A method for preparing a nitrate-reducing electrocatalyst

Abstract

The preparation method of the nitrate reduction electrocatalyst disclosed in the application comprises the following steps: preparation of a copper complex precursor, preparation of nitrogen-sulfur double-doped carbon loaded copper nanosheet Cu / NSC, and preparation of nitrogen-sulfur double-doped carbon loaded copper oxide nanosheet catalyst CuO / NSC. The copper complex precursor is obtained through a simple coordination reaction, and the copper oxide nanosheet catalyst is obtained through high-temperature calcination. The preparation method is simple, realizes the coordination of dimethylglyoxime and Cu 2+ , and the prepared copper oxide nanosheet catalyst has a large specific surface area and a large number of reaction active sites, has significant activity for nitrate reduction reaction, and has high stability, solving the problem that Cu-based electrocatalysts are deactivated due to passivation, leaching and corrosion after long-term use. Meanwhile, the introduction of the carbon carrier enhances the enrichment of the catalyst to NO3 ‑ and intermediates, and improves the rate of nitrate reduction reaction.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of electrocatalysis, and particularly relates to a preparation method of a nitrate reduction electrocatalyst. BACKGROUND

[0002] Among many nitrate removal technologies, electrocatalytic removal of nitrate is a very promising solution, and is expected to become a powerful means to meet the growing demand for nitrate and restore the global nitrogen balance.

[0003] Compared with nitrogen, the bond energy of N=O in nitrate is only 204 kJ mol -1 , and the solubility of nitrate in aqueous solution is very high, making it easier to reduce nitrate to ammonia than to reduce nitrogen to ammonia, and making it easier to extend the electrocatalytic reduction of nitrate to other applications, such as energy storage. However, the nitrate reduction reaction involves an eight-electron transfer process, and the product is complex, usually with a high reaction kinetic energy barrier. Therefore, the selection of catalyst is crucial.

[0004] Cu-based electrocatalysts have been widely studied in nitrate reduction reactions due to their excellent electrochemical activity, tunable electronic structure and low cost. However, Cu-based electrocatalysts must address two problems: first, the deactivation of the catalyst due to passivation, leaching and corrosion after long-term use; second, the accumulation of nitrite during the nitrate reduction reaction, which is a major quasi-stable intermediate and a carcinogenic substance more toxic than nitrate. Extending the electrolysis time and increasing the current density can further reduce nitrite and promote its conversion to nitrogen and ammonia, but these steps result in higher energy consumption. Therefore, the present application proposes a preparation method of a nitrate reduction electrocatalyst, which introduces nitrogen and sulfur double-doped carbon supports into Cu-based catalysts to improve the existing problems of easy corrosion and poor stability of Cu-based catalysts, and further improve the nitrate electroreduction activity and selectivity of Cu-based catalysts. SUMMARY

[0005] The purpose of the present application is to solve the problems of poor stability of nitrate reduction catalysts and accumulation of nitrite, and to provide a preparation method of a nitrate reduction electrocatalyst with high activity and high stability.

[0006] The technical scheme adopted by the present application to solve the above technical problems is: a preparation method of a nitrate reduction electrocatalyst, comprising the following steps:

[0007] (1) Preparation of copper complex precursor: first, 0.5-2 mmol of copper chloride is dissolved in 5-20 mL of anhydrous ethanol to obtain solution A; then 1-4 mmol of dimethylglyoxime (DMG) and 1-4 mmol of thiourea (Tu) are dissolved in 10-30 mL of anhydrous ethanol to obtain solution B; solution A and solution B are mixed, and stirring is carried out at room temperature for 6-24 hours; after the reaction is completed, the white solid is centrifuged, washed and dried to obtain the DMG-Cu-Tu complex, which is the copper complex precursor;

[0008] (2) Preparation of nitrogen-sulfur co-doped carbon supported copper nanosheet Cu / NSC: the DMG-Cu-Tu complex prepared in step (1) is placed in a tube furnace, and is heated to 600-900 ℃ at a heating rate of 2-10 ℃ / min, and is calcined for 2-4 hours; after the calcination is completed, natural cooling is carried out to room temperature to obtain the nitrogen-sulfur co-doped carbon supported copper nanosheet Cu / NSC;

[0009] (3) Preparation of nitrogen-sulfur co-doped carbon supported copper oxide nanosheet catalyst CuO / NSC: the nitrogen-sulfur co-doped carbon supported copper nanosheet Cu / NSC prepared in step (2) is placed in a muffle furnace, and is heated to 200-350 ℃ at a heating rate of 5 ℃ / min, and is calcined for 1-2 hours; after the calcination is completed, natural cooling is carried out to room temperature to obtain the nitrogen-sulfur co-doped carbon supported copper oxide nanosheet catalyst CuO / NSC, which is the nitrate salt reduction electrocatalyst.

