Method for electrocatalytic reduction of carbon dioxide into carbon monoxide by using gallium-based liquid alloy catalyst

Abstract

The invention discloses a method for electrocatalytic reduction of carbon dioxide into carbon monoxide by using a gallium-based liquid alloy catalyst. According to the method, a gallium-based liquid alloy catalyst is used as a working electrode, a platinum sheet electrode is used as a counter electrode, an Ag / AgCl electrode is used as a reference electrode, an organic aqueous solution is used as an electrolyte, carbon dioxide is introduced, and carbon monoxide is prepared through electrocatalytic reduction, the preparation method of the gallium-based liquid alloy catalyst comprises the following steps: smelting liquid metal gallium, indium and tin to obtain a gallium-indium-tin alloy; adding cerium powder into the gallium-indium-tin alloy, and carrying out ball-milling mixing; and roasting the ball-milled mixture. The alloy is prepared by combining a high-temperature melting method on the basis of a mechanical ball-milling method, so that active sites of cerium in the gallium-indium-tin alloy are increased, the Faraday efficiency is remarkably improved, and the gallium-indium-tin alloy has good catalytic performance.

Description

Technical Field

[0001] The invention belongs to the technical field of carbon dioxide resource utilization and relates to a method for electrocatalytically reducing carbon dioxide to carbon monoxide using a gallium-based liquid alloy catalyst. Background Art

[0002] In recent years, human dependence on fossil fuels has led to an increase in the concentration of CO2 in the atmosphere year by year. To solve this problem, it is urgent to develop efficient CO2 reduction catalysts. Traditional solid catalysts are prone to catalytic site blockage, leading to catalyst deactivation and other problems, while liquid metal catalysts can effectively avoid this problem. In liquid metal catalysts, the solubility of generally active metal elements in liquid metal is extremely low, but adding a very small amount of trace elements to liquid metal can cause a huge change in the properties of the liquid metal itself. Different active ingredients have a great impact on liquid metal catalysts. At the same time, the current method of adding active trace materials to liquid metal is limited to mechanical grinding, which can easily lead to incomplete dissolution of active ingredients and affect the catalytic effect of liquid metal catalysts. Summary of the invention

[0003] In view of the above-mentioned problems, the object of the present invention is to provide a method for preparing a gallium-based liquid alloy catalyst for electrocatalytic reduction of carbon dioxide. Since carbon monoxide is flammable, it can be used as a fuel in industry for welding or cutting metals and can be used as a reducing agent in organic synthesis, such as in the production of methanol, synthetic ammonia, sugars, etc. At the same time, in the metallurgical industry, carbon monoxide can be used to reduce metal oxides to obtain pure metals. Therefore, the object of the present invention is to provide a method for preparing a gallium-based liquid alloy catalyst for electrocatalytic reduction of carbon dioxide to produce carbon monoxide. The present invention adopts a preparation method combining mechanical ball milling alloy with molten alloy method to increase the solubility of active ingredients and increase the degree of alloying to prepare a more uniform liquid metal catalyst and improve its reaction activity.

[0004] To achieve this object, the present invention adopts the following technical solutions.

[0005] A method for electrocatalytically reducing carbon dioxide to carbon monoxide using a gallium-based liquid alloy catalyst, wherein the gallium-based liquid alloy catalyst is used as a working electrode, a platinum sheet electrode is used as a counter electrode, an Ag / AgCl electrode is used as a reference electrode, an organic aqueous solution is used as an electrolyte, carbon dioxide is introduced, and carbon monoxide is obtained through electrocatalytic reduction; wherein: the preparation method of the gallium-based liquid alloy catalyst comprises:

[0006] (1) At a certain temperature, metal gallium, metal indium and metal tin are smelted to obtain a gallium-indium-tin alloy;

[0007] (2) adding cerium powder to gallium-indium-tin alloy and performing ball milling mixing in a sealed state;

[0008] (3) calcining the ball-milled mixture in an inert atmosphere to obtain the gallium-based liquid metal catalyst.

[0009] In the present invention, the concentration of electrolyte in the organic aqueous solution electrolyte is 0.1-0.2 mol / L, and the water content is 2-3 mol / L.

[0010] In the present invention, the electrolyte in the organic solution electrolyte is tetrabutylammonium hexafluorophosphate, and the solvent is N,N-dimethylformamide.

[0011] In the present invention, the time for introducing carbon dioxide before the reaction is 20-40 minutes, and the flow rate of introducing carbon dioxide is 20-60 mL / min; the flow rate of introducing carbon dioxide during the reaction is 20-60 mL / min to maintain a carbon dioxide saturated state.

[0012] In the present invention, the reaction conditions are normal temperature and pressure, and the reaction voltage is -1.8 to -2.4V.

