A high-pH stable solution suitable for metal cation system, and a preparation method and application thereof

Abstract

The application discloses a high-pH stable solution suitable for a metal cation system, and a preparation method and application thereof. The solution comprises, in percentage by mass, 2-20% of a strong alkali electrolyte, 0.5-5% of a metal ion source, 2-8% of a composite stabilizer, 0.1-0.5% of a surfactant, 0.05-0.3% of a dispersant, and the balance of deionized water. The solution prepared by the application can make metal ions stably exist and coexist for more than 30 days under strong alkaline conditions with a pH of 11-14, has the characteristics of non-toxicity and excellent stability, can be directly used for preparing an alkaline electrolytic water hydrogen / oxygen evolution catalyst, and can also be used as a self-repairing functional electrolyte to realize in-situ repair of the catalyst in a long cycle process.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical technology and relates to a high pH stable solution suitable for metal cation systems, its preparation method, and its application. Background Technology

[0002] Alkaline water electrolysis for hydrogen production has become a crucial technological pathway for new energy hydrogen production due to its low electrolyte cost, significant advantages in hydrogen evolution reaction kinetics, and the ability to use non-precious metal catalysts. In alkaline water electrolysis hydrogen production systems, the performance of the electrode catalyst directly determines the electrolysis efficiency and equipment lifespan. Multi-metal composite catalysts (such as Ni-Fe, Ni-Co, Ni-Fe-Co, Ni-Mo, Co-W, etc.) are widely studied and applied due to their excellent hydrogen / oxygen evolution activity.

[0003] To achieve precise preparation of multi-metal composite catalysts, electrodeposition is often used to construct metal composite coatings on the electrode substrate surface. Meanwhile, to improve the long-term stability of catalysts, the development of self-healing catalysts has become a hot topic. The core of these self-healing catalysts is to replenish the catalyst at its loss sites using metal ions pre-reserved in solution. However, under alkaline conditions, most metal ions (such as Fe)... 2+ Fe 3+ Co 2+ Ni 2+ Cr 3+ Mo 6+ (etc.) are prone to hydrolysis reactions to generate hydroxide precipitates, which leads to instability of the solution system, making it impossible to meet the uniform supply of metal ions during the electrodeposition process, and also making it difficult to achieve the controllable release of metal ions during the self-repair process.

[0004] In the prior art, in order to improve the stability of metal ions in alkaline systems, complexing agents such as ammonia and ethylenediaminetetraacetic acid are often added. However, there are the following drawbacks: (1) Ammonia complexing agents are volatile, which leads to unstable solution pH and complexing ability, affecting electrodeposition effect and catalyst performance; (2) Complexing agents such as ethylenediaminetetraacetic acid are easily decomposed under strong alkaline conditions, and their complexing ability with some metal ions is limited, making it impossible to achieve long-term stable coexistence of multiple metal ions; (3) Some complexing agents are toxic, which does not meet the requirements of green industrial production, and may remain in the catalyst, reducing its catalytic activity.

[0005] Therefore, developing a stable solution that can achieve stable coexistence of multiple metal ions under high pH conditions (pH=11~14), is non-toxic, and is compatible with alkaline electrodeposition processes and self-healing catalyst preparation is of great significance for promoting the industrial application of alkaline water electrolysis hydrogen production technology. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention aims to provide a high-pH stable solution suitable for metal cation systems, its preparation method, and its application. The solution, by mass percentage, comprises: 2-20% strong alkaline electrolyte, 0.5-5% metal ion source, 2-8% composite stabilizer, 0.1-0.5% surfactant, 0.05-0.3% dispersant, and the balance being deionized water. The solution prepared by this invention allows metal ions to remain stable / coexist for over 30 days under strongly alkaline conditions with a pH of 11-14. It exhibits non-toxicity and excellent stability, and can be directly used to prepare alkaline water electrolysis hydrogen / oxygen evolution catalysts. It can also serve as a self-healing electrolyte to achieve in-situ catalyst repair during long-cycle processes.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A high pH stable solution suitable for metal cation systems, comprising, by mass percentage: 2-20% strong base electrolyte, 0.5-5% metal ion source, 2-8% composite stabilizer, 0.1-0.5% surfactant, 0.05-0.3% dispersant, with the balance being deionized water; The pH value of the high pH stable solution suitable for metal cation systems is 11-14, and the metal ions are stable in the solution for more than 30 days.

[0008] As a limitation of the present invention, the strong alkaline electrolyte is one or more of potassium hydroxide, sodium hydroxide, or sodium carbonate.

[0009] As another limitation of the present invention, the metal ion source is a soluble salt corresponding to the metal ion; the metal ion includes a main catalytically active metal ion, and optionally includes an auxiliary metal ion, wherein the main catalytically active metal ion is Ni. 2+ Co 2+ Fe 2+ Fe 3+ One or more of the following, with Mn as the auxiliary metal ion. 2+ Cu 2+ Zn 2+ Al 3+ Cr 3+ Ti 4+ Zr 4+ Mo 6+ W 6+ One or more of the following; the soluble salt is one or more of nitrate, sulfate, chloride or acetate.

