A platinum-titanium alloy integrated cathode with a gradient interdiffusion interface, a preparation method and applications thereof

Abstract

The application discloses a platinum-titanium alloy integrated cathode with a gradient interdiffusion interface, a preparation method and application thereof. The cathode comprises a titanium substrate and a platinum-titanium alloy functional layer formed on the surface of the titanium substrate, wherein the platinum-titanium alloy functional layer comprises a platinum-titanium interdiffusion layer and a platinum-rich catalytic layer, and the platinum element and the titanium element in the platinum-titanium interdiffusion layer are gradiently distributed along the thickness direction. The preparation method comprises depositing a multilayer metal precursor containing a platinum layer and a titanium layer on the surface of the titanium substrate, and inducing interfacial interdiffusion of platinum and titanium through heat treatment. The obtained cathode has an adhesive-free, integrated metal interface and a platinum-rich hydrogen evolution surface, can reduce the interface resistance, improve the catalytic layer bonding strength, and improve the stability of anion exchange membrane water electrolysis hydrogen production under high current density and fluctuating power input.

Description

Technical Field

[0001] This invention belongs to the field of electrocatalysis and water electrolysis for hydrogen production technology, specifically relating to an integrated platinum-titanium alloy cathode for anion exchange membrane water electrolysis, its preparation method, and its application. Background Technology

[0002] Hydrogen energy is an important clean energy carrier, and hydrogen production via renewable electricity-driven water electrolysis is considered a crucial pathway to achieving low-carbon or zero-carbon hydrogen production. Anion exchange membrane water electrolysis technology combines some advantages of traditional alkaline water electrolysis and proton exchange membrane water electrolysis, featuring compact device structure, high hydrogen purity, fast dynamic response, and the ability to use non-precious metal anode materials, making it a promising candidate for application in renewable energy hydrogen production.

[0003] In anion exchange membrane water electrolysis, the cathode primarily undertakes the hydrogen evolution reaction. Since the hydrogen evolution reaction in alkaline or near-neutral environments typically involves steps such as water molecule dissociation, hydrogen intermediate adsorption, and hydrogen generation, its reaction kinetics are much slower than in acidic environments. Therefore, platinum-based materials remain one of the commonly used catalytic materials for improving the hydrogen evolution activity of the cathode. Existing platinum-based cathodes typically employ platinum-carbon catalysts, platinum nanoparticles, platinum-based alloy particles, or platinum-supported composite materials, and the catalytic layer is constructed using methods such as spraying, brushing, drop coating, or hot pressing.

[0004] However, traditional powdered platinum-based catalyst layers typically require carbon supports, ionomers, or polymer binders for construction. This type of structure has the following drawbacks in actual electrolyzer operation: First, multiple solid-solid interfaces exist between the catalyst particles, conductive substrate, ionomer, and membrane, easily leading to increased interfacial contact resistance. Second, binders or ionomers may cover some active sites, reducing the effective utilization rate of platinum active components. Third, the catalyst layer and substrate rely mainly on physical adhesion or weak chemical bonding, making them susceptible to erosion by large amounts of hydrogen bubbles and localized stress disturbances during high current density operation, leading to catalyst layer cracking, detachment, or interfacial failure. Fourth, the carbon support may deteriorate under long-term electrochemical conditions or start-up / shutdown disturbances, affecting the long-term stability of the electrode.

[0005] Furthermore, as anion exchange membrane water electrolysis develops towards higher current density, lower precious metal loading, and direct coupling with renewable energy, the cathode electrode not only needs to possess high intrinsic catalytic activity but also good interfacial electron transport capabilities, mechanical bonding strength, bubble release capacity, and adaptability to dynamic operating conditions. Under fluctuating power input conditions such as solar and wind power, the electrolyzer experiences rapid changes in current density, low-load operation, start-up, shutdown, or intermittent operation. The weak interfacial structure in traditional coated catalyst layers is more susceptible to repeated electrochemical polarization, bubble generation, and stress changes, thus accelerating performance degradation.