[0013] In the present invention, in step (1), the mass ratio of metal gallium, metal indium and metal tin is 68.5:21.5:10, the smelting temperature is 200-250° C., and the smelting time is 2-4 hours.

[0014] In the present invention, in step (2), the amount of cerium powder added is 0.5-3wt% based on the total mass of cerium powder and gallium indium tin alloy as 100%; the operating frequency of the ball mill is 50-70Hz, and the ball milling time is 20-40min.

[0015] In the present invention, in step (3), the inert atmosphere is nitrogen, the calcination temperature is 500-1300° C., and the calcination time is 0.5 h-1.5 h.

[0016] Compared with the sample after ball milling in step (2), the liquid metal after high-temperature calcination is still amorphous. High-temperature calcination does not fundamentally change its structure, but there are fewer undissolved active element particles inside it. Calcination effectively promotes the dissolution of active particles in its liquid metal, thereby reducing its charge and mass transfer resistance and enhancing its catalytic efficiency.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] Compared with the gallium-based liquid alloy catalyst after direct melt ball milling, the present invention effectively promotes the dissolution of active particles in its liquid metal through roasting, so that its charge and mass transfer resistance is reduced; comparing the liquid metal prepared by the roasting method and the liquid metal prepared by the ball milling method, the catalytic performance of the liquid metal prepared by the roasting method is better than that prepared by the ball milling method. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1The scanning electron microscope image of the gallium-based liquid metal alloy catalyst prepared in Example 1 of the present invention; (a) surface SEM image, (b) cerium element EDS analysis image.

[0020] Figure 2 XRD diagrams of the gallium-based liquid metal alloy catalysts prepared in Example 1 and Comparative Example 1 of the present invention.

[0021] Figure 3 CV curves of electrocatalytic reduction of carbon dioxide by gallium-based liquid metal alloy catalysts prepared in Examples 1 and 2 of the present invention and Comparative Example 1.

[0022] Figure 4 The Faraday efficiency of electrocatalytic generation of carbon dioxide by the gallium-based liquid metal alloy catalyst prepared in Examples 1, 2, 3 of the present invention and Comparative Example 1. DETAILED DESCRIPTION

[0023] The present invention is further described in detail below in conjunction with specific implementation modes, but the protection scope of the present invention is not limited to the described contents.

[0024] Example 1

[0025] 1. Preparation of Gallium-based Liquid Alloy Catalyst

[0026] (1) placing metal gallium, metal indium, and metal tin in a crucible at a mass ratio of 68.5%:21.5%:10%, and melting them in a muffle furnace at a temperature of 200° C. to obtain a gallium-indium-tin alloy;

[0027] (2) In a glove box, 1 wt% cerium powder was added to the gallium-indium-tin alloy, and after simple mixing, the mixture was transferred to a sealed ball mill. The ball mill body was made of polytetrafluoroethylene, and the ball mill beads were equipped with a plasma-sprayed zirconium oxide coating to prevent corrosion by liquid metal during the ball milling process. The ball milling time was 30 min and the frequency was 50 Hz.

[0028] (3) After the ball milling is completed, the mixture is transferred to a crucible, calcined in a vacuum muffle furnace at 1000° C. for 30 min, and then taken out to obtain a gallium-indium-tin-cerium alloy, such as Figure 1 shown.

[0029] 2. Electrocatalytic reduction of carbon dioxide using gallium-based liquid alloy catalysts

[0030] A gallium-based liquid alloy catalyst is used as the working electrode, a platinum electrode is used as the counter electrode, an Ag / AgCl electrode is used as the reference electrode, and an organic solution is used as the electrolyte. The concentration of tetrabutylammonium hexafluorophosphate in the organic solution is 0.1 mol / L, and the content of water is 2 mol / L. Before the reaction, carbon dioxide is passed into the electrolyte at a flow rate of 50 ml / min to saturate the electrolyte for at least 30 minutes. During the reaction, the electrolyte is passed at a flow rate of 50 ml / min to maintain the carbon dioxide saturation state. The end of the reactor is connected to a GC gas chromatograph to detect the hydrogen and carbon monoxide produced by the reaction. Constant potential electrolysis is carried out at room temperature and pressure at a potential of -2.4V.

[0031] Figure 3 This is the CV curve of the electrocatalytic reduction of carbon dioxide by the gallium-based liquid metal alloy catalyst prepared in Example 1 of the present invention. The current density can reach 7 mA / cm 2 .

