Recyclable platinum-nickel electrode and application thereof

Abstract

The invention provides a recyclable platinum-nickel electrode and application thereof. The platinum-nickel electrode is treated by a specific regeneration method and is prepared according to a specific preparation method, the platinum-nickel electrode has the advantage of high full-life-cycle economy, and particularly, in the regeneration method of the platinum-nickel electrode, a large-area electrode net does not need to be cut or crushed, and a selective electrochemical corrosion mode is adopted, so that the regeneration efficiency of the platinum-nickel electrode is greatly improved. The purpose of removing the catalytic component platinum from the electrode and re-depositing the catalytic component platinum on the electrode can be achieved, the process is simple and compact, the process can be completed by using a conventional electrolytic tank or electroplating equipment, and the cost is low; and the alkaline electrolyte solution is used as the electrolyte, so that the use of strong acid and strong oxidant in the conventional precious metal recovery process is avoided, the equipment corrosion is slowed down, and the operation safety is improved.

Description

Technical Field

[0001] The invention relates to the technical field of water electrolysis, and in particular to a recyclable platinum-nickel electrode and application thereof. Background Art

[0002] Among the key components of alkaline electrolyzers, the cathode electrode is the core component, which usually adopts a nickel-based metal mesh coated with a non-precious metal coating. However, when facing high current density (more than 10,000A / m 2 ), in order to improve performance, nickel-based electrodes with platinum as the active component are usually selected. However, the platinum component is easy to agglomerate and deactivate in harsh electrochemical environments (such as shutdown). As the use time of the electrolyzer increases, the regeneration of the electrode or the recycling of the active component becomes an important issue to reduce the cost of green hydrogen production, especially in the recovery of precious metals.

[0003] Traditional precious metal recovery processes, such as the recovery of electronic devices, three-way catalysts or industrial catalysts, mainly rely on strong acidic and strong oxidizing chemical dissolution methods. For example, the paper "Platinum Recycling Going Green via Induced Surface Potential Alteration Enabling Fast and Efficient Dissolution" uses CO gas to induce transient Pt dissolution to recover Pt under low acid concentration and room temperature conditions; or it is assisted by electrochemical reactions to promote dissolution and finally recover soluble platinum salts in the solution. For example, the paper "Environmentally Friendly Carbon-Preserving Recovery of Noble Metals From Supported Fuel Cell Catalysts" uses electrochemical potential cycles between 0.5 and 1.1 V to completely dissolve powdered platinum nanoparticles of fuel cell catalysts in 0.1M HClO4 and 0.1M HCl at room temperature.

[0004] Traditional processes are suitable for the recycling of powdered or small-area plate-shaped materials, but alkaline water electrolysis electrodes are usually larger in size, such as round rigid metal mesh with a diameter greater than 1.85 meters. If traditional processes are used, a large amount of corrosive chemicals such as sulfuric acid, hydrofluoric acid, hydrochloric acid, hydrogen peroxide, etc. will be required. At the same time, the required equipment is large in size, high in cost, and the process is dangerous. These factors significantly increase the life cycle cost of platinum-based alkaline cathode electrodes.

[0005] In addition, in the preparation process of platinum-nickel electrodes, the prior art usually adopts the method of external growth on the surface of the substrate to construct a high specific surface area porous or ordered structure (nanowires, nanoflowers, nanorods, etc.), and on this basis loads highly dispersed platinum nanoparticles. However, during the electrochemical reaction of the electrode, the surface epitaxially grown porous structure is easy to fall off from the surface of the substrate, and the active catalytic component platinum will also fall off, resulting in the platinum-nickel electrode being unable to be used and recycled.

[0006] Therefore, developing a recyclable platinum-nickel electrode is crucial for the sustainable development of the green hydrogen production industry. Summary of the invention

[0007] The main purpose of the present invention is to provide a recyclable platinum-nickel electrode and its application, so as to solve the problems in the prior art that the catalytic components on the surface of the substrate of the platinum-nickel electrode are easy to fall off during use and the substrate is easily damaged in the process of recovering precious metals, and the equipment required for the recovery process is large in size and the process is dangerous, resulting in high recovery costs.

[0008] In order to achieve the above-mentioned object, according to one aspect of the present invention, a recyclable platinum-nickel electrode is provided. The platinum-nickel electrode is prepared using the following method: step S11, immersing the nickel mesh in a metal melt for alloying to obtain a first electrode mesh; step S12, immersing the first electrode mesh in an alkaline solution for chemical corrosion to obtain a second electrode mesh; step S13, placing the second electrode mesh in a preparation electrolytic cell, wherein the electrolyte of the preparation electrolytic cell includes a first hydroxide, a first complexing agent, a first anode sacrificial agent and a first platinum precursor salt, and passing a first direct current to perform a first electrodeposition to obtain a platinum-nickel electrode; The platinum-nickel electrode is regenerated using the following method: step S21, placing the used platinum-nickel electrode in a regeneration electrolytic cell, the electrolyte of the regeneration electrolytic cell includes a second hydroxide and a second chelating agent, and an alternating current is introduced to perform electrocorrosion to obtain a third electrode network; step S22, adding a second platinum precursor salt to the regeneration electrolytic cell, and introducing a second direct current to perform a second electrodeposition to obtain a regenerated platinum-nickel electrode; wherein the pH of the electrolyte of the regeneration electrolytic cell is 10-14, and the voltage of the alternating current is 0.1-1.2V.

[0009] Further, in step S11, the metal in the metal melt includes one or more of zinc, aluminum and magnesium; and / or the purity of the metal melt is ≥99.5%; and / or the alloying time is 0.5 to 10 hours.

[0010] Further, in step S12, the alkaline solution includes a third hydroxide, and the mass concentration of the third hydroxide is 10-30%; and / or, the third hydroxide includes one or more of sodium hydroxide, potassium hydroxide and lithium hydroxide; preferably, the alkaline solution also includes a corrosion inhibitor; more preferably, the mass concentration of the corrosion inhibitor is 0.1-10%, and the corrosion inhibitor includes one or more of ammonium molybdate, sodium molybdate, potassium sodium tartrate and potassium chromate; and / or, in step S12, the first electrode mesh is immersed in the alkaline solution for chemical corrosion until no bubbles are generated on the surface of the first electrode mesh, thereby obtaining a second electrode mesh.