[0006] Titanium and titanium-based materials possess excellent electrical conductivity, mechanical strength, and corrosion resistance, and are often used as current collectors, diffusion layers, or metal substrates in water electrolysis devices. Directly constructing platinum catalytic components on the surface of a titanium substrate holds promise for reducing the hierarchical interfaces in powdered catalytic layers and improving electrode structural stability. However, simple platinum layer deposition or platinum particle loading typically forms a relatively sharp metal interface between the platinum layer and the titanium substrate. This interface may still exhibit insufficient bonding strength, increased interfacial resistance, or catalytic layer delamination under long-term high current density operation and bubble scouring conditions. Furthermore, a large platinum layer thickness increases the amount of precious metals required; conversely, a small platinum layer thickness may lead to insufficient catalytic activity or an unstable interfacial structure.

[0007] Therefore, existing technologies still require an anion exchange membrane water electrolysis cathode material and its preparation method that can simultaneously achieve high hydrogen evolution activity, low interfacial resistance, strong interfacial bonding, and dynamic operating stability. In particular, it is necessary to construct a stable metal interdiffusion interface or gradient bonding interface between the titanium substrate and the platinum catalyst layer through reasonable interfacial structure design, so as to improve the long-term operational stability of the platinum-based cathode under high current density and fluctuating power input conditions. Summary of the Invention

[0008] To address the problems existing in current anion exchange membrane water electrolysis cathodes, such as high interfacial contact resistance of the catalyst layer, insufficient bonding strength between the catalyst layer and the substrate, susceptibility to structural failure due to bubble erosion under high current density, and insufficient long-term stability under fluctuating power input conditions, this invention provides an integrated platinum-titanium alloy cathode with a gradient interdiffusion interface, its preparation method, and its applications.

[0009] This cathode improves the interfacial stability, electron transport capacity, and hydrogen evolution durability of the electrode in the process of hydrogen production by anion exchange membrane water electrolysis by constructing a platinum-titanium interdiffusion layer and a platinum enrichment catalytic layer on the surface of a titanium substrate, thereby forming a continuous metal bonding interface between the catalytic active surface and the metal substrate.

[0010] To achieve the above objectives, the present invention adopts the following technical solution:

[0011] The present invention provides an integrated platinum-titanium alloy cathode with a gradient interdiffusion interface. The integrated platinum-titanium alloy cathode is a self-supporting metal cathode without carbon carrier and polymer binder, comprising a titanium substrate and a platinum-titanium alloy functional layer directly formed on the surface of the titanium substrate.

[0012] The platinum-titanium alloy functional layer includes a platinum-titanium interdiffusion layer and a platinum enrichment catalyst layer in sequence along the direction away from the titanium substrate, and the platinum-titanium interdiffusion layer directly connects the titanium substrate and the platinum enrichment catalyst layer;

[0013] In the platinum-titanium interdiffusion layer, platinum and titanium coexist, and along the thickness direction of the platinum enrichment catalytic layer pointing towards the titanium substrate, the atomic fraction of titanium increases overall, while the atomic fraction of platinum decreases overall, forming a continuous composition gradient. The platinum-titanium interdiffusion layer has a Pt–Ti coordination structure, and the platinum content of the platinum enrichment catalytic layer is higher than that of the adjacent platinum-titanium interdiffusion layer, which is used to catalyze the cathode hydrogen evolution reaction.

[0014] Furthermore, the titanium substrate is one or more of the following: titanium sheet, titanium mesh, titanium felt, titanium foam, titanium foil, titanium fiber felt, titanium microporous plate, titanium array substrate, or titanium substrate with micro / nano structures on its surface.

[0015] Furthermore, the platinum-titanium interdiffusion layer and the titanium substrate form a continuous metal interface, and the platinum-titanium interdiffusion layer and the platinum-enriched catalyst layer form a continuous transition interface, thereby reducing the multi-level interfaces between catalyst particles, binders, conductive supports and metal substrates in traditional coated catalyst layers.

[0016] Furthermore, the total platinum loading in the platinum-titanium alloy functional layer is 0.001–1.0 mg cm⁻¹. −2 Preferably 0.005–0.5 mg cm −2 More preferably 0.01–0.2 mg cm −2 .

