An electrode recovery method

Abstract

This application proposes an electrode recycling method, comprising: separating the electrode substrate and the catalyst layer on the surface of a waste electrode to obtain the electrode substrate and the catalyst layer; subjecting the catalyst layer to a sulfidation reaction with sulfur, converting the active catalyst component in the catalyst layer into a sulfide; reacting the sulfide with a carbon source to form a precursor, followed by calcination to obtain a regenerated catalyst product. The electrode recycling method of this application, by separating the electrode substrate and catalyst layer of the waste electrode, converting the active catalyst component into a sulfide, and then calcining and reducing the sulfide with a carbon source, can achieve the recovery of the active catalyst component in the catalyst layer of the waste electrode and catalyst regeneration. Simultaneously, the sulfur introduced during the sulfidation process enters the carbon support and can interact with the active component of the catalyst layer itself, increasing the catalytic effect.

Description

Technical Field

[0001] This application relates to the field of hydrogen energy and fuel cell technology, and in particular to an electrode recovery method. Background Technology

[0002] In water electrolysis hydrogen production units, electrodes are the core components that determine the energy consumption of hydrogen production. Electrode materials involve various metals such as nickel, iron, and cobalt. Some hydrogen production units also involve precious metals, such as foreign alkaline water electrolysis hydrogen production units (platinum, etc.) and general PEM hydrogen production units (platinum, iridium, etc.). As the installed capacity of electrolyzers increases, large amounts of nickel, platinum, iridium, and other metals will be consumed, posing resource constraints to the development of green hydrogen production.

[0003] Therefore, it is necessary to recover and reuse the effective components in waste electrodes to reduce the pressure on new metal mining capacity. Currently, due to the fact that the cumulative installed capacity of electrolyzers worldwide has not yet reached a significant scale and the electrolyzers have been in use for a relatively short period of time, a mature electrode recycling process has not yet been developed, and research on electrode recycling from hydrogen production electrolyzers is also very limited.

[0004] Electrolytic hydrogen production electrodes can be divided into two parts: the electrode substrate and the catalyst layer. The catalyst layer often contains precious metals and other components. Waste electrodes are usually caused by the loss of the effective components (i.e., active components) of the catalyst layer, while the electrode substrate remains largely unchanged. Traditional recycling processes often involve directly crushing the waste material and then collecting the metal components using methods such as acid leaching. This leads to waste of the electrode substrate and generates a large amount of wastewater, creating an environmental burden. Furthermore, the purification of the recovered metal components is cumbersome, costly, and has a low recycling rate. In addition, the recovered active components of the catalyst layer often cannot directly form a catalyst and require further conversion processes.

[0005] Therefore, there is a need to develop an electrode recycling method that can achieve the recycling of the electrode substrate without damaging the electrode substrate, has a high recycling rate of catalytic active components, integrates the recycling and regeneration catalyst formation process, has good catalytic effect of the regenerated catalyst, has a small environmental burden, and is low cost. Summary of the Invention

[0006] In view of this, this application aims to at least partially solve one of the technical problems in the related art. To this end, embodiments of this application propose an electrode recovery method.

[0007] The electrode recovery method of this application embodiment includes:

[0008] The electrode substrate of the waste electrode is separated from the catalyst layer on its surface to obtain the electrode substrate and the catalyst layer.

[0009] The catalyst layer is subjected to a sulfidation reaction with sulfur, and the active catalyst component in the catalyst layer is converted into sulfide.

[0010] The sulfide is reacted with a carbon source to form a precursor, which is then calcined to obtain a regenerated catalyst product.

[0011] In some embodiments, the mass ratio of the catalyst layer to sulfur is 1:(1-4).

[0012] In some embodiments, the temperature of the vulcanization reaction is 1000-1200°C.

[0013] In some embodiments, the vulcanization reaction takes 1-5 hours.

[0014] In some embodiments, the pressure of the vulcanization reaction is 0.5-1.5 atm.

[0015] In some embodiments, during the sulfidation reaction, the sulfur element is carried by an inert gas and reacts countercurrently with the catalyst layer.

[0016] In some embodiments, the electrode recovery method further includes the steps of wet ball milling and spray drying the precursor sequentially before calcination.

[0017] In some embodiments, the electrode recycling method further includes the step of reusing the electrode substrate after cleaning it with at least one of acid washing, alkali washing, and water washing.

[0018] In some embodiments, the electrode recovery method further includes a step of converting the catalyst layer into catalyst layer powder before subjecting the catalyst layer to a sulfidation reaction with sulfur.

[0019] In some embodiments, the carbon source includes at least one of graphene, activated carbon, and graphitic carbon nitride.

[0020] In some embodiments, the mass ratio of the sulfide to the carbon source is 1:(1-5).

[0021] In some embodiments, the calcination temperature is 600-800℃ and the calcination time is 1.5-4.5h.

[0022] In some embodiments, when the waste electrode is an electrode for alkaline water electrolysis to produce hydrogen, the method for separating the electrode substrate from the catalyst layer on its surface is an electrochemical method.

[0023] In some embodiments, when the waste electrode is a proton exchange membrane electrode, the method for separating the electrode substrate from the catalyst layer on its surface is an impregnation method.

[0024] In some embodiments, the electrochemical method includes the step of alternatingly electrolyzing the waste electrode in an electrolyte by switching between cathode and anode.

[0025] In some embodiments, the impregnation solution used in the impregnation method is an alkaline solution or a small molecule alcohol.

[0026] In some embodiments, the electrolyte includes at least one of sodium carbonate-sodium potassium tartrate aqueous solution, disodium hydrogen phosphate-sodium hydroxide aqueous solution, and sodium carbonate-sodium bicarbonate aqueous solution.

[0027] In some embodiments, both the cathode and the anode are the waste electrodes.

