Preparation method of nitrate reduction electrocatalyst

Abstract

The preparation method of the nitrate reduction electrocatalyst disclosed by the invention comprises the following steps: preparing a copper complex precursor, preparing a nitrogen and sulfur double-doped carbon loaded copper nanosheet Cu / NSC, and preparing a nitrogen and sulfur double-doped carbon loaded copper oxide nanosheet catalyst CuO / NSC. A 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, and realizes coordination of dimethylglyoxime and Cu < 2 + >. Meanwhile, the prepared copper oxide nanosheet catalyst has a relatively large specific surface area and rich reaction active sites, has remarkable activity on nitrate reduction reaction, has high stability, and solves the problem that a Cu-based electrocatalyst is inactivated due to passivation, leaching and corrosion after being used for a long time. Meanwhile, due to introduction of the carbon carrier, the enrichment effect of the catalyst on NO3 <-> and an intermediate is enhanced, and the rate of nitrate reduction reaction is increased.

Description

Technical Field

[0001] The invention belongs to the technical field of electrocatalysis, and particularly relates to a method for preparing a nitrate reduction electrocatalyst. Background Art

[0002] Over the past century, the rapid increase in anthropogenic nitrogen-containing pollutants has led to a serious imbalance in the global nitrogen cycle and caused many ecological and environmental problems. The accumulation of nitrates in groundwater can cause eutrophication of water bodies, while excessive nitrate content in surface water and drinking water can pose a threat to human health. Among many nitrate removal technologies, electrocatalytic nitrate removal is a very promising solution and is expected to become a powerful means to meet the growing demand for nitrates and restore the global nitrogen balance.

[0003] Compared to nitrogen, the bond energy of N=O in nitrate is only 204 kJ mol -1 , and the high solubility of nitrate in aqueous solutions makes the process of nitrate reduction to ammonia easier to achieve than the process of nitrogen reduction to ammonia, and also makes it easier to extend the electrocatalytic nitrate reduction to other applications, such as energy storage. However, the nitrate reduction reaction involves an eight-electron transfer process, the products are complex, and usually have a high reaction kinetic energy barrier. Therefore, the choice 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 solve two problems: one is the deactivation of the catalyst due to passivation, leaching and corrosion after long-term use; the other is the accumulation of nitrite during the nitrate reduction reaction, which is a major quasi-stable intermediate and a carcinogen that is more toxic than nitrate. Prolonging the electrolysis time and increasing the current density can further reduce nitrite and promote its conversion to nitrogen and ammonia, but these steps lead to higher energy consumption. Therefore, the present invention proposes a method for preparing a nitrate reduction electrocatalyst, introducing a nitrogen-sulfur dual-doped carbon carrier into a Cu-based catalyst, improving the problems of easy corrosion and poor stability of existing Cu-based catalysts, and further improving the nitrate electroreduction activity and selectivity of the Cu-based catalyst. Summary of the invention

[0005] The purpose of the present invention is to provide a method for preparing a nitrate reduction electrocatalyst with high activity and high stability in order to solve the problems of poor stability of nitrate reduction catalysts and accumulation of nitrite.

[0006] The technical solution adopted by the present invention to solve the above technical problem is: a method for preparing a nitrate reduction electrocatalyst, comprising the following steps:

[0007] (1) Preparation of a copper complex precursor: First, 0.5-2 mmol of copper chloride is dissolved in 5-20 mL of anhydrous ethanol to obtain a 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 a solution B; then, the solution A and the solution B are mixed and stirred at room temperature for 6-24 hours. After the reaction is completed, the white solid is centrifuged, washed, and dried to obtain a DMG-Cu-Tu complex, which is a copper complex precursor;

[0008] (2) Preparation of nitrogen-sulfur dual-doped carbon-supported copper nanosheets Cu / NSC: placing the DMG-Cu-Tu complex prepared in step (1) in a tube furnace, heating the temperature to 600-900° C. at a heating rate of 2-10° C. / min, calcining for 2-4 hours, and naturally cooling to room temperature after calcination to obtain nitrogen-sulfur dual-doped carbon-supported copper nanosheets Cu / NSC;

[0009] (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, heated to 200-350°C at a heating rate of 5°C / min, calcined for 1-2 hours, and naturally cooled to room temperature after calcination to obtain nitrogen-sulfur dual-doped carbon-supported copper oxide nanosheet catalyst CuO / NSC, which is a nitrate reduction electrocatalyst.