[0017] Furthermore, the thickness of the platinum enrichment catalyst layer is 1–100 nm, preferably 5–50 nm; the thickness of the platinum-titanium interdiffusion layer is 1–300 nm, preferably 5–150 nm.

[0018] Furthermore, the integrated platinum-titanium alloy cathode is a self-supporting metal cathode with no carbon carrier, no polymer binder, or low binder content.

[0019] The present invention also provides a method for preparing the above-mentioned integrated platinum-titanium alloy cathode, comprising the following steps:

[0020] S1, providing a titanium substrate, and cleaning, drying or surface pretreatment of the titanium substrate;

[0021] S2, depositing a multilayer metal precursor containing a platinum layer and a titanium layer on the surface of the titanium substrate;

[0022] S3, the multilayer metal precursor is heat-treated to cause interfacial interdiffusion of platinum and titanium elements, forming a platinum-titanium alloy functional layer including a platinum-titanium interdiffusion layer and a platinum enrichment catalyst layer on the surface of the titanium substrate, thereby obtaining the integrated platinum-titanium alloy cathode.

[0023] Further, in step S1, the surface pretreatment includes one or more of the following: mechanical polishing, chemical cleaning, acid washing, alkaline washing, plasma treatment, etching, anodizing, sandblasting, annealing pretreatment, or micro / nano arraying treatment.

[0024] Further, in step S2, the multilayer metal precursor is one of Pt / Ti, Ti / Pt, Pt / Ti / Pt, Ti / Pt / Ti / Pt, or a multi-period Pt / Ti alternating layer structure.

[0025] Further, in step S2, the deposition method is magnetron sputtering, electron beam evaporation, thermal evaporation, atomic layer deposition, pulsed laser deposition, electrodeposition, chemical plating, or a combination thereof.

[0026] Further, in step S2, the thickness of the platinum-containing monolayer is 1–100 nm, and the thickness of the titanium monolayer is 0.1–100 nm.

[0027] Further, in step S3, the heat treatment temperature is 300–900 ℃, preferably 400–800 ℃, and more preferably 500–700 ℃.

[0028] Further, in step S3, the heat treatment time is 1 min–10 h, preferably 10 min–5 h, and more preferably 0.5–3 h.

[0029] Further, in step S3, the heat treatment atmosphere is nitrogen, argon, helium, hydrogen, a hydrogen-argon mixture, a hydrogen-nitrogen mixture, vacuum, or a combination thereof.

[0030] The present invention also provides an anion exchange membrane water electrolyzer, the anion exchange membrane water electrolyzer comprising a cathode, an anode, and an anion exchange membrane disposed between the cathode and the anode, wherein the cathode is the aforementioned integrated platinum-titanium alloy cathode with a gradient interdiffusion interface.

[0031] Furthermore, the anode is a nickel-iron-based catalytic electrode, a nickel-iron layered double hydroxide electrode, a nickel-iron phosphide electrode, a nickel-iron sulfide electrode, a nickel-molybdenum-based electrode, a cobalt-iron-based electrode, a noble metal oxide electrode, or a composite electrode thereof.

[0032] Furthermore, the electrolyte in the anion exchange membrane water electrolyzer is deionized water, pure water, potassium hydroxide aqueous solution, sodium hydroxide aqueous solution, carbonate aqueous solution, low-concentration alkaline aqueous solution, or a combination thereof.

[0033] Furthermore, the anion exchange membrane water electrolyzer is suitable for a current density range of 0.01–10 A cm⁻², and is preferably suitable for high current density operating conditions of 0.1–5 A cm⁻².

[0034] Furthermore, the anion exchange membrane water electrolyzer is suitable for constant current input, stepped current input, circulating current input, start-stop operation, low load maintenance operation, and fluctuating power input conditions such as solar energy, wind energy, or solar / wind energy coupling.