[0028] In some embodiments, the electrolysis process conditions are: temperature 40-60℃, current density 4-10A / dm³. 2 pH 10-13, time 1-4h, the cathode and the anode are alternated 2-5 times.

[0029] In some embodiments, the catalyst layer further includes impurities shed from the electrode substrate, and the electrode recovery method further includes:

[0030] The sulfide is obtained by separating the sulfide from the oxides of impurities detached from the electrode substrate using a sulfide flotation method.

[0031] In some embodiments, the electrode recovery method further includes the step of recombining the regenerated catalyst product with the electrode matrix to form a regenerated electrode.

[0032] The technical solution provided in this application has at least the following beneficial effects:

[0033] 1. After separating the electrode substrate and catalyst layer of the waste electrode, the active components of the catalyst layer are converted into sulfides. The sulfides are then calcined and reduced with a carbon source, which can realize the recovery of the active components of the catalyst in the catalyst layer of the waste electrode and the regeneration of the catalyst. At the same time, the sulfur element introduced during the sulfidation process enters the carbon support and can interact with the active components of the catalyst layer itself, thereby increasing the catalytic effect.

[0034] 2. The catalyst layer on the surface of the waste electrode is separated from the electrode substrate by a simple impregnation method or electrochemical method. The separation efficiency is higher than 95% and the electrode substrate is not damaged. Therefore, the electrode substrate can be directly reused after simple cleaning.

[0035] 3. By utilizing the difference in thermodynamics between the active components of the catalyst layer of the waste electrode and the impurities detached from the electrode substrate during the sulfidation reaction, the active components such as precious metals in the catalyst layer on the surface of the waste electrode can be separated and recovered, thus avoiding the generation of large amounts of acid and alkaline wastewater.

[0036] 4. The regenerated catalyst can be directly combined with the original electrode substrate through simple coating to become a new electrode, which is beneficial for electrode production and integration.

[0037] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through practice of the present application. Attached Figure Description

[0038] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:

[0039] Figure 1 This is a flowchart illustrating an exemplary embodiment of the electrode recovery method of this application. Detailed Implementation

[0040] The embodiments of this application are described in detail below, with examples of these embodiments illustrated in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application.

[0041] In the application, the disclosure of the numerical range includes all values ​​throughout the range and the disclosure of further subdivisions of the range, including the endpoints and subranges given for these ranges.

[0042] Unless otherwise specified, all raw materials and equipment involved in the application are those that can be manufactured commercially or by known methods; and all methods involved are conventional methods unless otherwise specified.

[0043] The electrode recovery method of this application includes the following steps:

[0044] S101. Separate the electrode substrate and the catalyst layer on the surface of the waste electrode to obtain the electrode substrate and the catalyst layer.

[0045] In the embodiments of this application, the method for separating the electrode substrate of the waste electrode from the catalyst layer on its surface is not limited, as long as it can ensure that the electrode substrate is not damaged and that the electrode substrate can be separated from the catalyst layer (e.g., laser cutting).

[0046] In the embodiments of this application, the waste electrode can be either an anode or a cathode.

[0047] In some embodiments, when the waste electrode is an electrode for alkaline water electrolysis to produce hydrogen, the method for separating the electrode substrate from the catalyst layer on its surface is an electrochemical method. It should be noted that the electrode substrate of the waste electrode for alkaline water electrolysis to produce hydrogen includes, but is not limited to, one of stainless steel plates, stainless steel mesh, nickel plates, nickel mesh, titanium plates, or titanium mesh, and the catalyst active component in the catalyst layer of the waste electrode for alkaline water electrolysis to produce hydrogen includes, but is not limited to, at least one of Ni, Co, and Mn.

[0048] In some embodiments, the electrochemical method includes the step of alternatingly electrolyzing the spent electrodes in an electrolyte solution by switching the cathode and anode. Both the cathode and anode are spent electrodes (including an electrode substrate and a catalyst layer). The electrolyte solution includes, but is not limited to, at least one of sodium carbonate-sodium potassium tartrate aqueous solution, disodium hydrogen phosphate-sodium hydroxide aqueous solution, and sodium carbonate-sodium bicarbonate aqueous solution; the mass concentration of the electrolyte in the electrolyte solution is 0.2-0.3 kg / L, for example, 0.2 kg / L, 0.25 kg / L, 0.3 kg / L, etc. As a non-limiting example, the mass ratio of sodium carbonate to sodium potassium tartrate in the sodium carbonate-sodium potassium tartrate aqueous solution is 1:0.5-2, the mass ratio of disodium hydrogen phosphate to sodium hydroxide in the disodium hydrogen phosphate-sodium hydroxide aqueous solution is 1:0.2-0.5, and the mass ratio of sodium carbonate to sodium bicarbonate is 1:0.5-4. The electrolysis process conditions include, but are not limited to: a temperature of 40-60°C and a current density of 4-10 A / dm³. 2 pH 10-13, time 1-4h, alternating between cathode and anode 2-5 times.

[0049] As a non-limiting example, the electrolysis process conditions include, but are not limited to, temperatures of 40°C, 45°C, 50°C, 55°C, or 60°C, and current densities of, but not limited to, 4A / dm³. 2 5A / dm 2 6A / dm 2 7A / dm 2 8A / dm 2 9A / dm 2 or 10A / dm 2The pH values ​​are including, but are not limited to, 10, 10.5, 11, 11.5, 12, 12.5, or 13; the time is including but is not limited to 1 hour, 1.3 hours, 1.5 hours, 2 hours, 3 hours, or 4 hours; and the number of cathode and anode alternations is 2, 3, 4, or 5 times. Electrolysis process conditions within the above ranges can ensure thorough removal of active metals from the catalyst layer without severely damaging the matrix, resulting in lower matrix impurity content in the recovered product and simpler matrix reprocessing and utilization. Exceeding these ranges may lead to incomplete catalyst layer recovery (too low current density, too low temperature, too low or too high pH, ​​too short time, too few alternations); or cause more severe damage to the matrix (too high current density, too high temperature, too long time, too many alternations).

