Preparation method and application of leaf-shaped Sn-Ni electrocatalytic oxidation electrode

Abstract

The present invention discloses a method for preparing a leaf-shaped Sn-Ni electrocatalytic oxidation electrode. Specifically, the method comprises the following steps: pre-treating a substrate made of a conductive material, placing the pre-treated substrate in a RECl3-PVP solution and mixing the mixture, sealing the mixture in an autoclave for reaction, performing solid-liquid separation, and washing the solid to obtain a self-cleaning light-emitting electrode substrate; using the self-cleaning light-emitting electrode substrate as a cathode and a graphite electrode as an anode, placing the anode and cathode electrodes in a Ni-Sn / SD electroplating solution, and performing electroplating at room temperature at a voltage of 5-15 V and a current density of 4-8 mA / cm 2 , and then air-dried after the reaction; the leaf-shaped Sn-Ni electrocatalytic oxidation electrode was applied to the degradation of ammonia nitrogen, with a nitrate nitrogen removal rate of more than 75%, a high electrode catalytic efficiency, and great application prospects.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrocatalytic water treatment, and in particular relates to a preparation method and application of a leaf-shaped Sn-Ni ammonia nitrogen selective electrocatalytic nitrification electrode. Background Art

[0002] In recent years, with the development of industrialization, the pollution problem caused by ammonia nitrogen wastewater has become increasingly serious. Ammonia nitrogen is one of the important factors that destroy the balance of water bodies and cause eutrophication of water bodies. Its excessive discharge will cause great harm to the ecological environment and human body. It will not only promote eutrophication of water bodies, but also produce odor and cause obstacles to water supply. Ammonia nitrogen in water mainly comes from wastewater and leachate discharge from industries such as fertilizers, leather making, breeding, petrochemicals, meat processing, as well as urban sewage and agricultural irrigation drainage. The World Health Organization and the U.S. Environmental Protection Agency limit the maximum pollutant content in drinking water to 50mg / L (NO3 - ) and 10mg / L (NO3-N). Therefore, how to remove ammonia nitrogen from wastewater economically and efficiently has become a research hotspot in recent years. Due to the environmental adaptability, stability and ease of operation of electrochemical technology, it is considered to be the most promising technology for industrial promotion.

[0003] Electrode materials influence both kinetics and product selectivity during electrochemical nitrate reduction. Therefore, the key to electrocatalytic reduction technology lies in the selection of electrode materials and catalysts. High-performance materials possess electrocatalytic properties, high conductivity, and stability. Precious metals such as Pt, Pd, and Ru, while exhibiting good electrocatalytic activity, are relatively expensive. Ni-Sn exhibits high reaction kinetics, but its reactivity is poor when used as a pure nickel cathode. Therefore, the introduction of Sn to modify electrode performance and surface morphology in order to identify superior electrodes is crucial for water treatment research. Summary of the Invention

[0004] In response to the problems in the prior art, the present invention provides a method for preparing a leaf-shaped Sn-Ni electrocatalytic oxidation electrode, which solves the problem of low wastewater treatment efficiency in the past and can be used for electrocatalytic reduction of nitrate nitrogen in water.

[0005] The preparation method of the leaf-shaped Sn-Ni electrocatalytic oxidation electrode of the present invention is as follows:

[0006] (1) After pre-treating a substrate made of a conductive material, the pre-treated substrate is placed in a RECl3-PVP solution and mixed evenly, then sealed in an autoclave, reacted at 160-200°C for 1-3 hours, solid-liquid separation, and the solid is cleaned to obtain a self-cleaning light-emitting electrode substrate;

[0007] The RECl3-PVP solution is prepared by dissolving RECl3 and polyvinyl pyrrolidone (PVP) in ethylene glycol respectively, stirring and mixing, and then adding the RECl3 solution dropwise to the polyvinyl pyrrolidone solution and mixing. The RECl3 is yttrium chloride, lanthanum chloride, cerium chloride, europium chloride or terbium chloride, and the mass ratio of RECl3 to polyvinyl pyrrolidone is 1:1-2.

[0008] The conductive material is one of titanium, ruthenium, ITO, and carbon cloth. The substrate pretreatment is to polish the conductive material with sandpaper and wash it with water, then wash it with acetone, anhydrous ethanol, and water in sequence, and dry it for use.

[0009] (2) nickel ammonium sulfate hexahydrate and stannous chloride are placed in water, mixed, and then sodium lauryl sulfate is added, and then sodium citrate is added and mixed to prepare a Ni-Sn / SD electrodeposition solution;

[0010] The molar ratio of nickel ammonium sulfate hexahydrate to stannous chloride is 1-4:1, the molar ratio of stannous chloride to sodium lauryl sulfate is 40-60:1, and the molar ratio of stannous chloride to sodium citrate is 20-40:1;

[0011] (3) The self-cleaning light-emitting electrode substrate of step (1) is used as the cathode and the graphite electrode is used as the anode. The cathode and anode electrodes are placed in the Ni-Sn / SD electroplating solution and electroplated at room temperature with a voltage of 5-15 V and a current density of 4-8 mA / cm 2 After the reaction, the leaf-shaped Sn-Ni electrocatalytic oxidation electrode was obtained by air drying.

