Method for preparing molybdenum-doped cuprous oxide catalytic electrode based on laser assistance and application of molybdenum-doped cuprous oxide catalytic electrode in ammonia synthesis
The preparation of molybdenum-doped cuprous oxide catalytic electrodes by laser assisting solves the problem of insufficient activity of copper-based catalysts in the process of nitrogen reduction in ammonia, and achieves efficient ammonia synthesis and stable nitrogen circulation.
Patent Information
- Application Number
- CN202510847795.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-24
- Publication Date
- 2025-09-02
AI Technical Summary
The existing copper-based catalysts lack electrocatalytic activity and selectivity during the process of nitrogen reduction to make ammonia, which limits the generation and hydrogenation of active hydrogen, resulting in low Faraday efficiency and ammonia yield.
Laser-assisted preparation of molybdenum-doped cuprous oxide catalytic electrodes, and Mo doping and laser irradiation are used to form high-valent and low-valent Mo in the copper-based catalyst, which promotes H2O dissociation, and activates nitrate in an alkaline environment to form effective synergistic adsorption sites and reduces the reaction energy barrier.
The Faraday efficiency and ammonia yield of nitrate are improved, and the efficient stability of the catalytic electrode and the synthesis of ammonia without carbon dioxide are achieved, which promotes the efficient development of nitrogen cycle.
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Abstract
Description
Technical Field
[0001] The present invention relates to a method for preparing a molybdenum-doped cuprous oxide catalytic electrode based on laser assistance and application thereof in synthesizing ammonia, belonging to the technical field of electrochemical catalysis. Background Art
[0002] Currently, large-scale industrial ammonia production relies on the HB process, which uses nitrogen and hydrogen as raw materials and produces ammonia at high temperatures. This process produces large amounts of carbon dioxide and other pollutants. To reduce energy consumption, nitrogen reduction and nitrate reduction methods have been proposed. However, due to the high energy required to dissociate the nitrogen triple bond in nitrogen (1942 kJ / mol), the low solubility of nitrogen in water, and the competing reaction of hydrogen evolution during electrolysis, Faradaic efficiency and ammonia yield are low.
[0003] The most commonly used substrates for nitrate reduction are copper, iron and cobalt, among which copper-based catalysts are more effective for NO3 − The electroreduction of NO3 is highly active because metallic copper, which has a large number of electrons occupying d orbitals, can donate electrons to NO3. − However, its electrocatalytic activity and selectivity are relatively poor, and Cu cannot fully activate interfacial water, thereby limiting the generation of active hydrogen and inhibiting the hydrogenation process. Summary of the Invention
[0004] Aiming at the problems of insufficient electrocatalytic activity and catalytic selectivity of copper-based catalysts in existing nitrogen reduction to ammonia production, which limit the generation of active hydrogen and inhibit the hydrogenation process, the present invention proposes a method for preparing molybdenum-doped cuprous oxide catalytic electrode based on laser assistance and its application in synthetic ammonia. The cuprous oxide catalytic electrode is prepared by doping with alkaline hydrogen-evolving element Mo and assisted by laser irradiation. The high valence state and low valence state of Mo in the catalytic electrode respectively show OH − and H − The binding energy accelerates the dissociation of H2O, making the molybdenum-doped cuprous oxide catalytic electrode have high nitrate Faradaic efficiency and ammonia yield, as well as cycle stability.
