Regeneration method of hydrogen evolution electrode

Abstract

The invention relates to the field of hydrogen production by alkaline electrolysis of water, in particular to a regeneration method of a hydrogen evolution electrode, and solves the problems that the surface of the hydrogen evolution electrode is inactivated and cannot be recycled in the prior art. The method comprises the following steps: washing a hydrogen evolution electrode to be regenerated with water; carrying out primary acid leaching on the washed hydrogen evolution electrode to be regenerated, synchronously adding a reducing agent, and then cleaning and drying; carrying out hot alkaline leaching treatment on the treated hydrogen evolution electrode to be regenerated; and finally, carrying out secondary acid leaching on the hydrogen evolution electrode to be regenerated after alkaline leaching, and cleaning to finish regeneration treatment. By adopting a stepped treatment strategy of weak acid pre-dissolving, strong alkali stripping and strong acid activation, deep repair and functional reconstruction of the surface and internal structure of the hydrogen evolution electrode are realized, and a choice is provided for cyclic utilization of the hydrogen evolution electrode.

Description

Technical Field

[0001] The invention relates to the field of hydrogen production by alkaline water electrolysis, and in particular to a regeneration method for a hydrogen evolution electrode. Background Art

[0002] In alkaline water electrolysis hydrogen production systems, electrodes, as one of the core components, are important components that promote hydrogen evolution reactions. As the site where electrochemical reactions occur, electrodes provide active reaction sites and reduce the energy barrier required for the reaction. At the same time, the structure and surface characteristics of the electrode materials greatly increase the active area, accelerate charge transfer and material diffusion, and speed up the reaction rate. In alkaline electrolyzers, electrodes are exposed to high temperature and strong alkaline conditions for a long time. The electrodes need to have corrosion resistance and high efficiency and stability. Currently, commercial electrodes are mainly nickel-based alloys. Raney nickel powder is sprayed onto the nickel mesh substrate by thermal spraying as the anode and cathode in the electrolyzer. This method is very mature and has been industrialized on a large scale.

[0003] Currently, industrial-grade alkaline electrolyzers are typically designed for a cumulative operating life of 10,000 to 80,000 hours, with actual operating time reaching several years. This requires their core components to be highly efficient and stable. During electrolytic cell operation, the metal pipes, acting as conductors, are located in the anode and cathode regions, where redox reactions occur, causing electrochemical corrosion. This is accompanied by adverse reactions such as alkaline corrosion, impurity-induced corrosion, and erosion by high-temperature electrolytes, leading to aging and corrosion of the metal pipes. Ions on the pipe surface dissolve into the electrolyte, where adsorption occurs at the anode and cathode under electrochemical reactions. After years of reaction, the electrode surfaces are completely coated with impurities.

[0004] These impurities, primarily iron and chromium ions, cover the active sites on the electrode surface, resulting in reduced electrochemical performance and increased energy consumption. In a few years or even longer, many OEMs will be faced with a large number of disassembled electrodes, their surfaces contaminated by metal ions and inactivated. Currently, there are no mature cleaning methods to treat disassembled electrodes, and replacing them with new ones increases costs and wastes resources. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for regenerating a hydrogen evolution electrode, which solves the problem in the prior art that the surface of the hydrogen evolution electrode is deactivated and cannot be regenerated.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is: The present invention provides a method for regenerating a hydrogen evolution electrode, comprising the following steps: (1) Washing the hydrogen evolution electrode to be regenerated with water; (2) acid leaching the hydrogen evolution electrode to be regenerated after water washing, adding a reducing agent simultaneously, and then washing and drying; (3) subjecting the hydrogen evolution electrode to be regenerated after the treatment in step (2) to hot alkaline leaching treatment; (4) performing a secondary acid leaching on the hydrogen evolution electrode to be regenerated after alkaline leaching, and completing the regeneration process after cleaning; The first acid leaching in step (2) uses a saturated weak acid solution, the alkali leaching in step (3) uses a strong alkali solution with a mass concentration of 30 wt% to 40 wt%, and the second acid leaching in step (4) uses a strong acid solution with a concentration of 1 to 3 M.

[0007] Furthermore, in step (1), the water washing pressure is 5-50 MPa, the water washing flow rate is 10-40 L / min, the water washing temperature is 50-60° C., and the water washing time is 60-180 s.