[0010] As a third limitation of the present invention, the composite stabilizer is composed of an organic amine compound and a hydroxycarboxylic acid compound in a mass ratio of (1:2) to (2:1), wherein the organic amine compound is one or more of ethanolamine, glucosamine, and ethylenediamine; and the hydroxycarboxylic acid compound is one or more of citric acid, tartaric acid, and malic acid.

[0011] Composite stabilizers enhance the stability of metal ions through synergistic complexation: the amino group (-NH2) of organic amine compounds provides lone pair electrons to form coordinate bonds with metal ions, while the hydroxyl group (-OH) and carboxyl group (-COOH) of hydroxycarboxylic acid compounds form stable five- or six-membered chelate structures with metal ions. The synergistic effect of the two can significantly enhance the complexation ability, while avoiding the decomposition problem of single stabilizers under strongly alkaline conditions.

[0012] As a fourth limitation of the present invention, the surfactant is sodium dodecylbenzenesulfonate or Tween 80; used to improve the dispersibility of the solution, avoid the problem of excessively high local concentration of metal ions during electrodeposition, and ensure the uniformity of the coating.

[0013] As a fifth limitation of the present invention, the dispersant is one or more of polyethylene glycol 2000-10000, polyvinyl alcohol, and polyvinylpyrrolidone; the dispersant can hinder the aggregation and growth of intermediate products of metal ion hydrolysis through the steric hindrance effect of the molecular chain, and form a dual stabilization mechanism of "synergistic complexation-steric hindrance" with the composite stabilizer, further reducing the probability of precipitation and prolonging the solution stabilization period.

[0014] As a further limitation of the present invention, when the metal ion is a single metal ion, it is only the main catalytic active metal ion; when the metal ion is two or more, it includes at least one main catalytic active metal ion and at least one auxiliary metal ion, and the molar ratio of the main catalytic active metal ion to the auxiliary metal ion is (1:0.2) to (1:1.5).

[0015] This invention also provides a method for preparing a high pH stable solution suitable for metal cation systems, comprising the following steps in sequence: S1. Place deionized water in a beaker, control the temperature at 25~40 ℃, and stir at a speed of 100~300 r·min. -1 Slowly add a strong base electrolyte and stir until completely dissolved to obtain a strong base mother liquor. S2. Add the composite stabilizer to the strong alkaline mother liquor from step S1 and continue stirring for 20-40 minutes. S3. Dissolve the metal ion source in deionized water to obtain a metal ion stock solution, and then, under stirring conditions, increase the concentration at a rate of 1-5 mL / min. -1The solution is added dropwise to the solution obtained in step S2 at a certain rate, and stirring is continued for 60-120 min after the addition is completed. S4. Add the surfactant to the solution obtained in step S3, stir for 30-60 min, then add the dispersant and continue stirring for 20-40 min; if the metal ion source contains Fe... 2+ Nitrogen gas is purged throughout steps S1 to S4 at a flow rate of 50–100 mL / min. -1 ; S5. Let the solution obtained in step S4 stand for 12-24 hours, filter, seal in a reagent bottle, and store away from light to obtain a high pH stable solution suitable for metal cation systems; containing Fe 2+ The solution needs to be filtered in a nitrogen protective hood, and after filtration, it should be sealed in a stoppered reagent bottle under nitrogen protection and stored away from light.

[0016] The high pH stable solution prepared by this invention, suitable for metal cation systems, can be used as an electrolyte in the electrodeposition preparation of hydrogen / oxygen evolution catalysts for alkaline water electrolysis, in long-cycle testing systems of alkaline water electrolysis three electrodes, and in the circulation systems of industrial alkaline electrolyzers. Specific applications and technical effects are as follows: 1. Application of catalyst electrodeposition preparation: Using this high pH stable solution as the electrolyte, a single metal coating or a multi-metal composite coating is deposited on the surface of a metal or conductive ceramic substrate to prepare an alkaline water electrolysis hydrogen / oxygen evolution catalyst. The high pH stability of the solution ensures that the electrodeposition process is stable and controllable, and the coating has a strong bond and excellent catalytic activity. 2. Self-healing application of a three-electrode long-cycle alkaline water electrolysis system: The high pH stable solution was directly used as the electrolyte to construct a three-electrode system, and long-cycle alkaline water electrolysis tests were carried out. During the test, the metal ions that detached from the catalyst surface dissolved in the solution and could form a dynamic ion pool with the homologous metal ions that were pre-stable in the solution. Under the drive of the electric field, they were redeposited at the catalyst loss sites, accurately realizing the in-situ self-healing of the catalyst and ensuring the stability of catalytic performance during the long-cycle test. 3. Self-healing application in industrial alkaline electrolyzers: This high-pH stable solution can be used as a dedicated electrolyte for industrial alkaline electrolyzers, directly adaptable to existing electrolyzer equipment. The electrolyte circulates between the electrolyzer body and the storage tank. During use, the types and proportions of metal ions in the solution can be adjusted according to the metal composition of the catalyst used in the electrolyzer. The metal ions detached from the catalyst can form a stable ion pool with the pre-placed ions in the solution. Under continuous industrial operation, the catalyst loss sites are dynamically replenished through electric field drive, effectively extending the overall service life of the electrolyzer.

[0017] The above-mentioned technical solution of the present invention is a whole in which each step is closely related and mutually influential, and together they determine the morphological characteristics and performance of the product.