[0012] Another object of the present invention is to apply the leaf-shaped Sn-Ni electrocatalytic oxidation electrode prepared by the above method to the degradation of ammonia nitrogen.

[0013] Advantages and technical effects of the present invention:

[0014] 1. After the electrode substrate of the present invention is doped with Sn-Ni, the electrochemical performance and surface morphology of the electrode are modified, so that it has good stability. At the same time, the leaf-shaped tip has the advantages of multiple reaction sites, good corrosion resistance, and a high specific surface area, which effectively improves the efficiency of electrocatalytic reduction of ammonia nitrogen and degradation of organic pollutants.

[0015] 2. The present invention selects two non-precious metals (Sn and Ni) as catalysts. Ni metal has a good promoting effect on the rate-limiting step of the nitrate reduction process. The electrolysis product of the Sn-Ni electrode is mainly nitrogen, with a selectivity between 50% and 70%. At the same time, the dendritic tips can generate a large voltage, thereby producing more active substances such as free radicals, thereby enhancing the degradation of pollutants in water;

[0016] 3. The present invention adopts electrodeposition preparation, which has a simple method, good stability and long storage time; the Sn-Ni nanoelectrode prepared by the present invention has better ammonia nitrogen and organic matter removal efficiency than conventional electrodes. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a SEM image of the leaf-shaped Sn-Ni electrocatalytic oxidation electrode prepared by the method of the present invention;

[0018] Figure 2 The ammonia nitrogen purification effect of the electrode in Example 1;

[0019] Figure 3 This is the ammonia nitrogen purification effect of the electrode in Example 2. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical solutions and advantages of the present invention more understandable, the present invention is further described in detail below with reference to the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention;

[0021] Example 1: Preparation and application of leaf-shaped Sn-Ni electrocatalytic oxidation electrode are as follows:

[0022] 1. Polish a titanium mesh with a purity of 99.9% and a thickness of 0.2 mm with 300-mesh and 600-mesh sandpaper until there are no scratches on the surface. Rinse the surface with deionized water and place it in acetone, anhydrous ethanol, and deionized water for 10 minutes each. Take it out and dry it for later use.

[0023] 2. Place the pretreated titanium mesh in a reaction vessel, dissolve 0.435g YCl3 and 0.676g PVP in 15mL and 30mL ethylene glycol, respectively. Then, under vigorous stirring, slowly drip the YCl3 solution into the PVP solution to form a uniform solution. Then, place it in an autoclave and seal it. After reacting at 180°C for 2h, separate the solid and liquid, and wash the solid with anhydrous ethanol and water three times each to obtain a self-cleaning light-emitting electrode substrate.

[0024] 3. Ammonium nickel sulfate hexahydrate and stannous chloride are placed in water, mixed, and then sodium lauryl sulfate is added, followed by sodium citrate, and mixed to prepare a Ni-Sn / SD electrodeposition solution, wherein the molar ratio of ammonium nickel sulfate hexahydrate to stannous chloride is 2:1, the molar ratio of stannous chloride to sodium lauryl sulfate is 50:1, and the molar ratio of stannous chloride to sodium citrate is 30:1;

[0025] 4. With the graphite electrode as the anode and the self-cleaning light-emitting electrode substrate as the cathode, the cathode and the cathode were placed in the Ni-Sn / SD electrodeposition solution and electrodeposited at room temperature with a voltage of 10 V and a current density of 5 mA / cm 2After 30 minutes of reaction, the Sn-Ni electrocatalytic oxidation electrode was obtained by natural air drying. The SEM image of the electrode is shown in Figure 1 The image shows that the material on the electrode grows on the substrate, forming an orderly fern-leaf-shaped structure through a certain crystal arrangement. This structure effectively increases the contact area between the electrode and the pollutant, and has excellent catalytic activity.

[0026] 5. Electrocatalytic reduction of simulated wastewater using the above-mentioned leaf-shaped Sn-Ni electrocatalytic oxidation electrode

[0027] 490 mL of wastewater containing 100 mg / L of nitrate nitrogen was simulated, 0.5 g / L of sodium sulfate was used as the electrolyte, the prepared leaf-like catalytic electrode was used as the cathode, the graphite electrode was used as the anode, and the distance between the cathode and the anode was 3 cm. At this time, the current density was 20 mA / cm 2 , the electrocatalytic reduction reaction was carried out for 2 hours. The relationship between the removal effect of nitrate nitrogen and time is shown in the figure. Figure 2 As shown, after 2 hours of electrocatalysis, the removal rate of nitrate nitrogen is 75%, and the electrode catalytic efficiency of the present invention is relatively high.