[0011] Further, in step S13, in the electrolyte for preparing the electrolytic cell, the molar concentration of the first hydroxide is 0.01-10 mol / L, the molar concentration of the first complexing agent is 0.01-1 mol / L, the molar concentration of the first anode sacrificial agent is 0.01-1 mol / L, and the molar concentration of the first platinum precursor salt is 0.01-0.4 mol / L; and / or, in the electrolyte for preparing the electrolytic cell, the first hydroxide includes one or more of sodium hydroxide, potassium hydroxide and lithium hydroxide; and / or, the first complexing agent includes one or more of cyanide, fluoride and chloride, and / or, the first anode sacrificial agent includes one or more of alcohol, alcoholamine and sulfide, and / or, the first platinum precursor salt includes an organic platinum salt and / or an inorganic platinum salt; and / or, the pH of the electrolyte for preparing the electrolytic cell is 10-14.

[0012] Furthermore, in step S13, in the first electrodeposition, the first direct current includes a constant direct current and / or a pulsed direct current, the voltage is 0.1 to 1.2 V, and the current density is 0.1 to 1.5 A / cm 2 ; and / or, the deposition time of the first electrodeposition is 10 to 300 minutes.

[0013] Further, in step S21, in the electrolyte of the regeneration electrolytic cell, the molar concentration of the second hydroxide is 0.01 to 10 mol / L, and the molar concentration of the second complexing agent is 0.01 to 1 mol / L; and / or, in the electrolyte of the regeneration electrolytic cell, the second hydroxide includes one or more of sodium hydroxide, potassium hydroxide and lithium hydroxide; and / or, the second complexing agent includes one or more of cyanide, fluoride and chloride.

[0014] Furthermore, in step S21, the voltage of the alternating current is 0.6 to 1 V, and the current density is 0.1 to 1.5 A / cm 2, the frequency is 0.01 to 1 Hz, and the waveform includes one or more of a sine wave, a sawtooth wave, a single-pulse square wave, a double-pulse square wave and a trapezoidal wave; and / or, the electrocorrosion time is 60 to 180 min; and / or, during the electrocorrosion process, the material in the regeneration electrolytic cell is homogenized, and the homogenization includes mechanical stirring and / or aeration; and / or, the temperature of the regeneration electrolytic cell is 80 to 95°C.

[0015] Further, in step S22, the second platinum precursor salt includes an organic platinum salt and / or an inorganic platinum salt; and / or, the molar ratio of the second hydroxide to the second platinum precursor salt is 100:1 to 10:1.

[0016] Furthermore, in step S22, in the second electrodeposition, the second direct current includes a constant direct current and / or a pulsed direct current, the voltage is 0.1 to 1.2 V, and the current density is 0.1 to 1.5 A / cm 2 ; and / or, the deposition time of the second electrodeposition is 30 to 120 minutes.

[0017] According to another aspect of the present invention, there is provided a water electrolysis system, comprising an electrode, wherein the electrode is the above-mentioned recyclable nickel-platinum electrode.

[0018] The present invention provides a recyclable platinum-nickel electrode, which is processed by a specific regeneration method, and the preparation method of the platinum-nickel electrode is optimized, and has the advantage of high economic efficiency throughout the life cycle. Specifically, in the preparation method of the platinum-nickel electrode of the present invention, by alloying the molten pore-forming metal with the nickel surface, and de-alloying by alkali solution immersion chemical corrosion, on the one hand, a substrate with high stability and high specific surface area is provided for the loading of the catalytic component platinum, so that the platinum particles have high dispersibility and can fully contact with the electrolyte, which is beneficial to the subsequent electrochemical corrosion-based electrode regeneration while improving the activity; on the other hand, the porous structure extending to the inside of the base material nickel can make the porous substrate structure of the platinum-nickel electrode not easily destroyed during the recycling process, so that in the regeneration of the electrode, the high specific surface area substrate can be kept intact while selectively dissolving platinum, and then there is no need to repeatedly prepare the porous nickel substrate, and the recovery of the catalytic active substance and the substrate is realized simultaneously.

[0019] Moreover, in the regeneration method of the platinum-nickel electrode of the present invention, there is no need to cut or break the large-area electrode mesh. The purpose of removing the catalytic component platinum from the electrode and redepositing it on the electrode can be achieved by selective electrochemical corrosion. The process is simple and compact, and can be completed using conventional electrolytic cells or electroplating equipment. There is no need to use additional large-scale equipment for recycling, and the cost is low. In addition, during the regeneration process, an alkaline electrolyte solution is used as the electrolyte, which avoids the use of strong acids and strong oxidants in conventional precious metal recovery processes, slows down equipment corrosion, improves operational safety, and reduces the cost of waste liquid treatment, which is conducive to promoting the sustainable development of the green hydrogen preparation industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The drawings constituting a part of the present application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0021] Figure 1 The SEM image of the regenerated platinum-nickel electrode of Example 1 of the present invention at a magnification of 50 times is shown;

[0022] Figure 2 The SEM image of the regenerated platinum-nickel electrode of Example 1 of the present invention at a magnification of 200 times is shown;

[0023] Figure 3 shows a SEM image of the regenerated platinum-nickel electrode of Example 1 of the present invention at a magnification of 2000 times; and

[0024] Figure 4 The SEM image of the regenerated platinum-nickel electrode of Example 1 of the present invention at a magnification of 20,000 times is shown. DETAILED DESCRIPTION

[0025] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings in combination with the embodiments and comparative examples.