[0050] In this embodiment, when the spent electrode is an electrode used for alkaline water electrolysis to produce hydrogen, the principle of separating the electrode substrate from its surface catalyst layer using an electrochemical method is as follows: During the period when the spent electrode is used as the anode, the active catalyst components in the catalyst layer on the electrode substrate surface are oxidized, and the structure becomes loose; during the period when the spent electrode is used as the cathode, the hydrogen evolution reaction generates gas in the catalyst layer, which has a scouring effect on the catalyst layer, weakening the bond between the catalyst layer and the electrode substrate. Since the electrochemical reactions all occur in the catalyst layer (the outermost part in contact with the electrolyte), they do not affect the electrode substrate.

[0051] If the electrochemical reaction takes a long time, is too vigorous, or if the electrolyte is too acidic or alkaline and therefore highly corrosive, the electrode substrate may continue to corrode after the catalyst layer peels off. Therefore, it is necessary to control the reaction time, current density, and pH of the electrochemical method within an appropriate range.

[0052] In other embodiments, when the spent electrode is a proton exchange membrane electrode, the method for separating the electrode substrate from the catalyst layer on its surface is an impregnation method. It should be noted that the electrode substrate of the spent proton exchange membrane electrode includes, but is not limited to, one of titanium plates or titanium meshes, and the catalyst active component in the catalyst layer of the spent proton exchange membrane electrode includes, but is not limited to, at least one of noble metals, such as at least one of Pt, Ir, and Ru.

[0053] In some embodiments, the impregnation solution used in the impregnation method is an alkaline solution. The alkaline solution includes, but is not limited to, sodium hydroxide solution, potassium hydroxide solution, sodium carbonate solution, etc.

[0054] In some embodiments, the impregnation method includes the following steps:

[0055] (1) Immerse the waste electrode in the impregnation solution for 3-8 minutes, and then heat it at 400-600℃ for 0.5-2 hours to obtain the impregnated waste electrode;

[0056] (2) After cooling the waste electrode after soaking in step (1), soak it in water at 80-110℃ for 0.5-1.5h to fully remove the adhering substances on the surface of the waste electrode after soaking.

[0057] (3) Take out the waste electrode after soaking in step (2), and dry it to obtain the electrode substrate;

[0058] (4) After soaking in step (2), the soaking solution is cooled, filtered and dried to obtain the catalyst layer powder.

[0059] In the embodiments of this application, when the waste electrode is a proton exchange membrane electrode, the principle of separating the electrode substrate from the catalyst layer on its surface by the impregnation method is that by selecting a suitable impregnation solution, only the catalyst layer is dissolved and the electrode substrate is not dissolved, so as to achieve the separation of the electrode substrate from the catalyst layer.

[0060] In some embodiments, the electrode recovery method further includes a step of converting the catalyst layer into catalyst layer powder before subjecting the catalyst layer to a sulfidation reaction with sulfur. Specifically, for the electrochemical method, the catalyst layer powder may be obtained by cooling, filtering, and drying the electrolyte after electrolysis; for the impregnation method, the above step (4) may be used; for the laser cutting method, the catalyst layer may be directly crushed, ground, etc. to form the catalyst layer powder.

[0061] In some embodiments, the catalyst layer further includes impurities shed from the electrode substrate, and the electrode recovery method further includes:

[0062] The sulfide is obtained by separating the sulfide from the oxides of impurities detached from the electrode matrix through sulfide flotation.

[0063] In some embodiments, the catalyst active component in the catalyst layer powder obtained after electrochemical treatment accounts for more than 75% by mass, with the remainder being impurities shed from the electrode substrate. In other embodiments of this application, the catalyst active component in the catalyst layer powder obtained after impregnation treatment accounts for more than 80% by mass, with the remainder being impurities shed from the electrode substrate.

[0064] In some embodiments, the purity of the sulfide obtained by sulfide flotation is above 99 wt%.

[0065] It should be noted that, in the embodiments of this application, the sulfidation reaction of impurities detached from the electrode substrate is thermodynamically more difficult than the sulfidation reaction of the active components of the catalyst in the catalyst layer. Therefore, only the active components of the catalyst in the catalyst layer undergo sulfidation reaction and are converted into sulfides, while the impurities detached from the electrode substrate do not undergo sulfidation reaction.

[0066] In some embodiments, the sulfide flotation method utilizes the enrichment effect of anionic collectors on sulfides to obtain sulfides with a purity of over 99%. As non-limiting examples, anionic collectors include, but are not limited to, xanthates, black powders, and sulfur-nitrogen compounds. Furthermore, it should be noted that the specific process of the sulfide flotation method described in the embodiments of this application is prior art and will not be elaborated upon here.

[0067] S102. The catalyst layer is subjected to a sulfidation reaction with sulfur, and the active components of the catalyst in the catalyst layer are converted into sulfides.

[0068] This application allows for the formation of sulfides from the active components of the catalyst in the catalyst layer by controlling the temperature, residence time, and partial pressure of the sulfidation reaction. It should be noted that the parameters and the catalyst layer for the sulfidation reaction can be integral or powdered (i.e., the aforementioned catalyst layer powder). However, the powdered form results in a faster sulfidation reaction rate due to its larger contact area with sulfur.

[0069] In some embodiments, the mass ratio of the catalyst layer to sulfur is (1:1) to (1:4), including but not limited to 1:1, 1:2, 1:3 or 1:4.

[0070] In some embodiments, the temperature of the vulcanization reaction is 1000-1200°C, including but not limited to 1000°C, 1050°C, 1100°C, 1150°C, or 1200°C.

[0071] In some embodiments, the vulcanization reaction time is 1-5 hours, including but not limited to 1 hour, 2 hours, 3 hours, 4 hours or 5 hours.