[0018] The above technical solution has the following advantages or beneficial effects: 1. The composite stabilizer and dispersant used in this invention can achieve long-term stable existence / coexistence of single metal ions or multiple metal ions in high pH (pH=11~14) systems, with a stability time of over 30 days, which can meet the requirements for metal ion supply stability in electrodeposition and self-repair processes under different metal ion systems. 2. The high pH stable solution prepared by this invention can be directly used as the electrolyte in long-cycle systems / industrial electrolyzers. After the metal ions that fall off the catalyst surface dissolve in the solution, they together with the homologous metal ions that are pre-stable in the solution to form an ion reservoir. During long-cycle electrolysis, they are redeposited at the catalyst loss sites by electric field drive, achieving in-situ repair, thereby improving the stability of the catalyst and reducing costs. 3. The composite stabilizer used in this invention is a non-toxic organic amine and hydroxycarboxylic acid compound, which does not produce volatile harmful substances, meets the requirements of green industrial production, and will not remain in the catalyst, thus not affecting the catalytic performance. 4. The preparation process of this invention does not require high temperature and high pressure conditions, is easy to operate, has low cost, and is easy to scale up for industrial production. 5. In this invention, the solution composition and the types, quantities, and proportions of metal ions can be flexibly adjusted according to the performance requirements of the alkaline water electrolysis hydrogen production catalyst. The main catalytic active ions include Ni. 2+ Co 2+ Fe 2+ Fe 3+ It supports single, binary, ternary and multi-metal ion systems, and is compatible with various soluble salts such as sulfates, chlorides, nitrates, and acetates, as well as different strong base combinations. It has a wide range of applications and better anti-precipitation effect. 6. This invention achieves ultra-long-term stability and excellent application performance of metal ions under high pH conditions through a synergistic stabilization mechanism of composite stabilizers, dispersants, and surfactants: the organic amines and hydroxycarboxylic acids in the composite stabilizer firmly "anchor" the metal ions through coordination bonds and chelation structures, thermodynamically inhibiting hydrolysis and precipitation, thus providing a foundation for stability; the dispersant utilizes the steric hindrance effect of long polymer chains to kinetically block the growth of micro-aggregates, extending the stabilization period; the surfactant regulates the microscopic uniformity of the solution and the behavior of the electrode interface by reducing surface tension, ensuring the stability of the dynamic process; without the composite stabilizer, the metal ions hydrolyze instantly, and the latter two cannot function; without the dispersant, although complexation can delay, it cannot prevent particle aggregation, significantly shortening the stabilization time; without the surfactant, the microscopic inhomogeneity of the solution leads to deterioration of application performance; the synergistic effect of the three makes the solution of this invention stable for more than 30 days at pH=11~14, with a transmittance retention rate of over 94%, and can meet the requirements of complex working conditions such as multi-metal systems, wide temperature range, and self-healing, achieving a unity of static storage and dynamic application.

[0019] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Attached Figure Description

[0020] Figure 1 The hydrogen evolution polarization curves of the catalysts prepared in Example 3 and Comparative Examples 6-8 of this invention are shown. Figure 2 The above are oxygen evolution polarization curves of the catalysts prepared in Example 3 and Comparative Examples 6-8 of this invention. Figure 3 This is a scan image of the catalyst prepared by solution electrodeposition on nickel foam according to Example 3 of the present invention; Figure 4 This is a scan image of the catalyst prepared by solution electrodeposition on nickel foam in Example 3 of the present invention after deactivation; Figure 5 The image shows a scan of the catalyst prepared by solution electrodeposition on nickel foam according to Example 3 of the present invention after deactivation and self-repair. Figure 6 The image shows the it curves of the catalyst prepared in Example 3 of this invention in a self-healing solution and 1.0 M KOH. Figure 7 The C values ​​obtained after data processing of the CV curves of the catalyst prepared in Example 3 of this invention at different stages were obtained. dl Line graph. Detailed Implementation

[0021] The following embodiments are merely some, not all, of the embodiments of the present invention. Therefore, the detailed descriptions of the embodiments provided below are not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0022] In this invention, unless otherwise specified, all equipment and raw materials are commercially available or commonly used in the industry. The methods described in the following embodiments are conventional methods in the art, unless otherwise specified. Example 1

[0023] This embodiment prepares a high-pH stable solution suitable for metal cation systems. The high-pH stable solution comprises: 12.0 g potassium hydroxide, 6.0 g sodium hydroxide, 2.0 g nickel sulfate hexahydrate, 1.0 g ferrous sulfate heptahydrate, 2.5 g ethanolamine, 2.5 g tartaric acid, 0.3 g Tween 80, 0.15 g polyethylene glycol 6000, and 73.55 g deionized water. The preparation process and steps are as follows: S1. Place 53.55 g of deionized water in a 250 mL beaker, control the temperature at 30 ℃, and stir at a rate of 200 r·min. -1 Nitrogen gas was used throughout the process (flow rate 80 mL / min). -1 To remove oxygen, slowly add 12.0 g of potassium hydroxide and 6.0 g of sodium hydroxide, stirring until completely dissolved to obtain a strong alkali mother liquor; S2. Add 2.5 g of ethanolamine and 2.5 g of tartaric acid to the strong alkali mother liquor, continue stirring and purge with nitrogen for 30 min to ensure that the stabilizer is evenly dispersed in the mother liquor; S3. Dissolve 2.0 g of nickel sulfate hexahydrate and 1.0 g of ferrous sulfate heptahydrate in 20.0 g of deionized water to obtain a metal ion stock solution. Dissolve the solution under stirring and nitrogen purging conditions at a rate of 1 mL / min. -1 Add dropwise to the solution obtained in step S2, and continue stirring for 90 min after the addition is complete; S4. Add 0.3 g of Tween 80 to the solution obtained in step S3 and stir for 40 min; then add 0.15 g of polyethylene glycol 6000, continue stirring, and purge with nitrogen for 30 min. S5. Let the solution obtained in step S4 stand for 18 h, filter it in a nitrogen protective hood, and then seal it in a nitrogen-protected stoppered reagent bottle to protect it from light, thus obtaining a high pH stable solution. Example 2

