A supported CuMnO x Composite cathode and method of making and use thereof

Abstract

The application discloses a supported CuMnO x The application discloses a composite cathode, a preparation method and application thereof. The method is as follows: after a porous metal substrate is subjected to electrochemical etching, copper is in-situ deposited on the surface of the substrate through electrodeposition to obtain a copper-plated cathode precursor; and the copper-plated cathode precursor is subjected to a hydrothermal reaction in a solution containing potassium permanganate to obtain the composite cathode. x The composite cathode catalyst has high porosity and rich specific surface area, increases active sites for electrocatalytic reduction of nitrate nitrogen, and can be stably operated for a long time under high-salt conditions, so that nitrate nitrogen in high-salt wastewater can be effectively removed. The composite cathode has low raw material cost, is environment-friendly, has simple preparation process, is easy to realize industrial production, and has wide market application prospect.

Description

TECHNICAL FIELD

[0001] The present application relates to a supported CuMnO x The present application relates to a supported CuMnO x The present application relates to a supported CuMnO BACKGROUND

[0002] In agricultural production, due to the large use of nitrogen fertilizer, and the discharge of a large amount of nitrate-containing waste water in the process of industrial manufacturing and metal processing, a large amount of nitrate enters the water body, causing environmental pollution. For the human body, when a large amount of nitrate enters the human body, it can cause the human body to suffer from methemoglobinemia and even cancer, causing great harm to human health. Therefore, nitrate degradation has become a problem that people have to solve.

[0003] Among the methods for treating nitrate, the physicochemical method inevitably has problems such as post-treatment, because the nitrate does not degrade and truly disappear in the process, but is only transferred or concentrated. Biological denitrification uses the metabolic activity of microorganisms to achieve the purpose of removing organic and inorganic pollutants in water, but the use of biological methods requires a long hydraulic retention time, and the treated water may be contaminated by microorganisms and their metabolites, and the treatment performance may also be affected by factors such as dissolved oxygen and temperature. As a green and environmentally friendly technology without secondary pollution, cathodic electrocatalytic reduction of nitrate is considered to be a very promising alternative method, but the current electrocatalytic reduction of nitrate technology generally has problems such as low removal rate of nitrate by cathode catalyst and poor stability of catalyst.

[0004] For example, Chinese patent 202210893962.9 discloses a preparation of vacancy ceria supported bimetallic nanoparticles and its application in electrocatalytic reduction of nitrate, and the disclosed vacancy ceria supported bimetallic nanoparticle catalyst has a nitrate removal rate of only 80% for 50 mg / L of nitrate, and its degradation efficiency needs to be improved. Chinese patent 202210563213.X discloses a preparation method of single-atom transition metal / nitrogen-doped mesoporous carbon material for electrocatalytic reduction of nitrate to produce nitrogen, and the disclosed single-atom iron / nitrogen-doped mesoporous carbon material has a nitrate removal rate of only 76.9% for 50 mg / L of nitrate wastewater, and the nitrate removal rate of the catalyst sample decreases to 67% after 6 cycles of degradation. As can be seen from the above, the catalytic activity and cycle stability of the electrocatalytic reduction of nitrate catalyst still need to be improved. SUMMARY

[0005] In view of the defects in the existing electrocatalytic reduction of nitrate technology, the first object of the present application is to provide a supported CuMnOx Composite cathode. The composite cathode uses porous metal as the substrate, and its high porosity and abundant specific surface area can effectively increase the electrocatalytic reduction of nitrate nitrogen CuMnO x The loading amount of active material, and the loaded CuMnO x The composite cathode's needle-like and flower-ball-like morphologies synergistically contribute to its excellent catalytic activity. The porous metal substrate also further enhances the cathode's corrosion resistance and stability, ensuring cycling stability.

[0006] The second object of the present invention is to provide a supported CuMnO x The invention discloses a method for preparing a composite cathode, which adopts a simple electrodeposition method and a hydrothermal method, has a simple preparation process, low raw material cost, and is conducive to large-scale industrial production and application.

[0007] The third object of the present invention is to provide a supported CuMnO x The application of composite cathode is to apply it to electrocatalytic reduction of nitrate nitrogen. x Under the joint action of active substances, more active sites can be provided to ensure the full reduction of nitrate nitrogen, thereby greatly improving the removal rate and stability of nitrate nitrogen under high salt conditions.

