Electrocatalytic material, preparation method and application thereof in electrooxidation of urea

Abstract

The application belongs to the technical field of electrocatalytic materials, and provides an electrocatalytic material, a preparation method and application of the electrocatalytic material in electrooxidation of urea, and the preparation method comprises the following steps: treating foamed nickel with nitric acid, ethanol and deionized water in sequence; dissolving nickel nitrate hexahydrate and potassium persulfate in deionized water, and then adding the treated foamed nickel, heating and reacting, cooling to room temperature, washing and drying to obtain an intermediate product; soaking the intermediate product in a solution containing sodium hypochlorite, collecting the product, and washing and drying. The S-NiOOH-Ni(OH)2 loaded on foamed nickel is prepared by two-step reaction of simple and readily available raw materials, the preparation method is simple, the required equipment and raw materials are abundant and low in price, easy to obtain and repeat, easy to control cost in industrial production, suitable for large-scale production, and stable in material quality; the prepared S-NiOOH-Ni(OH)2 electrocatalytic material loaded on foamed nickel can be used for urea wastewater treatment.

Description

Technical Field

[0001] This invention belongs to the field of electrocatalytic materials technology, and particularly relates to an electrocatalytic material, its preparation method, and its application in the electro-oxidation of urea. Background Technology

[0002] Urea, with the chemical formula CO(NH2)2, is a colorless or white needle- or rod-shaped crystal. It is currently the most widely used nitrogen fertilizer product with the highest nitrogen content on the market. Urea is also widely used in pharmaceuticals, food, cosmetics, textiles, and other fields, and is an important raw material for manufacturing chemical products such as melamine, urea-formaldehyde resin, and explosives. Due to the large production and consumption of urea, a large amount of urea wastewater (wastewater containing urea) is inevitably generated. This wastewater contains a large amount of ammonia nitrogen, and if directly discharged into the environment, it will inevitably cause environmental pollution. If it enters rivers and lakes, it will cause eutrophication, produce unpleasant odors, and even lead to mass fish deaths.

[0003] Currently, the main methods for treating urea wastewater include chemical catalytic hydrolysis, thermodynamic hydrolysis, urease hydrolysis, chemical oxidation, and biological hydrolysis. Among these, thermodynamic hydrolysis is the most widely used technology in practice. However, it is carried out under high temperature and high pressure conditions, which requires high conditions, large power, and high energy consumption, making it difficult for most small and medium-sized enterprises to afford. The above-mentioned urea wastewater treatment methods all suffer from problems such as high equipment investment costs and high condition requirements in industrial applications. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing electrocatalytic materials, aiming to solve the problems mentioned in the background art.

[0005] The present invention is implemented as follows: a method for preparing an electrocatalytic material includes the following steps:

[0006] The nickel foam was treated sequentially with nitric acid, ethanol, and deionized water.

[0007] Nickel nitrate hexahydrate and potassium persulfate were dissolved in deionized water, and then the treated nickel foam was added. The mixture was heated to react, and after the reaction was completed, it was cooled to room temperature. The product was collected, washed with ethanol and deionized water, and then dried to obtain the intermediate product, nickel foam loaded with Ni(OH)2@Ni(SO4). 0.3 (OH) 1.4 ;

[0008] The intermediate product was soaked in a solution containing sodium hypochlorite, the product was collected, washed with ethanol and deionized water, and then dried to obtain S-NiOOH-Ni(OH)2 electrocatalytic material supported on nickel foam.

[0009] Preferably, in the step of treating the nickel foam sequentially with nitric acid, ethanol and deionized water, the treatment is ultrasonic treatment for 10-15 min, and the concentration of the nitric acid is 1-1.2 mol / L.

[0010] Preferably, in the step of dissolving nickel nitrate hexahydrate and potassium persulfate in deionized water, the mass-to-volume ratio (g:g:mL) of nickel nitrate hexahydrate, potassium persulfate, and deionized water is 0.58-2.32:0.1-0.4:30-60.

[0011] Preferably, in the step of carrying out the heating reaction, the heating temperature is 140-160 °C and the time is 8-12 h.