[0072] In some embodiments, the pressure of the vulcanization reaction is 0.5-1.5 atm, including but not limited to 0.5 atm, 1 atm or 1.5 atm.

[0073] In some embodiments, during the sulfidation reaction, sulfur is carried by an inert gas and reacts countercurrently with the catalyst layer. The inert gas includes, but is not limited to, at least one of nitrogen, helium, and argon.

[0074] In some embodiments, sulfur can be sulfur powder, and the mass ratio of sulfur powder to inert gas is 1:(8-12), including but not limited to 1:8, 1:9, 1:10, 1:11 or 1:12.

[0075] In some embodiments, the sulfidation reaction is carried out in an industrial high-temperature reactor (also known as a high-temperature furnace) or the like, and the loading rate of powdered materials (including catalyst layer powder and sulfur powder) in the reaction bed is 60-75%, including but not limited to 60%, 65%, 70% or 75%.

[0076] S103. The sulfide is reacted with a carbon source to form a precursor, which is then calcined to obtain a regenerated catalyst product.

[0077] In some embodiments, the carbon source includes, but is not limited to, at least one of graphene, activated carbon, and graphitic carbon nitride (g-C3N4).

[0078] In some embodiments, the mass ratio of sulfide to carbon source is (1:1) to (1:5), including but not limited to 1:1, 1:2, 1:3, 1:4 or 1:5.

[0079] In some embodiments, the calcination temperature is 600-800°C and the calcination time is 1.5-4.5 h. As a non-limiting example, the calcination temperature includes, but is not limited to, 600°C, 650°C, 700°C, 750°C or 800°C.

[0080] In some embodiments, the electrode recovery method further includes the steps of wet ball milling and spray drying the precursor sequentially before calcination. This ensures that the obtained regenerated catalyst product has the target particle size. As a non-limiting example, wet ball milling can reduce the particle size of the precursor to 1-5 μm. The spray drying temperature is 100-150°C, including but not limited to 100°C, 110°C, 120°C, 130°C, 140°C, or 150°C.

[0081] In some embodiments, the electrode recycling method further includes a step of reusing the electrode substrate after cleaning it with at least one of acid washing, alkaline washing, and water washing. As a possible example, when the electrode substrate is a titanium substrate (e.g., titanium plate or titanium mesh), acid washing is used to clean the electrode substrate; when the electrode substrate is a stainless steel substrate (e.g., stainless steel plate or stainless steel mesh) or a nickel substrate (e.g., nickel plate or nickel mesh), alkaline washing is used to clean the electrode substrate. The acid washing process conditions are: washing with a 0.5M sulfuric acid aqueous solution 2-3 times. The alkaline washing process conditions are: washing with a 0.5M sodium carbonate aqueous solution 2-3 times.

[0082] As a non-limiting example, the regenerated catalyst product can be recombined with the electrode substrate to form a regenerated electrode, wherein the regenerated catalyst product is combined with the electrode substrate by means including but not limited to coating, electroplating, etc.

[0083] As a possible example, such as Figure 1 As shown, the electrode recovery method of this application includes the following steps:

[0084] 1) Separation of catalyst layer and electrode substrate: The electrode substrate of the waste electrode is separated from the catalyst layer on its surface by electrochemical method or alkaline impregnation method to obtain the electrode substrate and the electrolyte or soaking solution containing the catalyst layer. Then the electrolyte or soaking solution containing the catalyst layer is cooled, filtered and dried to obtain the catalyst layer powder.

[0085] 2) The active components of the catalyst in the catalyst layer are converted into sulfides: The catalyst layer powder is subjected to a sulfidation reaction with sulfur element, and the active components of the catalyst in the catalyst layer are converted into sulfides. The impurities in the electrode substrate in the catalyst layer are converted into oxides of the impurities.

[0086] 3) Recovery of active components of catalyst in catalyst layer: Sulfides and oxides of detached impurities are separated by sulfide flotation to obtain sulfides.

[0087] 4) Catalyst regeneration: The sulfide is reacted with the carbon source to form a precursor, which is then subjected to wet ball milling, spray drying and calcination to obtain the regenerated catalyst product.

[0088] 5) Forming a regenerated electrode: The regenerated catalyst product is recombined with the electrode substrate through coating or other methods to form a regenerated electrode.

[0089] It should be noted that, in the embodiments of this application, the following method can be used to determine whether the electrode substrate is damaged after the separation of the electrode substrate from the catalyst layer of the waste electrode:

[0090] Weighing was used to compare the weight of the separated electrode substrate with that of the original electrode substrate. If the weight loss rate was less than 2.5%, it indicated that the separated electrode substrate was not damaged as a whole.

[0091] The electrode recovery method provided in this application has at least the following beneficial effects:

[0092] 1. After separating the electrode substrate and catalyst layer of the waste electrode, the active components of the catalyst layer are converted into sulfides. The sulfides are then calcined and reduced with a carbon source, which can realize the recovery of the active components of the catalyst in the catalyst layer of the waste electrode and the regeneration of the catalyst. At the same time, the sulfur element introduced during the sulfidation process enters the carbon support and can interact with the active components of the catalyst layer itself, thereby increasing the catalytic effect.

[0093] 2. The separation of the catalyst layer from the electrode substrate on the surface of the waste electrode is achieved by a simple alkaline solution method or electrochemical method. The separation efficiency is higher than 95% and the electrode substrate is not damaged. Therefore, the electrode substrate can be directly reused after simple cleaning.

[0094] 3. By utilizing the difference in thermodynamics between the active components of the catalyst layer of the waste electrode and the impurities detached from the electrode substrate during the sulfidation reaction, the active components such as precious metals in the catalyst layer on the surface of the waste electrode can be separated and recovered, thus avoiding the generation of large amounts of acid and alkaline wastewater.