[0026] As described in the background of the present invention, the prior art has the problem that the catalytic components on the surface of the substrate of the platinum-nickel electrode are easy to fall off during use and the substrate is easy to be damaged in the process of recovering precious metals, and the equipment required for the recovery process is large in size and the process is dangerous, resulting in high recovery costs. In order to solve the above problems, in a typical embodiment of the present invention, a recyclable platinum-nickel electrode is provided. The platinum-nickel electrode is prepared using the following method: step S11, immersing the nickel mesh in a metal melt for alloying to obtain a first electrode mesh; step S12, immersing the first electrode mesh in an alkaline solution for chemical corrosion to obtain a second electrode mesh; step S13, placing the second electrode mesh in a preparation electrolytic cell, the electrolyte of the preparation electrolytic cell includes a first hydroxide, a first complexing agent, a first anode sacrificial agent and a first platinum precursor salt, and a first direct current is passed to perform a first electrodeposition to obtain a platinum-nickel electrode; The platinum-nickel electrode is regenerated using the following method: step S21, placing the used platinum-nickel electrode in a regeneration electrolytic cell, the electrolyte of the regeneration electrolytic cell includes a second hydroxide and a second chelating agent, and an alternating current is introduced to perform electrocorrosion to obtain a third electrode network; step S22, adding a second platinum precursor salt to the regeneration electrolytic cell, and introducing a second direct current to perform a second electrodeposition to obtain a regenerated platinum-nickel electrode; wherein the pH of the electrolyte of the regeneration electrolytic cell is 10-14, and the voltage of the alternating current is 0.1-1.2V.

[0027] After a lot of theoretical research and experimental verification, the inventors found that in the Pt-H2O Pourbiax phase diagram, within a specific pH range (10-14) and voltage range (0.1-1.2V), when Pt is used as an anode, oxidative dissolution occurs and OH is formed. - Soluble Pt(OH)4 as ligand 2- In contrast, in the Ni-H2O Pourbiax phase diagram at pH = 8 to 14, nickel exists in the form of solid hydroxide or oxide, and does not thermodynamically dissolve under electrochemical action.

[0028] Therefore, based on the difference in electrochemical dissolution behavior of Ni and Pt in alkaline electrolyte, the present application particularly utilizes electrolysis. Specifically, a platinum-nickel electrode is placed in an electrolyte of specific components, the voltage and electrolyte pH range are controlled during the electrocorrosion process, and the Pt in the nickel-platinum electrode is selectively corroded to form a soluble Pt complex, thereby achieving effective separation of Ni and Pt components for the purpose of recovering the platinum-nickel electrode.

[0029] In addition, in the regeneration method of the platinum-nickel electrode of the present application, an alkaline solution is used as an electrolyte, a nickel-platinum electrode mesh is connected to the cathode in an electrolytic cell, an alternating current is first connected between the nickel-platinum electrode mesh and the counter electrode to dissolve Pt, and then a direct current is passed to make Pt re-deposited on the electrode surface in a highly dispersed form, thereby regenerating a platinum-nickel electrode. It should be emphasized that the present application particularly uses an alkaline electrolyte solution as an electrolyte during the regeneration process, which can effectively avoid the use of strong acids and strong oxidants in conventional precious metal recovery processes, slow down equipment corrosion, improve operational safety, and reduce the cost of waste liquid treatment.

[0030] Moreover, compared with the prior art, the regeneration method of the present application does not require cutting or crushing of large-area electrode meshes. Through selective electrochemical corrosion, platinum can be removed from the electrode and redeposited on the electrode. The process is simple and compact and can be completed using conventional electrolytic cells or electroplating equipment. It is low-cost, has low process risks, and can regenerate platinum-nickel electrodes in batches.

[0031] In addition, in order to strengthen the above-mentioned electrocorrosion behavior and improve the electrochemical performance of the electrode, the inventor has specially optimized the preparation method of the platinum-nickel electrode. First, the nickel mesh is immersed in the molten metal to form a layer of alloy on the surface of the nickel mesh, and then the electrode mesh is immersed in an alkaline solution to obtain a nickel mesh substrate with a surface rich in porous structure, large specific surface area and strong stability. Subsequently, platinum is loaded on the surface of the porous structure by electrodeposition, which can effectively improve the dispersibility and activity of Pt on the surface of the nickel mesh substrate. The porous nickel mesh substrate has a high specific surface area, a porous structure and high stability. During the deposition process, Pt can be evenly dispersed on the surface of the substrate. On the one hand, it is beneficial to suppress the deactivation of the platinum component due to agglomeration and extend the service life of the platinum-nickel electrode. On the other hand, compared with the Raney nickel treatment process in the prior art, the preparation method of this application forms an integrated tight connection between the porous nickel structure and the substrate while maintaining a high specific surface area, so that the substrate is not easy to fall off during the subsequent recovery process, which is beneficial to the recycling and regeneration of the platinum-nickel electrode, and has the advantage of high economic efficiency throughout the life cycle.

[0032] In summary, in the preparation method of the platinum-nickel electrode of the present application, by alloying the molten pore-forming metal with the nickel surface and de-alloying by alkaline solution immersion chemical corrosion, on the one hand, a substrate with high stability and high specific surface area is provided for the loading of the catalytic component platinum, so that the platinum particles have high dispersibility and can fully contact with the electrolyte, which not only improves the activity but also facilitates the subsequent regeneration of the electrode based on electrochemical corrosion; on the other hand, the porous structure extending into the interior of the base material nickel can make the porous substrate structure of the platinum-nickel electrode not easily destroyed during the recycling process, so that in the regeneration of the electrode, the high specific surface area substrate can maintain its integrity while selectively dissolving platinum, thereby eliminating the need to repeatedly prepare the porous nickel substrate, and simultaneously realizing the recovery of the catalytically active substance and the substrate.

[0033] In the regeneration method of the platinum-nickel electrode of the present application, there is no need to cut or crush the large-area electrode mesh. The purpose of removing the catalytic component platinum from the electrode and redepositing it on the electrode is achieved by selective electrochemical corrosion. The process is simple and compact, and can be completed using conventional electrolytic cells or electroplating equipment. There is no need to use additional large-scale equipment for recycling, and the cost is low. In addition, during the regeneration process, an alkaline electrolyte solution is used as the electrolyte, which avoids the use of strong acids and strong oxidants in conventional precious metal recovery processes, slows down equipment corrosion, improves operational safety, and reduces the cost of waste liquid treatment. The platinum-nickel electrode of the present application has the advantage of high economy throughout the entire life cycle from preparation to regeneration.

[0034] In order to further improve the specific surface area and stability of the substrate in the platinum-nickel electrode, and reduce the introduction of impurities, in a preferred embodiment, the metal in the metal melt includes one or more of zinc, aluminum and magnesium; and / or, the purity of the metal melt is ≥99.5%; preferably, when the purity of zinc in the metal melt is ≥99.9%, the heating temperature of the metal melt is 450-500°C; when the purity of aluminum in the metal melt is ≥99.9%, the heating temperature of the metal melt is 700-750°C; and / or, when preparing the metal melt, the heating atmosphere is an inert gas or a vacuum environment, preferably argon and / or helium; and / or, the alloying time is 0.5-10h. Under the above conditions, the alloying reaction is more sufficient, and it is not easy to be oxidized to form the corresponding alloy oxide, which is more conducive to the formation of a porous substrate structure, thereby more conducive to avoiding the shedding of platinum in the electrode and damage to the substrate.

