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CN-122010247-A - Manufacturing method and application of electrode for electrocatalytic reduction of nitrate

CN122010247ACN 122010247 ACN122010247 ACN 122010247ACN-122010247-A

Abstract

The invention discloses a manufacturing method of an electrode for electrocatalytic reduction of nitrate, an electrode product and application thereof, and belongs to the technical field of electrochemical water treatment of environmental engineering. The invention adopts a sol-gel-step heat treatment method to prepare a titanium-based double-layer structure cobalt-doped tin dioxide electrode, wherein the bottom layer is an antimony-containing cobalt-tin oxide conductive layer, the surface layer is an antimony-free cobalt-tin oxide catalytic layer, and the mol ratio of tin to cobalt of the two layers is 5:1-7:1. The invention overcomes the technical prejudice that the titanium-based antimony doped tin dioxide electrode in the field can only be used for anodic oxidation and can not be used for cathodic nitrate reduction, the Faraday efficiency of the prepared electrode in 1000mg/L high-concentration nitrate wastewater is up to 97.2%, the ammonia nitrogen selectivity is 99.3%, the performance attenuation of continuous operation for 500h is only 6.3%, and the electrode has high catalytic activity, high product selectivity and long-term operation stability, is suitable for the treatment of various nitrate polluted water bodies, and can synchronously realize harmless treatment of pollutants and recycling of ammonia nitrogen.

Inventors

  • WANG DONGLIANG
  • HE JIAQING
  • WU JINGXUAN
  • LI YUXIAO
  • ZHANG JIAQUAN
  • ZHANG YANLIN
  • LIU ZIGUO
  • ZHENG HAN

Assignees

  • 湖北理工学院

Dates

Publication Date
20260512
Application Date
20260309

Claims (10)

  1. 1. A method for manufacturing an electrode for electrocatalytic reduction of nitrate, comprising the steps of: S1, providing a titanium substrate, and sequentially carrying out sand blasting treatment and oxalic acid solution etching activation treatment on the surface of the titanium substrate to complete pretreatment; S2, respectively preparing an antimony-containing cobalt-tin oxide sol A and an antimony-free cobalt-tin oxide sol B, wherein the sol A and the sol B both use alcohols as solvents and organic acids as complexing agents, and the molar ratio of tin element to cobalt element is 5:1-7:1; S3, uniformly coating the sol A on the surface of the pretreated titanium substrate, drying at 100-140 ℃ and carrying out isothermal heat treatment at 400-500 ℃ for 8-15min, and repeating the coating-drying-heat treatment steps for 5-10 times to form a conductive bottom layer on the surface of the titanium substrate, wherein the coating times of the conductive bottom layer are not less than the coating times of the subsequent catalytic surface layer; S4, uniformly coating the sol B on the surface of the conductive bottom layer, repeating the coating for 5-10 times by adopting the same drying and single heat treatment process as in the step S3 to form a catalytic surface layer, wherein the isothermal heat treatment time of 400-500 ℃ after the last coating is prolonged to 1.5-3h, and is longer than the previous single heat treatment time, and cooling to obtain the cobalt-doped tin dioxide titanium-based electrode.
  2. 2. The method according to claim 1, wherein the molar ratio of tin element to cobalt element in the sol a and the sol B is 6:1.
  3. 3. The preparation method of the organic acid complexing agent according to claim 1, wherein the antimony source in the sol A is at least one of antimonous oxide and antimonous chloride, the alcohol solvent is at least one of ethylene glycol and absolute ethyl alcohol, and the organic acid complexing agent is at least one of citric acid and oxalic acid.
  4. 4. The method according to claim 1, wherein the step of coating, drying and heat-treating the sol A is repeated 8 times in step S3, and the step of coating, drying and heat-treating the sol B is repeated 7 times in step S4.
  5. 5. The method according to claim 1, wherein the rate of rise and fall of all heat treatment steps in steps S3 and S4 is 3-8 ℃.
  6. 6. The method according to claim 1, wherein in the step S1, the oxalic acid solution etching activation treatment is specifically that the titanium substrate after sand blasting is placed in 8-12wt% oxalic acid solution with constant temperature of 90-100 ℃ and soaked in water bath for 3-5 hours, and the treated titanium substrate is placed in 4-6wt% oxalic acid solution for sealing and preservation.
  7. 7. The method according to claim 1, wherein the amount of sol a or sol B applied once per square centimeter of the titanium substrate surface is 40 to 50 μl.
  8. 8. An electrode for electrocatalytic reduction of nitrate is characterized by comprising a titanium substrate, an antimony-containing cobalt-tin oxide conductive bottom layer sintered on the surface of the titanium substrate and an antimony-free cobalt-tin oxide catalytic surface layer sintered on the surface of the conductive bottom layer, wherein the molar ratio of tin element to cobalt element in the conductive bottom layer to the catalytic surface layer is 5:1-7:1, the thickness of the conductive bottom layer is 8-12 mu m, and the thickness of the catalytic surface layer is 5-8 mu m.
  9. 9. An electrocatalytic treatment method for water nitrate is characterized by taking the electrode as a working cathode, taking a titanium-based noble metal oxide electrode as an anode and taking a saturated KCl filled Ag/AgCl electrode as a reference electrode, constructing a three-electrode constant potential electrolysis system, and applying a constant working potential of-0.8 to-1.6V to the working cathode to a water body with nitrate concentration of 100-2000mg/L, pH value of 5-9 and sodium sulfate supporting electrolyte of 0.02-0.1mol/L, so as to directionally convert the nitrate in the water body into ammonia nitrogen through electrocatalytic reduction.
  10. 10. The method according to claim 9, wherein the constant operating potential is-1.0 to-1.4V, and the nitrate concentration of the water body is 500-1500mg/L.