[0012] Preferably, the method for preparing the sodium hypochlorite-containing solution is as follows: dissolving sodium hydroxide in a sodium hypochlorite solution, wherein the effective chlorine content of the sodium hypochlorite solution is 3-15%, and the weight-to-volume ratio of sodium hydroxide to sodium hypochlorite solution (g:mL) is 0.8-3.2:10-40.

[0013] Preferably, in the step of soaking the intermediate product in a solution containing sodium hypochlorite, the soaking time is 1-4 h and the temperature is 30-35 °C.

[0014] Another objective of this invention is to provide an S-NiOOH-Ni(OH)2 electrocatalytic material supported on nickel foam, which is prepared using the above-described preparation method.

[0015] Another objective of this invention is to provide an application of S-NiOOH-Ni(OH)2 electrocatalytic material supported on nickel foam in the electro-oxidation of urea.

[0016] Preferably, the electro-oxidation of urea is carried out in an H-type cell, with the S-NiOOH-Ni(OH)2 electrocatalytic material loaded on the nickel foam as the working electrode, a platinum sheet as the counter electrode, a mercury-mercury oxide electrode as the reference electrode, potassium hydroxide and urea as the anolyte, and potassium hydroxide as the catholyte, driving the urea to undergo an electro-oxidation reaction under energized conditions.

[0017] Preferably, the potential applied during energization is 1.1-1.7 V compared to the standard hydrogen electrode.

[0018] This invention provides a method for preparing an electrocatalytic material. Using readily available raw materials, a two-step reaction is used to prepare S-NiOOH-Ni(OH)2 supported on nickel foam. The preparation method is simple, the required equipment and raw materials are abundant and inexpensive, easy to obtain and reproducible, and the cost is easy to control in industrial production. It is suitable for large-scale production, and the material quality is stable. The prepared S-NiOOH-Ni(OH)2 electrocatalytic material supported on nickel foam can be used for urea wastewater treatment. Attached Figure Description

[0019] Figure 1 This is a transmission electron microscope image of the S-NiOOH-Ni(OH)2 electrocatalytic material supported on nickel foam provided in Example 1 of the present invention;

[0020] Figure 2 The near-side X-ray absorption fine structure spectra of sulfur in the S-NiOOH-Ni(OH)2 electrocatalytic material supported on nickel foam provided in Example 1 of the present invention and in different comparative samples;

[0021] Figure 3 The K-edge normalized absorption spectra of the S-NiOOH-Ni(OH)2 electrocatalytic material supported on nickel foam provided in Example 1 of this invention and different comparative samples;

[0022] Figure 4 This is a comparison of the linear sweep voltammetry curves of the samples prepared in Example 1 and Comparative Example 1 of this invention in a mixed electrolyte of potassium hydroxide and urea.

[0023] Figure 5 The curve showing the current versus time of the S-NiOOH-Ni(OH)2 electrocatalytic material supported on nickel foam provided in Example 1 of this invention;

[0024] Figure 6 The curve showing the change of urea feedstock concentration over time during the urea oxidation process is shown in Example 1 of this invention, which describes the application of the S-NiOOH-Ni(OH)2 electrocatalytic material supported on nickel foam.

[0025] Figure 7 To apply the S-NiOOH-Ni(OH)2 electrocatalytic material supported on nickel foam provided in Example 1 of this invention to the NH4 product during urea oxidation... + Concentration change curve over time. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0027] An electrocatalytic material of S-NiOOH-Ni(OH)2 supported on nickel foam, the preparation method of which includes the following steps:

[0028] S1. Cut the nickel foam NF into 3-10 cm pieces. 2 To meet the specifications, the cut nickel foam was ultrasonicated in 1 mol / L nitric acid for 10 min, in ethanol for 10 min, and in deionized water for 10 min in sequence.

[0029] S2. In the step of dissolving nickel nitrate hexahydrate and potassium persulfate in deionized water, the range is nickel nitrate hexahydrate (0.58-2.32 g), potassium persulfate (0.1-0.4 g), and water (30-60 mL). The treated nickel foam is also added to the solution in the reaction vessel and heated (150 °C, 10 h). After the reaction is completed and cooled to room temperature, the product is collected, washed with ethanol and deionized water, and then dried to obtain the intermediate product.