[0035] In a preferred embodiment, in step S12, the first alkaline solution includes a third hydroxide, and the mass concentration of the third hydroxide is 10-30%; and / or, the third hydroxide includes one or more of sodium hydroxide, potassium hydroxide and lithium hydroxide; preferably, the alkaline solution also includes a corrosion inhibitor, and more preferably, the mass concentration of the corrosion inhibitor is 0.1-10%, and the corrosion inhibitor includes one or more of ammonium molybdate, sodium molybdate, sodium potassium tartrate and potassium chromate; and / or, in step S12, the first electrode mesh is immersed in an alkaline solution for chemical corrosion until no bubbles are generated on the surface of the first electrode mesh, thereby obtaining a second electrode mesh. Under the above conditions, a porous and highly stable substrate can be obtained more quickly and effectively, the dispersibility and activity of the platinum particles are higher, and the substrate of the platinum-nickel electrode is less likely to fall off during the regeneration process.

[0036] Regarding the types of the first hydroxide, the first complexing agent, the first anode sacrificial agent and the first platinum precursor salt in the electrolyte for preparing the electrolytic cell, the commonly used types in the technical field can be used, and their contents can be adjusted according to actual conditions. After a large number of experiments, the inventors have optimized the components of the electrolyte for preparing the electrolytic cell. In a preferred embodiment, in step S13, in the electrolyte for preparing the electrolytic cell, the molar concentration of the first hydroxide is 0.01-10 mol / L, the molar concentration of the first complexing agent is 0.01-1 mol / L, the molar concentration of the first anode sacrificial agent is 0.01-1 mol / L, and the molar concentration of the first platinum precursor salt is 0.01-0.4 mol / L; and / or, in the electrolyte for preparing the electrolytic cell, the first hydroxide includes sodium hydroxide, potassium hydroxide and lithium hydroxide. One or more of; and / or the first complexing agent includes one or more of cyanide, fluoride and chloride, preferably one or more of potassium cyanide, sodium cyanide, potassium chloride, sodium chloride, sodium fluoride and potassium fluoride; and / or the first anode sacrificial agent includes one or more of alcohol, alcohol amine and sulfide, preferably one or more of methanol, ethanol, ethylene glycol and propylene glycol, and / or, the first platinum precursor salt includes an organic platinum salt and / or an inorganic platinum salt, preferably one or more of chloroplatinic acid, potassium chloroplatinate and sodium chloroplatinate; and / or, the pH of the electrolyte for preparing the electrolytic cell is 10 to 14. Under the above conditions, the dispersibility and activity of Pt deposited on the surface of the nickel mesh substrate are better, which is more conducive to extending the life cycle of the platinum nickel electrode. Moreover, during the regeneration process, the recovery rate of Pt is higher, which is conducive to reducing the recovery cost of the platinum nickel electrode.

[0037] In a preferred embodiment, in step S13, in the first electrodeposition, the first direct current includes a constant direct current and / or a pulsed direct current, the voltage is 0.1 to 1.2 V, and the current density is 0.1 to 1.5 A / cm 2 ; Preferably, when the first direct current is a pulsed direct current, the pulse width is 1 to 120 seconds and the pulse interval is 0.1 to 300 seconds; and / or, the deposition time of the first electrodeposition is 10 to 300 minutes. Under the above conditions, the thickness distribution of the Pt deposition layer is more uniform and the efficiency is faster.

[0038] In order to make Pt oxidized and dissolved more fully, and thus to separate Pt and Ni more effectively, in a preferred embodiment, in step S21, in the electrolyte of the regeneration electrolytic cell, the molar concentration of the second hydroxide is 0.01-10 mol / L, and the molar concentration of the second complexing agent is 0.01-1 mol / L; and / or, in the electrolyte of the regeneration electrolytic cell, the second hydroxide includes one or more of sodium hydroxide, potassium hydroxide and lithium hydroxide; and / or, the second complexing agent includes one or more of cyanide, fluoride and chloride, preferably one or more of potassium cyanide, sodium cyanide, potassium chloride, sodium chloride, sodium fluoride and potassium fluoride. Preferably, the electrolyte of the regeneration electrolytic cell includes: 0.1-0.25 mol / L of sodium hydroxide and 0.01-0.1 mol / L of sodium fluoride.

[0039] Based on similar reasons, in a preferred embodiment, in step S21, a graphite electrode is used as a counter electrode, and the graphite electrode is a thin sheet or rod array, arranged on one side or both sides of the noble metal electrode; and / or, the area ratio of the graphite electrode to the platinum nickel electrode is 0.1 to 10; and / or, the voltage of the alternating current is 0.6 to 1V, and the current density is 0.1 to 1.5A / cm 2 , the frequency is 0.01-1 Hz, and the waveform includes one or more of a sine wave, a sawtooth wave, a single-pulse square wave, a double-pulse square wave and a trapezoidal wave; and / or, the electrocorrosion time is 60-180 min, preferably 60-120 min; and / or, the material in the regeneration electrolytic cell is homogenized during the electrocorrosion process, and the homogenization includes mechanical stirring and / or aeration; and / or, the temperature of the regeneration electrolytic cell is 80-95°C; and / or, the electrolytic cell is a square or circular single-chamber structure. It should be noted that the present application uses alternating current with specific parameters in electrochemical corrosion, which can put the nickel-platinum electrode in a periodic oxidation / reduction cycle, an oxidation reaction occurs when the electrode is at the anode, and a short reduction reaction occurs when it is at the cathode, which is more conducive to avoiding PtO on the electrode surface. x The surface passivation and electrochemical corrosion rate slowdown caused by species transition growth are more conducive to improving the dissolution rate of Pt and accelerating the regeneration rate.