[0032] Example 2

[0033] 1. Preparation of Gallium-based Liquid Alloy Catalyst

[0034] (1) placing metal gallium, metal indium, and metal tin in a crucible at a mass ratio of 68.5%:21.5%:10%, and melting them in a muffle furnace at a temperature of 200° C. to obtain a gallium-indium-tin alloy;

[0035] (2) In a glove box, 1 wt% cerium powder was added to the gallium-indium-tin alloy, and after simple mixing, the mixture was transferred to a sealed ball mill. The ball mill body was made of polytetrafluoroethylene, and the ball mill beads were equipped with a plasma-sprayed zirconium oxide coating to prevent corrosion by liquid metal during the ball milling process. The ball milling time was 30 min and the frequency was 50 Hz.

[0036] (3) After ball milling, the mixture was transferred to a crucible, calcined at 800°C in a vacuum muffle furnace for 30 min, and then taken out.

[0037] 2. Electrocatalytic reduction of carbon dioxide using gallium-based liquid alloy catalysts

[0038] A gallium-based liquid alloy catalyst is used as the working electrode, a platinum electrode is used as the counter electrode, an Ag / AgCl electrode is used as the reference electrode, and an organic solution is used as the electrolyte. The concentration of tetrabutylammonium hexafluorophosphate in the organic solution is 0.1 mol / L, and the content of water is 2 mol / L. Before the reaction, carbon dioxide is passed into the electrolyte at a flow rate of 50 ml / min to saturate the electrolyte for at least 30 minutes. During the reaction, the electrolyte is passed at a flow rate of 50 ml / min to maintain the carbon dioxide saturation state. The end of the reactor is connected to a GC gas chromatograph to detect the hydrogen and carbon monoxide produced by the reaction. Constant potential electrolysis is carried out at room temperature and pressure at a potential of -2.4V.

[0039] Example 3

[0040] 1. Preparation of Gallium-based Liquid Alloy Catalyst

[0041] (1) placing metal gallium, metal indium, and metal tin in a crucible at a mass ratio of 68.5%:21.5%:10%, and melting them in a muffle furnace at a temperature of 200° C. to obtain a gallium-indium-tin alloy;

[0042] (2) In a glove box, 1 wt% cerium powder was added to the gallium-indium-tin alloy, and after simple mixing, the mixture was transferred to a sealed ball mill. The ball mill body was made of polytetrafluoroethylene, and the ball mill beads were equipped with a plasma-sprayed zirconium oxide coating to prevent corrosion by liquid metal during the ball milling process. The ball milling time was 30 min and the frequency was 50 Hz.

[0043] (3) After ball milling, the mixture was transferred to a crucible, calcined at 500°C for 30 min in a vacuum muffle furnace, and then taken out.

[0044] 2. Electrocatalytic reduction of carbon dioxide using gallium-based liquid alloy catalysts

[0045] A gallium-based liquid alloy catalyst is used as the working electrode, a platinum electrode is used as the counter electrode, an Ag / AgCl electrode is used as the reference electrode, and an organic solution is used as the electrolyte. The concentration of tetrabutylammonium hexafluorophosphate in the organic solution is 0.1 mol / L, and the content of water is 2 mol / L. Before the reaction, carbon dioxide is passed into the electrolyte at a flow rate of 50 ml / min to saturate the electrolyte for at least 30 minutes. During the reaction, the electrolyte is passed at a flow rate of 50 ml / min to maintain the carbon dioxide saturation state. The end of the reactor is connected to a GC gas chromatograph to detect the hydrogen and carbon monoxide produced by the reaction. Constant potential electrolysis is carried out at room temperature and pressure and a potential of -2.4V.

[0046] Comparative Example 1

[0047] 1. Preparation of Gallium-based Liquid Alloy Catalyst

[0048] (1) placing metal gallium, metal indium, and metal tin in a crucible at a mass ratio of 68.5%:21.5%:10%, and melting them in a muffle furnace at a temperature of 200° C. to obtain a gallium-indium-tin alloy;

[0049] (2) In a glove box, 1 wt% cerium powder was added to the gallium-indium-tin alloy, and after simple mixing, it was transferred to a sealed ball mill. The ball mill body was made of polytetrafluoroethylene, and the ball milling beads were equipped with a plasma-sprayed zirconium oxide coating to prevent corrosion by liquid metal during the ball milling process. The ball milling time was 30 min and the frequency was 50 Hz to obtain a gallium-based liquid metal catalyst. XRD comparison of the catalyst and the catalyst prepared in Example 1 Figure 2As shown, the amorphous structure of the catalyst has not changed. 2. Electrocatalytic reduction of carbon dioxide using gallium-based liquid alloy catalysts

[0050] A gallium-based liquid alloy catalyst is used as the working electrode, a platinum sheet electrode is used as the counter electrode, an Ag / AgCl electrode is used as the reference electrode, and an organic solution is used as the electrolyte. The concentration of tetrabutylammonium hexafluorophosphate in the organic solution is 0.1 mol / L, and the content of water is 2 mol / L. Before the reaction, carbon dioxide is passed into the electrolyte at a flow rate of 50 ml / min to saturate the electrolyte for at least 30 minutes. During the reaction, the electrolyte is passed at a flow rate of 50 ml / min to maintain the carbon dioxide saturation state. The end of the reactor is connected to a GC gas chromatograph to detect the hydrogen and carbon monoxide produced by the reaction. Electrolysis is carried out at room temperature and pressure at a potential of -2.4 V.