[0028] Example 2: Preparation and application of leaf-shaped Sn-Ni electrocatalytic oxidation electrode are as follows:

[0029] 1. Polish the ITO plate with a purity of 99.9% and a thickness of 0.2 mm with 300-mesh and 600-mesh sandpaper until there are no scratches on the surface. Rinse the surface with deionized water, then place it in acetone, anhydrous ethanol, and deionized water for ultrasonic treatment for 10 minutes each, then take it out and dry it for later use.

[0030] 2. Place the pretreated ITO substrate in a reaction vessel, dissolve 0.435g EuCl3 and 0.676g PVP in 15mL and 30mL ethylene glycol, respectively, and then slowly drip the EuCl3 solution into the PVP solution under vigorous stirring to form a uniform solution. Then, place it in an autoclave and seal it. After reacting at 180°C for 2h, separate the solid and liquid, and wash the solid with anhydrous ethanol and water three times each to obtain a self-cleaning light-emitting electrode substrate;

[0031] 3. Nickel ammonium sulfate hexahydrate and stannous chloride are placed in water, mixed, and then sodium lauryl sulfate is added, followed by sodium citrate, and mixed to prepare a Ni-Sn / SD electrodeposition solution, wherein the molar ratio of nickel ammonium sulfate hexahydrate to stannous chloride is 1:1, the molar ratio of stannous chloride to sodium lauryl sulfate is 45:1, and the molar ratio of stannous chloride to sodium citrate is 35:1;

[0032] 4. Using the graphite electrode as the anode and the self-cleaning light-emitting electrode substrate as the cathode, the cathode and the cathode were placed in the Ni-Sn / SD electrodeposition solution and electrodeposited at room temperature with a voltage of 8 V and a current density of 7 mA / cm 2 After 25 min of reaction, the mixture was naturally air-dried to obtain a leaf-shaped Sn-Ni electrocatalytic oxidation electrode.

[0033] 5. Simulate 490 mL of wastewater containing 100 mg / L of nitrate nitrogen, use 0.5 g / L sodium sulfate as electrolyte, the prepared leaf-like catalytic electrode as cathode, the graphite electrode as anode, and the distance between the cathode and anode is 3 cm. At this time, the current density is 20 mA / cm 2 , the electrocatalytic reduction reaction was carried out for 2 hours. The relationship between the removal effect of nitrate nitrogen and time is shown in the figure. Figure 3 As shown, after 2 hours of electrocatalysis, the removal rate of nitrate nitrogen is 82%, and the electrode catalytic efficiency of the present invention is relatively high.

Claims

1. A method for preparing a leaf-shaped Sn-Ni electrocatalytic oxidation electrode, characterized in that: Here are the steps: (1) After pre-treating the substrate made of conductive material, the pre-treated substrate is placed in a RECl3-PVP solution and mixed evenly, then sealed in an autoclave, reacted at 160-200°C for 1-3h, solid-liquid separation, and the solid is washed to obtain a light-emitting electrode substrate; (2) nickel ammonium sulfate hexahydrate and stannous chloride are placed in water, mixed, and then sodium lauryl sulfate is added, and then sodium citrate is added and mixed to prepare a Ni-Sn / SD electrodeposition solution; (3) The light-emitting electrode substrate of step (1) is used as the cathode and the graphite electrode is used as the anode. The cathode and anode electrodes are placed in the Ni-Sn / SD electroplating solution and electroplated at room temperature with a voltage of 5-15 V and a current density of 4-8 mA / cm 2 After the reaction, the leaf-shaped Sn-Ni electrocatalytic oxidation electrode was obtained by air drying. The RECl3-PVP solution is prepared by dissolving RECl3 and polyvinyl pyrrolidone in ethylene glycol respectively, stirring and mixing, and then adding the RECl3 solution dropwise to the polyvinyl pyrrolidone solution and mixing. The RECl3 is yttrium chloride or europium chloride, and the mass ratio of RECl3 to polyvinyl pyrrolidone is 1:1-2.

2. The method for preparing the leaf-shaped Sn-Ni electrocatalytic oxidation electrode according to claim 1, wherein: The conductive material is one of titanium, ruthenium, ITO, and carbon cloth. The substrate pretreatment is that the conductive material is polished with sandpaper and cleaned with water, and then cleaned with acetone, anhydrous ethanol, and water in sequence, and dried for use.

3. The method for preparing the leaf-shaped Sn-Ni electrocatalytic oxidation electrode according to claim 1, wherein: The molar ratio of nickel ammonium sulfate hexahydrate to stannous chloride is 1-4:1, the molar ratio of stannous chloride to sodium lauryl sulfate is 40-60:1, and the molar ratio of stannous chloride to sodium citrate is 20-40:

1.

4. Use of the leaf-shaped Sn-Ni electrocatalytic oxidation electrode prepared by the method for preparing the leaf-shaped Sn-Ni electrocatalytic oxidation electrode according to any one of claims 1 to 3 in nitrate nitrogen degradation.

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