[0040] In a preferred embodiment, in step S22, the second platinum precursor salt includes an organic platinum salt and / or an inorganic platinum salt, preferably one or more of chloroplatinic acid, potassium chloroplatinate and sodium chloroplatinate; and / or the molar ratio of the second hydroxide to the second platinum precursor salt is 100: 1 to 10: 1. Under the above conditions, Pt can be more fully and effectively deposited on the electrode surface, which is more conducive to improving the electrochemical performance of the regenerated platinum nickel electrode.

[0041] In order to make Pt deposit more fully and quickly and obtain a regenerated platinum-nickel electrode with higher quality and more uniform thickness, in a preferred embodiment, in step S22, in the second electrodeposition, the second direct current includes a constant direct current and / or a pulsed direct current, the voltage is 0.1-1.2V, and the current density is 0.1-1.5A / cm 2 ; Preferably, when the second direct current is a pulsed direct current, the pulse width is 1 to 120 s and the pulse interval is 0.1 to 300 s; and / or, the deposition time of the second electrodeposition is 30 to 120 min.

[0042] In another typical embodiment of the present invention, a water electrolysis system is also provided, including an electrode, wherein the electrode includes the above-mentioned recyclable platinum-nickel electrode. As mentioned above, the platinum-nickel electrode of the present application has high economic efficiency throughout its life cycle, and Pt is evenly dispersed on the surface of the substrate. When used in the field of water electrolysis, it has excellent electrochemical performance, and the active ingredients are not easily deactivated. Moreover, the recovery equipment of the electrode is small in size, the process is less dangerous, and the recovery cost is low, which is conducive to promoting the sustainable development of the green hydrogen preparation industry.

[0043] Typically but not limiting, in step S21, the voltage of the alternating current is 0.1V, 0.2V, 0.4V, 0.6V, 0.8V, 1V, 1.2V or a range consisting of any two of them; in step S22, the pH of the third alkaline solution is 10, 11, 12, 13, 14 or a range consisting of any two of them.

[0044] The present application is further described in detail below in conjunction with specific embodiments. These embodiments should not be construed as limiting the scope of protection claimed in the present application.

[0045] Example 1

[0046] The preparation method of the platinum nickel electrode comprises the following steps:

[0047] Step S11, in a helium atmosphere, heating the zinc ingot to 500° C. to melt it, and then completely immersing a 46-mesh 0.25 mm wire diameter nickel mesh into the metal melt (the purity of zinc is 99.9%) for 2 hours to obtain a first electrode mesh;

[0048] Step S12, immersing the first electrode mesh in an alkaline aqueous solution at 80° C. (wherein the mass concentration of potassium hydroxide is 30 wt %, and the mass concentration of the corrosion inhibitor potassium sodium tartrate is 5 wt %) to perform a dezincification treatment until no bubbles are generated on the surface of the first electrode mesh; then rinsing the surface of the electrode mesh with clean water until it is neutral, to obtain a second electrode mesh;

[0049] Step S13, placing the second electrode mesh in the preparation electrolytic cell, using the second electrode mesh as the first working electrode, and preparing platinum precursor salt chloroplatinic acid, complexing agent barium chloride, cationic sacrificial agent methanol and potassium hydroxide with concentrations of 0.05 mol / L, 0.1 mol / L, 0.5 mol / L and 0.1 mol / L respectively as the plating solution (pH is 13), using a pulsed square wave DC current to plate the second electrode mesh, at a voltage of 1.2 V and a current density of 0.1 A / cm 2 Under the conditions of pulse width of 10s, pulse interval of 0.1s and electrolyte temperature of 80°C, the first electrodeposition was carried out for 30min to obtain a platinum-nickel electrode.

[0050] The regeneration method of the platinum nickel electrode comprises the following steps:

[0051] Step S21, using ultrapure water to clean the used platinum-nickel electrode, in a square single-chamber regeneration electrolytic cell, using the platinum-nickel electrode as the second working electrode, using a solution containing 1 mol / L potassium hydroxide and 0.01 mol / L sodium cyanide, pH 14, and temperature 80°C as the electrolyte, using a rod-shaped array graphite electrode as the counter electrode, the area ratio of the graphite electrode to the platinum-nickel electrode is 1:1, and passing an alternating current with a trapezoidal waveform between the two electrodes, with a frequency of 0.1 Hz, a voltage of 1.2 V, and a current density of 0.1 A / cm 2 , and the electrolyte is stirred by aeration for 2 hours to obtain a third electrode network;

[0052] Step S22, using the rod-shaped array graphite electrode as the anode, adding the second platinum precursor salt chloroplatinic acid to the regeneration electrolytic cell, and controlling the molar concentration of the platinum precursor salt in the electrolyte to be 0.01 mol / L and the pH to be 13, using a pulsed square wave DC current to plate the electrode mesh, at a voltage of 1.2 V and a current density of 0.1 A / cm 2 Under the conditions of pulse width 0.1s, pulse interval 0.1s and electrolyte temperature 80°C, the second electrodeposition was carried out for 30min to obtain a regenerated platinum-nickel electrode.

[0053] The SEM image of the regenerated platinum-nickel electrode at 50 times magnification is shown in Figure 1 , see the SEM image at 200 times magnification Figure 2 , see the SEM image at 2000 times magnification Figure 3 , see the SEM image at 20000 times magnification Figure 4 As can be seen from the figure, the surface of the nickel substrate is rough after alloying and dealloying, and its specific surface area is correspondingly large. At the same time, evenly dispersed nano-Pt particles can be observed on the surface under high magnification.

[0054] The platinum-nickel electrode was used as the working electrode, a potassium hydroxide solution with a mass fraction of 30% was used as the electrolyte, and a pure nickel mesh electrode was used as the counter electrode. Water electrolysis was performed to produce hydrogen at a working temperature of 92° C. and a pressure of 1.60 MPa.

[0055] Example 2

[0056] The only difference from Example 1 is:

[0057] Step S11, in an argon atmosphere, heating the aluminum ingot to 700° C. to melt it, and then completely immersing the nickel mesh in the metal melt (with a purity of 99.9%) for 10 hours to obtain a first electrode mesh.

[0058] Example 3

[0059] The only difference from Example 1 is:

[0060] Step S11, in a helium atmosphere, heating the zinc ingot to 500°C to melt it, and then completely immersing the nickel mesh in the metal melt (with a purity of 99.9%) for 0.5 h to obtain a first electrode mesh.