[0035] The present invention also provides the application of the above-mentioned integrated platinum-titanium alloy cathode in hydrogen production by water electrolysis, especially in hydrogen production by anion exchange membrane water electrolysis, alkaline water electrolysis, low-concentration alkaline electrolysis, and pure water or near-neutral water electrolysis.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] First, this invention forms a platinum-titanium gradient interdiffusion layer with continuously varying composition between the titanium substrate and the platinum-enriched catalyst layer through thermally induced interdiffusion, transforming the traditional sharp platinum / titanium interface into a continuous metal transition interface. This gradient structure allows interfacial loads and stresses to be transferred stepwise within a certain thickness range, effectively mitigating localized stress concentrations caused by repeated bubble generation and desorption during high-current-density hydrogen evolution, significantly reducing the risk of catalyst layer cracking, peeling, and interfacial contact failure, and fundamentally improving the structural stability of the electrode.

[0038] Secondly, this invention constructs an integrated continuous metal system consisting of a platinum-enriched catalyst layer, a platinum-titanium interdiffusion layer, and a titanium substrate. The surface platinum-enriched layer safeguards the hydrogen evolution active sites, while the underlying interdiffusion layer simultaneously serves as a mechanical anchor and electron transport channel, enabling catalytic function and interfacial stability to be synergistically achieved within the same system. Furthermore, this electrode eliminates the need for carbon supports and polymer binders, avoiding the multi-level contact interfaces between catalyst particles, carbon supports, binders, and the metal substrate found in traditional powder-coated catalyst layers. This eliminates the binder's coverage of the active surface while maintaining a continuous, low-resistance electron transport path, thereby improving the utilization rate of the platinum active component and the electron conduction efficiency.

[0039] Third, the improvement in interface stability brought about by this invention is not only reflected in the static bonding state, but also shows outstanding performance during high current density and dynamic current input processes. The gradient interdiffusion interface can effectively buffer the sudden changes in interface stress during repeated increases and decreases in current density, low load maintenance, or start-up and shutdown processes, maintaining the structural and conductive continuity between the catalyst layer and the titanium substrate. This significantly improves the electrode's adaptability to fluctuating power inputs such as solar and wind power, meeting the operational requirements of anion exchange membrane water electrolysis in practical renewable energy scenarios.

[0040] Fourth, this invention allows for flexible control of the interdiffusion degree, platinum enrichment layer thickness, and interface structure by adjusting parameters such as the deposition sequence and thickness of the platinum and titanium layers, as well as the heat treatment temperature, time, and atmosphere. This enables synergistic optimization of surface hydrogen evolution activity, interfacial bonding strength, and electron transport capability. Furthermore, this electrode can be directly used as the cathode of an electrolyzer, eliminating the need for complex processes such as traditional catalyst slurry preparation, spraying, and binder curing. This simplifies the preparation process, improves the consistency of the electrode structure, and enhances assembly stability, demonstrating promising prospects for industrial application. Attached Figure Description

[0041] Figure 1 This is a schematic diagram of the fabrication process of the integrated platinum-titanium alloy cathode with a gradient interdiffusion interface described in this invention.

[0042] Figure 2 This is a schematic diagram showing the cross-sectional structure changes of the integrated platinum-titanium alloy cathode before and after heat treatment according to the present invention. Before heat treatment, it is a multilayer metal precursor with a platinum-containing layer and a titanium layer on the surface of a titanium substrate. After heat treatment, a platinum-enriched catalytic layer and a platinum-titanium interdiffusion layer are formed.

[0043] Figure 3 The cross-sectional morphology and characterization diagram of the platinum-titanium alloy integrated cathode in the embodiment of the present invention are shown in the figure (a is the original interface and element distribution diagram in the unannealed state, and b is the Pt-Ti interdiffusion layer and element mixing formed after annealing at 550℃).

[0044] Figure 4 This is a schematic diagram of the assembly structure of the integrated platinum-titanium alloy cathode of the present invention used in an anion exchange membrane water electrolyzer.

[0045] Figure 5 This is a comparison diagram of the structure and electrochemical performance of the integrated platinum-titanium alloy cathodes obtained at different heat treatment temperatures in the embodiments of the present invention.