[0008] In order to achieve the above technical objectives, the present invention provides a supported CuMnO x A method for preparing a composite cathode comprises electrochemically etching a porous metal substrate and then in-situ depositing copper on its surface by electrodeposition to obtain a copper-plated cathode precursor; the copper-plated cathode precursor is placed in a solution containing potassium permanganate and subjected to a hydrothermal reaction to obtain the composite cathode.

[0009] In the technical solution of the present invention, the porous metal substrate is first subjected to electrochemical etching and roughening treatment, so that the porous metal substrate has a larger specific surface area, thereby further increasing the CuMnO x The loading amount of active substances effectively improves the efficiency of electrocatalytic reduction of nitrate nitrogen. Then, a layer of copper with uniform thickness is deposited on the surface of the porous metal substrate by in-situ electrodeposition, thereby obtaining a cathode precursor with uniform copper plating on the surface. Finally, potassium permanganate is first reduced to a low-valent state of Mn through a hydrothermal reaction. 2+ , then Mn 2+ and Cu 2+ Ion coordination in solution and in situ generation of passivated CuMnO supported on porous metal substrates x nuclear.

[0010] As a preferred solution, the porous metal substrate comprises at least one of porous nickel, foamed nickel and foamed copper. The preferred porous metal substrate of the present application not only has a high specific surface area and porosity, but also has excellent corrosion resistance, which can improve the cycle stability of the composite cathode. Further preferably, the porous metal substrate is porous nickel.

[0011] As a preferred solution, the porosity of the porous metal substrate is 30-98% and the average pore size is 1-300 μm. The porous metal substrate used in the present application has a large porosity, which means that the porous metal substrate has a larger specific surface area than ordinary metals, so that more CuMnO x The active substance enables the composite cathode to have a higher nitrate nitrogen removal efficiency. Further preferably, the porosity is 80-98% and the average pore size is 1-20 μm.

[0012] As a preferred solution, the electrolyte used in the electrochemical etching is at least one of H2SO4 solution, HCl solution and HNO3 solution; the concentration of hydrogen ions in the electrolyte is 0.5-3.0 mol / L; the control voltage for the electrochemical etching is 0.2-2.0 V, and the cyclic voltammetry number is 10-100. The present application optimizes the processing voltage and the required concentration of hydrogen ions for the electrochemical etching. Within the range, the voltage and the concentration of hydrogen ions can effectively increase the surface defects of the porous metal substrate, form a nanostructured corrosion layer, and enable the etched porous metal substrate to have a uniform morphology and a rich specific surface area. If the voltage is too high or the concentration of hydrogen ions is too large, the substrate will be eroded and fall off in a large area. If the voltage is too low or the concentration of hydrogen ions is too small, the etching time will be greatly increased, resulting in increased energy consumption.

[0013] As a preferred solution, the electrodeposition solution used in the electrodeposition comprises: 0.05-0.50 mol / L Cu 2+ , 0.25-2.50 mol / L HBO3, 0.15-1.50 mol / L NH4Cl and 0.20-2.50 mol / L Na3C6H5O7·2H2O. The HBO3 added in the electrodeposition solution can act as a buffer to adjust the pH value in the electrodeposition solution. Controlling the pH value helps to stabilize the composition and structure of the deposit, thereby affecting the performance and quality of the electrodeposited film. The added Na3C6H5O7·2H2O acts as a complexing agent, which forms a complex with copper ions, helps to regulate the reduction and deposition behavior of copper ions in the electrodeposition process, and at the same time, HBO3 and Na3C6H5O7·2H2O can also adjust the current density in the electrolyte, so that the current flows more uniformly through each part of the object being deposited, thereby achieving more uniform deposition effect. By adjusting the Cu 2+The concentration can effectively control the morphology of the deposited copper and make the deposition thickness more uniform.

[0014] As a preferred solution, the Cu 2+ from at least one of Cu(CH3COO)2, CuSO4, Cu(NO3)2 and CuCl2.