[0061] Example 4

[0062] The only difference from Example 1 is:

[0063] Step S12, immersing the first electrode mesh in an alkaline aqueous solution at 80° C. (wherein the mass concentration of sodium hydroxide is 10wt%, and the concentration of the corrosion inhibitor sodium molybdate is 10wt%) for dezincification treatment until no bubbles are generated on the surface of the first electrode mesh; then rinsing the electrode surface with clean water until it is neutral to obtain a second electrode mesh.

[0064] Example 5

[0065] The only difference from Example 1 is:

[0066] Step S12, immersing the first electrode mesh in an alkaline aqueous solution at 80° C. (wherein the mass concentration of sodium hydroxide is 30wt%, and the concentration of the corrosion inhibitor ammonium molybdate is 0.1wt%) for dezincification treatment until no bubbles are generated on the surface of the first electrode mesh; then rinsing the electrode surface with clean water until it is neutral to obtain a second electrode mesh.

[0067] Example 6

[0068] The only difference from Example 1 is:

[0069] Step S13, preparing an electrolyte for an electrolytic cell including potassium chloroplatinate, potassium cyanide, a first anode sacrificial agent (methanol) and sodium hydroxide, with concentrations of 0.01 mol / L, 1 mol / L, 1 mol / L and 0.01 mol / L, respectively, and a pH of 10.

[0070] Example 7

[0071] The only difference from Example 1 is:

[0072] Step S13, preparing an electrolyte for an electrolytic cell including sodium chloroplatinate, potassium fluoride, a first anode sacrificial agent (propylene glycol) and potassium hydroxide, with concentrations of 0.4 mol / L, 0.01 mol / L, 0.01 mol / L and 10 mol / L, respectively, and a pH of 14.

[0073] Example 8

[0074] The only difference from Example 1 is:

[0075] Step S13, using a pulsed square wave DC current to plate the first electrode mesh at a current density of 1.5 A / cm 2 Under the conditions of 100 s for pulse width, 300 s for pulse interval and 80°C for electrolyte temperature, the first electrodeposition was carried out for 10 min to obtain a platinum-nickel electrode.

[0076] Example 9

[0077] The only difference from Example 1 is:

[0078] Step S13, plating the first electrode mesh with a constant direct current at a current density of 1.5 A / cm 2 Under the conditions of 30 ℃ and electrolyte temperature of 80 ℃, the first electrodeposition was carried out for 60 minutes to obtain a platinum-nickel electrode.

[0079] Example 10

[0080] The only difference from Example 1 is:

[0081] Step S21, use ultrapure water to clean the used platinum-nickel electrode, in a square single-chamber regeneration electrolytic cell, use the platinum-nickel electrode as the second working electrode, use a solution containing 0.25 mol / L sodium hydroxide and 0.01 mol / L sodium fluoride, pH 14, and temperature 95°C as the electrolyte, and use a thin-sheet graphite electrode (arranged on both sides of the platinum-nickel electrode) as the counter electrode, and the area ratio of the graphite electrode to the platinum-nickel electrode is 10.

[0082] Embodiment 11

[0083] The only difference from Example 1 is:

[0084] Step S21, use ultrapure water to clean the used platinum-nickel electrode, in a circular single-chamber regeneration electrolytic cell, use the platinum-nickel electrode as the second working electrode, use a solution containing 0.1 mol / L sodium hydroxide and 0.1 mol / L sodium chloride, pH 10, and temperature 80°C as the electrolyte, and use a thin sheet graphite electrode (arranged on a single side of the platinum-nickel electrode) as the counter electrode, and the area ratio of the graphite electrode to the platinum-nickel electrode is 0.1.

[0085] Example 12

[0086] The only difference from Example 1 is:

[0087] Step S21: Sine wave AC is passed between the two electrodes, with a voltage of 0.6V and a current density of 0.1A / cm 2 , frequency is 1 Hz, and the electrolyte is stirred by aeration for 1 hour to obtain a third electrode network.

[0088] Embodiment 13

[0089] The only difference from Example 1 is:

[0090] Step S21: Sawtooth alternating current with a voltage of 0.8V and a current density of 1.5A / cm2 is passed between the two electrodes. 2 , frequency is 0.01 Hz, and the electrolyte is mechanically stirred for 3 hours to obtain a third electrode network.

[0091] Embodiment 14

[0092] The only difference from Example 1 is:

[0093] Step S22, adding a second platinum precursor salt potassium chloroplatinate to the regeneration electrolytic cell, and controlling the content of the platinum precursor salt in the electrolyte to be 0.01 mol / L and the pH to be 10, using a pulsed square wave DC current to plate the electrode mesh at a voltage of 1.2 V and a current density of 0.1 A / cm 2 , pulse width 1s, pulse interval 1s, electrolyte temperature 80°C, the second electrodeposition was carried out for 30min to obtain a regenerated platinum-nickel electrode.

[0094] Embodiment 15

[0095] The only difference from Example 1 is:

[0096] Step S22, adding a second platinum precursor salt sodium chloroplatinate to the regeneration electrolytic cell, and controlling the content of the platinum precursor salt in the electrolyte to be 0.1 mol / L and the pH to be 14, using a constant direct current to plate the electrode mesh, at a voltage of 0.1 V and a current density of 1 A / cm 2Under the conditions of 30 ℃ and electrolyte temperature of 80 ℃, the second electrodeposition was carried out for 120 minutes to obtain a regenerated platinum-nickel electrode.

[0097] Comparative Example 1

[0098] The only difference from Example 1 is:

[0099] When preparing the platinum-nickel electrode, the conventional method of thermally spraying nickel-aluminum alloy on the surface of the nickel mesh is adopted to replace step S11 in Example 1.

[0100] Analysis shows that the surface nickel-aluminum alloy and the nickel mesh substrate are connected mainly by physical adhesion, and the bonding strength between the two is relatively low. During the electrolysis of water, the surface structure can fall off due to the generated bubbles and the scouring of the electrolyte flow.

[0101] Comparative Example 2

[0102] The only difference from Example 1 is:

[0103] When preparing the platinum-nickel electrode, the conventional impregnation sintering method is used to load platinum on the porous nickel surface, replacing step S11 in Example 1.

