Preparation method and application of nickel-based bimetallic multifunctional catalyst

Abstract

The invention discloses a preparation method of a nickel-based bimetallic multifunctional catalyst, which comprises the following steps: firstly, carrying out simple thiocyanate bridging coordination reaction to obtain a thiocyanate bridging complex precursor DMG-SCN-NiCo-Tu, and then carrying out high-temperature calcination to obtain a nickel-cobalt oxide nano catalyst NiCoO. The nickel-cobalt oxide nano catalyst NiCoO is a high-activity nickel-based bimetallic multifunctional catalyst. The preparation method is simple, dimethylglyoxime DMG and nickel-cobalt bimetallic coordination is achieved, meanwhile, the catalytic activity of the nickel-based catalyst is enhanced through introduction of the second metal Co, the prepared nickel-based bimetallic multifunctional catalyst has the large specific surface area and rich reaction active sites, the catalytic activity of the catalyst is remarkably enhanced, and the catalyst has the good application prospect. The problems of low electro-catalysis reaction activity and poor selectivity of a nickel-based single metal catalyst are solved, and the nickel-based single metal catalyst can be used as a catalyst for electro-catalysis nitrate reduction and urea oxidation.

Description

Technical Field

[0001] The invention belongs to the technical field of electrocatalysis, and specifically relates to a preparation method and application of a nickel-based bimetallic multifunctional catalyst. 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 nitrogen-containing pollutants in groundwater will cause eutrophication of water bodies, while excessive levels of nitrogen-containing pollutants in surface water and drinking water will pose a threat to human health. Among the many technologies for removing nitrogen-containing pollutants, electrocatalytic removal of nitrogen-containing pollutants (including nitrates and urea) is a very promising solution and is expected to become a powerful means to meet the needs of removing nitrogen-containing pollutants and restoring global nitrogen balance. The selection of a suitable catalyst is the key to increasing the rate of catalytic reaction.

[0003] Precious metal catalysts have excellent catalytic performance, but their high price limits their widespread application. Therefore, non-precious metal catalysts, especially Ni, NiO and Ni(OH) 2 Ni-based electrocatalysts such as nickel-based electrocatalysts have certain electrocatalytic performance for various electrochemical reactions due to the structural characteristics of the valence layer 3d orbital that is not fully filled with electrons, and are very potential catalysts to replace precious metals. However, the catalytic activity of single metal Ni-based catalysts is relatively low. Therefore, the present invention provides a preparation method and application of a nickel-based bimetallic multifunctional catalyst, which introduces a second metal into the nickel-based catalyst to improve the performance of the nickel-based catalyst. At the same time, electrochemical reactions show that the catalyst prepared by the method has excellent urea oxidation and nitrate reduction performance. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a method for preparing a nickel-based bimetallic multifunctional catalyst and its application in view of the deficiencies in the prior art. The preparation method is simple, and the prepared nickel-based bimetallic multifunctional catalyst has a large specific surface area and abundant reaction active sites, which significantly enhances the catalytic activity of the catalyst, solves the problems of low electrocatalytic reaction activity and poor selectivity of nickel-based monometallic catalysts, and can be used as a catalyst for electrocatalytic nitrate reduction and urea oxidation.

[0005] The technical solution adopted by the present invention to solve the above technical problems is: a method for preparing a nickel-based bimetallic multifunctional catalyst, comprising the following steps:

[0006] (1) Preparation of thiocyanate bridged complex precursor: First, 0.5-1 mmol nickel nitrate and 0.5-1 mmol cobalt nitrate are dissolved in 10-20 mL anhydrous ethanol to obtain solution A; then 2-4 mmol potassium thiocyanate is dissolved in 10-20 mL anhydrous ethanol to obtain solution B; then solution A and solution B are mixed, stirred evenly, and the precipitate is filtered to obtain a transparent solution C;

[0007] 1-4 mmol of dimethylglyoxime (DMG) and 1-4 mmol of thiourea (Tu) were ultrasonically dissolved in 20-40 mL of anhydrous ethanol to obtain a colorless transparent solution D;

[0008] Solution C and solution D are mixed and stirred at room temperature for 6 to 24 hours. After the reaction is completed, the brown solid is centrifuged and washed with anhydrous ethanol and dried at 60° C. to obtain a thiocyanate-bridged complex precursor DMG-SCN-NiCo-Tu.

[0009] (2) Preparation of nickel cobalt oxide nanocatalyst: The thiocyanate bridged complex precursor DMG-SCN-NiCo-Tu prepared in step (3) is placed in a muffle furnace, heated to 300-600°C at a heating rate of 2-10°C / min, and calcined for 1-3 hours. After calcination, the mixture is naturally cooled to room temperature to obtain a nickel cobalt oxide nanocatalyst NiCoO, which is a nickel-based bimetallic multifunctional catalyst.