[0015] As a preferred solution, the electrodeposition control voltage is -0.5 to -2.5 V, and the time is 30 to 300 s. In the present application, the in-situ electrodeposition time is too short to deposit enough and uniform copper on the surface of the porous metal substrate, so that the CuMnOx on the surface of the composite cathode is not enough. x The active material content is reduced; and the deposition time is too long to increase the copper content and its thickness, cover the microporous structure of the porous metal surface, and also make the CuMnOx on the surface of the porous metal substrate not enough. x The active material load is reduced.

[0016] As a preferred solution, the concentration of potassium permanganate in the solution containing potassium permanganate is 2 to 100 mmol / L. In the present application, the concentration of the potassium permanganate solution is suitable for the prepared supported CuMnOx composite cathode. x The morphology of the composite cathode has a direct impact. When the concentration of potassium permanganate is less than 2 mmol / L, the prepared supported CuMnOx composite cathode has only one morphology of flower ball and the efficiency of catalytic degradation of nitrate nitrogen is low; and when the concentration of potassium permanganate is 2 to 100 mmol / L, the prepared supported CuMnOx composite cathode has two morphologies of needle and flower ball, and the two morphologies can synergistically promote the efficiency of catalytic degradation of nitrate nitrogen.

[0017] As a preferred solution, the solution containing potassium permanganate further contains 1 to 100 mmol / L of neutral sulfate and 2 to 100 mmol / L of H2SO4; the neutral sulfate used in the present application can be K2SO4, Na2SO4, NiSO4 and CuSO4.

[0018] As a preferred solution, the solid-liquid ratio of the copper-plated cathode precursor to the solution containing potassium permanganate is (0.5 to 5 g) to 80 mL.

[0019] As a preferred solution, the hydrothermal reaction conditions are: temperature is 100 to 300℃, and time is 2 to 8h.

[0020] As a preferred solution, the in-situ electrodeposition method adopts a three-electrode system, with Ag / AgCl as the reference electrode, a platinum electrode as the counter electrode, and a porous metal substrate after electro-etching as the working electrode; it is inserted into the electrodeposition solution for electrodeposition, the voltage and electrodeposition time are controlled, and after the electrode is removed, it is washed with deionized water and anhydrous ethanol to obtain a copper-plated cathode precursor.

[0021] The present invention also provides a supported CuMnO x The composite cathode is obtained by the above preparation method.

[0022] As a preferred solution, the CuMnO x CuMnO in composite cathode x The Cu:Mn atomic ratio is (1-5):1. The present invention controls the concentration of potassium permanganate in the hydrothermal reaction solution to obtain CuMnOx composite cathodes with different atomic ratios, wherein the needle-shaped Cu:Mn atomic ratio is (2-3):1, and the flower-shaped Cu:Mn atomic ratio is (1-2):1. By doping manganese ions into the copper oxide and cuprous oxide lattices, a large number of oxygen vacancies can be synergistically generated to increase adsorption sites and active sites for catalytic degradation of nitrate nitrogen. In addition, the doping of manganese ions changes the electronic structure of copper, enriching electrons in the oxidized state of copper, thereby increasing the rate of electron transfer from the catalyst surface to nitrate ions.

[0023] The present invention also provides a supported CuMnO x The application of composite cathode in the electrocatalytic reduction of nitrate nitrogen greatly improves the removal rate and stability of nitrate nitrogen under high salinity conditions.

[0024] As a preferred solution, the electrocatalytic reduction of Cl in the raw material - Concentration ≤ 20000mg / L, SO4 2- Concentration ≤5000mg / L.

[0025] The supported CuMnO prepared by the present invention x The composite cathode's ability to effectively and stably remove nitrate nitrogen in high-salt environments stems from the fact that, while cuprous oxide is commonly used to effectively reduce nitrates, pure cuprous oxide is easily reduced to elemental copper during the nitrate reduction process, rapidly reducing the catalyst's effectiveness. Manganese oxide, on the other hand, can maintain a stable valence state even at high reduction potentials. The present invention incorporates manganese into the cuprous oxide and copper oxide lattices to stabilize the copper valence state. This improves the stability of cuprous oxide and copper oxide at high reduction potentials, preventing their reduction to elemental copper and resulting in reduced activity. This ensures the composite cathode's ability to catalyze and reduce nitrates over a long period of time.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1) The present invention uses porous metal as a substrate, which has a high porosity and a rich specific surface area, increasing the active sites for the electrocatalytic reduction of nitrate nitrogen. In addition, the use of a porous metal substrate can greatly improve the corrosion resistance of the composite cathode.