[0104] Analysis shows that during the high-temperature calcination and decomposition of platinum metal salt into platinum, platinum particles agglomerate on the porous nickel surface, and the specific surface area is lower under the same platinum loading conditions, so the catalytic activity is lower. In addition, the contact area with the electrolyte is small during the regeneration process, and the rate of platinum dissolution through electrochemical corrosion is slow.

[0105] Comparative Example 3

[0106] The only difference from Example 1 is:

[0107] In step S21, a strong acid (sulfuric acid) is used to recover the platinum-nickel electrode.

[0108] Analysis showed that the electrodes quickly dissolved in the acid solution and could not be used again.

[0109] The characteristics and electrochemical performance test results of the platinum-nickel electrodes prepared in the above examples and comparative examples are shown in Table 1.

[0110] Test method:

[0111] Platinum loading test: Tested in accordance with GB / T 30902-2014.

[0112] Test whether the catalyst on the surface of the nickel mesh substrate has fallen off: ultrasonic oscillation method is used: specifically, in the ultrasonic peeling rate test system, the ultrasonic treatment method is used to immerse the test electrode in the ultrasonic instrument test solution, and the ultrasonic oscillation treatment is carried out for 1 hour under the conditions of frequency 40Hz and power 200W, and the change value of the electrode mass before and after ultrasonic oscillation is measured to evaluate the catalyst shedding. The electrode is rinsed with pure water and ethanol successively; the electrode is treated at 70℃ and vacuum degree ≤200Pa for at least 2 hours; the initial mass of 3 electrodes is weighed with an accuracy of 0.1mg; the electrode is placed flat in a 250mL glass beaker container containing 200mL pure water, the beaker is placed in the middle of the ultrasonic instrument and fixed, water is added to the ultrasonic instrument until the water level in the inner tank is 50mm, and then treated at a temperature of 30℃±1℃ for 60 minutes; the terminal mass of the electrode after ultrasound is weighed to obtain the shedding of the surface catalyst.

[0113] Hydrogen evolution overpotential test: Cut the electrode into a 1.5 cm long and 1 cm wide rectangular block, fix it with an electrode clamp, and use it as a working electrode for oxygen evolution reaction in alkaline electrolyte. In the three-electrode test system, the platinum wire is the counter electrode, the mercury / mercury oxide electrode is the reference electrode, and the effective area of ​​the working electrode immersed in the electrolyte is 1 cm 2 The test system selected 1 mol / L potassium hydroxide as the electrolyte. The electrode was tested at 100 mA / cm using linear voltammetry. 2 The linear voltammetric scan rate was 5 mV / s for the hydrogen evolution overpotential at the current density.

[0114] Table 1

[0115]

[0116]

[0117] From the above, it can be seen that by comparing Example 1 with Examples 2 and 3, the type of metal melt in step S12 and the heating atmosphere during the preparation process affect the performance and production cost of the platinum-nickel electrode. By comparing Example 1 with Examples 4 and 5, it can be seen that the hydroxide and corrosion inhibitor in the dealloying process of step S12 are related to the dealloying efficiency, the specific surface area and activity of the electrode. By comparing Example 1 with Examples 6 and 7, it can be seen that the type and concentration of chloroplatinate, complexing agent, and positive sacrificial agent in the electrolyte of the electrolytic cell prepared in step S13 will affect the microstructure of platinum nanoparticles and the loading amount on the substrate, thereby affecting the performance of the electrode. By comparing Example 1 with Examples 8 and 9, it can be seen that the current parameters in step S13 affect the loading amount of platinum and the specific surface area of ​​the electrode, thereby affecting the performance of the electrode.

[0118] By comparing Example 1 with Examples 10 and 11, it can be seen that the components of the electrolyte in step S21, the placement of the regeneration electrode and the counter electrode graphite plate affect the dissolution and deposition efficiency of platinum in the electrolyte, and thus affect the Pt loading and electrode performance after regeneration. By comparing Example 1 with Examples 12 and 13, it can be seen that during the regeneration process of step S21, the AC parameters affect the dissolution of platinum and the electrode performance. By comparing Example 1 with Examples 14 and 15, it can be seen that during the regeneration process of step S22, the electrolyte components affect the state of platinum on the electrode surface after regeneration, and thus affect the performance of the electrode after regeneration.

[0119] Comparative Example 1 and Comparative 1 show that the porous nickel coating is constructed by conventionally thermally spraying nickel aluminum alloy on the surface of the nickel mesh, and its specific surface area is relatively low, and the surface porous nickel structure is easily detached from the substrate surface, so the catalytic activity is relatively low and the performance decreases significantly after the regeneration step, and the regeneration effect cannot be achieved. Comparative Example 1 and Comparative 2 show that the conventional impregnation sintering method is used to carry out platinum loading on the porous nickel surface, and the platinum nanoparticles on its surface have poor dispersibility, low activity, and low Pt dissolution rate during the regeneration process, resulting in poor electrode regeneration effect. Comparative Example 1 and Comparative 3 show that the platinum nickel electrode is recovered using strong acid (sulfuric acid), and the electrode is completely dissolved in the solution and is thoroughly damaged.

[0120] Compared with the comparative example, the electrodes of each embodiment of the present invention have the advantage of high economic efficiency throughout the life cycle. Specifically, in the preparation method of the platinum-nickel electrode of the present invention, by alloying the molten pore-forming metal with the nickel surface, and de-alloying by alkali solution immersion chemical corrosion, on the one hand, a substrate with high stability and high specific surface area is provided for the loading of the catalytic component platinum, so that the platinum particles have high dispersibility and can be fully in contact with the electrolyte, which is beneficial to the subsequent electrochemical corrosion-based electrode regeneration while improving the activity; on the other hand, the porous structure extending to the inside of the base material nickel can make the porous substrate structure of the platinum-nickel electrode not easily destroyed during the recycling process, so that the high specific surface area substrate can be kept intact while selectively dissolving platinum in the regeneration of the electrode, and then there is no need to repeatedly prepare the porous nickel substrate, and the recovery of the catalytic active substance and the substrate is realized simultaneously.