[0005] A method for preparing a molybdenum-doped cuprous oxide catalytic electrode based on laser assistance, the specific steps are as follows: (1) Dissolve Na2MoO4 and C4H6CuO4·H2O in deionized water to obtain solution A, add sodium salicylate to solution A, and mix well to obtain solution B; (2) The copper foam is placed in solution B and subjected to a hydrothermal reaction at a temperature of 170-210°C for 4-8 hours. The copper foam is then irradiated with a laser to obtain a molybdenum-doped cuprous oxide catalytic electrode. The laser beam is focused on a small area on the electrode surface (especially on the Cu2O matrix formed after the hydrothermal reaction), generating an extremely high local instantaneous temperature (much higher than the hydrothermal reaction temperature). The ultra-fast high temperature causes the local material to melt, vaporize, and rapidly quench (cool). In Cu2O, the Cu2O at high temperature + Disproportionation reaction occurs: 2Cu + →Cu 0 +Cu 2 + , producing a small amount of metallic copper (Cu 0 ) nanoparticles or island structures, metal Cu 0 It has strong reducing properties and can be adjacent to or doped in the Mo in the Cu2O lattice 6+ ions are partially reduced to Mo 4+ At the same time, the high temperature environment itself provides a reducing atmosphere; and the metal Cu 0 Nanoparticles can generate localized surface plasmon resonance under laser irradiation, which highly localizes the light energy and converts it into "hot electrons". High-energy hot electrons can be directly injected into the adjacent Mo 6+ , and restore it to Mo 4+ High-energy laser photons directly excite electrons in Cu2O, and the conduction band electrons (e - ) can be adsorbed on the electrode surface or doped in the lattice of Mo 6 + Ion capture reduces it to a lower valence Mo. The laser-induced drastic temperature change (melting-quenching) and possible ablation / shock wave effect will introduce a large number of point defects (such as oxygen vacancies V_O, copper vacancies V_Cu) and lattice distortion in the Cu2O lattice. Oxygen vacancies (V_O) are reducing sites that can provide electrons or change the local electronic environment, which is beneficial to stabilizing the lower valence Mo. At the same time, as Mo 4+ Stable anchor point.
[0006] Preferably, in step (1), the molar ratio of Na2MoO4 and C4H6CuO4.H2O is 1:3~3:1, and the concentration of Na2MoO4 in solution A is 0.4~1.6 mol / L.
[0007] Preferably, in step (1), the molar ratio of the total molar amount of Na2MoO4 and C4H6CuO4.H2O to sodium salicylate is 1:1-6.
[0008] Preferably, the laser power in step (2) is 4-12 W, the scanning rate is 400-800 nm / s, and the laser frequency is 20-50 kHz. The laser irradiation can cause the surface grains of the catalytic electrode to be refined to the nanoscale through laser thermal shock, increase the exposure of active sites, and promote the adsorption of reactants; the local high temperature of laser irradiation promotes the desorption of oxygen atoms to form oxygen vacancies, enhances the adsorption of nitrates, and promotes electron transfer; laser irradiation can promote the partial reduction of the surface layer to metallic copper, forming a Cu2O / Cu heterostructure, optimizing the adsorption energy of the intermediate, and reducing the reaction energy barrier; laser irradiation can quickly fix the doped molybdenum atoms, prevent the segregation of the doping elements, and maintain the activity stability.
[0009] The molybdenum-doped cuprous oxide catalytic electrode is used in the reduction of nitrate to produce ammonia. A three-electrode system is formed by using the molybdenum-doped cuprous oxide catalytic electrode as a working electrode, a platinum electrode as a counter electrode, and an Hg / HgO electrode as a reference electrode. Constant voltage catalytic nitrate reduction to produce ammonia is carried out in an H-type electrolytic cell, and the electrolyte of the H-type electrolytic cell is a potassium hydroxide-potassium nitrate solution.
[0010] Preferably, the H-type electrolytic cell is divided into an anode region and a cathode region by a cation exchange membrane. More preferably, the cation exchange membrane is a Nafion 117 proton exchange membrane or a FuMAFKS cation exchange membrane.
[0011] Preferably, the concentration of potassium hydroxide in the electrolyte is 0.1-1 mol / L, and the concentration of potassium nitrate is 0.1-0.5 mol / L.
[0012] Preferably, the voltage is -0.1~-0.6V.
