A tin-gallium co-doped cupric oxide-based catalyst, a preparation method and application thereof

Abstract

The application provides a tin-gallium co-doped copper oxide-based catalyst and a preparation method and application thereof, and belongs to the technical field of electrocatalytic reduction of carbon dioxide. First, copper salt, tin salt and gallium salt are dispersed in water, an alkali solution is added dropwise, and then standing is performed to obtain a mixture; then the mixture is sequentially subjected to a hydrothermal reaction, centrifugal separation and drying to obtain the tin-gallium co-doped copper oxide-based catalyst. The tin-gallium co-doped copper oxide-based catalyst prepared by the application has more stable reaction active sites, faster electron transfer rate, more stable performance and higher electrocatalytic carbon dioxide conversion efficiency compared with other copper oxide-based catalysts of the same type.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electrocatalytic reduction of carbon dioxide, and particularly relates to a tin-gallium co-doped copper oxide-based catalyst and a preparation method and application thereof. BACKGROUND

[0002] The growing energy demand and dependence on fossil fuels have led to an increasing amount of carbon dioxide emissions, which poses a serious threat to the global environment and climate. In order to break this cycle and achieve a circular economy, carbon dioxide electrochemical reduction (CO2RR) provides a promising solution that can convert carbon dioxide into valuable chemicals and fuels using renewable electricity.

[0003] Among the diverse products of CO2RR, carbon monoxide (CO) is a particularly attractive product because it can bring very high economic returns per mole of electron consumed and can serve as a versatile building block for a variety of organic compounds and liquid fuels. However, pursuing high CO selectivity and activity in CO2RR is challenging due to the complex reaction pathways and the fierce competition with the hydrogen evolution reaction (HER). Noble metal catalysts, such as gold (Au) and silver (Ag), exhibit excellent CO production performance with low onset potential and high CO selectivity. However, their high cost and scarcity limit their industrial feasibility. In order to achieve an economic and scalable conversion of CO2 to CO, we need to strive to find economically efficient catalysts that can skillfully coordinate key parameters such as low overpotential, high current density, high selectivity, and long durability.

[0004] Copper (Cu) is a unique metal in the field of electrocatalysis, which can significantly activate CO2 and generate a variety of products, including hydrocarbons and oxygen-containing compounds. However, despite this advantage of high activity, the selectivity of elemental Cu is poor, especially for single-carbon products such as CO and formate. In order to solve this problem, in recent years, single-atom site catalysts (SACs) based on Cu have been developed to improve the selectivity of single-carbon products in CO2RR. By alloying with single-atom metals, the electronic structure of the Cu metal matrix can be fine-tuned to achieve the optimal balance of desorption and adsorption rates of reactants and intermediates, thereby achieving the desired selectivity for specific products. For example, previous studies have shown that lowering the d-band state of Cu active sites near the isolated dopant weakens the binding strength of CO * and enhances the adsorption / activation of CO2. This greatly reduces the probability of CO * -CO * coupling and inhibits the formation of C 2+ products. In addition, it has been proven that Cu catalysts have high mobility in the CO2RR environment and can form active nanoparticles through in-situ structural evolution.

[0005] However, the single-atom catalyst has obvious disadvantages, because only one element is doped, the active site is single, and the single-atom site is dispersed due to the substrate loading rate problem, the unit density is small, and the overall catalytic performance is limited. Therefore, it is of great significance to study a tin-gallium co-doped copper oxide-based catalyst and its preparation method to improve the selectivity and activity of CO and achieve long-term stability. SUMMARY

[0006] The purpose of the present application is to provide a preparation method of a tin-gallium co-doped copper oxide-based catalyst to solve the problem of low CO selectivity in the electrochemical reduction reaction of carbon dioxide in the prior art.

[0007] In order to achieve the above-mentioned purpose of the application, the present application provides the following technical solutions:

[0008] The present application provides a preparation method of a tin-gallium co-doped copper oxide-based catalyst, comprising the following steps:

[0009] (1) dispersing copper salt, tin salt and gallium salt in water, adding alkali solution dropwise and then standing to obtain a mixture;

[0010] (2) sequentially performing hydrothermal reaction, centrifugal separation and drying on the mixture to obtain a tin-gallium co-doped copper oxide-based catalyst.

[0011] As a preferred, in the step (1), the copper salt comprises copper nitrate, copper sulfate or copper chloride; the tin salt comprises tin chloride or tin nitrate; the gallium salt comprises gallium nitrate or gallium chloride; and the alkali solution is potassium hydroxide solution or sodium hydroxide solution.

[0012] As a preferred, in the step (1), the molar ratio of the copper salt, the tin salt and the gallium salt is 1:0.01-0.1:0.005-0.05.