[0121] Moreover, in the regeneration method of the platinum-nickel electrode of the present invention, there is no need to cut or break the large-area electrode mesh. The purpose of removing the catalytic component platinum from the electrode and redepositing it on the electrode can be achieved by selective electrochemical corrosion. The process is simple and compact, and can be completed using conventional electrolytic cells or electroplating equipment. There is no need to use additional large-scale equipment for recycling, and the cost is low. In addition, during the regeneration process, an alkaline electrolyte solution is used as the electrolyte, which avoids the use of strong acids and strong oxidants in conventional precious metal recovery processes, slows down equipment corrosion, improves operational safety, and reduces the cost of waste liquid treatment, which is conducive to promoting the sustainable development of the green hydrogen preparation industry.

[0122] In addition, it can be seen that when all process parameters are within the preferred range of the present invention, the catalytic components and substrates in the platinum-nickel electrode are easier to recycle and the recycling cost is lower.

[0123] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A recyclable platinum-nickel electrode, characterized in that: The platinum nickel electrode was prepared using the following method: Step S11, immersing the nickel mesh in a metal melt to perform alloying to obtain a first electrode mesh; Step S12, immersing the first electrode mesh in an alkaline solution to perform chemical corrosion to obtain a second electrode mesh; Step S13, placing the second electrode mesh in a preparation electrolytic cell, wherein the electrolyte of the preparation electrolytic cell comprises a first hydroxide, a first complexing agent, a first anode sacrificial agent and a first platinum precursor salt, and passing a first direct current to perform a first electrodeposition to obtain the platinum-nickel electrode; The platinum nickel electrode is regenerated using the following method: Step S21, placing the used platinum-nickel electrode in a regeneration electrolytic cell, wherein the electrolyte of the regeneration electrolytic cell includes a second hydroxide and a second complexing agent, and passing alternating current to perform electrical corrosion to obtain a third electrode mesh; Step S22, adding a second platinum precursor salt into the regeneration electrolytic cell, and passing a second direct current to perform a second electrodeposition to obtain a regenerated platinum-nickel electrode; Wherein, the pH of the electrolyte of the regeneration electrolytic cell is 10-14, and the voltage of the alternating current is 0.1-1.2V.

2. The platinum-nickel electrode according to claim 1, characterized in that: In the step S11, In the metal melt, the metal includes one or more of zinc, aluminum and magnesium; and / or, The purity of the metal melt is ≥ 99.5%; and / or, The alloying time is 0.5 to 10 hours.

3. The platinum-nickel electrode according to claim 1 or 2, characterized in that: In the step S12, The alkaline solution includes a third hydroxide, and the mass concentration of the third hydroxide is 10-30%; and / or the third hydroxide includes one or more of sodium hydroxide, potassium hydroxide and lithium hydroxide; Preferably, the alkaline solution further comprises a corrosion inhibitor; more preferably, the mass concentration of the corrosion inhibitor is 0.1-10%, and the corrosion inhibitor comprises one or more of ammonium molybdate, sodium molybdate, sodium potassium tartrate and potassium chromate; and / or, In the step S12, the first electrode mesh is immersed in the alkaline solution to perform the chemical etching until no bubbles are generated on the surface of the first electrode mesh, thereby obtaining the second electrode mesh.

4. The platinum-nickel electrode according to any one of claims 1 to 3, characterized in that In step S13, In the electrolyte for preparing the electrolytic cell, the molar concentration of the first hydroxide is 0.01-10 mol / L, the molar concentration of the first complexing agent is 0.01-1 mol / L, the molar concentration of the first anode sacrificial agent is 0.01-1 mol / L, and the molar concentration of the first platinum precursor salt is 0.01-0.4 mol / L; and / or, In the electrolyte for preparing the electrolytic cell, the first hydroxide includes one or more of sodium hydroxide, potassium hydroxide and lithium hydroxide; and / or, the first complexing agent includes one or more of cyanide, fluoride and chloride, and / or, the first anode sacrificial agent includes one or more of alcohol, alcohol amine and sulfide, and / or, the first platinum precursor salt includes an organic platinum salt and / or an inorganic platinum salt; and / or, The pH of the electrolyte for preparing the electrolytic cell is 10-14.

5. The platinum-nickel electrode according to any one of claims 1 to 4, characterized in that: In step S13, In the first electrodeposition, the first direct current includes a constant direct current and / or a pulsed direct current, the voltage is 0.1 to 1.2 V, and the current density is 0.1 to 1.5 A / cm 2 and / or, The deposition time of the first electrodeposition is 10 to 300 minutes.

6. The platinum-nickel electrode according to any one of claims 1 to 5, characterized in that: In the step S21, In the electrolyte of the regeneration electrolytic cell, the molar concentration of the second hydroxide is 0.01 to 10 mol / L, and the molar concentration of the second complexing agent is 0.01 to 1 mol / L; and / or, In the electrolyte of the regeneration electrolytic cell, the second hydroxide includes one or more of sodium hydroxide, potassium hydroxide and lithium hydroxide; and / or the second complexing agent includes one or more of cyanide, fluoride and chloride.

7. The platinum-nickel electrode according to any one of claims 1 to 6, characterized in that In the step S21, The voltage of the alternating current is 0.6-1V, and the current density is 0.1-1.5A / cm 2 , the frequency is 0.01 to 1 Hz, and the waveform includes one or more of a sine wave, a sawtooth wave, a single pulse square wave, a double pulse square wave and a trapezoidal wave; and / or, The electrocorrosion time is 60 to 180 minutes; and / or, During the electro-corrosion process, the material in the regeneration electrolytic cell is homogenized, wherein the homogenization includes mechanical stirring and / or aeration; and / or, The temperature of the regeneration electrolytic cell is 80-95°C.

8. The platinum-nickel electrode according to any one of claims 1 to 7, characterized in that In step S22, The second platinum precursor salt comprises an organic platinum salt and / or an inorganic platinum salt; and / or, The molar ratio of the second hydroxide to the second platinum precursor salt is 100:1 to 10:

1.

9. The platinum-nickel electrode according to any one of claims 1 to 8, characterized in that In step S22, In the second electrodeposition, the second direct current includes a constant direct current and / or a pulsed direct current, the voltage is 0.1 to 1.2 V, and the current density is 0.1 to 1.5 A / cm 2 and / or, The deposition time of the second electrodeposition is 30 to 120 minutes.

10. A water electrolysis system, comprising electrodes, characterized in that: The electrode comprises the recyclable platinum nickel electrode according to any one of claims 1 to 9.

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