[0010] Compared with the prior art, the present application has the following advantages:

[0011] 1) The preparation method of the nitrate salt reduction electrocatalyst of the present application first obtains a copper complex precursor through a simple coordination reaction, and then obtains a copper oxide nanosheet catalyst through high-temperature calcination, and the copper oxide nanosheet catalyst is the nitrate salt reduction electrocatalyst. The preparation method of the present application is simple, and realizes the coordination of dimethylglyoxime and Cu 2+ . At the same time, the prepared copper oxide nanosheet catalyst has a large specific surface area and a large number of reaction active sites, and has remarkable activity for nitrate salt reduction reaction.

[0012] 2) The prepared copper oxide nanosheet catalyst has high stability, and solves the problem that Cu-based electrocatalysts are deactivated due to passivation, leaching and corrosion after long-term use. At the same time, the introduction of the carbon support enhances the enrichment of the catalyst to NO3 - and intermediates, and improves the rate of nitrate salt reduction reaction. BRIEF DESCRIPTION OF DRAWINGS

[0013] Figure 1 SEM image of the DMG-Cu-Tu complex prepared in Example 1;

[0014] Figure 2 The image shows a SEM image of the copper oxide nanosheet catalyst CuO / NSC prepared in Example 1.

[0015] Figure 3 The LSV scan comparison diagrams are shown for the copper oxide nanosheet catalyst CuO / NSC prepared in Example 1 in 0.5 mol / L Na2SO4 + 0.1 mol / L KNO3 and 0.5 mol / L Na2SO4 electrolytes, respectively. Detailed Implementation

[0016] The present invention will be further described below with reference to specific embodiments and accompanying drawings, but the embodiments do not limit the present invention in any way. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in this technical field. Unless otherwise specified, the reagents and materials used in the present invention are all commercially available.

[0017] Example 1: A method for preparing a nitrate reduction electrocatalyst, comprising the following steps:

[0018] (1) Preparation of the copper complex precursor: First, 0.5 mmol of copper chloride was dissolved in 5 mL of anhydrous ethanol to obtain solution A; then, 1 mmol of dimethylglyoxime (DMG) and 1 mmol of thiourea (Tu) were dissolved in 30 mL of anhydrous ethanol to obtain solution B; then, solutions A and B were mixed and stirred at room temperature for 6 hours. After the reaction was completed, the white solid was centrifuged, washed, and dried to obtain the DMG-Cu-Tu complex, which is the copper complex precursor. Its SEM image is shown in [image missing]. Figure 1 ;

[0019] (2) Preparation of nitrogen-sulfur dual-doped carbon-supported copper nanosheets Cu / NSC: The DMG-Cu-Tu complex prepared in step (1) was placed in a tube furnace and heated to 800°C at a heating rate of 5°C / min. After calcination, it was naturally cooled to room temperature to obtain nitrogen-sulfur dual-doped carbon-supported copper nanosheets Cu / NSC.

[0020] (3) Preparation of nitrogen-sulfur dual-doped carbon-supported copper oxide nanosheet catalyst CuO / NSC: The nitrogen-sulfur dual-doped carbon-supported copper nanosheet Cu / NSC prepared in step (2) was placed in a muffle furnace and heated to 200℃ at a heating rate of 5℃ / min, and calcined for 1 hour. After calcination, it was naturally cooled to room temperature to obtain the nitrogen-sulfur dual-doped carbon-supported copper oxide nanosheet catalyst CuO / NSC, which is the nitrate reduction electrocatalyst. Its SEM image is shown in […]. Figure 2 .

[0021] Depend on Figure 2It can be seen that the copper oxide nanosheet catalyst CuO / NSC has a uniform sheet structure, can provide a larger specific surface area and a large number of reaction active sites for the electrochemical reaction, and is helpful to improve the catalytic activity.

[0022] The LSV scanning comparison chart of the copper oxide nanosheet catalyst CuO / NSC prepared in Example 1 in 0.5 mol / L Na2SO4+0.1 mol / L KNO3 and 0.5 mol / L Na2SO4 electrolyte is shown in Figure 3 . It can be seen that the copper oxide nanosheet catalyst CuO / NSC has excellent nitrate reduction activity. Figure 3

[0023] Example 2: A preparation method of a nitrate reduction electrocatalyst, comprising the following steps:

[0024] (1) Preparation of a copper complex precursor: first, 1 mmol of copper chloride is dissolved in 10 mL of anhydrous ethanol to obtain solution A; then, 2 mmol of dimethylglyoxime (DMG) and 2 mmol of thiourea (Tu) are dissolved in 20 mL of anhydrous ethanol to obtain solution B; solution A and solution B are mixed, and the mixture is stirred at room temperature for 12 hours. After the reaction is completed, the white solid is centrifuged, washed and dried to obtain a DMG-Cu-Tu complex, which is the copper complex precursor;

[0025] (2) Preparation of nitrogen and sulfur double-doped carbon loaded copper nanosheet Cu / NSC: the DMG-Cu-Tu complex prepared in step (1) is placed in a tube furnace, and heated to 800℃ at a heating rate of 5℃ / min, and calcined for 2 hours. After the calcination is completed, the mixture is naturally cooled to room temperature to obtain the nitrogen and sulfur double-doped carbon loaded copper nanosheet Cu / NSC;

[0026] (3) Preparation of nitrogen and sulfur double-doped carbon loaded copper oxide nanosheet catalyst CuO / NSC: the nitrogen and sulfur double-doped carbon loaded copper nanosheet Cu / NSC prepared in step (2) is placed in a muffle furnace, and heated to 200℃ at a heating rate of 5℃ / min, and calcined for 1 hour. After the calcination is completed, the mixture is naturally cooled to room temperature to obtain the nitrogen and sulfur double-doped carbon loaded copper oxide nanosheet catalyst CuO / NSC, which is the nitrate reduction electrocatalyst.

[0027] Example 3: A preparation method of a nitrate reduction electrocatalyst, comprising the following steps:

[0028] ​(1) Preparation of copper complex precursor: first, 2 mmol of copper chloride was dissolved in 20 mL of anhydrous ethanol to obtain solution A; then 4 mmol of dimethylglyoxime (DMG) and 4 mmol of thiourea (Tu) were dissolved in 30 mL of anhydrous ethanol to obtain solution B; solution A and solution B were mixed, and the reaction was stirred at room temperature for 18 hours; after the reaction was completed, the white solid was centrifuged, washed and dried to obtain the DMG-Cu-Tu complex, which was the copper complex precursor;

[0029] (2) Preparation of nitrogen-sulfur co-doped carbon supported copper nanosheet Cu / NSC: the DMG-Cu-Tu complex prepared in step (1) was placed in a tube furnace and heated to 800℃ at a heating rate of 3℃ / min, and calcined for 2 hours; after calcination was completed, the sample was naturally cooled to room temperature to obtain the nitrogen-sulfur co-doped carbon supported copper nanosheet Cu / NSC;

[0030] (3) Preparation of nitrogen-sulfur co-doped carbon supported copper oxide nanosheet catalyst CuO / NSC: the nitrogen-sulfur co-doped carbon supported copper nanosheet Cu / NSC prepared in step (2) was placed in a muffle furnace and heated to 300℃ at a heating rate of 5℃ / min, and calcined for 1 hour; after calcination was completed, the sample was naturally cooled to room temperature to obtain the nitrogen-sulfur co-doped carbon supported copper oxide nanosheet catalyst CuO / NSC, which was a nitrate salt reduction electrocatalyst.

Claims

1. A method for preparing a nitrate reduction electrocatalyst, characterized in that, Includes the following steps: (1) Preparation of copper complex precursor: First, 0.5-2 mmol of copper chloride was dissolved in 5-20 mL of anhydrous ethanol to obtain solution A; then 1-4 mmol of dimethylglyoxime and 1-4 mmol of thiourea were dissolved in 10-30 mL of anhydrous ethanol to obtain solution B; then solution A and solution B were mixed and stirred at room temperature for 6-24 hours. After the reaction was completed, the white solid was centrifuged, washed and dried to obtain DMG-Cu-Tu complex, which is the copper complex precursor; (2) Preparation of nitrogen-sulfur dual-doped carbon-supported copper nanosheets Cu / NSC: The DMG-Cu-Tu complex prepared in step (1) was placed in a tube furnace and heated to 600-900℃ at a heating rate of 2-10℃ / min. After calcination for 2-4 hours, it was naturally cooled to room temperature to obtain nitrogen-sulfur dual-doped carbon-supported copper nanosheets Cu / NSC. (3) Preparation of nitrogen-sulfur dual-doped carbon-supported copper oxide nanosheet catalyst CuO / NSC: The nitrogen-sulfur dual-doped carbon-supported copper nanosheet Cu / NSC prepared in step (2) is placed in a muffle furnace and heated to 200-350℃ at a heating rate of 5℃ / min. It is calcined for 1-2 hours and then naturally cooled to room temperature to obtain the nitrogen-sulfur dual-doped carbon-supported copper oxide nanosheet catalyst CuO / NSC, which is the nitrate reduction electrocatalyst.

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