[0013] As a preferred, in the step (1), the molar volume ratio of the copper salt and the alkali solution is 5-10 mmol:5-15 mL, and the concentration of the alkali solution is 1-1.5 mol / L.

[0014] As a preferred, in the step (1), the standing time is 4-8 h.

[0015] As a preferred, in the step (2), the temperature of the hydrothermal reaction is 120-140℃, and the time of the hydrothermal reaction is 10-14 h.

[0016] As a preferred, in the step (3), the temperature of the drying is 50-70℃, and the time of the drying is 20-28 h.

[0017] The application provides a preparation method of the above-mentioned tin-gallium co-doped copper oxide-based catalyst, and the tin-gallium co-doped copper oxide-based catalyst is represented as CuO / Sn x -Ga y , wherein 0.01<=x<=0.1, 0.005<=y<=0.05.

[0018] The application provides an application of the above-mentioned tin-gallium co-doped copper oxide-based catalyst in electrochemical reduction of carbon dioxide.

[0019] The application has the following beneficial effects:

[0020] (1) The application mainly adopts a water bath method to prepare the catalyst, and has the characteristics of simple and convenient preparation process, good repeatability, strong controllability, mild treatment condition, short reaction time, low energy consumption and environmental friendliness, is suitable for mass production, and has certain application prospect.

[0021] (2) The tin-gallium co-doped copper oxide-based catalyst prepared by the application has more stable reaction active sites, faster electron transfer rate, more stable performance and higher electrocatalytic carbon dioxide conversion efficiency compared with other copper-based oxide catalysts of the same type.

[0022] (3) The tin-gallium co-doped copper oxide-based catalyst prepared by the application combines a metal base with two single-atom metal additives, tin (Sn) and gallium (Ga), and the single atoms synergistically change the electronic structure of Cu, which is conducive to the generation of CO and inhibits the hydrogen evolution reaction (HER), and also improves the stability of the catalyst by preventing atomic aggregation. The faradic efficiency of the three-metal alloy prepared in the experiment reaches more than 99% at a potential of-0.6V (vs RHE), and the current density at the potential is about 110mA / cm 2 , and the catalyst has excellent CO selectivity. The long-term stability is maintained at-150mA / cm 2 for 75h, and the FECO is higher than 95%. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 The XRD pattern of the CuO / Sn 0.02 -Ga 0.005 catalyst prepared in Example 2 is shown in the following figure.

[0024] Figure 2 The SEM-EDS pattern of the CuO / Sn 0.02 -Ga 0.005 catalyst prepared in Example 2 is shown in the following figure.

[0025] Figure 3 The SEM-EDS pattern of the CuO / Sn 0.02 -Ga0.005 Comparison of electrocatalytic performance of CuO catalyst prepared in Catalyst and Comparative Example 1;

[0026] Figure 4 CuO / Sn 0.02 -Ga 0.005 EIS diagram of CuO catalyst prepared in Catalyst and Comparative Example 1;

[0027] Figure 5 CuO / Sn 0.02 -Ga 0.005 Cdl diagram of CuO catalyst prepared in Catalyst and Comparative Example 1. DETAILED DESCRIPTION

[0028] The present application provides a preparation method of a tin-gallium co-doped copper oxide-based catalyst, comprising the following steps:

[0029] (1) dispersing copper salt, tin salt and gallium salt in water, adding alkali solution dropwise and then standing to obtain a mixture;

[0030] (2) sequentially performing hydrothermal reaction, centrifugal separation and drying on the mixture to obtain a tin-gallium co-doped copper oxide-based catalyst.

[0031] In the present application, in step (1), the copper salt comprises copper nitrate, copper sulfate or copper chloride; the tin salt comprises tin chloride or tin nitrate; the gallium salt comprises gallium nitrate or gallium chloride; and the alkali solution is potassium hydroxide solution or sodium hydroxide solution.

[0032] In the present application, in step (1), the molar ratio of the copper salt, the tin salt and the gallium salt is 1:0.01-0.1:0.005-0.05, preferably 1:0.02-0.08:0.005-0.04, and further preferably 1:0.02:0.005-0.02.

[0033] In the present application, in step (1), the molar volume ratio of the copper salt and the alkali solution is 5-10 mmol:5-15 mL, preferably 5 mmol:10 mL or 10 mmol:10 mL; the concentration of the alkali solution is 1-1.5 mol / L, preferably 1.1-1.4 mol / L, and further preferably 1.2-1.3 mol / L.

[0034] In the present application, the alkali solution is added dropwise within 1 minute; and after the copper salt, the tin salt and the gallium salt are dispersed in water and the alkali solution is added dropwise, the standing is preferably followed by stirring for 1 h.