[0095] 4. The regenerated catalyst can be directly combined with the original electrode substrate through simple coating to become a new electrode, which is beneficial for electrode production and integration.

[0096] The following non-limiting embodiments further illustrate certain features of the present technology.

[0097] Example 1

[0098] The electrode recycling method in this embodiment involves a waste electrode, specifically an alkaline water electrolysis hydrogen production electrode mesh. The electrode mesh, serving as the electrode substrate, is made of iron, and its surface catalytic layer is a nickel metal coating. The active component of the catalyst is nickel. The method includes the following steps:

[0099] 1) Catalyst layer-electrode substrate separation: Waste alkaline water electrolysis hydrogen production electrode mesh was placed in an electrochemical reaction tank, and alternating anode and cathode electrolysis was performed. The electrolyte was a sodium tartrate-sodium carbonate aqueous solution with a mass concentration of 0.25 kg / L (the mass ratio of sodium tartrate to sodium carbonate was 1:1). Both the cathode and anode were waste electrodes from this embodiment. The electrolysis process conditions were: temperature: 50℃; current density: 7 A / dm³. 2 pH: 11.5; Electrolysis time: 1.3 h; Number of cathode and anode alternations: 2. After electrolysis, the electrode substrate and electrode mesh were removed and air-dried. The electrode mesh could be reused after simple water washing. The recovery rate of the catalyst layer on the electrode mesh surface was 98.5%. After cooling, filtering, and drying the electrolyte, the catalyst layer powder was obtained. In the catalyst layer powder, the mass fraction of the active catalyst component, nickel oxide, was 75%, and the remaining components were impurities (Fe oxide) shed from the electrode substrate; the particle size range of the catalyst layer powder was 10-100 μm.

[0100] The weight of the electrode substrate (electrode mesh) after separation of the waste electrode was compared with that of the original electrode substrate by weighing method. The weight loss rate was less than 1.2%, indicating that the electrode substrate as a whole was not damaged.

[0101] 2) Conversion of the active component of the catalyst layer into sulfides: The sulfidation reaction is carried out using a conventional high-temperature industrial reactor. The catalyst layer powder obtained in step 1) is added from the top of the high-temperature reactor, while sulfur powder and nitrogen gas (mass ratio 1:10) are injected from the bottom of the reactor. The loading rate of powder materials (catalyst layer powder and sulfur powder) in the reaction bed is 70%. The mass ratio of sulfur powder to catalyst layer powder is 1:1. The sulfidation reaction temperature is 1000℃, and the sulfidation reaction pressure in the reaction bed is 1 atm. The sulfur powder is converted into a gaseous state at high temperature and reacts with the catalyst layer powder in the sulfidation reaction. The residence time of the catalyst layer powder in the reaction bed (i.e., the sulfidation reaction time) is 1 hour.

[0102] 3) Recovery of active catalyst components from the catalyst layer: Since the sulfidation reaction of iron impurities in the electrode substrate is thermodynamically more difficult than the sulfidation reaction of nickel, the active catalyst component in the catalyst layer, nickel sulfides and iron oxides are obtained at the reaction outlet. After the reaction, 98 wt% of the nickel metal is converted into sulfides, which are separated from the iron oxides by flotation to obtain nickel sulfide with a purity of 99.5 wt%. The flotation is carried out using an industrial flotation machine with xanthate-based flotation agents (such as KAX) at a molar fraction of 1-10 mM.

[0103] 4) Catalyst regeneration: A certain amount of graphene is added to the obtained flotation solution (containing 15 wt% nickel sulfide), with the amount of graphene added being 15% of the total mass of the flotation solution. The mixture of flotation solution and graphene is ball-milled (the ball mill operates at a frequency of 300 rpm for 12 hours) to obtain a homogeneous mixture (i.e., precursor solution), in which the average particle size of the solid material is 1-5 μm.

[0104] Subsequently, the homogeneous mixture was spray-dried at 125°C using a spray dryer, and the dried powder was calcined at 700°C for 3 hours under an argon atmosphere to obtain the regenerated catalyst product, which had an average particle size of 10-30 μm.

[0105] 5) Forming a regenerated electrode: The regenerated catalyst product obtained in step 4) is recombined with the modified electrode substrate (electrode mesh) obtained in step 1) through a coating process to form a new electrode, thereby realizing the regeneration cycle of the electrode.

[0106] The electrocatalytic performance of the regenerated and original catalysts was detected using linear sweep voltammetry. The hydrogen evolution overpotential of the catalyst decreased from -237 mV to -178 mV, indicating an improvement in electrochemical activity. This is likely due to the presence of sulfur, which forms sulfur-carbon doping in the support, creating a metal-support interaction and increasing the metal's dispersion on the support surface. Simultaneously, sulfur atoms act as electron-donating groups, assisting the hydrogen evolution reaction and enhancing catalytic activity.

[0107] Example 2

[0108] The electrode recycling method in this embodiment involves a proton exchange membrane electrolysis water electrolysis hydrogen production electrode diffusion layer. The electrode diffusion layer, serving as the electrode substrate, is made of titanium mesh, and its surface catalytic layer is a platinum metal coating. The active component of the catalyst is platinum. The method includes the following steps:

[0109] 1) Separation of Catalyst Layer and Electrode Substrate: Waste PEM electrolytic cell diffusion layer sheets were immersed in an alkaline solution (25wt% NaOH solution) for 5 minutes, then heated in a 500℃ reactor for 1 hour. The sheets were removed, allowed to cool naturally in air, and then immersed in water at 90℃ for 1 hour to thoroughly remove surface contaminants. The sheets were then removed, dried, and washed with water for later use. The catalyst layer recovery rate was 97%. The soaking solution obtained from water immersion was cooled, filtered, and dried to obtain catalyst layer powder. The catalyst layer powder contained 80wt% platinum oxide, the active catalyst component, with the remainder being matrix impurities (Ti oxide). The particle size range of the catalyst layer powder was 10-50 μm.