[0024] This embodiment prepares a high pH stable solution suitable for metal cation systems. The high pH stable solution comprises: 8.0 g potassium hydroxide, 0.5 g cobalt chloride hexahydrate, 0.7 g glucosamine, 0.9 g malic acid, 0.4 g citric acid, 0.1 g sodium dodecylbenzenesulfonate, 0.3 g polyvinylpyrrolidone, and 89.1 g deionized water. The preparation process and steps are as follows: S1. Place 69.1 g of deionized water in a 250 mL beaker, control the temperature at 25 ℃, and stir at a rate of 100 r·min. -1 Slowly add 8.0 g of potassium hydroxide and stir until completely dissolved to obtain a strong alkali mother liquor; S2. Add 0.7 g g glucosamine, 0.9 g malic acid and 0.4 g citric acid to the strong alkaline mother liquor from step S1, and continue stirring for 20 min to ensure that the stabilizer is evenly dispersed in the mother liquor. S3. Dissolve 0.5 g of cobalt chloride hexahydrate in 20.0 g of deionized water to prepare a metal ion stock solution. Then, under stirring conditions, spray the solution at a rate of 3 mL / min. -1 Add dropwise to the solution obtained in step S2, and continue stirring for 60 min after the addition is complete; S4. Add 0.1 g sodium dodecylbenzenesulfonate to the solution obtained in step S3 and stir for 30 min; then add 0.3 g polyvinylpyrrolidone and continue stirring for 20 min. S5. Let the solution obtained in step S4 stand for 12 h, filter it in a nitrogen protective hood, and then seal it in a nitrogen-protected stoppered reagent bottle to protect it from light, thus obtaining a high pH stable solution. Example 3

[0025] This embodiment prepares a high-pH stable solution suitable for metal cation systems. The high-pH stable solution comprises: 10.0 g potassium hydroxide, 2.0 g sodium carbonate, 1.5 g nickel sulfate hexahydrate, 1.0 g cobalt sulfate heptahydrate, 0.5 g manganese sulfate monohydrate, 0.25 g zirconium sulfate tetrahydrate, 3.0 g ethylenediamine, 1.5 g citric acid, 0.4 g sodium dodecylbenzenesulfonate, 0.1 g polyvinyl alcohol, and 79.75 g deionized water. The preparation process and steps are as follows: S1. Place 59.75 g of deionized water in a 250 mL beaker, control the temperature at 40 ℃, and stir at a rate of 300 r·min. -1 Slowly add 10.0 g of potassium hydroxide and 2.0 g of sodium carbonate, and stir until completely dissolved to obtain a strong alkali mother liquor; S2. Add 3.0 g of ethylenediamine and 1.5 g of citric acid to the strong alkaline mother liquor from step S1, and continue stirring for 40 min to ensure that the stabilizer is evenly dispersed in the mother liquor. S3. Dissolve 1.5 g nickel sulfate hexahydrate, 1.0 g cobalt sulfate heptahydrate, 0.5 g manganese sulfate monohydrate, and 0.25 g zirconium sulfate tetrahydrate in 20.0 g deionized water, and stir at a rate of 2 mL / min. -1 Add dropwise to the solution obtained in step S2, and continue stirring for 120 min after the addition is complete; S4. Add 0.4 g of sodium dodecylbenzenesulfonate to the solution obtained in step S3 and stir for 60 min; then add 0.1 g of polyvinyl alcohol and continue stirring for 40 min. S5. Let the solution obtained in step S4 stand for 24 h, filter it in a nitrogen protective hood, and then seal it in a nitrogen-protected stoppered reagent bottle to protect it from light, thus obtaining a high pH stable solution. Example 4