[0035] In the present application, in step (1), the standing time is 4-8 h, preferably 5-7 h, and further preferably 6 h.

[0036] In the present application, in the step (2), the temperature of the hydrothermal reaction is 120-140℃, preferably 125-135℃, and further preferably 130℃; the time of the hydrothermal reaction is 10-14h, preferably 11-13h, and further preferably 12h.

[0037] In the present application, in the step (3), the temperature of the drying is 50-70℃, preferably 55-65℃, and further preferably 60℃; the time of the drying is 20-28h, preferably 22-26h, and further preferably 24h.

[0038] The present application provides a preparation method of the above-mentioned CuO / Sn x -Ga y , wherein 0.01≤x≤0.1 and 0.005≤y≤0.05.

[0039] In the present application, x represents the molar ratio of tin and copper oxide, and y represents the molar ratio of gallium and copper oxide.

[0040] The technical solutions provided by the present application will be described in detail below in combination with examples, but they should not be understood as limiting the scope of protection of the present application.

[0041] Example 1

[0042] 5mmol of Cu(NO3)2·3H2O, 0.1mmol of SnCl4·5H2O and 0.05mmol of gallium nitrate were dissolved in 50mL of deionized water, stirred uniformly, and then 10mL of potassium hydroxide solution (concentration of 1.2mol / L) was added dropwise within 1min, and the stirring was continued for 1h, and then the mixture was left to stand at room temperature for 6h, and then the mixture was transferred to a 100mL polytetrafluoroethylene liner, and then placed in a hydrothermal reactor, and the temperature was raised to 130℃, and kept at 130℃ for 12h, and then the reaction product was cooled to room temperature, and then centrifuged, and then washed with anhydrous ethanol for three times, and finally placed in a vacuum drying oven at a temperature of 60℃ for drying for 24h, to obtain CuO / Sn 0.02 -Ga 0.01 catalyst.

[0043] Example 2

[0044] The difference from Example 1 is that the amount of Cu(NO3)2·3H2O is 10mmol, and the amount of SnCl4·5H2O is 0.2mmol, to obtain CuO / Sn 0.02 -Ga 0.005 catalyst, and the other conditions are the same.

[0045] Example 3

[0046] The difference from Example 1 is that the amount of gallium nitrate used is 0.1 mmol, and the CuO / Sn 0.02 -Ga 0.02 catalyst, and other conditions were the same.

[0047] Comparative Example 1

[0048] 5 mmol Cu(NO3)2·3H2O was dissolved in 50 mL of deionized water and stirred evenly. Then, 10 mL of potassium hydroxide solution (concentration of 1.2 mol / L) was added dropwise within 1 minute. After stirring for 1 hour, the mixture was allowed to stand at room temperature for 6 hours. The mixture was then transferred to a 100 mL polytetrafluoroethylene liner and placed in a hydrothermal reactor. The temperature was raised to 130°C and kept at 130°C for 12 hours. After the reaction was completed, the reaction product was cooled to room temperature, centrifuged, washed three times with anhydrous ethanol, and finally dried in a vacuum drying oven at 60°C for 24 hours to obtain a CuO catalyst.

[0049] Figure 1 The CuO / Sn prepared in Example 2 0.02 -Ga 0.005 The XRD pattern of the catalyst, Figure 1 It can be seen that CuO / Sn 0.02 -Ga 0.005 The peak position of CuO is consistent with that of copper oxide, which proves that CuO / Sn 0.02 -Ga 0.005 The catalyst is mainly copper oxide structure, and doping does not change the structure of copper oxide.

[0050] Figure 2 The CuO / Sn prepared in Example 2 0.02 -Ga 0.005 SEM-EDS image of the catalyst. From the SEM image, we can see that CuO / Sn 0.02 -Ga 0.005 The catalyst is a flake structure, and EDS images show that CuO / Sn 0.02 -Ga 0.005 There are two elements, Sn and Ga, in the catalyst, and the two doping elements are evenly distributed in the catalyst.

[0051] Figure 3 The CuO / Sn prepared in Example 2 0.02 -Ga 0.005 The electrocatalytic performance comparison of the CuO catalyst prepared in Example 1 is shown in FIG. Figure 3It can be seen that within the tested potential range, whether in terms of Faraday efficiency or current density, the performance of copper oxide doped with Sn and Ga is significantly improved.

[0052] Figure 4 The CuO / Sn prepared in Example 2 0.02 -Ga 0.005 The EIS diagrams of the CuO catalyst prepared from the catalyst and Comparative Example 1 are shown in FIG. Figure 4 It can be seen that the doping of tin and gallium diatoms reduces the impedance of the catalyst and speeds up charge transfer, which shows that diatomic doping improves the efficiency of the catalyst.