[0110] The weight of the electrode substrate (sheets) after separation of the waste electrode was compared with that of the original electrode substrate by weighing method. The weight loss rate was less than 1.7%, indicating that the electrode substrate as a whole was not damaged.

[0111] 2) Conversion of the active component of the catalyst layer into sulfides: The sulfidation reaction is carried out using a conventional high-temperature industrial reactor. The catalyst layer powder obtained in step 1) is added from the top of the high-temperature reactor, while sulfur powder and nitrogen gas (mass ratio 1:10) are injected from the bottom of the reactor. The loading rate of powder materials (catalyst layer powder and sulfur powder) in the reaction bed is 65%. The mass ratio of sulfur powder to catalyst layer powder is 1:1. The sulfidation reaction temperature is 1200℃, and the sulfidation reaction pressure in the reaction bed is 1 atm. The sulfur powder is converted into a gaseous state at high temperature and reacts with the catalyst layer powder in the sulfidation reaction. The residence time of the catalyst layer powder in the reaction bed (i.e., the sulfidation reaction time) is 2.5 h.

[0112] 3) Recovery of active components from the catalyst layer: Since the sulfidation reaction of titanium, an impurity in the electrode substrate, is thermodynamically more difficult than that of platinum (Pt), Pt sulfides and titanium oxides are obtained at the reaction outlet. After the reaction, 98 wt% of the Pt metal is converted into sulfides, which are then separated from the titanium oxides by flotation to obtain sulfides with a purity of over 99.7 wt%. Flotation is carried out using an industrial flotation machine with xanthate-based flotation agents (such as KAX) at a molar fraction of 1-10 mM.

[0113] 4) Catalyst regeneration: A certain amount of graphene is added to the obtained flotation solution (platinum sulfide content is 15 wt%), the amount of graphene added being 15% of the total mass of the flotation solution. The mixture of flotation solution and graphene is ball-milled (ball mill operating frequency is 300 rpm, ball milling time is 12 h) to obtain a homogeneous mixture (i.e., precursor solution), in which the average particle size of solid matter is 1-5 μm.

[0114] The homogeneous mixture was spray-dried at 140°C using a spray dryer. The dried powder was then calcined at 700°C for 3 hours under an argon atmosphere to obtain a regenerated catalyst product with an average particle size of 10-30 μm.

[0115] 5) Forming a regenerated electrode: The regenerated catalyst product obtained in step 4) is recombined with the modified electrode substrate (sheet) obtained in step 1) through a coating process to form a new electrode, thereby realizing the regeneration cycle of the electrode.

[0116] The electrocatalytic performance of the regenerated catalyst and the original catalyst was detected using linear sweep voltammetry. The hydrogen evolution overpotential of the catalyst decreased from -73 mV to -55 mV, indicating an improvement in electrochemical activity. This is likely due to the presence of sulfur, which forms sulfur-carbon doping in the support, creating a metal-support interaction and increasing the metal's dispersion on the support surface. Simultaneously, sulfur atoms act as electron-donating groups, assisting the hydrogen evolution reaction and enhancing catalytic activity.

[0117] Example 3

[0118] This embodiment is basically the same as embodiment 1, except that:

[0119] In step 1), the electrolysis process conditions are: temperature: 40℃; current density: 4A / dm³. 2 pH: 10; Electrolysis time: 4 h; Number of cathode and anode alternations: 4 times. The recovery rate of the catalyst layer on the electrode mesh surface was 97%. After electrolysis, the electrolyte was cooled, filtered, and dried to obtain catalyst layer powder. In the catalyst layer powder, the mass fraction of the active catalyst component, nickel oxide, was 81%.

[0120] The weight of the electrode substrate (electrode mesh) after separation of the waste electrode was compared with that of the original electrode substrate by weighing method. The weight loss rate was less than 0.5%, indicating that the electrode substrate as a whole was not damaged.

[0121] The electrocatalytic performance of the regenerated and original catalysts was detected using linear sweep voltammetry. The hydrogen evolution overpotential of the catalyst decreased from -237 mV to -179 mV, indicating an improvement in electrochemical activity. This is likely due to the presence of sulfur, which forms sulfur-carbon doping in the support, creating a metal-support interaction and increasing the metal's dispersion on the support surface. Simultaneously, sulfur atoms act as electron-donating groups, assisting the hydrogen evolution reaction and enhancing catalytic activity.

[0122] Example 4

[0123] This embodiment is basically the same as embodiment 1, except that:

[0124] In step 1), the electrolysis process conditions are: temperature: 60℃; current density: 9A / dm³. 2 pH: 12.5; Electrolysis time: 3 h; Number of cathode and anode alternations: 5 times. The recovery rate of the catalyst layer on the electrode mesh surface was 99.5%. After electrolysis, the electrolyte was cooled, filtered, and dried to obtain catalyst layer powder. In the catalyst layer powder, the mass fraction of the active catalyst component, nickel oxide, was 75%.

[0125] The weight of the electrode substrate (electrode mesh) after separation of the waste electrode was compared with that of the original electrode substrate by weighing method. The weight loss rate was less than 2.3%, indicating that the electrode substrate as a whole was not damaged.

[0126] The electrocatalytic performance of the regenerated and original catalysts was detected using linear sweep voltammetry. The hydrogen evolution overpotential of the catalyst decreased from -237 mV to -173 mV, indicating an improvement in electrochemical activity. This is likely due to the presence of sulfur, which forms sulfur-carbon doping in the support, creating a metal-support interaction and increasing the metal's dispersion on the support surface. Simultaneously, sulfur atoms act as electron-donating groups, assisting the hydrogen evolution reaction and enhancing catalytic activity.

[0127] Example 5

[0128] This embodiment is basically the same as embodiment 1, except that:

[0129] In step 2), the mass ratio of the catalyst layer powder to the sulfur powder is 1:4, the sulfidation reaction temperature is 1100℃, and the residence time of the catalyst layer powder in the reaction bed is 3h.