[0028] 2) The present invention adopts in-situ electrodeposition and hydrothermal method to prepare supported CuMnO x Composite cathode, by controlling the concentration of potassium permanganate, needle-shaped and flower-shaped supported CuMnO can be prepared simultaneously x The composite cathode incorporates manganese ions into the copper oxide and cuprous oxide lattices, synergistically creating a large number of oxygen vacancies that increase the adsorption and active sites for catalytic degradation of nitrate nitrogen, significantly increasing the rate of electron transfer from the catalyst surface to nitrate ions. The method of the present invention is simple and controllable, facilitating the design of related electrode preparation equipment. The electrode preparation is cost-effective, facilitating large-scale industrial production and application.

[0029] 3) Supported CuMnO prepared by the present invention x The composite cathode can degrade nitrate nitrogen at a higher current density, has the basis for industrial application, and is — The removal rate of nitrate nitrogen under high-salinity conditions can still reach more than 98%. It can effectively remove nitrate nitrogen in high-salinity wastewater and has broad market application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 The porous nickel-loaded CuMnO prepared in Example 1 and Example 2 of the present invention x XRD patterns of composite cathode and Cu / porous nickel, where CuMnO x / Porous nickel-1 is the porous nickel loaded with CuMnO prepared in Example 1 x Composite cathode, CuMnO x / Porous nickel-2 is the porous nickel loaded with CuMnO prepared in Example 2 x Composite cathode, Cu / porous nickel material is the copper-plated cathode precursor prepared in Example 1.

[0031] Figure 2 The CuMnO prepared in Example 2 of the present invention x / porous nickel-2 composite cathode.

[0032] Figure 3 The CuMnO prepared in Comparative Example 3 of the present invention x / porous nickel composite cathode.

[0033] Figure 4 The CuMnO in Examples 2, 3 and 4 of the present inventionx porous nickel-2 composite cathode, CuMnO x foam nickel composite cathode and CuMnO x linear sweep voltammogram comparison chart of foam copper composite cathode and metal Ti, wherein the linear scanning speed is 10 mV / s, the voltage range is 0~ -1.8V, NO3 - -N concentration is 100 mg / L, and the electrolyte is composed of 2000 mg / L Cl - and 0.05 mol / L Na2SO4.

[0034] Figure 5 porous nickel supported CuMnO composite cathode prepared in Example 2 of the present application after electrochemical etching treatment x porous nickel supported CuMnO composite cathode prepared in Comparative Example 1 without electrochemical etching treatment x linear sweep voltammogram comparison chart of porous nickel supported CuMnO composite cathode, wherein the linear scanning speed is 10 mV / s, the voltage range is 0~ -1.8V, NO3 — -N concentration is 100 mg / L, and the electrolyte is composed of 2000 mg / L Cl — and 0.05 mol / L Na2SO4.

[0035] Figure 6 CuMnO with copper electrodeposition time of 240 s prepared in Example 2 of the present application x porous nickel composite cathode and CuMnO with copper electrodeposition time of 15 s prepared in Comparative Example 2 x linear sweep voltammogram comparison chart of porous nickel composite cathode and CuMnO with copper electrodeposition time of 15 s prepared in Comparative Example 2, wherein the linear scanning speed is 10 mV / s, the voltage range is 0~ -1.8V, NO3 — -N concentration is 100 mg / L, and the electrolyte is composed of 2000 mg / L Cl — and 0.05 mol / L Na2SO4.

[0036] Figure 7 porous nickel supported CuMnO composite cathode prepared in Example 2 of the present application x porous nickel supported CuMnO composite cathode prepared in Comparative Example 3 x comparison of test results of electrocatalytic reduction of nitrate nitrogen removal rate of porous nickel supported CuMnO composite cathode and porous nickel supported CuMnO composite cathode prepared in Comparative Example 3, wherein the electrocatalytic reduction raw material is NO3 — -N concentration is 100 mg / L, and the electrolyte is composed of 2000 mg / L Cl — and 0.05 mol / L Na2SO4.