[0026] This embodiment prepares a high-pH stable solution suitable for metal cation systems. The high-pH stable solution comprises: 20.0 g sodium hydroxide, 1.0 g nickel acetate tetrahydrate, 0.1 g sodium molybdate dihydrate, 0.13 g sodium tungstate dihydrate, 2.0 g ethanolamine, 3.0 g ethylenediamine, 3.0 g malic acid, 0.5 g Tween 80, 0.2 g polyethylene glycol 10000, 0.1 g polyvinyl alcohol, and 69.97 g deionized water. The preparation process and steps are as follows: S1. Place 49.97 g of deionized water in a 250 mL beaker, control the temperature at 35 ℃, and stir at a rate of 250 r·min. -1 Slowly add 20.0 g of sodium hydroxide and stir until completely dissolved to obtain a strong alkali mother liquor; S2. Add 2.0 g ethanolamine, 3.0 g ethylenediamine and 3.0 g malic acid to the strong alkaline mother liquor from step S1, and continue stirring for 30 min to ensure that the stabilizer is evenly dispersed in the mother liquor. S3. Dissolve 1.0 g nickel acetate tetrahydrate, 0.1 g sodium molybdate dihydrate, and 0.13 g sodium tungstate dihydrate in 20.0 g deionized water, and stir at a rate of 2.5 mL / min. -1 Add dropwise to the solution obtained in step S2, and continue stirring for 100 min after the addition is complete; S4. Add 0.5 g of Tween 80 to the solution obtained in step S3 and stir for 50 min; then add 0.2 g of polyethylene glycol 10000 and 0.1 g of polyvinyl alcohol, and continue stirring for 30 min. S5. Let the solution obtained in step S4 stand for 20 h, filter it in a nitrogen protective hood, and then seal it in a nitrogen-protected stoppered reagent bottle to protect it from light, thus obtaining a high pH stable solution. Example 5

[0027] This embodiment prepares a high-pH stable solution suitable for metal cation systems. The high-pH stable solution comprises: 9.0 g potassium hydroxide, 1.0 g sodium carbonate, 1.8 g cobalt nitrate hexahydrate, 0.78 g anhydrous copper acetate, 0.49 g zinc sulfate heptahydrate, 0.29 g titanium sulfate, 0.38 g chromium trichloride hexahydrate, 1.0 g ethanolamine, 0.5 g g glucosamine, 1.0 g citric acid, 1.0 g tartaric acid, 1.0 g malic acid, 0.3 g Tween 80, 0.1 g polyethylene glycol 2000, 0.1 g polyvinylpyrrolidone, and 81.26 g deionized water. The preparation process and steps are as follows: S1. Place 61.26 g of deionized water in a 250 mL beaker, control the temperature at 30℃, and stir at a rate of 210 r·min. -1 Slowly add 9.0 g of potassium hydroxide and 1.0 g of sodium carbonate, and stir until completely dissolved to obtain a strong alkali mother liquor; S2. Add 1.0 g ethanolamine, 0.5 g g glucosamine, 1.0 g citric acid, 1.0 g tartaric acid and 1.0 g malic acid to the strong alkaline mother liquor from step S1, and continue stirring for 30 min to ensure that the stabilizer is evenly dispersed in the mother liquor. S3. Dissolve 1.8 g cobalt nitrate hexahydrate, 0.78 g anhydrous copper acetate, 0.49 g zinc sulfate heptahydrate, 0.29 g titanium sulfate, and 0.38 g chromium trichloride hexahydrate in 20.0 g deionized water, and stir at a rate of 1.5 mL / min. -1 Add dropwise to the solution obtained in step S2, and continue stirring for 95 min after the addition is complete; S4. Add 0.3 g Tween 80 to the solution obtained in step S3 and stir for 40 min; then add 0.1 g polyethylene glycol 2000 and 0.1 g polyvinylpyrrolidone and continue stirring for 32 min. S5. Let the solution obtained in step S4 stand for 19 h, filter it in a nitrogen protective hood, and then seal it in a nitrogen-protected stoppered reagent bottle to protect it from light, thus obtaining a high pH stable solution. Example 6

[0028] This embodiment prepares a high-pH stable solution suitable for metal cation systems. The high-pH stable solution comprises: 1.0 g potassium hydroxide, 1.0 g sodium hydroxide, 2.6 g ferric nitrate nonahydrate, 2.4 g aluminum sulfate octadecylhydrate, 1.0 g ethanolamine, 1.0 g glucosamine, 1.0 g ethylenediamine, 1.0 g tartaric acid, 1.0 g malic acid, 0.1 g sodium dodecylbenzenesulfonate, 0.03 g polyvinyl alcohol, 0.02 g polyvinylpyrrolidone, and 87.85 g deionized water. The preparation process and steps are as follows: S1. Place 67.85 g of deionized water in a 250 mL beaker, control the temperature at 35 ℃, and stir at a rate of 200 r·min. -1 Slowly add 1.0 g of potassium hydroxide and 1.0 g of sodium hydroxide, and stir until completely dissolved to obtain a strong alkali mother liquor; S2. Add 1.0 g ethanolamine, 1.0 g g glucosamine, 1.0 g ethylenediamine, 1.0 g tartaric acid and 1.0 g malic acid to the strong alkaline mother liquor from step S1, and continue stirring for 35 min to ensure that the stabilizer is evenly dispersed in the mother liquor. S3. Dissolve 2.6 g of ferric nitrate nonahydrate and 2.4 g of aluminum sulfate octahydrate in 20.0 g of deionized water, and stir at a rate of 5 mL / min. -1 Add dropwise to the solution obtained in step S2, and continue stirring for 100 min after the addition is complete; S4. Add 0.1 g sodium dodecylbenzenesulfonate to the solution obtained in step S3 and stir for 50 min; then add 0.03 g polyvinyl alcohol and 0.02 g polyvinylpyrrolidone and continue stirring for 35 min. S5. Let the solution obtained in step S4 stand for 18 h, filter it in a nitrogen protective hood, and then seal it in a nitrogen-protected stoppered reagent bottle to protect it from light, thus obtaining a high pH stable solution.