[0010] The nickel-based bimetallic multifunctional catalyst prepared by the preparation method of the present invention has high activity and can be used as a catalyst for electrocatalytic nitrate reduction and urea oxidation.

[0011] Compared with the prior art, the present invention has the following advantages: the preparation method of the nickel-based bimetallic multifunctional catalyst of the present invention first obtains the thiocyanate bridged complex precursor DMG-SCN-NiCo-Tu by a simple thiocyanate bridged coordination reaction, and then obtains the nickel-cobalt oxide nanocatalyst NiCoO by high-temperature calcination. The nickel-cobalt oxide nanocatalyst NiCoO is a highly active nickel-based bimetallic multifunctional catalyst, which can be used as a catalyst for electrocatalytic nitrate reduction and urea oxidation. The preparation method of the present invention is simple, and the coordination of diacetyl oxime DMG and nickel-cobalt bimetallic is achieved. At the same time, the introduction of the second metal Co enhances the catalytic activity of the nickel-based catalyst. The prepared nickel-based bimetallic multifunctional catalyst has a large specific surface area and abundant reactive active sites, which significantly enhances the catalytic activity of the catalyst and solves the problem of low electrocatalytic reaction activity and poor selectivity of nickel-based monometallic catalysts. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 This is a SEM image of the thiocyanate bridged complex precursor DMG-SCN-NiCo-Tu prepared in Example 1;

[0013] Figure 2 This is a SEM image of the nickel cobalt oxide nanocatalyst NiCoO prepared in Example 1;

[0014] Figure 3 The nickel cobalt oxide nanocatalyst NiCoO prepared in Example 1 was respectively 2 SO 4 +0.1mol / LKNO 3 and 0.5 mol / L Na 2 SO 4 Comparison of LSV scans in electrolyte;

[0015] Figure 4 These are LSV scanning comparison diagrams of the nickel cobalt oxide nanocatalyst NiCoO prepared in Example 1 in 1 mol / L KOH+0.33 mol / LUrea (urea) and 1 mol / L KOH electrolytes. 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] Embodiment 1: The preparation method of nickel-based bimetallic multifunctional catalyst comprises the following steps:

[0018] (1) Preparation of thiocyanate bridged complex precursor: First, 0.5 mmol nickel nitrate (Ni(NO 3 ) 2 ) and 0.5 mmol cobalt nitrate (Co(NO 3 ) 2 ) was dissolved in 10 mL of anhydrous ethanol to obtain solution A; then 2 mmol of potassium thiocyanate (KSCN) was dissolved in 10 mL of anhydrous ethanol to obtain solution B; then solution A and solution B were mixed, stirred evenly, and the precipitate was filtered to obtain a transparent solution C;

[0019] 2 mmol of dimethylglyoxime (DMG) and 2 mmol of thiourea (Tu) were ultrasonically dissolved in 30 mL of anhydrous ethanol to obtain a colorless transparent solution D;

[0020] Solution C and solution D were mixed and stirred at room temperature for 12 hours. After the reaction, the brown solid was centrifuged and washed with anhydrous ethanol and dried at 60°C to obtain the thiocyanate bridged complex precursor DMG-SCN-NiCo-Tu. The SEM image is shown in FIG. Figure 1 ;

[0021] (2) Preparation of nickel cobalt oxide nanocatalyst: The thiocyanate bridged complex precursor DMG-SCN-NiCo-Tu prepared in step (3) was placed in a muffle furnace, heated to 550°C at a heating rate of 3°C / min, and calcined for 2 hours. After calcination, it was naturally cooled to room temperature to obtain a nickel cobalt oxide nanocatalyst NiCoO, which is a nickel-based bimetallic multifunctional catalyst. Its SEM image is shown in Figure 2 .

[0022] Depend on Figure 1 and Figure 2 It can be seen that the prepared thiocyanate-bridged complex precursor DMG-SCN-NiCo-Tu and nickel cobalt oxide nanocatalyst NiCoO have an octahedral structure, which can provide abundant surface catalytic active sites and help improve the catalytic activity.

[0023] The nickel cobalt oxide nanocatalyst NiCoO prepared in Example 1 was 2 SO 4 +0.1mol / LKNO 3 and 0.5 mol / L Na 2 SO 4 The comparison of LSV scan in electrolyte is shown in Figure 3 .

[0024] The LSV scanning comparison diagrams of the nickel cobalt oxide nanocatalyst NiCoO prepared in Example 1 in 1 mol / L KOH+0.33 mol / L Urea and 1 mol / L KOH electrolytes are shown in Figure 4 .

[0025] Depend on Figure 3 and Figure 4 It can be seen that the prepared nickel cobalt oxide nanocatalyst NiCoO has excellent electrocatalytic performance in nitrate reduction and urea oxidation.