[0037] Figure 8 porous nickel supported CuMnO composite cathode prepared in Example 2 of the present application xCycling stability performance plot and nitrogen selectivity of the composite cathode, where each cycle was electrolyzed for 2 h in galvanostatic mode at a current density of 40 mA cm -2 , NO3 - - N concentration of 100 mg / L, electrolyte consisting of 2000 mg / L Cl - and 0.05 mol / L Na2SO4. DETAILED DESCRIPTION

[0038] Other advantages and benefits of the present application will become apparent to those skilled in the art, upon consideration of the disclosure or may be learned by the practice of the application without additional experimentation. The meaning of a phrase on the form "one of" includes both "one, but not the other" and "one, and the other".

[0039] The application will be further described by reference to the following drawings and examples, which are provided as further examples of specific embodiments of the application and are not intended to limit the scope of the application. The following examples are provided to further illustrate the application and should not be construed as limiting the application as other embodiments can be devised and practiced by one of ordinary skill in the art without departing from the intended scope of the application.

[0040] The method for preparing the porous nickel in the examples and comparative examples of the present application is as follows: 5 g of polyvinyl butyral and 50 mL of ethanol are mixed uniformly to form a transparent colloid, and then 5 g of high-purity nickel powder and 5 g of the colloid are mixed to form a bubble-free metal slurry. The slurry is smoothly spread on a clean glass plate and aged for 12 hours to obtain a Ni powder / PVB raw foil. Then, the raw foil is placed on a hollow Al2O3 plate and sintered in a vacuum sintering furnace (1.0 x 10 -5 Pa). The heating rate is 5°C / min -1 , and the sintering is performed at 450°C, 550°C and 850°C for 2 hours, 2 hours and 3 hours, respectively. Finally, the sample is directly quenched from 900°C to 600°C, and then cooled to room temperature in the furnace to prepare a porous nickel substrate (porosity of 80-98%, average pore diameter of 1-20 μm).

[0041] The porosity of the foamed nickel used in the examples and comparative examples of the present application is 30-85%, and the average pore diameter is 20-300 μm (purchased from Cyber Alloys, model 110 PPI).

[0042] The porosity of the foamed copper used in the examples and comparative examples of the present application is 30-85%, and the average pore diameter is 20-300 μm (purchased from Cyber Alloys, model 110).

[0043] Example 1

[0044] 1) The porous nickel substrate is cut to size as 2 cm x 3.5 cm, then the porous nickel substrate is cleaned with deionized water and acetone for 3 times respectively to remove the oil stains on the surface of the porous nickel substrate, an electrolyte of 1M H2SO4 is prepared, and the porous nickel electrode is treated with cyclic voltammetry curve for 20 cycles in the voltage range of 0.2-1.0V (vs. Ag / AgCl) to obtain a roughened porous nickel substrate.

[0045] 2) An electrodeposition solution with a composition of 0.1 mol / L CuSO4, 0.25 mol / L HBO3, 0.15 mol / L NH4Cl, and 0.20 mol / L Na3C6H5O7·2H2O is prepared, a three-electrode system is used, Ag / AgCl is used as the reference electrode, platinum electrode is used as the counter electrode, and the roughened porous nickel substrate obtained in step 1) is used as the working electrode; the working electrode is inserted into the electrodeposition solution for electrodeposition, the voltage is controlled at -0.8V, and the electrodeposition time is 60s to obtain a copper-plated cathode precursor.

[0046] 3) A hydrothermal solution of 5mmol / L KMnO4, 5mmol / L CuSO4, and 5mmol / L H2SO4 is prepared, the copper-plated cathode precursor is placed in a polytetrafluoroethylene reactor together with the hydrothermal solution, the solid-liquid ratio of the copper-plated cathode precursor and the hydrothermal solution is 0.8g:80mL, then the hydrothermal reaction is carried out at 160℃ for 8h, after the reactor is cooled, the electrode is cleaned with deionized water and ethanol for 3 times, then it is placed in a vacuum drying box for drying at 60℃ for standby, and a CuMnO x / porous nickel-1 composite cathode is obtained.