[0013] The principle of nitrate reduction to ammonia by molybdenum-doped cuprous oxide catalytic electrode: Molybdenum doping is conducive to the dissociation of H2O to form *H in an alkaline environment, which is beneficial to the subsequent hydrogenation step of ammonia synthesis, but Mo 6+ A higher content will occupy Cu + sites, inhibiting the electron transfer of Cu2O. After laser 6+ Partially reduced to Mo 4+ , Mo 4+ (4d 2 ) and the d orbital energy of nitrate (NO3 -) has a better energy match with the antibonding orbital (π*) of the Cu atom, especially with the p orbital of the N atom, which can promote the weakening of the NO bond in the nitrate ion and the transfer of charge from Mo to the NO antibonding orbital, effectively activating the inert NO bond, thereby improving the activity of the catalyst; the doped Mo atoms (and the O atoms around them) can form cooperative adsorption sites with the adjacent Cu atoms. The Mo site tends to adsorb N atoms, while the Cu site tends to adsorb O atoms. This dual-site adsorption mode can effectively lengthen and weaken the NO bond, significantly reducing the first step of deoxidation (*NO3 - >*NO2 - ) energy barrier; at the same time, the large number of oxygen vacancies introduced by the laser are strong Lewis acid sites, which can strongly adsorb and polarize the O atoms in the nitrate ion, further promoting the breaking and activation of the NO bond and stabilizing the key nitrogen-containing intermediate *NO2 - etc.; Mo sites (especially Mo 4+ ) and oxygen vacancies for intermediates such as nitrite (NO2 - Molybdenum-doped cuprous oxide catalytic electrodes have strong adsorption and stabilization effects on hydroxylamine (NH2OH), preventing them from desorption or side reactions such as disproportionation, and guiding the reaction path toward ammonia production. Therefore, molybdenum-doped cuprous oxide catalytic electrodes have high ammonia yields, high Faradaic efficiency, and good stability.
[0014] The beneficial effects of the present invention are: (1) The present invention utilizes alkaline hydrogen-evolving element Mo doping and laser irradiation to assist in preparing a cuprous oxide catalytic electrode, and the preparation process is simple; (2) The high valence state of Mo and the low valence state of Mo in the cuprous oxide catalytic electrode of the present invention respectively exhibit OH − and H − The binding energy accelerates the dissociation of H2O, making the molybdenum-doped cuprous oxide catalytic electrode have high nitrate Faradaic efficiency and ammonia yield, as well as cycle stability; it can realize carbon dioxide-free ammonia synthesis and promote the efficient development of the nitrogen cycle. BRIEF DESCRIPTION OF THE DRAWINGS
[0015] Figure 1 This is a scanning electron microscope image of the molybdenum-doped cuprous oxide catalytic electrode of Example 1; Figure 2 This is a transmission electron microscope (TEM) image of the molybdenum-doped cuprous oxide catalytic electrode of Example 1; Figure 3 This is the elemental distribution diagram (EDS) of the molybdenum-doped cuprous oxide catalytic electrode in Example 1; Figure 4 This is the XRD pattern of the molybdenum-doped cuprous oxide catalytic electrode of Example 1; Figure 5 This is a graph showing the Faradaic efficiency and ammonia yield of ammonia produced at different voltages using a molybdenum-doped cuprous oxide catalytic electrode according to Example 1; Figure 6 This is a cycle test diagram of the molybdenum-doped cuprous oxide catalytic electrode in Example 1 at an applied voltage of -0.5V vs. RHE. DETAILED DESCRIPTION
[0016] The present invention will be further described in detail below in conjunction with specific embodiments, but the protection scope of the present invention is not limited to the contents described above.
[0017] Example 1: A method for preparing a molybdenum-doped cuprous oxide catalytic electrode based on laser assistance, the specific steps are as follows: (1) Na2MoO4 and C4H6CuO4·H2O were dissolved in deionized water to obtain solution A, sodium salicylate was added to solution A, and the mixture was mixed to obtain solution B; the molar ratio of Na2MoO4 to C4H6CuO4·H2O was 1:3, the concentration of Na2MoO4 in solution A was 0.4 mol / L; and the molar ratio of the total molar amount of Na2MoO4 and C4H6CuO4·H2O to sodium salicylate was 1:6; (2) placing the copper foam in solution B, hydrothermally reacting it at a temperature of 190°C for 6 hours, and then irradiating it with a laser to obtain a molybdenum-doped cuprous oxide catalytic electrode; the laser power is 6 W, the scanning rate is 500 nm / s, and the laser frequency is 30 kHz; The scanning electron microscope image of the molybdenum-doped cuprous oxide catalytic electrode of this embodiment is shown in FIG. Figure 1 , indicating that the laser-assisted Mo-doped CuO catalytic electrode material has a uniform shape and an irregular polyhedral morphology; The transmission electron microscope (TEM) image of the molybdenum-doped cuprous oxide catalytic electrode of this embodiment is shown in FIG. Figure 2 , the spacing of the lattice fringes in high-resolution TEM (HRTEM) is 0.307 nm, which is attributed to the (220) crystal plane of Cu; The element distribution diagram (EDS) of the molybdenum-doped