[0008] Furthermore, in step (2), the weak acid used in the primary acid leaching is a mixture of one or more selected from the group consisting of formic acid, acetic acid, citric acid, malic acid and lactic acid.

[0009] Furthermore, in step (2), the acid leaching time is 24 to 96 hours, and the acid leaching temperature is room temperature.

[0010] Furthermore, in step (2), the reducing agent is a mixture of one or more selected from ascorbic acid, hydroxylamine sulfate, thioglycolic acid and sodium sulfite.

[0011] Furthermore, the mass ratio of the weak acid used in the primary acid leaching to the reducing agent is (15-25):1.

[0012] Furthermore, in step (2), during one acid leaching, the hydrogen evolution electrode to be regenerated is subjected to ultrasonic treatment, the ultrasonic medium is the saturated weak acid solution, the ultrasonic frequency is 30-50 KHz, the ultrasonic duration is 1-2 hours, and the ultrasonic power is 300-400W.

[0013] Furthermore, in step (3), the strong alkali used in alkaline leaching is potassium hydroxide, barium hydroxide, calcium hydroxide or sodium hydroxide.

[0014] Furthermore, in step (3), the alkali leaching time is 12 to 48 hours, and the alkali leaching temperature is 70 to 80°C.

[0015] Furthermore, the strong acid used in the secondary acid leaching in step (4) is a mixture of one or more selected from sulfuric acid, hydrochloric acid, nitric acid, chloric acid and metaphosphoric acid.

[0016] Furthermore, in step (4), the secondary acid leaching time is 1 to 3 hours, and the acid leaching temperature is room temperature.

[0017] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art: The present invention uses a three-step method of "weak acid pre-dissolution + strong base stripping + strong acid activation" to remove ions and impurities adsorbed on the electrode surface and inside the coating in stages, reconstruct the porous structure of the electrode active layer, restore its specific surface area and catalytic active sites, and achieve deep repair and functional reconstruction of the surface and internal structure of the hydrogen evolution electrode.

[0018] Furthermore, the use of a reducing agent is also involved in the primary acid leaching process, which aims to inhibit the generation of trivalent iron ions through the reducing agent. This is because trivalent iron ions can corrode the electrode coating, and the use of the reducing agent can reduce the trivalent iron ions dissolved in the weak acid used in the primary acid leaching to divalent iron ions, thereby avoiding damage to the electrode coating. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Hereinafter, some specific embodiments of the present invention will be described in detail in an illustrative and non-limiting manner with reference to the accompanying drawings. The same reference numerals in the accompanying drawings indicate the same or similar components or parts. It should be understood by those skilled in the art that these drawings are not necessarily drawn to scale. In the accompanying drawings: Figure 1 This is a SEM morphology image of the hydrogen evolution electrode provided by the present invention that has not been regenerated; Figure 2 This is a SEM morphology image of the hydrogen evolution electrode after regeneration obtained according to Example 1 of the present invention; Figure 3 LSV curve diagram of the regenerated electrode and the non-regenerated electrode provided in the embodiment of the present invention; Figure 4 This is a flow chart of the hydrogen evolution electrode regeneration method of the present invention. DETAILED DESCRIPTION

[0020] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0021] Example 1: This embodiment provides a method for regenerating a hydrogen evolution electrode, comprising the following steps: (1) First, the hydrogen evolution electrode to be regenerated is cleaned with deionized water at 60°C under high pressure. The water pressure is controlled at 10 MPa, the flow rate is 25 L / min, the cleaning distance between the water source and the hydrogen evolution electrode is 250 mm, the spray angle is 90°, the moving speed is 0.3 m / s, and the cleaning time is 120 s to remove impurities visible to the naked eye on the electrode surface. (2) Prepare a saturated citric acid solution by weighing 650 g of citric acid and dissolving it in 1000 mL of deionized water. Simultaneously, add 50 g of ascorbic acid. Soak the electrode after high-pressure cleaning in the citric acid solution for 48 h. During the soaking period, remove the electrode and perform ultrasonic treatment at a frequency of 40 kHz and a power of 300 W for 1 h. The ultrasonic medium is the prepared citric acid solution. (3) Place the electrode treated in step (2) in pure water and wash it repeatedly for 5 to 10 times to remove the acid remaining on the surface, and let it dry naturally; (4) Place the dried electrode in 30wt% KOH (potassium hydroxide), heat to 80℃, soak for 24h, take it out, and dry it at 60℃; (5) Place the electrode after alkaline immersion in 3M hydrochloric acid solution, soak for 1 hour, take it out and rinse it with pure water to complete the electrode regeneration.