[0029] Comparative Example To investigate the effects of different additives on the performance of the product during the preparation process of this invention, the following comparative experiments were conducted. Different solutions for metal cation systems were prepared in the following comparative examples: Comparative Example 1 This comparative example prepares a solution for a metal cation system. The preparation process is similar to that of Example 3, except that in step S2, ethylenediamine and citric acid are not added, and the total mass of the solution is made up to 100 g with deionized water. The remaining components, amounts, and preparation methods are the same as in Example 3.

[0030] Comparative Example 2 This comparative example prepares a solution for a metal cation system. The preparation process is similar to that of Example 3, except that in step S2, citric acid is replaced with ethylenediamine, i.e., the total mass of ethylenediamine is 4.5 g. The remaining components, amounts, and preparation methods are the same as in Example 3.

[0031] Comparative Example 3 This comparative example prepares a solution for a metal cation system. The preparation process is similar to that of Example 3, except that in step S2, ethylenediamine is replaced with citric acid, i.e., the total mass of citric acid is 4.5 g. The remaining components, amounts, and preparation methods are the same as in Example 3.

[0032] Comparative Example 4 This comparative example prepares a solution for a metal cation system. The preparation process is similar to that of Example 3, except that in step S2, 3.0 g of ethylenediamine and 1.5 g of citric acid are replaced with 4.5 g of ethylenediaminetetraacetic acid. The remaining components, amounts, and preparation methods are the same as in Example 3.

[0033] Comparative Example 5 This comparative example prepares a solution for a metal cation system. The preparation process is similar to that of Example 3, except that in step S2, 3.0 g of ethylenediamine and 1.5 g of citric acid are replaced with 4.5 g of ammonia. The remaining components, amounts, and preparation methods are the same as in Example 3.

[0034] Comparative Example 6 This comparative example prepares a solution for a metal cation system. The preparation process is similar to that of Example 3, except that sodium dodecylbenzenesulfonate is not added in step S4, and the total mass of the solution is made up to 100 g with deionized water. The remaining components, amounts and preparation methods are the same as in Example 3.

[0035] Comparative Example 7 This comparative example prepares a solution for a metal cation system. The preparation process is similar to that of Example 3, except that in step S4, polyvinyl alcohol is not added, and the total mass of the solution is made up to 100 g with deionized water. The other components, amounts, and preparation methods are the same as in Example 3.

[0036] Comparative Example 8 This comparative example prepares a solution for a metal cation system. The preparation process is similar to that of Example 3, except that in step S4, sodium dodecylbenzenesulfonate and polyvinyl alcohol are not added, and the total mass of the solution is made up to 100 g with deionized water. The remaining components, amounts and preparation methods are the same as in Example 3.

[0037] Performance testing The solutions for metal cation systems prepared in Examples 1-6 and Comparative Examples 1-8 of this invention were subjected to a series of tests, as detailed below: 1. Stability test of the solutions obtained in Example 3 and Comparative Examples 1-5: 50 mL of the solutions prepared in Example 3 and Comparative Examples 1-5 were sealed in identical transparent stoppered glass bottles and stored away from light. Samples were removed every 7 days, equilibrated at room temperature for 30 min, and the pH of the solution was measured using pH paper. If the pH was below 11, a small amount of the corresponding strong alkaline electrolyte was immediately added, stirred until completely dissolved, and the pH was restored to 11-14. The solution was then stored away from light. The transmittance (T%) of the solution was measured at 600 nm using a UV-Vis spectrophotometer, with deionized water as a blank control (T=100%). The transmittance was measured initially (day 0) and on day 30, three times for each group. The transmittance retention rate was calculated (transmittance retention rate = transmittance on day 30 / initial transmittance × 100%). The precipitation of the solution was observed simultaneously, and the stability time (in days) was recorded. The stability test results of the solutions obtained in Example 3 and Comparative Examples 1-5 are shown in Table 1.

[0038] Table 1. Stability test results of the solutions obtained in Example 3 and Comparative Examples 1-5 As shown in Table 1, Example 3 of the present invention achieved a transmittance retention rate of 94.5% and a metal ion stability time of up to 40 days due to the synergistic complexation effect of organic amines and hydroxycarboxylic acid compounds. Comparative Example 1, lacking a composite stabilizer, experienced instantaneous hydrolysis and precipitation of metal ions under strong alkaline conditions, failing to form a stable solution, thus making it impossible to test transmittance and stability time. Comparative Examples 2-3 (using a single stabilizer) and 4-5 (using a traditional complexing agent) showed significantly shortened stability times and a marked decrease in transmittance retention. Furthermore, Comparative Example 5 used ammonia as a complexing agent, which is volatile, causing the solution pH to drop below 11 during storage. Although a corresponding strong alkali was added to restore the pH, the complexation structure between ammonia and metal ions was destroyed, resulting in irreversible decay of the complexation ability, thus leading to the shortest stability time. These results fully demonstrate that the composite stabilizer significantly enhances the complexation ability through the synergistic effect of the amino coordination bond and the chelation structure of hydroxyl and carboxyl groups, avoiding the defects of single stabilizers or traditional complexing agents such as easy decomposition, volatility, and toxic residues, providing a core guarantee for the long-term stability of metal ions.