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

[0011] 1) The preparation method of the nitrate reduction electrocatalyst of the present invention first obtains a copper complex precursor by a simple coordination reaction, and then obtains a copper oxide nanosheet catalyst by high temperature calcination. The copper oxide nanosheet catalyst is the nitrate reduction electrocatalyst. The preparation method of the present invention is simple and realizes the reaction of diacetyl oxime with Cu 2+ At the same time, the prepared copper oxide nanosheet catalyst has a large specific surface area and abundant reactive sites, and has significant activity in the nitrate reduction reaction.

[0012] 2) The copper oxide nanosheet catalyst prepared by the present invention has high stability, which solves the problem of catalyst deactivation due to passivation, leaching and corrosion of Cu-based electrocatalysts after long-term use. At the same time, the introduction of carbon carriers enhances the catalyst's ability to react with NO3 - As well as the enrichment of intermediates, the rate of nitrate reduction reaction is increased. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0014] Figure 2 This is a SEM image of the copper oxide nanosheet catalyst CuO / NSC prepared in Example 1;

[0015] Figure 3 These are LSV scanning comparison diagrams 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 electrolytes, respectively. DETAILED DESCRIPTION

[0016] The present invention is further described below in conjunction with specific examples and accompanying drawings, but the embodiments do not limit the present invention in any form. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art. Unless otherwise specified, the reagents and materials used in the present invention are commercially available.

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

[0018] (1) Preparation of 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 solution A and solution 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 DMG-Cu-Tu complex, which is the copper complex precursor. Its SEM image is shown in FIG. 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) is placed in a tube furnace, heated to 800° C. at a heating rate of 5° C. / min, and calcined for 2 hours. After calcination, the mixture is 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, heated to 200° C. at a heating rate of 5° C. / min, and calcined for 1 hour. After calcination, it was naturally cooled to room temperature to obtain nitrogen-sulfur dual-doped carbon-supported copper oxide nanosheet catalyst CuO / NSC, which is a nitrate reduction electrocatalyst. Its SEM image is shown in FIG. Figure 2 .

[0021] Depend on Figure 2It can be seen that the copper oxide nanosheet catalyst CuO / NSC has a uniform layer structure, which can provide a large specific surface area and abundant reaction active sites for electrochemical reactions, and help improve the catalytic activity.

[0022] The LSV scanning comparison diagram 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 FIG. Figure 3 .Depend on Figure 3 It can be seen that the copper oxide nanosheet catalyst CuO / NSC has excellent nitrate reduction activity.

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

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

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

[0026] (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, heated to 200°C at a heating rate of 5°C / min, and calcined for 1 hour. After calcination, it is naturally cooled to room temperature to obtain nitrogen-sulfur dual-doped carbon-supported copper oxide nanosheet catalyst CuO / NSC, which is a nitrate reduction electrocatalyst.

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

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

[0029] (2) Preparation of nitrogen-sulfur dual-doped carbon-supported copper nanosheets Cu / NSC: The DMG-Cu-Tu complex prepared in step (1) is placed in a tube furnace, heated to 800° C. at a heating rate of 3° C. / min, and calcined for 2 hours. After calcination, it is naturally cooled to room temperature to obtain nitrogen-sulfur dual-doped carbon-supported copper nanosheets Cu / NSC;

[0030] (3) Preparation of nitrogen-sulfur dual-doped carbon-loaded copper oxide nanosheet catalyst CuO / NSC: The nitrogen-sulfur dual-doped carbon-loaded copper nanosheet Cu / NSC prepared in step (2) is placed in a muffle furnace, heated to 300°C at a heating rate of 5°C / min, and calcined for 1 hour. After calcination, it is naturally cooled to room temperature to obtain nitrogen-sulfur dual-doped carbon-loaded copper oxide nanosheet catalyst CuO / NSC, which is a nitrate reduction electrocatalyst.

Claims

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

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