[0047] Example 2

[0048] 1) The porous nickel substrate is cut to size as 2 cm x 3.5 cm, then the porous nickel substrate is cleaned with deionized water and acetone for 3 times respectively to remove the oil stains on the surface of the porous nickel substrate, an electrolyte of 1M H2SO4 is prepared, and the porous nickel electrode is treated with cyclic voltammetry curve for 40 cycles in the voltage range of 0.2-1.0V (vs. Ag / AgCl) to obtain a roughened porous nickel substrate;

[0049] 2) An electrodeposition solution with a composition of 0.1 mol / L CuSO4, 0.25 mol / L HBO3, 0.15 mol / L NH4Cl, and 0.20 mol / L Na3C6H5O7·2H2O is prepared, a three-electrode system is used, Ag / AgCl is used as the reference electrode, platinum electrode is used as the counter electrode, and the roughened porous nickel substrate obtained in step 1) is used as the working electrode; the working electrode is inserted into the electrodeposition solution for electrodeposition, the voltage is controlled at -0.8V, and the electrodeposition time is 240s to obtain a copper-plated cathode precursor.

[0050] 3) Preparation of a hydrothermal solution of 20 mmol / L KMnO4, 20 mmol / L CuSO4 and 20 mmol / L H2SO4, which is placed in a polytetrafluoroethylene reaction kettle together with the copper-plated cathode precursor, the solid-liquid ratio of the copper-plated cathode precursor and the hydrothermal solution being 0.8 g:80 mL, then hydrothermal reaction at 200°C for 8 h, after the reaction kettle is cooled, the electrode is taken out and cleaned with deionized water and ethanol for 3 times, then placed in a vacuum drying box for drying at 60°C for standby, to obtain CuMnO x / porous nickel-2 composite cathode.

[0051] Example 3

[0052] 1) The size of the foam nickel substrate is cut to 2 cm x 3.5 cm, then the foam nickel substrate is cleaned with deionized water and acetone for 3 times respectively to remove the oil stains and impurities on the surface of the foam nickel substrate, a 1M H2SO4 electrolyte is prepared, and the foam nickel electrode is treated with 40 cycles of cyclic voltammetry curve in the voltage range of 0.2-1.0V (vs. Ag / AgCl) to obtain a roughened foam nickel substrate;

[0053] 2) Preparation of an electrodeposition solution with a composition of 0.1 mol / L CuSO4, 0.25 mol / L HBO3, 0.15 mol / L NH4Cl, 0.20 mol / L Na3C6H5O7·2H2O, using a three-electrode system, Ag / AgCl as the reference electrode, platinum electrode as the counter electrode, and the foam nickel substrate after roughening treatment in step 1) as the working electrode; insert it into the electrodeposition solution for electrodeposition, control the voltage at -0.8V, and the electrodeposition time is 240s, to obtain a copper-plated cathode precursor.

[0054] 3) Preparation of a hydrothermal solution of 20 mmol / L KMnO4, 20 mmol / L CuSO4 and 20 mmol / L H2SO4, which is placed in a polytetrafluoroethylene reaction kettle together with the copper-plated cathode precursor, the solid-liquid ratio of the copper-plated cathode precursor and the hydrothermal solution being 0.8 g:80 mL, then hydrothermal reaction at 200°C for 8 h, after the reaction kettle is cooled, the electrode is taken out and cleaned with deionized water and ethanol for 3 times, then placed in a vacuum drying box for drying at 60°C for standby, to obtain CuMnO x / foam nickel composite cathode.

[0055] Example 4

[0056] 1) The foam copper substrate was cut into 2 cm x 3.5 cm in size, and then the foam copper substrate was cleaned with deionized water and acetone for 3 times respectively to remove the oil stains and impurities on the surface of the foam copper substrate, an electrolyte of 1M H2SO4 was prepared, and the foam copper electrode was treated by 40 cycles of cyclic voltammetry curve in the voltage range of 0.2-1.0V (vs. Ag / AgCl) to obtain a roughened foam copper substrate;

[0057] 2) An electrodeposition solution with a composition of 0.1mol / L CuSO4, 0.25mol / L HBO3, 0.15mol / L NH4Cl, and 0.20mol / L Na3C6H5O7·2H2O was prepared, a three-electrode system was used, Ag / AgCl was used as the reference electrode, platinum electrode was used as the counter electrode, and the foam copper substrate after roughening treatment in step 1) was used as the working electrode; the working electrode was inserted into the electrodeposition solution for electrodeposition, the voltage was controlled at -0.8V, and the electrodeposition time was 240s to obtain a copper-plated cathode precursor.