[0130] In step 3), after the sulfidation reaction, 99.5 wt% of nickel metal is converted into sulfides, which are separated from iron oxides by flotation to obtain nickel sulfide with a purity of 99.7 wt%.

[0131] The electrocatalytic performance of the regenerated and original catalysts was detected using linear sweep voltammetry. The hydrogen evolution overpotential of the catalyst decreased from -237 mV to -167 mV, indicating an improvement in electrochemical activity. This is likely due to the presence of sulfur, which forms sulfur-carbon doping in the support, creating a metal-support interaction and increasing the metal's dispersion on the support surface. Simultaneously, sulfur atoms act as electron-donating groups, assisting the hydrogen evolution reaction and enhancing catalytic activity.

[0132] Example 6

[0133] This embodiment is basically the same as embodiment 1, except that:

[0134] In step 2), the mass ratio of the catalyst layer powder to the sulfur powder is 1:2.5, the sulfidation reaction temperature is 1200℃, and the residence time of the catalyst layer powder in the reaction bed is 4h.

[0135] In step 3), after the sulfidation reaction, 99 wt% of nickel metal is converted into sulfides, which are separated from iron oxides by flotation to obtain nickel sulfide with a purity of 99.5 wt%.

[0136] The electrocatalytic performance of the regenerated and original catalysts was detected using linear sweep voltammetry. The hydrogen evolution overpotential of the catalyst decreased from -237 mV to -171 mV, indicating an improvement in electrochemical activity. This is likely due to the presence of sulfur, which forms sulfur-carbon doping in the support, creating a metal-support interaction and increasing the metal's dispersion on the support surface. Simultaneously, sulfur atoms act as electron-donating groups, assisting the hydrogen evolution reaction and enhancing catalytic activity.

[0137] Example 7

[0138] This embodiment is basically the same as embodiment 1, except that:

[0139] In step 4), a certain amount of graphene is added to the obtained flotation solution (containing 15 wt% nickel sulfide), with the amount of graphene added being 75% of the total mass of the flotation solution.

[0140] The electrocatalytic performance of the regenerated and original catalysts was detected using linear sweep voltammetry. The hydrogen evolution overpotential of the catalyst decreased from -237 mV to -226 mV, indicating an improvement in electrochemical activity. This is likely due to the presence of sulfur, which forms sulfur-carbon doping in the support, creating a metal-support interaction and increasing the metal's dispersion on the support surface. Simultaneously, sulfur atoms act as electron-donating groups, assisting the hydrogen evolution reaction and enhancing catalytic activity.

[0141] Example 8

[0142] This embodiment is basically the same as embodiment 1, except that:

[0143] In step 4), a certain amount of graphene is added to the obtained flotation solution (containing 15 wt% nickel sulfide), with the amount of graphene added being 45% of the total mass of the flotation solution.

[0144] The electrocatalytic performance of the regenerated and original catalysts was detected using linear sweep voltammetry. The hydrogen evolution overpotential of the catalyst decreased from -237 mV to -221 mV, indicating an improvement in electrochemical activity. This is likely due to the presence of sulfur, which forms sulfur-carbon doping in the support, creating a metal-support interaction and increasing the metal's dispersion on the support surface. Simultaneously, sulfur atoms act as electron-donating groups, assisting the hydrogen evolution reaction and enhancing catalytic activity.

[0145] Example 9

[0146] This embodiment is basically the same as embodiment 1, except that:

[0147] The electrode substrate is a nickel plate, the catalyst layer is a cobalt metal coating, and the active component of the catalyst is cobalt.

[0148] Weighing was used to compare the weight of the electrode substrate (nickel plate) after separation of the waste electrode with that of the original electrode substrate. The weight loss rate was less than 1.3%, indicating that the electrode substrate was not damaged as a whole.

[0149] The electrocatalytic performance of the regenerated and original catalysts was detected using linear sweep voltammetry. The hydrogen evolution overpotential of the catalyst decreased from -199 mV to -163 mV, indicating an improvement in electrochemical activity. This is likely due to the presence of sulfur, which forms sulfur-carbon doping in the support, creating a metal-support interaction and increasing the metal's dispersion on the support surface. Simultaneously, sulfur atoms act as electron-donating groups, assisting the hydrogen evolution reaction and enhancing catalytic activity.

[0150] Example 10

[0151] This embodiment is basically the same as embodiment 2, except that:

[0152] In step 1), the impregnation solution was a 20 wt% NaOH solution, and the impregnation time was 8 min. The recovery rate of the catalyst layer on the sheet surface was 90%. The content of platinum oxide, the active catalyst component, in the catalyst layer powder was 85 wt%.

[0153] Weighing was used to compare the weight of the electrode substrate (sheets) after separation of the waste electrode with that of the original electrode substrate. The weight loss rate was less than 1.3%, indicating that the electrode substrate as a whole was not damaged.

[0154] The electrocatalytic performance of the regenerated catalyst and the original catalyst was detected using linear sweep voltammetry. The hydrogen evolution overpotential of the catalyst decreased from -73 mV to -52 mV, indicating an improvement in electrochemical activity. This is likely due to the presence of sulfur, which forms sulfur-carbon doping in the support, creating a metal-support interaction and increasing the metal's dispersion on the support surface. Simultaneously, sulfur atoms act as electron-donating groups, assisting the hydrogen evolution reaction and enhancing catalytic activity.

[0155] Example 11

[0156] This embodiment is basically the same as embodiment 2, except that:

[0157] The catalytic layer on the surface of the electrode substrate is a Pt-Ir metal coating (Pt and Ir in a mass ratio of 1:1), and the active components of the catalyst are Pt and Ir.

