CuSn-6 is shown in (c) and (f) of Figure 9. It can be seen that the nanowire array structure was severely damaged, collapsed, and aggregated into clusters, indicating that the copper hydroxide was directly treated with a reducing agent. The reduction of the nanowires to copper destroys the nanowire array structure.

Electrocatalytic performance test:

(1) Electrocatalytic carbon dioxide reduction

The performance test of electrocatalytic carbon dioxide reduction was carried out in H-type electrolytic cell with CuSn-6 as the working electrode, silver/silver chloride as the reference electrode, and platinum sheet as the counter electrode. Specifically, fixed-charge electrolysis was performed in 0.5 mol/L potassium bicarbonate saturated with _CO at a voltage of -1.4 V vs. RHE. During the test, it was found that the current density increased linearly from the initial 105 mA/cm ² to 132 mA/cm ² in 2 hours, and the Faradaic efficiency of formic acid was only 31.5%, as shown in FIG. 12 .

Comparative Example 6

This comparative example provides a copper-tin composite material, the preparation method of which is different from that of Example 1 mainly in that in this comparative example, after electrodeposition of tin, the sample is calcined in a pure argon atmosphere. Other operations are the same as in Example 1.

The copper-tin composite material of this comparative example is designated as CuSn-7.

Structure Characterization:

The high-resolution scanning electron microscope image of CuSn-7 is shown in Fig. 13, and the XRD pattern is shown in Fig. 14. It can be seen from Figures 13 and 14 that although the samples of CuSn-7 heat-treated in high-purity argon still maintain the morphology of nanowire arrays, in CuSn-7, in addition to the appearance of Cu ₆ Sn ₅ and Cu ₃ Sn alloys In addition to the diffraction peaks, there are also diffraction peaks related to SnO and CuO, indicating that heat treatment in a pure argon atmosphere easily leads to oxidation of easily oxidized copper and tin metals.

Electrocatalytic performance test:

(1) Electrocatalytic carbon dioxide reduction

The performance of electrocatalytic carbon dioxide reduction was tested in an H-type electrolytic cell with CuSn-7 as the working electrode, silver/silver chloride as the reference electrode, and platinum sheet as the counter electrode. Specifically, fixed-charge electrolysis was performed in 0.5 mol/L potassium bicarbonate saturated with _CO at a voltage of -1.4 V vs. RHE. During the test, it was found that the current density decreased from the initial 138mA/cm ² to 123mA/cm ² , and then gradually increased to 140mA/cm ² . The reason for the current density changing from large to small should be due to the presence of oxides on the catalyst surface in carbon dioxide. The reduction occurs at the negative potential of reduction, which consumes electricity; meanwhile, the Faradaic efficiency of formic acid under CuSn-7 electrocatalysis is only 67%, as shown in Figure 15.

Comparative Example 7

This comparative example provides a copper-tin composite material, the preparation method of which is different from that of Example 1 mainly in that: this comparative example does not carry out calcination after electrodeposition of tin. Other operations are the same as in Example 1.

The copper-tin composite material of this comparative example is designated as CuSn-8. The XRD results of CuSn-8 showed diffraction peaks related to metal tin.

The electrocatalytic carbon dioxide reduction performance of CuSn-8 was tested according to the same method as in Example 1, and the results are shown in FIG. 16 . The test results reflect that under the potential of -1.4V vs. RHE, the Faradaic efficiency of formic acid is significantly reduced by no calcination after electrodeposition of tin, which is only about 44%. At the same time, the current density is unstable. With the extension of the test time, The current density gradually decreases.

The performance test results of the electrocatalytic carbon dioxide reduction of CuSn-1 to CuSn-8 are summarized in Table 1 below:

Table 1. Test results of electrocatalytic carbon dioxide reduction performance

Note: The working electrode area was fixed at 2cm ² during the performance test of each example and comparative example.

The above-mentioned embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited by the above-mentioned embodiments, and any other changes, modifications, substitutions, combinations, The simplification should be equivalent replacement manners, which are all included in the protection scope of the present invention.

Claims (11)

1. A copper-tin composite material is characterized in that: the copper-tin alloy nanowire/copper-tin alloy composite material consists of a copper substrate and a copper-tin alloy nanowire loaded on the copper substrate; the copper-tin alloy nanowire is made of Cu ₃ Sn and Cu ₆ Sn ₅ And (4) forming.

2. The copper-tin composite material of claim 1, wherein: in the copper-tin alloy nanowire, the mass content of tin is 0.7-13%.

3. A method for preparing the copper-tin composite material as claimed in any one of claims 1 to 2, characterized in that: the method comprises the following steps:

(1) growing copper hydroxide nanowires in situ on a copper substrate;

(2) heating the copper hydroxide nanowires to obtain copper oxide nanowires;

(3) reducing the copper oxide nanowires into copper nanowires by an electrochemical reduction method;

(4) depositing tin on the copper nanowires;

(5) and (5) calcining the sample obtained in the step (4) to obtain the copper-tin composite material.

4. The method for preparing the copper-tin composite material according to claim 3, wherein the method comprises the following steps: in the step (2), the copper hydroxide nanowires are heated to obtain the copper oxide nanowires, specifically, the copper oxide nanowires are subjected to heat treatment at 150-350 ℃ in an oxygen-containing atmosphere to obtain the copper oxide nanowires.

5. The method for preparing the copper-tin composite material according to claim 3, wherein: in the step (3), the electrochemical reduction process is specifically that in an electrochemical reduction electrolyte, a copper substrate on which the copper oxide nanowires grow is used as a working electrode to perform constant current reduction.

6. The method for preparing the copper-tin composite material according to claim 3, wherein: in the step (4), the method for depositing tin adopts an electrodeposition method.

7. The method for preparing the copper-tin composite material according to claim 6, wherein: the electrodeposition method is specifically to use Sn ²⁺ And (4) taking the solution as an electrodeposition electrolyte, taking the copper substrate with the copper nanowires grown obtained in the step (3) as a working electrode, and performing constant-current electrodeposition of tin.

8. The method for preparing the copper-tin composite material according to claim 3, wherein: in the step (5), the calcining temperature is 260-340 ℃.

9. The method for preparing the copper-tin composite material according to claim 8, wherein: the calcination process is carried out in a mixed gas of hydrogen and an inert gas.

10. Use of the copper-tin composite material according to any one of claims 1 to 2 for the preparation of an electrode.

11. Use of the copper-tin composite material according to any one of claims 1 to 2 in electrocatalytic carbon dioxide reduction and/or electrocatalytic methanol oxidation.

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