[0051] Depend on Figure 3 It can be seen that compared with Examples 1 and 2, the current density of Example 1 is smaller and the overall catalytic efficiency is low.

[0052] The Faraday efficiencies of Examples 1, 2, 3 and Comparative Example 1 are calculated by the following formula (1): Figure 4 It can be seen that the Faraday efficiency of the catalyst prepared by the calcination method is significantly improved compared with that prepared by the ball milling method.

[0053]

[0054] Where n is the amount of the target product gas that can be calculated by the peak area detected in the gas chromatograph, Q is the total charge, F is the Faraday constant, which is 96485 mol / C, P is the gas pressure at the chromatographic injection point, which is a standard atmospheric pressure, and v is the gas flow rate (m / s) entering the chromatographic 3 / s), R is the ideal gas constant) is taken as 8.314 Jmol -1 K -1 , T is the temperature of the chromatographic injection port (K).

Claims

1. A method for electrocatalytically reducing carbon dioxide to carbon monoxide using a gallium-based liquid alloy catalyst, characterized in that: The method uses a gallium-based liquid alloy catalyst as a working electrode, a platinum sheet electrode as a counter electrode, an Ag / AgCl electrode as a reference electrode, an organic aqueous solution as an electrolyte, introduces carbon dioxide, and produces carbon monoxide through electrocatalytic reduction; wherein: the preparation method of the gallium-based liquid alloy catalyst includes: (1) At a certain temperature, metal gallium, metal indium and metal tin are melted to obtain a gallium-indium-tin alloy; (2) adding cerium powder to gallium-indium-tin alloy and performing ball milling mixing in a sealed state; (3) The ball-milled mixture is calcined in an inert atmosphere to obtain a gallium-based liquid metal catalyst.

2. The method for electrocatalytic reduction of carbon dioxide to carbon monoxide using a gallium-based liquid alloy catalyst according to claim 1, characterized in that: The concentration of electrolyte in the organic aqueous solution electrolyte is 0.1-0.2 mol / L, and the water content is 2-3 mol / L.

3. The method for electrocatalytic reduction of carbon dioxide to carbon monoxide using a gallium-based liquid alloy catalyst according to claim 1, characterized in that: The electrolyte in the organic solution electrolyte is tetrabutylammonium hexafluorophosphate, and the solvent is N,N-dimethylformamide.

4. The method for electrocatalytic reduction of carbon dioxide to carbon monoxide using a gallium-based liquid alloy catalyst according to claim 1, characterized in that: The time for introducing carbon dioxide before the reaction is 20-40 minutes, and the flow rate of introducing carbon dioxide is 20-60 mL / min; the flow rate of introducing carbon dioxide during the reaction is 20-60 mL / min to maintain the carbon dioxide saturation state.

5. The method for electrocatalytic reduction of carbon dioxide to carbon monoxide using a gallium-based liquid alloy catalyst according to claim 1, characterized in that: The reaction conditions are normal temperature and pressure, the constant voltage method is adopted, and the reaction voltage is -1.8~-2.4V.

6. The method for electrocatalytic reduction of carbon dioxide to carbon monoxide using a gallium-based liquid alloy catalyst according to claim 1, characterized in that: In step (1), the mass ratio of metal gallium, metal indium and metal tin is 68.5:21.5:10, the smelting temperature is 200-250° C., and the smelting time is 2-4 hours.

7. The method for electrocatalytic reduction of carbon dioxide to carbon monoxide using a gallium-based liquid alloy catalyst according to claim 1, characterized in that: In step (2), based on the total mass of cerium powder and gallium indium tin alloy as 100%, the amount of cerium powder added is 0.5-3wt%; the operating frequency of the ball mill is 50-70 Hz, and the ball milling time is 20-40 min.

8. The method for electrocatalytic reduction of carbon dioxide to carbon monoxide using a gallium-based liquid alloy catalyst according to claim 1, characterized in that: In step (3), the inert atmosphere is nitrogen, the calcination temperature is 500-1300°C, and the calcination time is 0.5h-1.5h.

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