[0158] Weighing was used to compare the weight of the electrode substrate (sheets) after separation of the waste electrodes with that of the original electrode substrate. The weight loss rate was less than 1.5%, indicating that the electrode substrate as a whole was not damaged.

[0159] The electrocatalytic performance of the regenerated catalyst and the original catalyst was detected using linear sweep voltammetry. The hydrogen evolution overpotential of the catalyst decreased from -67 mV to -49 mV, indicating an improvement in electrochemical activity. This is likely due to the presence of sulfur, which forms sulfur-carbon doping in the support, creating a metal-support interaction and increasing the metal's dispersion on the support surface. Simultaneously, sulfur atoms act as electron-donating groups, assisting the hydrogen evolution reaction and enhancing catalytic activity.

[0160] Comparative Example 1

[0161] This comparative example is basically the same as Example 1, except that:

[0162] In step 1), the electrolysis process conditions are: temperature: 35℃; current density: 3A / dm³. 2 pH: 9; Electrolysis time: 0.5 h; Number of cathode and anode alternations: 1. The recovery rate of the catalyst layer on the electrode mesh surface was 45%. After cooling, filtering, and drying the electrolyte, catalyst layer powder was obtained. In the catalyst layer powder, the mass fraction of the active catalyst component, nickel oxide, was 80%.

[0163] The weight of the electrode substrate (electrode mesh) after separation of the waste electrode was compared with that of the original electrode substrate by weighing method. The weight loss rate was less than 0.5%, indicating that the electrode substrate as a whole was not damaged.

[0164] Comparative Example 2

[0165] This comparative example is basically the same as Example 1, except that:

[0166] In step 1), the electrolysis process conditions are: temperature: 65℃; current density: 12A / dm³. 2 pH: 14; Electrolysis time: 5 h; Number of cathode and anode alternations: 6. The recovery rate of the catalyst layer on the electrode mesh surface was 80%. After cooling, filtering, and drying the electrolyte, catalyst layer powder was obtained. The mass fraction of nickel oxide, the active catalyst component, in the catalyst layer powder was 65%. This may be because the high current density and excessively vigorous reaction led to uneven removal of the catalyst layer and excessive damage to the matrix in some areas.

[0167] The weight of the electrode substrate (electrode mesh) after separation of the waste electrodes was compared with that of the original electrode substrate using a weighing method, and the weight loss rate was approximately 5%.

[0168] In this application, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0169] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations on the present application. Ordinary technicians in this field can change, modify, replace and modify the above embodiments within the scope of the present application.

Claims

1. An electrode recovery method, characterized in that, include: The electrode substrate of the waste electrode is separated from the catalyst layer on its surface to obtain the electrode substrate and the catalyst layer. The catalyst layer is subjected to a sulfidation reaction with sulfur, and the active catalyst component in the catalyst layer is converted into sulfide; the catalyst layer also includes impurities shed from the electrode substrate. The sulfide and impurities detached from the electrode substrate are separated by sulfide flotation to obtain the sulfide; The sulfide is reacted with a carbon source to form a precursor, which is then calcined to obtain a regenerated catalyst product. In the sulfidation reaction, the sulfur element is carried by an inert gas; the temperature of the sulfidation reaction is 1000-1200℃. The waste electrode is an electrode for alkaline water electrolysis to produce hydrogen or a proton exchange membrane electrode, and the electrode substrate of the proton exchange membrane electrode includes a titanium mesh or a titanium plate.

2. The electrode recovery method according to claim 1, characterized in that, The mass ratio of the catalyst layer to sulfur is 1:(1-4). And / or, the vulcanization reaction time is 1-5 hours; And / or, the pressure of the vulcanization reaction is 0.5-1.5 atm.

3. The electrode recovery method according to claim 1, characterized in that, In the sulfidation reaction, the sulfur element reacts in a countercurrent manner with the catalyst layer.

4. The electrode recovery method according to claim 1, characterized in that, The electrode recovery method further includes the steps of wet ball milling and spray drying the precursor sequentially before calcination; And / or, the electrode recycling method further includes the step of reusing the electrode substrate after cleaning it with at least one of acid washing, alkali washing, and water washing; And / or, the electrode recovery method further includes the step of converting the catalyst layer into catalyst layer powder before subjecting the catalyst layer to a sulfidation reaction with sulfur.

5. The electrode recovery method according to claim 1, characterized in that, The carbon source includes at least one of graphene, activated carbon, and graphitic carbon nitride. And / or, the mass ratio of the sulfide to the carbon source is 1:(1-5); And / or, the calcination temperature is 600-800℃, and the calcination time is 1.5-4.5h.

6. The electrode recovery method according to claim 1, characterized in that, When the waste electrode is an electrode for alkaline water electrolysis to produce hydrogen, the method for separating the electrode substrate from the catalyst layer on its surface is an electrochemical method. And / or, when the waste electrode is a proton exchange membrane electrode, the method for separating the electrode substrate from the catalyst layer on its surface is the impregnation method.

7. The electrode recovery method according to claim 6, characterized in that, The electrochemical method includes the step of alternatingly electrolyzing the waste electrode in an electrolyte by switching between the cathode and the anode; And / or, the impregnation method uses an alkaline solution as the impregnation liquid.

8. The electrode recovery method according to claim 7, characterized in that, The electrolyte includes at least one of sodium carbonate-sodium potassium tartrate aqueous solution, disodium hydrogen phosphate-sodium hydroxide aqueous solution, and sodium carbonate-sodium bicarbonate aqueous solution. And / or, both the cathode and the anode are the waste electrodes; And / or, the electrolysis process conditions are: temperature 40-60℃, current density 4-10A / dm³. 2 pH 10-13, time 1-4h, the cathode and the anode are alternated 2-5 times.

9. The electrode recovery method according to any one of claims 1 to 8, characterized in that, The electrode recycling method further includes the step of recombining the regenerated catalyst product with the electrode matrix to form a regenerated electrode.

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