[0058] 3) A hydrothermal solution of 20mmol / L KMnO4, 20mmol / L CuSO4 and 20mmol / L H2SO4 was prepared, and the copper-plated cathode precursor was placed in a polytetrafluoroethylene reaction kettle together with the hydrothermal solution, the solid-liquid ratio of the copper-plated cathode precursor and the hydrothermal solution was 0.8g:80mL, and then the hydrothermal reaction was carried out at 200℃ for 8h, after the reaction kettle was cooled, the electrode was cleaned with deionized water and ethanol for 3 times, and then was placed in a vacuum drying box for drying at 60℃ for standby, to obtain a CuMnOx / foam copper composite cathode. x / foam copper composite cathode.

[0059] Comparative Example 1

[0060] The difference between this comparative example and Example 2 is only that the porous nickel substrate is only cleaned with deionized water and acetone, and is not subjected to electrochemical etching treatment, and the rest of the steps and conditions are consistent, to obtain a CuMnOx / porous nickel composite cathode. x / porous nickel composite cathode.

[0061] Comparative Example 2

[0062] The difference between this comparative example and Example 2 is that the electrodeposition time in step 2) is changed to 15s, and the rest of the steps and conditions are consistent, to obtain a CuMnOx / porous nickel composite cathode.

[0063] Comparative Example 3

[0064] The difference between this comparative example and Example 2 is only that the hydrothermal solution in step 3) is changed to 1mmol / L KMnO4, 20mmol / L CuSO4 and 20mmol / L H2SO4, and the rest of the steps and conditions are consistent, to obtain a CuMnOx / porous nickel composite cathode.

[0065] Depend on Figure 1 and Figure 2 It can be seen that the needle-shaped and flower-shaped CuMnO x Nanocompounds. In the present invention, two forms of CuMnO are prepared. x The compounds can synergistically catalyze the reduction of nitrates, effectively improving the removal effect of nitrates.

[0066] Figure 4 For the porous nickel loaded CuMnO in Example 2, Example 3 and Example 4 x , nickel foam loaded CuMnO x and copper foam loaded CuMnO x The comparison of the linear sweep voltammetric curve of Ti and the metallic Ti shows that the porous metal substrate prepared by the present invention is loaded with CuMnO x The composite cathode has a higher and greater reduction current density than metallic Ti, indicating that the catalyst has better catalytic performance for the degradation of nitrate nitrogen.

[0067] Figure 5 The porous nickel loaded CuMnO prepared in Example 2 of the present invention after electrochemical etching treatment x Composite cathode and porous nickel loaded CuMnO prepared in Comparative Example 1 without electrochemical etching x The comparison of the linear sweep voltammetric curves of the composite cathode shows that the porous nickel loaded with CuMnO after electrochemical etching. x The composite cathode has a larger reduction current density, indicating that the catalyst can load more CuMnO after electrochemical etching treatment. x Active substances have better catalytic performance for the degradation of nitrate nitrogen.

[0068] Figure 6 The porous nickel loaded CuMnO prepared in Example 2 of the present invention with a copper plating time of 240s x Composite cathode and Comparative Example 2 prepared by copper plating time of 15s porous nickel loaded CuMnO x Comparison of linear sweep voltammetry curves of composite cathodes. As shown in the figure, due to the short copper plating time, sufficient and uniform copper element was not deposited on the porous nickel surface, resulting in the porous nickel prepared in Comparative Example 2 loaded with CuMnO x The composite cathode's response current density to nitrate decreases. The porous nickel-loaded CuMnO prepared in Example 2, whose electrodeposition time is within the scope of the present invention, x The composite cathode has higher response current density and catalytic performance.