[0022] Example 2: This embodiment provides a method for regenerating a hydrogen evolution electrode. The only difference between this embodiment and the first embodiment is that the water pressure in step (1) is 5 MPa and the cleaning time is 180 s; the acid leaching time in step (2) is 24 h, and the electrode regeneration is finally completed.

[0023] Example 3: This embodiment provides a method for regenerating a hydrogen evolution electrode. The only difference between this embodiment and the first embodiment is that the acid leaching time in step (2) is 72 hours; the alkaline leaching time in step (4) is 12 hours, and the electrode regeneration is finally completed.

[0024] Example 4 This embodiment provides a method for regenerating a hydrogen evolution electrode. The only difference between this embodiment and the first embodiment is that the weak acid used in step (2) is acetic acid; the base used in step (4) is 40 wt % sodium hydroxide, and the electrode regeneration is finally completed.

[0025] Example 5 This embodiment provides a method for regenerating a hydrogen evolution electrode. The only difference between this embodiment and the first embodiment is that the base used in step (4) is 35 wt% potassium hydroxide; the strong acid used in step (5) is 1 M hydrochloric acid, and the electrode regeneration is finally completed.

[0026] Example 6 This embodiment provides a method for regenerating a hydrogen evolution electrode, which differs from the first embodiment only in that, in step (4), the heating temperature is 70° C.; in step (5), the secondary acid leaching time is 3 h, and the electrode regeneration is finally completed.

[0027] Example 7 This embodiment provides a method for regenerating a hydrogen evolution electrode. The only difference between this embodiment and the first embodiment is that the soaking time in citric acid in step (2) is 96 hours, and the soaking time in KOH in step (4) is 48 hours. Finally, the electrode regeneration is completed.

[0028] Comparative Example 1: This embodiment provides a method for regenerating a hydrogen evolution electrode, which differs from the first embodiment only in that the weak acid used in step (2) is saturated oxalic acid.

[0029] Comparative Example 2: This embodiment provides a method for regenerating a hydrogen evolution electrode, which differs from the first embodiment only in that, in step (4), the alkali solution soaking temperature is room temperature.

[0030] Comparative Example 3: This embodiment provides a method for regenerating a hydrogen evolution electrode, which differs from the first embodiment only in that the weak acid used in step (2) is acetic acid, the acid leaching time is 720 h, and no ultrasonic operation is performed during the leaching.

[0031] Comparative Example 4: This embodiment provides a method for regenerating a hydrogen evolution electrode, which differs from the first embodiment only in that the weak acid used in step (2) is acetic acid, the acid leaching time is 168 h, and the acid leaching temperature is 50°C.

[0032] Comparative Example 5: This embodiment provides a method for regenerating a hydrogen evolution electrode, which differs from the first embodiment only in that, in step (5), the secondary acid leaching time is 4 hours.

[0033] In the present invention, the performance tests and characterizations of the hydrogen evolution electrodes treated in the above embodiments and comparative examples are carried out, as follows: The SEM morphology of the unregenerated electrode and the hydrogen evolution electrode after regeneration treatment in Example 1 was characterized. Figure 1 It can be seen that the surface of the unregenerated electrode is contaminated by the diaphragm and impurities, and many impurities are adsorbed in the porous structure of the coating cross section, which seriously affects its hydrogen evolution performance and stability. Figure 2 It can be seen that after the regeneration treatment in Example 1, the electrode surface is clean and pollution-free, and the impurity adsorption inside the coating is significantly reduced.

[0034] In the present invention, the Bio-Logic electrochemical workstation was used to select a saturated calomel reference electrode to test the LSV (linear sweep voltammetry) curves of the regenerated electrode and the unregenerated electrode in Example 1 of the present invention. Figure 3 As shown in Table 3, the results show that at a current density of 500 mA / cm 2Under these conditions, the overpotential of the regenerated electrode in Example 1 is 354 mV, which is 70 mV higher than the hydrogen evolution performance of the non-regenerated electrode, and the effect is significant.