cuprous oxide catalytic electrode of this embodiment is shown in Figure 3 , Cu, Mo, and O elements are evenly distributed on the catalyst surface; The XRD pattern of the molybdenum-doped cuprous oxide catalytic electrode of this embodiment is shown in FIG. Figure 4 , there are only two crystal phases of Cu and Cu2O in the molybdenum-doped cuprous oxide catalyst; In this embodiment, a platinum-doped cuprous oxide catalytic electrode is used in the reduction of nitrate to produce ammonia. A three-electrode system is formed, comprising a platinum-doped cuprous oxide catalytic electrode as a working electrode, a platinum electrode as a counter electrode, and an Hg / HgO electrode as a reference electrode. The nitrate reduction to produce ammonia is catalyzed in an H-type electrolytic cell at a constant potential (voltages of -0.2, -0.3, -0.4, -0.5, and -0.6 V, respectively, relative to a reversible hydrogen electrode) for 2 h. The H-type electrolytic cell is separated into an anode region and a cathode region by a cation exchange membrane (Nafion 117 proton exchange membrane). The electrolyte of the H-type electrolytic cell is a potassium hydroxide-potassium nitrate solution, wherein the potassium hydroxide concentration in the electrolyte is 1 mol / L and the potassium nitrate concentration is 0.1 mol / L. The Faradaic efficiency and ammonia yield were measured by ultraviolet spectrophotometer, and the calculation formula was as follows: The Faraday efficiency formula of ammonia is: FE=(8*F*C*V) / (17*Q); The formula for ammonia yield is: Y (mg / (cm 2 •h))=(C*V / S*t); Where 8 is the number of transferred electrons, F is the Faraday constant, C is the ammonia concentration (mg / L), V is the electrolyte volume (mL), Q is the charge (C), and S is the electrode area (cm 2 ), t is the reaction time (h); The Faraday efficiency and ammonia yield of the molybdenum-doped cuprous oxide catalytic electrode at different voltages in this embodiment are shown in FIG. Figure 5 ,from Figure 5 It can be seen that with the increase of voltage, the ammonia yield and Faradaic efficiency of the molybdenum-doped cuprous oxide catalytic electrode are improved, and the best is achieved at -0.5V vs. RHE (ammonia yield is 10.9mg / L). -1 cm -2 , Faradaic efficiency is 94.3%), but it decreases at -0.6 V vs. RHE because the generation of H2 dominates; In this embodiment, the stability test of the molybdenum-doped cuprous oxide catalytic electrode was carried out at a constant voltage of -0.5V (relative to the reversible hydrogen electrode). The stability test of the molybdenum-doped cuprous oxide catalytic electrode at an applied voltage of -0.5V vs. RHE is shown in the graph. Figure 6 , after working continuously for 20 hours, it still maintains good stability, indicating that it can work stably for a long time.
[0018] Example 2: A method for preparing a molybdenum-doped cuprous oxide catalytic electrode based on laser assistance, the specific steps are as follows: (1) Na2MoO4 and C4H6CuO4·H2O were dissolved in deionized water to obtain solution A, sodium salicylate was added to solution A, and the mixture was mixed to obtain solution B; the molar ratio of Na2MoO4 to C4H6CuO4·H2O was 1:1, the concentration of Na2MoO4 in solution A was 0.8 mol / L; the molar ratio of the total molar amount of Na2MoO4 and C4H6CuO4·H2O to sodium salicylate was 1:4; (2) placing the copper foam in solution B, hydrothermally reacting it at a temperature of 200°C for 5 hours, and then irradiating it with a laser to obtain a molybdenum-doped cuprous oxide catalytic electrode; the laser power is 4 W, the scanning rate is 400 nm / s, and the laser frequency is 20 kHz; In this embodiment, a platinum-doped cuprous oxide catalytic electrode is used in the reduction of nitrate to produce ammonia. A three-electrode system is formed, comprising a platinum-doped cuprous oxide catalytic electrode as a working electrode, a platinum electrode as a counter electrode, and an Hg / HgO electrode as a reference electrode. The nitrate reduction to produce ammonia is carried out in an H-type electrolytic cell at a constant potential (-0.5 V relative to a reversible hydrogen electrode) for 2 hours. The H-type electrolytic cell is separated into an anode region and a cathode region by a cation exchange membrane (Nafion 117 proton exchange membrane). The electrolyte of the H-type electrolytic cell is a potassium hydroxide-potassium nitrate solution, wherein the potassium hydroxide concentration in the electrolyte is 1 mol / L and the potassium nitrate concentration is 0.1 mol / L. The Faradaic efficiency and ammonia yield were measured by ultraviolet spectrophotometer, and the calculation formula was as follows: The Faraday efficiency formula of ammonia is: FE=(8*F*C*V) / (17*Q); The formula for ammonia yield is: Y (mg / (cm 2 •h))=(C*V / S*t); Where 8 is the number of transferred electrons, F is the Faraday constant, C is the ammonia concentration (mg / L), V is the electrolyte volume (mL), Q is the charge (C), and S is the electrode area (cm 2 ), t is the reaction time (h); The molybdenum-doped cuprous oxide catalytic electrode of this embodiment has a Faradaic efficiency of 78% at a constant voltage of -0.5 V (relative to the reversible hydrogen electrode) and an ammonia yield of 7.6 mg / (cm 2 •h).