[0030] S3. The intermediate product was reacted in a sodium hypochlorite solution (0.8-3.2 g sodium hydroxide dissolved in 10-40 mL of sodium hypochlorite solution with an effective chlorine content of 6%) for 3 h (temperature 35 ℃), washed with deionized water and dried to obtain the final product, namely S-NiOOH-Ni(OH)2 electrocatalytic material supported on nickel foam.

[0031] The above-mentioned S-NiOOH-Ni(OH)2 electrocatalyst material supported on nickel foam is applied to the electrocatalytic oxidation of urea. The specific steps include: setting up an H-type electrolytic cell as the electrochemical reaction cell, adopting a three-electrode system, using the S-NiOOH-Ni(OH)2 electrocatalyst supported on nickel foam as the working electrode, the reference electrode as a mercury-mercury oxide electrode, the counter electrode as a platinum sheet, and the electrolyte as a 1 mol / L potassium hydroxide solution and a 0.33 mol / L urea solution. The potential applied when energized is 1.1-1.7 V compared to the standard hydrogen electrode.

[0032] The specific implementation of the present invention will be described in detail below with reference to specific embodiments.

[0033] Example 1: An electrocatalytic material of S-NiOOH-Ni(OH)2 supported on nickel foam, the specific preparation method of which is as follows:

[0034] Cut the 6 cm 2Rectangular nickel foam was treated sequentially with nitric acid, ethanol, and deionized water. Analytical grade nickel nitrate hexahydrate (1.16 g) and potassium persulfate (0.2 g) were dissolved in deionized water (30 mL) to obtain a solution. The treated nickel foam was added to the solution and heated in a high-pressure reactor at 150 °C for 10 h. After the reaction was completed and cooled to room temperature, the product was collected, washed with ethanol and deionized water, and then dried to obtain an intermediate product. This intermediate product was reacted in a sodium hypochlorite solution (1.6 g sodium hydroxide and 20 mL sodium hypochlorite solution with 6% available chlorine) at 35 °C for 3 h to obtain S-NiOOH-Ni(OH)2 electrocatalyst material supported on nickel foam.

[0035] Example 2: An S-NiOOH-Ni(OH)2 electrocatalytic material supported on nickel foam, the specific preparation method of which is as follows:

[0036] Cut the 10 cm 2 Rectangular nickel foam was treated sequentially with nitric acid, ethanol, and deionized water. Analytical grade nickel nitrate hexahydrate (2.32 g) and potassium persulfate (0.4 g) were dissolved in deionized water (60 mL) to obtain a solution. The treated nickel foam was added to the solution and heated in a high-pressure reactor at 150 °C for 10 h. After the reaction was completed and cooled to room temperature, the product was collected, washed with ethanol and deionized water, and then dried to obtain an intermediate product. This intermediate product was reacted in a sodium hypochlorite solution (3.2 g sodium hydroxide and 40 mL sodium hypochlorite solution with 6% available chlorine) at 35 °C for 3 h to obtain S-NiOOH-Ni(OH)2 electrocatalyst material supported on nickel foam.

[0037] Example 3: An electrocatalytic material of S-NiOOH-Ni(OH)2 supported on nickel foam, the specific preparation method of which is as follows:

[0038] Cut the 6 cm 2 Rectangular nickel foam was treated sequentially with nitric acid, ethanol, and deionized water. Analytical grade nickel nitrate hexahydrate (1.16 g) and potassium persulfate (0.2 g) were dissolved in deionized water (30 mL) to obtain a solution. The treated nickel foam was added to the solution and heated in a high-pressure reactor at 150 °C for 10 h. After the reaction was completed and cooled to room temperature, the product was collected, washed with ethanol and deionized water, and then dried to obtain an intermediate product. This intermediate product was reacted in a sodium hypochlorite solution (1.6 g sodium hydroxide and 20 mL sodium hypochlorite solution with an effective chlorine content of 3%) at 35 °C for 3 h to obtain S-NiOOH-Ni(OH)2 electrocatalyst material supported on nickel foam.