[0035] In addition, the elemental composition and content of the electrodes were analyzed using EDS technology. Table 1 shows the elemental content of the unregenerated electrodes measured by EDS. It can be seen that the mass fraction of Fe is as high as 42.6%, and the mass fraction of Cr is 17.3%. Both Fe and Cr originate from within the pipe. Tables 2 and 3 show that the regeneration process of the present invention significantly reduces the Fe and Cr contents in the hydrogen evolution electrodes of Examples 1 to 7, achieving electrode regeneration.

[0036] Table 1 EDS element measurement results of unregenerated hydrogen evolution electrode Table 2 EDS element measurement results of hydrogen evolution electrode in Example 1 Table 3 EDS measurement results of hydrogen evolution overpotential and Fe and Cr elements of the unregenerated electrode and various examples In summary, the hydrogen evolution electrode regeneration method disclosed in this invention achieves deep recovery of electrode performance through a three-step collaborative process. The core of this method lies in the step-by-step treatment strategy of "weak acid predissolution - strong base stripping - strong acid activation," which achieves deep repair and functional restoration of the hydrogen evolution electrode's surface and internal structure, providing a reliable technical solution for the recycling of hydrogen evolution electrodes.

[0037] The above embodiments are only for illustrating the technical concept and features of the present invention. Their purpose is to enable people familiar with this technology to understand the contents of the present invention and implement them accordingly. They are not intended to limit the scope of protection of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for regenerating a hydrogen evolution electrode, characterized in that: The following steps are involved: (1) Washing the hydrogen evolution electrode to be regenerated with water; (2) acid leaching the hydrogen evolution electrode to be regenerated after water washing, adding a reducing agent simultaneously, and then washing and drying; (3) subjecting the hydrogen evolution electrode to be regenerated after the treatment in step (2) to hot alkaline leaching treatment; (4) performing a secondary acid leaching on the hydrogen evolution electrode to be regenerated after alkaline leaching, and completing the regeneration process after cleaning; In step (2), the first acid leaching adopts a saturated weak acid solution, the alkali leaching in step (3) adopts a strong alkali solution with a mass concentration of 30 wt% to 40 wt%, and the second acid leaching in step (4) adopts a strong acid solution with a concentration of 1 to 3 M.

2. The method for regenerating a hydrogen evolution electrode according to claim 1, wherein: In step (1), the water washing pressure is 5~50MPa, the water washing flow rate is 10~40L / min, the water washing temperature is 50~60℃, and the water washing time is 60~180s.

3. The regeneration method of a hydrogen evolution electrode according to claim 1, characterized in that: In step (2), the weak acid used in the primary acid leaching is a mixture of one or more selected from formic acid, acetic acid, citric acid, malic acid and lactic acid.

4. A method for regenerating a hydrogen evolution electrode according to claim 1 or 3, characterized in that: In step (2), the acid leaching time is 24 to 96 hours, and the acid leaching temperature is room temperature.

5. The method for regenerating a hydrogen evolution electrode according to claim 1, wherein: In step (2), the reducing agent is a mixture of one or more selected from ascorbic acid, hydroxylamine sulfate, thioglycolic acid and sodium sulfite.

6. The method for regenerating a hydrogen evolution electrode according to claim 1, wherein: In step (2), during one acid leaching, the hydrogen evolution electrode to be regenerated is subjected to ultrasonic treatment, the ultrasonic medium is the saturated weak acid solution, the ultrasonic frequency is 30-50 KHz, the ultrasonic duration is 1-2 h, and the ultrasonic power is 300-400 W.

7. The method for regenerating a hydrogen evolution electrode according to claim 1, wherein: In step (3), the strong alkali used for alkali leaching is potassium hydroxide, sodium hydroxide, barium hydroxide or calcium hydroxide.

8. A method for regenerating a hydrogen evolution electrode according to claim 1 or 7, characterized in that: In step (3), the alkali immersion time is 12 to 48 hours, and the alkali immersion temperature is 70 to 80°C.

9. The method for regenerating a hydrogen evolution electrode according to claim 1, wherein: The strong acid used in the secondary acid leaching in step (4) is a mixture of one or more selected from sulfuric acid, hydrochloric acid, nitric acid, chloric acid and metaphosphoric acid.

10. A method for regenerating a hydrogen evolution electrode according to claim 1 or 9, characterized in that: In step (4), the secondary acid leaching time is 1 to 3 hours, and the acid leaching temperature is room temperature.

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