[0019] Example 3: A method for preparing a molybdenum-doped cuprous oxide catalytic electrode based on laser assistance, the specific steps are as follows: (1) Na2MoO4 and C4H6CuO4·H2O were dissolved in deionized water to obtain solution A, sodium salicylate was added to solution A, and the mixture was mixed to obtain solution B; the molar ratio of Na2MoO4 to C4H6CuO4·H2O was 3:1, the concentration of Na2MoO4 in solution A was 1.2 mol / L; the molar ratio of the total molar amount of Na2MoO4 and C4H6CuO4·H2O to sodium salicylate was 1:2; (2) placing the copper foam in solution B, hydrothermally reacting it at a temperature of 170°C for 8 hours, and then irradiating it with a laser to obtain a molybdenum-doped cuprous oxide catalytic electrode; the laser power is 12 W, the scanning rate is 800 nm / s, and the laser frequency is 60 kHz; In this embodiment, a platinum-doped cuprous oxide catalytic electrode is used in the reduction of nitrate to produce ammonia. A three-electrode system is formed, comprising a platinum-doped cuprous oxide catalytic electrode as a working electrode, a platinum electrode as a counter electrode, and an Hg / HgO electrode as a reference electrode. The nitrate reduction to produce ammonia is catalyzed in an H-type electrolytic cell at a constant potential (-0.5 V relative to a reversible hydrogen electrode) for 2 hours. The H-type electrolytic cell is separated into an anode region and a cathode region by a cation exchange membrane (Nafion 117 proton exchange membrane). The electrolyte of the H-type electrolytic cell is a potassium hydroxide-potassium nitrate solution, wherein the potassium hydroxide concentration in the electrolyte is 0.5 mol / L and the potassium nitrate concentration is 0.2 mol / L. The Faradaic efficiency and ammonia yield were measured by ultraviolet spectrophotometer, and the calculation formula was as follows: The Faraday efficiency formula of ammonia is: FE=(8*F*C*V) / (17*Q); The formula for ammonia yield is: Y (mg / (cm 2 •h))=(C*V / S*t); Where 8 is the number of transferred electrons, F is the Faraday constant, C is the ammonia concentration (mg / L), V is the electrolyte volume (mL), Q is the charge (C), and S is the electrode area (cm 2 ), t is the reaction time (h); The molybdenum-doped cuprous oxide catalytic electrode of this embodiment has a Faradaic efficiency of 87% at a constant voltage of -0.5 V (relative to the reversible hydrogen electrode) and an ammonia yield of 10.2 mg / (cm 2 •h).