[0039] 2. Stability and application performance tests of solutions in Examples 3 and Comparative Examples 6-8: The solutions obtained from Comparative Examples 6 to 8 were tested according to the stability test method for the solutions obtained from Comparative Examples 1 to 5. The specific results are shown in Table 2.

[0040] In addition, the application performance of the solutions obtained in Example 3 and Comparative Examples 6-8 was tested. The specific test methods and steps are as follows: (1) Electrodeposition process: The solutions prepared in Example 3 and Comparative Examples 6-8 were used as electrolytes. Both the anode and cathode were pretreated nickel foam (ultrasonically cleaned for 15 min in 3.0 M HCl, anhydrous ethanol, and deionized water sequentially). Electrode deposition was carried out at 30 mA·cm⁻¹. -2 Electrodeposition was performed under constant current conditions for 20 min. After deposition, the surface was rinsed with deionized water and then vacuum dried at 70 °C for 5 min to obtain the target catalyst. (2) Catalytic activity: The hydrogen evolution and oxygen evolution polarization curves of the target catalyst were tested in 1.0 M KOH electrolyte.

[0041] Table 2. Stability test results of solutions obtained from Comparative Examples 6-8 As shown in Table 2, the transmittance retention and stabilization time of the solutions obtained in Comparative Examples 6-8 were significantly lower than those in Example 3. Furthermore, considering the hydrogen evolution polarization curves (…), Figure 1 ) and oxygen evolution polarization curve ( Figure 2 As can be seen, compared with Example 3, the hydrogen evolution and oxygen evolution polarization curves of Comparative Examples 6-8 show lower catalytic activity, indicating that the surfactant can optimize the solution dispersibility and avoid local aggregation of metal ions, and the dispersant can inhibit the aggregation and growth of hydrolysis intermediates. The two work together to further extend the stabilization period, while ensuring the catalytic kinetic performance of the electrodeposition catalyst.

[0042] 3. Experimental testing of catalyst self-healing Catalyst preparation: The high pH solution prepared in Example 3 was used as the electrolyte. Both the anode and cathode were pretreated nickel foam (ultrasonically cleaned for 15 min each in 3.0 M HCl, anhydrous ethanol, and deionized water sequentially). The electrolyte was prepared at 30 mA·cm⁻¹. -2 Electrodeposition was performed under constant current conditions for 20 min. After deposition, the surface was rinsed with deionized water and then vacuum dried at 70 °C for 5 min to obtain the target catalyst. The obtained catalyst was then tested as follows: (1) The target catalyst was tested in the solution prepared in Example 3 and in a 1.0 M KOH solution, and the it curve was recorded. (2) In the range of 0.32~0.42 V vs. RHE, use 20~200 mV·s -1 The target catalyst was subjected to CV testing at different scan rates, and CV curves were recorded. Cp was calculated by linearly fitting the slope of the current density difference to the scan rate. dl Value, denoted as C dl,1Then, the target catalyst was placed in a 1.0 M KOH electrolyte and a three-electrode system was used at 1.0 A·cm⁻¹. -2 Constant current electrolysis was performed for 1 h under high current density conditions. The catalyst was deactivated by the scouring effect of bubbles generated by the vigorous hydrogen evolution under high current density, the local temperature rise on the electrode surface, and the excessive oxidation of active sites. After deactivation, the CV was measured again, and C was calculated. dl , denoted as C dl,2 The deactivated catalyst was transferred to the high pH stable solution prepared in Example 3 and heated at 30 mA·cm⁻¹. -2 Repair under the condition for 6 hours, test and calculate C dl , denoted as C dl,3。 Figures 3-5 The scan images of the catalyst prepared by solution electrodeposition on nickel foam according to Example 3 of the present invention, the scan images after deactivation, and the scan images after deactivation and self-repair are shown. It can be seen from the images that the catalyst prepared based on the solution of Example 3 has a uniform structure. Figure 3 ), after deactivation by high current density, the surface damage is obvious ( Figure 4 However, after repair in a solution containing homologous metal ions, the structure was basically restored. Figure 5 The it curves of the catalyst tested in high pH solution and 1.0 M KOH (). Figure 6 The data shows that at 200 mA·cm -2 At a constant current density, using the solution from Example 3 as the catalyst in the electrolyte, the current density decay rate was significantly lower than that of the catalyst in a conventional 1.0 M KOH electrolyte. This indicates that the pre-stabilized homologous metal ions in the solution constitute a dynamic ion pool, effectively compensating for the loss of active sites in the catalyst during the test, thereby maintaining stable current output. The reversibility of this process was further confirmed by changes in the electrochemical active surface area (ECSA).

[0043] Figure 7 The CV curves of the catalyst prepared in Example 3 were tested at different stages, and the C values ​​were obtained through data processing. dl The graph shows the initial double-layer capacitance C of the catalyst. dl,1 After forced inactivation at high current density, the concentration of C decreased significantly. dl,2 However, after repair in the solution of Example 3, C dl,3 The catalyst has essentially recovered to its initial level. These results demonstrate that the solution prepared in this invention can achieve in-situ directional deposition of metal ions to catalyst loss sites through an electric field, thus completing efficient self-repair and providing a reliable solution to the problem of long-term catalyst stability.