[0069] Figure 3The porous nickel supported CuMnO prepared in the present application comparative example 3 x SEM images of the composite cathode, Figure 7 The porous nickel supported CuMnO prepared in the present application example 2 x The composite cathode and the porous nickel supported CuMnO prepared in comparative example 3 x Comparison of the removal rate of nitrate nitrogen by electrocatalytic reduction of the composite cathode. From the results of Figure 3 And Figure 7 It can be seen that the porous nickel supported CuMnO prepared in comparative example 3 x The composite cathode only has one flower ball morphology, and the corresponding nitrate nitrogen removal efficiency is much lower than that of the porous nickel supported CuMnO prepared in example 2 with double morphology x The composite cathode, which shows that the porous nickel supported CuMnO with double morphology x The composite cathode has more advantages in synergistically catalyzing the degradation of nitrate.

[0070] Figure 8 The porous nickel supported CuMnO prepared in the present application example 2 x The cycle stability performance chart and nitrogen selectivity of the composite cathode. From the results of Figure 8 It is shown that when the catalyst electrocatalytically reduces nitrate nitrogen, the nitrate nitrogen removal rate and nitrogen (N2) selectivity of 20 cycles are both maintained above 98%, showing good cycle stability.

[0071] The above is only the preferred embodiment of the present application, not other forms of the present application, any skilled in the art may use the above disclosed technical content to change or modify as equivalent examples of equivalent changes. But any simple modification, equivalent change and improvement made on the basis of the technical essence of the present application to the above examples without departing from the technical scheme of the present application still belongs to the protection scope of the present application technical scheme.

Claims

1. A supported CuMnO x The method for preparing a composite cathode is characterized by: After electrochemically etching a porous metal substrate, copper is in situ deposited on the surface of the porous metal substrate by electrodeposition to obtain a copper-plated cathode precursor; the copper-plated cathode precursor is placed in a solution containing potassium permanganate and subjected to a hydrothermal reaction to obtain the copper-plated cathode precursor; The concentration of potassium permanganate in the solution containing potassium permanganate is 2 to 100 mmol / L; The electrochemical etching control voltage is 0.2-2.0V; the hydrogen ion concentration of the electrolyte used in the electrochemical etching is 0.5-3.0mol / L; The supported CuMnO x The composite cathode has both flower ball and needle morphology; the loaded CuMnO x The composite cathode is used to electrocatalytically reduce nitrate nitrogen in high-salinity wastewater to produce nitrogen gas.

2. A supported CuMnO according to claim 1 x The method for preparing a composite cathode is characterized by: The porous metal substrate is at least one of porous nickel, foam nickel and foam copper; The porosity of the porous metal substrate is 30-98%, and the average pore diameter is 1-300 μm.

3. A supported CuMnO according to claim 1 x The method for preparing a composite cathode is characterized by: The electrolyte used in the electrochemical etching is at least one of H2SO4 solution, HCl solution and HNO3 solution; The cyclic voltammetry number of the electrochemical etching is 10-100.

4. A supported CuMnO according to any one of claims 1 to 3 x The method for preparing a composite cathode is characterized by: The electroplating solution used in the electroplating includes: 0.05~0.50mol / L Cu 2+ , 0.25~2.50 mol / L HBO3, 0.15~1.50mol / L NH4Cl and 0.20~2.50mol / L Na3C6H5O7·2H2O.

5. A supported CuMnO according to claim 1 x The method for preparing a composite cathode is characterized by: The electrodeposition control voltage is -0.5 to -2.5 V, and the time is 30 to 300 s.

6. A supported CuMnO according to claim 5 x The method for preparing a composite cathode is characterized by: The solution containing potassium permanganate further contains 1-100 mmol / L of neutral sulfate and 2-100 mmol / L of H2SO4; The solid-to-liquid ratio of the copper-plated cathode precursor to the solution containing potassium permanganate is (0.5-5 g):80 mL.

7. A supported CuMnO according to claim 1 x The method for preparing a composite cathode is characterized by: The conditions of the hydrothermal reaction are: temperature of 100-300° C. and time of 2-8 h.

8. A supported CuMnO x A composite cathode, characterized in that: Obtained by the preparation method according to any one of claims 1 to 7.

9. A supported CuMnO according to claim 8 x A composite cathode, characterized in that: The CuMnO x CuMnO in composite cathode x The Cu:Mn atomic ratio is (1~5):

1.

10. A supported CuMnO according to claim 8 or 9 x The application of composite cathode is characterized by: Applied to the electrocatalytic reduction of nitrate nitrogen in high-salt wastewater to produce nitrogen gas.

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