[0039] Example 4: An electrocatalytic material of S-NiOOH-Ni(OH)2 supported on nickel foam, the specific preparation method of which is as follows:

[0040] Cut the 6 cm 2 Rectangular nickel foam was treated sequentially with nitric acid, ethanol, and deionized water. Analytical grade nickel nitrate hexahydrate (1.16 g) and potassium persulfate (0.2 g) were dissolved in deionized water (30 mL) to obtain a solution. The treated nickel foam was added to the solution and heated in a high-pressure reactor at 150 °C for 10 h. After the reaction was completed and cooled to room temperature, the product was collected, washed with ethanol and deionized water, and then dried to obtain an intermediate product. This intermediate product was reacted in a sodium hypochlorite solution (1.6 g sodium hydroxide and 20 mL sodium hypochlorite solution with an effective chlorine content of 15%) at 35 °C for 3 h to obtain S-NiOOH-Ni(OH)2 electrocatalyst material supported on nickel foam.

[0041] Example 5: An electrocatalytic material of S-NiOOH-Ni(OH)2 supported on nickel foam, the specific preparation method of which is as follows:

[0042] Cut the 6 cm 2 Rectangular nickel foam was treated sequentially with nitric acid, ethanol, and deionized water. Analytical grade nickel nitrate hexahydrate (1.16 g) and potassium persulfate (0.2 g) were dissolved in deionized water (30 mL) to obtain a solution. The treated nickel foam was added to the solution and heated in a high-pressure reactor at 150 °C for 10 h. After the reaction was completed and cooled to room temperature, the product was collected, washed with ethanol and deionized water, and then dried to obtain an intermediate product. This intermediate product was reacted in a sodium hypochlorite solution (1.6 g sodium hydroxide and 20 mL sodium hypochlorite solution with 6% available chlorine) at 35 °C for 2 h to obtain S-NiOOH-Ni(OH)2 electrocatalyst material supported on nickel foam.

[0043] Example 6: An electrocatalytic material of S-NiOOH-Ni(OH)2 supported on nickel foam, the specific preparation method of which is as follows:

[0044] Cut the 6 cm 2Rectangular nickel foam was treated sequentially with nitric acid, ethanol, and deionized water. Analytical grade nickel nitrate hexahydrate (1.16 g) and potassium persulfate (0.2 g) were dissolved in deionized water (30 mL) to obtain a solution. The treated nickel foam was added to the solution and heated in a high-pressure reactor at 150 °C for 10 h. After the reaction was completed and cooled to room temperature, the product was collected, washed with ethanol and deionized water, and then dried to obtain an intermediate product. This intermediate product was reacted in a sodium hypochlorite solution (1.6 g sodium hydroxide and 20 mL sodium hypochlorite solution with 6% available chlorine) at 35 °C for 4 h to obtain S-NiOOH-Ni(OH)2 electrocatalyst material supported on nickel foam.

[0045] Comparative Example 1: A Ni-OOH electrocatalytic material supported on nickel foam, the specific preparation method of which is as follows:

[0046] Cut the 6 cm 2 Rectangular nickel foam was treated sequentially with nitric acid, ethanol, and deionized water. The raw materials selected were analytical grade nickel nitrate hexahydrate (0.44 g) and urea (0.12 g), dissolved in deionized water (30 mL). The treated nickel foam was added to the solution and heated in a high-pressure reactor at 200 °C for 12 h. After the reaction was completed and cooled to room temperature, the product was collected, washed with ethanol and deionized water, and then dried to obtain an intermediate product. The intermediate product was reacted in a sodium hypochlorite solution (1.6 g sodium hydroxide and 20 mL sodium hypochlorite solution with an effective chlorine content of 6%) at 35 °C for 3 h to obtain the final product, nickel foam supported on a NiOOH-Ni(OH)2 electrocatalytic material.

[0047] Performance testing:

[0048] The S-NiOOH-Ni(OH)2 electrocatalytic material supported on nickel foam prepared in Example 1 was analyzed, and the transmission electron microscope image is shown below. Figure 1 As shown, this proves that the material is made of Ni(SO4). 0.3 (OH) 1.4 Composed of NiOOH; its near-side X-ray absorption fine structure spectra of sulfur in different comparison samples are as follows: Figure 2 As shown, the presence of a +6 valence sulfur oxide peak in S-NiOOH-Ni(OH)2 indicates that the sulfur element in this material exists in the form of sulfate. Comparative analysis with nickel hydroxide and nickel foil samples yielded the following K-edge normalized absorption spectrum: Figure 3 As shown, this proves that the valence state of nickel in S-NiOOH-Ni(OH)2 exceeds +2.