[0044] 4. Stability and low-temperature compatibility tests of the high pH stable solutions prepared in Examples 1-6: The high pH stable solutions prepared in Examples 1-6 were tested according to the stability test method for the solutions obtained in Comparative Examples 1-5 (wherein, Example 1 required sealing in a stoppered glass bottle under nitrogen protection); in addition, the six groups of solutions were placed in a low temperature environment of 5 ℃ and observed for crystallization within 7 days. The specific results are shown in Table 3.

[0045] Table 3. Results of stability and low-temperature compatibility tests of the solutions obtained in Examples 1-6. As shown in Table 3, the solutions obtained in Examples 1-6 maintained a transmittance of ≥94% for 30 days and showed no crystallization at a low temperature of 5 °C. The core reason for this low-temperature stability is that the saturated solubility of potassium hydroxide (~100 g / 100 g water), sodium hydroxide (~46 g / 100 g water), and sodium carbonate (~9.8 g / 100 g water) at 5 °C is higher than the concentration of the strong alkali in each example, thus avoiding the thermodynamic basis of crystallization at the concentration level. Furthermore, the composite stabilizer and dispersant synergistically reduce the electrolyte activity coefficient, further inhibiting crystal nucleation and growth, thus blocking the crystallization process at the kinetic level. These results demonstrate that the proposed scheme has good component flexibility and process adaptability, meeting the requirements of industrial electrolyzers for long-term stable operation of the electrolyte.

[0046] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A high pH stable solution suitable for metal cation systems, characterized in that, By mass percentage, it includes: 2-20% strong alkaline electrolyte, 0.5-5% metal ion source, 2-8% composite stabilizer, 0.1-0.5% surfactant, 0.05-0.3% dispersant, and the balance is deionized water; The pH value of the high pH stable solution suitable for metal cation systems is 11-14.

2. The high pH stable solution suitable for metal cation systems according to claim 1, characterized in that, The strong alkaline electrolyte is one or more of potassium hydroxide, sodium hydroxide, or sodium carbonate.

3. The high pH stable solution suitable for metal cation systems according to claim 1, characterized in that, The metal ion source is a soluble salt corresponding to the metal ion; the metal ion includes the main catalytically active metal ion and optionally includes auxiliary metal ions, wherein the main catalytically active metal ion is Ni. 2+ Co 2+ Fe 2+ Fe 3+ One or more of the following, with Mn as the auxiliary metal ion. 2+ Cu 2+ Zn 2+ Al 3+ Cr 3+ Ti 4+ Zr 4+ Mo 6+ W 6+ One or more of the following; the soluble salt is one or more of nitrate, sulfate, chloride or acetate.

4. A high pH stable solution suitable for metal cation systems according to claim 3, characterized in that, When the metal ion is a single metal ion, it is only the main catalytic active metal ion; when the metal ion is two or more, it includes at least one main catalytic active metal ion and at least one auxiliary metal ion, and the molar ratio of the main catalytic active metal ion to the auxiliary metal ion is (1:0.2) to (1:1.5).

5. A high pH stable solution suitable for metal cation systems according to claim 1, characterized in that, The composite stabilizer is composed of organic amine compounds and hydroxycarboxylic acid compounds in a mass ratio of (1:2) to (2:1). The organic amine compounds are one or more of ethanolamine, glucosamine, and ethylenediamine; the hydroxycarboxylic acid compounds are one or more of citric acid, tartaric acid, and malic acid.

6. A high pH stable solution suitable for metal cation systems according to claim 1, characterized in that, The surfactant is sodium dodecylbenzenesulfonate or Tween 80.

7. A high pH stable solution suitable for metal cation systems according to claim 1, characterized in that, The dispersant is one or more of polyethylene glycol 2000-10000, polyvinyl alcohol, and polyvinylpyrrolidone.

8. A method for preparing a high pH stable solution suitable for a metal cation system according to any one of claims 1 to 7, characterized in that, Follow these steps in sequence: S1. Place deionized water in a beaker, control the temperature at 25~40 ℃, and stir at a speed of 100~300 r·min. -1 Slowly add a strong base electrolyte and stir until completely dissolved to obtain a strong base mother liquor. S2. Add the composite stabilizer to the strong alkaline mother liquor from step S1 and continue stirring for 20-40 minutes. S3. Dissolve the metal ion source in deionized water to obtain a metal ion stock solution, and then, under stirring conditions, increase the concentration of the metal ion source at a rate of 1-5 mL / min. -1 The solution is added dropwise to the solution obtained in step S2 at a certain rate, and stirring is continued for 60-120 min after the addition is completed. S4. Add the surfactant to the solution obtained in step S3, stir for 30-60 min, then add the dispersant and continue stirring for 20-40 min. S5. Let the solution obtained in step S4 stand for 12-24 hours, filter it, seal it in a reagent bottle and store it in the dark to obtain a high pH stable solution suitable for metal cation systems.

9. An application of a high pH stable solution suitable for metal cation systems, characterized in that, The high pH stable solution prepared by the method described in claim 8 can be used as an electrolyte for electrodeposition preparation of hydrogen / oxygen evolution catalysts in alkaline water electrolysis, long-circulation systems of three electrodes in alkaline water electrolysis, and circulation systems of industrial alkaline electrolyzers.

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