Description

Manufacturing method and application of electrode for electrocatalytic reduction of nitrate Technical Field The invention belongs to the technical field of electrochemical water treatment in environmental engineering, and particularly relates to a preparation method of a titanium-based electrode for electrocatalytic reduction of nitrate, an electrode product prepared by the method, and application of the electrode in water nitrate pollution treatment. Background Nitrate pollution is a prominent water environment problem in the global scope, excessive nitrate can cause eutrophication after entering a water body, the balance of a water ecological system is destroyed, and meanwhile, the nitrate can be converted into nitrite after entering a human body through drinking water, so that serious threat is caused to the health of the human body. The existing water nitrate removal technology mainly comprises three major categories, namely a physical method, a chemical method and a biological method, wherein the physical method such as ion exchange, reverse osmosis, electrodialysis and the like can only realize the phase transfer of nitrate, cannot complete the thorough degradation of pollutants, is easy to produce secondary pollution and high in subsequent treatment cost, the chemical reduction method needs to add a large amount of strong reducing agent, has high operation cost and large process control difficulty, is easy to introduce new pollutants, and the biological denitrification method has strict requirements on environmental conditions such as water temperature, pH value, dissolved oxygen, carbon nitrogen ratio and the like, has poor adaptability to industrial wastewater with high salt and toxic substances, particularly cannot stably treat high-concentration nitrate wastewater, and has serious application scene. The electrocatalytic reduction denitrification technology can directionally reduce nitrate into ammonia nitrogen capable of being recycled under mild conditions, has the advantages of both pollutant harmlessness and resource recycling, and becomes a research hot spot in the field of water treatment in recent years. The reaction efficiency and the product selectivity of the electrocatalytic reduction of nitrate are based on the intrinsic characteristics of an electrode catalyst, in the prior study, transition metal oxides such as copper, iron, cobalt and the like show certain ammonia nitrogen selectivity, but the problems of low electrocatalytic efficiency and serious hydrogen evolution side reaction are commonly existed, while the tin oxide-based material has certain nitrate reduction activity, but pure-phase tin oxide has poor conductivity and insufficient mechanical stability, and cannot be prepared into an integrated electrode capable of being industrially applied, and the prior study also does not realize the stable and efficient operation of the integrated electrode in high-concentration nitrate wastewater. The titanium-based coating electrode has been applied in the field of water treatment anodic oxidation in a large scale because of excellent conductivity, corrosion resistance and mechanical stability, wherein the titanium-based antimony doped tin dioxide electrode is a classical anodic catalytic electrode, but the field has long-standing common technical prejudice that the electrode is only suitable for anodic oxidation scenes, if the electrode is used in a cathodic reduction environment, an antimony dopant in the electrode can be reduced and dissolved out, so that the conductivity of the electrode is rapidly reduced, meanwhile, the hydrogen evolution overpotential of the electrode is low, serious hydrogen evolution side reaction can occur when the electrode is used in a cathode, and the requirement of electrocatalytic reduction of nitrate can not be met completely. In the prior art, although a small amount of modification is carried out on the titanium-based tin dioxide electrode for nitrate reduction, the contradiction between the conductivity and the catalytic activity of the electrode can not be solved all the time, the high ammonia nitrogen selectivity, the high Faraday efficiency and the long-term operation stability can not be considered, and the industrial treatment requirement of the wide concentration range, especially the high concentration nitrate wastewater can be met by a non-mature scheme. Disclosure of Invention In view of the above, the invention provides a method for manufacturing an electrode for electrocatalytic reduction of nitrate, an electrode product manufactured by the method, and a water nitrate treatment method based on the electrode, which aim to overcome the defects in the prior art, solve the technical problems that the titanium-based tin dioxide electrode cannot take conductivity, catalytic activity, product selectivity and long-term stability into account, and break through the technical prejudice that the titanium-based antimony doped tin dioxide electrode can