[0049] The samples prepared in Example 1 and Comparative Example 1 were cut to suitable specifications and used as electrocatalytic materials to test their electro-oxidation performance in urea solution. An H-type electrolytic cell was set up as the electrochemical reaction cell, employing a three-electrode system. The anode and cathode chambers were separated by anion exchange membranes. The sample was used as the working electrode, a platinum sheet as the counter electrode, and a mercury / mercury oxide electrode as the reference electrode. The electrolyte was a 1 mol / L potassium hydroxide and 0.33 mol / L urea solution. Testing with an electrochemical workstation showed that the applied potential during energization was 1.1-1.7 V compared to the standard hydrogen electrode, yielding the following results: Figure 4 The linear sweep voltammetry curve shown is based on Figure 4 It can be seen that the electrocatalytic material prepared in the embodiments of the present invention achieves a flux of 505 mA / cm² in a solution of 1 mol / L potassium hydroxide and 0.33 mol / L urea. 2 The required current density is only 1.4 V (relative to the standard hydrogen electrode); stability tests were performed on the sample prepared in Example 1, and the current-time curve is shown below. Figure 5 As shown; when the sample prepared in Example 1 was used as an electrocatalytic material to test its electro-oxidation performance in urea solution, the curve of the change of raw material concentration over time was obtained as shown. Figure 6 As shown, the product NH4 + The concentration change curve over time is shown in the figure. Figure 7 As shown.

[0050] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing an electrocatalytic material, characterized by, The method comprises the following steps: The nickel foam is treated with nitric acid, ethanol and deionized water in sequence; Dissolve nickel nitrate hexahydrate, potassium persulfate and deionized water in a mass-volume ratio of 0.58-2.32:0.1-0.4:30-60 g:g:mL, then add treated foamed nickel, heat and react, cool to room temperature after reaction, collect the product, wash with ethanol and deionized water, and dry to obtain the intermediate product foamed nickel loaded with Ni(OH)2@Ni(SO4) 0.3 (OH) 1.4 ; The intermediate product is soaked in a solution containing sodium hypochlorite, and the product is collected, washed with ethanol and deionized water, and dried to obtain the S-NiOOH-Ni(OH)2 electrocatalytic material loaded on the nickel foam, wherein the solution containing sodium hypochlorite is prepared by dissolving sodium hydroxide in a sodium hypochlorite solution, the effective chlorine content of the sodium hypochlorite solution is 3-15%, and the weight-volume ratio g:mL of the sodium hydroxide and sodium hypochlorite solution is 0.8-3.2:10-40.

2. The method of claim 1, wherein the electrocatalytic material is prepared by a method comprising: In the step of treating the nickel foam with nitric acid, ethanol and deionized water in sequence, the treatment is ultrasonic treatment, the time is 10-15 min, and the concentration of the nitric acid is 1-1.2 mol / L.

3. The method of claim 1, wherein the electrocatalytic material is prepared by a method comprising: In the step of heating reaction, the heating temperature is 140-160 ℃, and the time is 8-12 h.

4. The method of claim 1, wherein the electrocatalytic material is prepared by a method comprising: In the step of soaking the intermediate product in the solution containing sodium hypochlorite, the soaking time is 1-4 h, and the temperature is 30-35 ℃.

5. A S-NiOOH-Ni(OH)2 electrocatalytic material supported on a foamed nickel, characterized in that, The S-NiOOH-Ni(OH)2 electrocatalytic material loaded on the nickel foam is prepared by the preparation method of any one of claims 1-4.

6. The S-NiOOH-Ni(OH)2 electrocatalytic material loaded on the nickel foam according to claim 5 is used in the electrooxidation of urea.

7. Use according to claim 6, characterized in that, The electrooxidation of urea is carried out in an H-type cell, the S-NiOOH-Ni(OH)2 electrocatalytic material loaded on the nickel foam is used as a working electrode, a platinum sheet is used as a counter electrode, a mercury-mercury oxide electrode is used as a reference electrode, potassium hydroxide and urea are used as an anode electrolyte, and potassium hydroxide is used as a cathode electrolyte, and the urea is driven to carry out an electrooxidation reaction under the condition of power supply.

8. Use according to claim 7, characterized in that, The potential applied during the power supply is 1.1-1.7 V compared with a standard hydrogen electrode.

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