[0020] Example 4: A method for preparing a molybdenum-doped cuprous oxide catalytic electrode based on laser assistance, the specific steps are as follows: (1) Na2MoO4 and C4H6CuO4·H2O were dissolved in deionized water to obtain solution A, sodium salicylate was added to solution A, and the mixture was mixed to obtain solution B; the molar ratio of Na2MoO4 to C4H6CuO4·H2O was 2:1, the concentration of Na2MoO4 in solution A was 0.1 mol / L; the molar ratio of the total molar amount of Na2MoO4 and C4H6CuO4·H2O to sodium salicylate was 1:1; (2) placing the copper foam in solution B, hydrothermally reacting it at a temperature of 180°C for 7 hours, and then irradiating it with a laser to obtain a molybdenum-doped cuprous oxide catalytic electrode; the laser power is 10 W, the scanning rate is 600 nm / s, and the laser frequency is 50 kHz; In this embodiment, a platinum-doped cuprous oxide catalytic electrode is used in the reduction of nitrate to produce ammonia. A three-electrode system is formed, comprising a platinum-doped cuprous oxide catalytic electrode as a working electrode, a platinum electrode as a counter electrode, and an Hg / HgO electrode as a reference electrode. The nitrate reduction to produce ammonia is carried out in an H-type electrolytic cell under constant voltage (-0.5 V relative to a reversible hydrogen electrode) for 2 hours. The H-type electrolytic cell is separated into an anode region and a cathode region by a cation exchange membrane (Nafion 117 proton exchange membrane). The electrolyte of the H-type electrolytic cell is a potassium hydroxide-potassium nitrate solution, wherein the potassium hydroxide concentration in the electrolyte is 0.5 mol / L and the potassium nitrate concentration is 0.5 mol / L. The Faradaic efficiency and ammonia yield were measured by ultraviolet spectrophotometer, and the calculation formula was as follows: The Faraday efficiency formula of ammonia is: FE=(8*F*C*V) / (17*Q); The formula for ammonia yield is: Y (mg / (cm 2 •h))=(C*V / S*t); Where 8 is the number of transferred electrons, F is the Faraday constant, C is the ammonia concentration (mg / L), V is the electrolyte volume (mL), Q is the charge (C), and S is the electrode area (cm 2 ), t is the reaction time (h); The molybdenum-doped cuprous oxide catalytic electrode of this embodiment has a Faradaic efficiency of 82% at a constant voltage of -0.5 V (relative to the reversible hydrogen electrode), and an ammonia yield of 9.4 mg / (cm 2 •h).
[0021] The above describes the specific embodiments of the present invention in detail, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge of ordinary technicians in this field without departing from the scope of the present invention.
Claims
1. A method for preparing a molybdenum-doped cuprous oxide catalytic electrode based on laser assistance, characterized in that: The specific steps are as follows: (1) Dissolve Na2MoO4 and C4H6CuO4·H2O in deionized water to obtain solution A, add sodium salicylate to solution A, and mix well to obtain solution B; (2) The copper foam was placed in solution B and subjected to hydrothermal reaction at a temperature of 170-200°C for 5-8 hours, and then laser irradiated to obtain a molybdenum-doped cuprous oxide catalytic electrode.
2. The method for preparing a molybdenum-doped cuprous oxide catalytic electrode based on laser assistance according to claim 1, characterized in that: In step (1), the molar ratio of Na2MoO4 and C4H6CuO4.H2O is 1:3~3:1, and the concentration of Na2MoO4 in solution A is 0.4~1.6 mol / L.
3. The method for preparing a molybdenum-doped cuprous oxide catalytic electrode based on laser assistance according to claim 1, characterized in that: In step (1), the molar ratio of the total molar amount of Na2MoO4 and C4H6CuO4.H2O to sodium salicylate is 1:1-6.
4. The method for preparing a molybdenum-doped cuprous oxide catalytic electrode based on laser assistance according to claim 1, characterized in that: In step (2), the laser power is 4-12 W, the scanning rate is 400-800 nm / s, and the laser frequency is 20-50 kHz.
5. Use of the molybdenum-doped cuprous oxide catalytic electrode prepared by the method according to any one of claims 1 to 4 in the production of ammonia by nitrate reduction.
6. The application according to claim 5, characterized in that: A three-electrode system is composed of a molybdenum-doped cuprous oxide catalytic electrode as a working electrode, a platinum electrode as a counter electrode, and a Hg / HgO electrode as a reference electrode. Constant-voltage catalytic nitrate reduction to produce ammonia is carried out in an H-type electrolytic cell, wherein the electrolyte of the H-type electrolytic cell is a potassium hydroxide-potassium nitrate solution.
7. The use according to claim 6, characterized in that: The H-type electrolytic cell is divided into an anode region and a cathode region by a cation exchange membrane.
8. The application according to claim 6, characterized in that: The concentration of potassium hydroxide in the electrolyte is 1-0.1 mol / L, and the concentration of potassium nitrate is 0.1-0.5 mol / L.
9. The application according to claim 6, characterized in that: The voltage is -0.1~-0.6V.