[0026] Embodiment 2: The preparation method of nickel-based bimetallic multifunctional catalyst comprises the following steps:

[0027] (1) Preparation of thiocyanate bridged complex precursor: First, 1 mmol nickel nitrate (Ni(NO 3 ) 2 ) and 1mmol cobalt nitrate (Co(NO 3 ) 2 ) was dissolved in 20 mL of anhydrous ethanol to obtain solution A; then 4 mmol of potassium thiocyanate (KSCN) was dissolved in 20 mL of anhydrous ethanol to obtain solution B; then solution A and solution B were mixed, stirred evenly, and the precipitate was filtered to obtain a transparent solution C;

[0028] 4 mmol of dimethylglyoxime DMG and 4 mmol of thiourea Tu were ultrasonically dissolved in 40 mL of anhydrous ethanol to obtain a colorless transparent solution D;

[0029] Solution C and solution D were mixed and stirred at room temperature for 12 hours. After the reaction, the brown solid was centrifuged and washed with anhydrous ethanol and dried at 60°C to obtain the thiocyanate bridged complex precursor DMG-SCN-NiCo-Tu.

[0030] (2) Preparation of nickel cobalt oxide nanocatalyst: The thiocyanate-bridged complex precursor DMG-SCN-NiCo-Tu prepared in step (3) is placed in a muffle furnace, heated to 550°C at a heating rate of 3°C / min, and calcined for 2 hours. After calcination, the mixture is naturally cooled to room temperature to obtain a nickel cobalt oxide nanocatalyst NiCoO, which is a nickel-based bimetallic multifunctional catalyst.

[0031] Embodiment 3: The preparation method of nickel-based bimetallic multifunctional catalyst comprises the following steps:

[0032] (1) Preparation of thiocyanate bridged complex precursor: First, 0.5 mmol nickel nitrate (Ni(NO 3 ) 2 ) and 0.5 mmol cobalt nitrate (Co(NO 3 ) 2 ) was dissolved in 10 mL of anhydrous ethanol to obtain solution A; then 2 mmol of potassium thiocyanate (KSCN) was dissolved in 10 mL of anhydrous ethanol to obtain solution B; then solution A and solution B were mixed, stirred evenly, and the precipitate was filtered to obtain a transparent solution C;

[0033] 2 mmol of dimethylglyoxime (DMG) and 2 mmol of thiourea (Tu) were ultrasonically dissolved in 30 mL of anhydrous ethanol to obtain a colorless transparent solution D;

[0034] Solution C and solution D were mixed and stirred at room temperature for 12 hours. After the reaction, the brown solid was centrifuged and washed with anhydrous ethanol and dried at 60°C to obtain the thiocyanate bridged complex precursor DMG-SCN-NiCo-Tu.

[0035] (2) Preparation of nickel cobalt oxide nanocatalyst: The thiocyanate-bridged complex precursor DMG-SCN-NiCo-Tu prepared in step (3) is placed in a muffle furnace, heated to 400°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 a nickel cobalt oxide nanocatalyst NiCoO, which is a nickel-based bimetallic multifunctional catalyst.

Claims

1. A method for preparing a nickel-based bimetallic multifunctional catalyst, characterized in that: The following steps are involved: (1) Preparation of thiocyanate bridged complex precursor: First, 0.5-1 mmol nickel nitrate and 0.5-1 mmol cobalt nitrate are dissolved in 10-20 mL anhydrous ethanol to obtain solution A; then 2-4 mmol potassium thiocyanate is dissolved in 10-20 mL anhydrous ethanol to obtain solution B; then solution A and solution B are mixed, stirred evenly, and the precipitate is filtered to obtain a transparent solution C; 1-4 mmol of diacetyl oxime and 1-4 mmol of thiourea are ultrasonically dissolved in 20-40 mL of anhydrous ethanol to obtain a colorless transparent solution D; Solution C and solution D are mixed and stirred at room temperature for 6 to 24 hours. After the reaction is completed, the brown solid is centrifuged and washed with anhydrous ethanol and dried at 60° C. to obtain a thiocyanate-bridged complex precursor DMG-SCN-NiCo-Tu. (2) Preparation of nickel cobalt oxide nanocatalyst: The thiocyanate bridged complex precursor DMG-SCN-NiCo-Tu prepared in step (3) is placed in a muffle furnace, heated to 300-600°C at a heating rate of 2-10°C / min, and calcined for 1-3 hours. After calcination, the mixture is naturally cooled to room temperature to obtain a nickel cobalt oxide nanocatalyst NiCoO, which is a nickel-based bimetallic multifunctional catalyst.

2. Use of the nickel-based bimetallic multifunctional catalyst prepared according to claim 1 in electrocatalytic nitrate reduction and urea oxidation.

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