[0053] Figure 5 The CuO / Sn prepared in Example 2 0.02 -Ga 0.005 The Cdl diagram of the CuO catalyst prepared by the catalyst and Comparative Example 1 is shown in FIG. Figure 5 It can be seen that the doping of tin and gallium diatoms increases the Cdl value of the catalyst, proving that more accessible active sites are exposed on its surface. The more active sites per the same area, the more conducive to catalysis.

[0054] Specific test plan:

[0055] (1) Preparation of the catalyst negative electrode: CuO / Sn prepared in Example 2 0.02 -Ga 0.01 The CuO catalyst prepared in Comparative Example 1 was prepared by mixing 10 mg of the catalyst with 0.5 ml of ethanol (97%), 0.5 ml of deionized water, and 0.05 ml of Nafion perfluorinated resin binder (5 wt %, DuPont 520). The mixture was ultrasonicated for 15 min to obtain a mixed solution, which was then added dropwise to the black surface of 1*1 cm gas diffusion carbon paper (SGL-29bc) and allowed to dry naturally.

[0056] (2) The prepared catalyst negative electrode, platinum counter electrode, and mercury / mercuric oxide reference electrode were assembled into a flow cell electrolytic cell.

[0057] (3) The test requires the use of a CH electrochemical workstation, a gas chromatograph, a peristaltic pump, 80 ml of potassium hydroxide solution (concentration 1 M) as the electrolyte, a peristaltic pump speed of 10 rpm, and CO2.

[0058] (4) The catalyst electrode was electroreduced in a potassium hydroxide solution electrolyte without CO2 at a voltage of -0.6V (vs. RHE) for 30 minutes, and then normal testing was performed with CO2: the appropriate potential was set, and each potential test was performed for 1 hour. The test results are as follows Figure 3 shown.

[0059] From the above examples, the application provides a copper oxide catalyst co-doped with tin and gallium, a preparation method and application thereof. First, copper salt, tin salt and gallium salt are dispersed in water, an alkali solution is added dropwise, and then standing is performed to obtain a mixture. Then, the mixture is sequentially subjected to hydrothermal reaction, centrifugal separation and drying to obtain the copper oxide catalyst co-doped with tin and gallium. The copper oxide catalyst co-doped with tin and gallium prepared by the application has more stable reaction active sites, faster electron transfer rate, more stable performance and higher carbon dioxide conversion efficiency than other copper oxide catalysts of the same type.

[0060] The above description is only preferred embodiments of the application, and it should be pointed out that, for those skilled in the art, without departing from the principles of the application, a number of improvements and refinements can be made, and these improvements and refinements should also be considered as the protection scope of the application.

Claims

1. A method for preparing a tin-gallium co-doped copper oxide-based catalyst, characterized in that: The steps include: (1) dispersing a copper salt, a tin salt, and a gallium salt in water, adding an alkaline solution dropwise thereto, and allowing the mixture to stand to obtain a mixture; (2) subjecting the mixture to a hydrothermal reaction, centrifugal separation, and drying in sequence to obtain a tin-gallium co-doped copper oxide-based catalyst; In the step (1), the molar ratio of copper salt, tin salt and gallium salt is 1:0.01-0.1:0.005-0.05; In the step (1), the molar volume ratio of the copper salt to the alkaline solution is 5-10 mmol:5-15 mL, and the concentration of the alkaline solution is 1-1.5 mol / L; In the step (1), the standing time is 4 to 8 hours.

2. The method for preparing a tin-gallium co-doped copper oxide-based catalyst according to claim 1, characterized in that: In step (1), the copper salt comprises copper nitrate, copper sulfate or copper chloride; the tin salt comprises tin chloride or tin nitrate; the gallium salt comprises gallium nitrate or gallium chloride; and the alkaline solution is potassium hydroxide solution or sodium hydroxide solution.

3. The method for preparing a tin-gallium co-doped copper oxide-based catalyst according to claim 1 or 2, characterized in that: In the step (2), the temperature of the hydrothermal reaction is 120-140° C., and the time of the hydrothermal reaction is 10-14 hours.

4. The method for preparing a tin-gallium co-doped copper oxide-based catalyst according to claim 3, characterized in that: In the step (2), the drying temperature is 50-70° C., and the drying time is 20-28 hours.

5. The tin-gallium co-doped copper oxide-based catalyst prepared by the method for preparing the tin-gallium co-doped copper oxide-based catalyst according to any one of claims 1 to 4, characterized in that: The Sn-Gallium co-doped copper oxide-based catalyst is represented by CuO / Sn x -Ga y , where 0.01≤x≤0.1, 0.005≤y≤0.

05.

6. Use of the tin-gallium co-doped copper oxide-based catalyst according to claim 5 in the electrochemical reduction of carbon dioxide.

Images