[0046] Figure 6 The figures show the test results of the high current density operation stability and fluctuating power input stability of the integrated platinum-titanium alloy cathode in the anion exchange membrane water electrolyzer of this invention (where a is the polarization curve of the electrolyzer using the integrated platinum-titanium alloy cathode, the unannealed Pt / Ti multilayer cathode, and the Pt / C cathode, respectively, and assembled with the same NiFeS anode, under the conditions of 60 ℃ and 0.1 M KOH; b is the comparison of the cell voltage of the above three electrolyzers at current densities of 0.5 A cm⁻², 1.0 A cm⁻², and 2.0 A cm⁻²; c is the cell voltage variation curve of the above three electrolyzers under constant current density with operating time). Detailed Implementation

[0047] The present invention will be further illustrated below with reference to the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. It should be noted that the terms "front," "rear," "left," "right," "up," and "down" used in the following description refer to directions in the accompanying drawings, and the terms "inner" and "outer" refer to directions toward or away from the geometric center of a specific component, respectively.

[0048] Example 1: Fabrication of an integrated platinum-titanium alloy cathode

[0049] This embodiment provides an integrated platinum-titanium alloy cathode with a gradient interdiffusion interface, and its preparation method is as follows.

[0050] First, a titanium substrate is provided. The titanium substrate can be a titanium sheet, titanium foil, titanium mesh, titanium felt, titanium foam, titanium microporous plate, or a titanium substrate with a micro / nano structure on its surface. In this embodiment, a titanium sheet is used as the substrate. After the titanium sheet is cut to a predetermined size, it is sequentially ultrasonically cleaned in acetone, ethanol, and deionized water to remove surface oil and particulate impurities. The cleaned titanium sheet is then dried with nitrogen or under vacuum before use.

[0051] Subsequently, a multilayer metal precursor is deposited on the surface of a titanium substrate. Specifically, a first platinum layer, a titanium intermediate layer, and a second platinum layer are sequentially deposited on the surface of the titanium substrate using magnetron sputtering, electron beam evaporation, thermal evaporation, atomic layer deposition, or other physical / chemical deposition methods to form a Pt / Ti / Pt multilayer metal precursor. The thickness of the first platinum layer is 1-100 nm, the thickness of the titanium intermediate layer is 0.1-100 nm, and the thickness of the second platinum layer is 1-100 nm.

[0052] In a preferred embodiment, a first platinum layer with a thickness of 25 nm, a titanium intermediate layer with a thickness of 1.5 nm, and a second platinum layer with a thickness of 15 nm are sequentially deposited on the surface of the titanium substrate in a direction from the titanium substrate outward, forming a Ti substrate / Pt / Ti / Pt multilayer metal precursor; the multilayer metal precursor is represented as Pt (15 nm) / Ti (1.5 nm) / Pt (25 nm) / Ti substrate in a direction from the outside to the inside of the cross section.

[0053] The first platinum layer, located close to the titanium substrate, forms a continuous metallic conductive layer and interdiffused with the titanium substrate and intermediate layer during heat treatment. The intermediate titanium layer, acting as a confined titanium source, forms a platinum-titanium interdiffusion region without significantly disrupting the platinum enrichment characteristics of the outer layer. The second platinum layer, located further from the titanium substrate, retains a continuous platinum-enriched catalytic surface after heat treatment. This asymmetric layer thickness design facilitates the formation of a continuous metallic transition structure between the platinum-enriched catalytic layer, the subsurface platinum-titanium interdiffusion layer, and the titanium substrate while controlling the amount of platinum used.

[0054] Then, the aforementioned multilayer metal precursor was heat-treated. A titanium substrate with the deposited Pt / Ti / Pt multilayer metal precursor was placed in a tube furnace and annealed under nitrogen, argon, a hydrogen-argon mixture, a hydrogen-nitrogen mixture, or vacuum conditions. The annealing temperature was 300–900 °C, and the annealing time was 1 min–10 h. During annealing, platinum and titanium interdiffusion occurred at the interface, transforming the originally relatively sharp platinum / titanium layered interface into a platinum-titanium interdiffusion interface with a gradient compositional distribution.

[0055] After annealing, the cathode is naturally cooled to room temperature to obtain an integrated platinum-titanium alloy cathode with a gradient interdiffusion interface. The specific fabrication process is as follows: Figure 1 As shown, the resulting cathode comprises a titanium substrate, a platinum-titanium interdiffusion layer on the surface of the titanium substrate, and a platinum-enriched catalytic layer on the outer surface. In the platinum-titanium interdiffusion layer, platinum and titanium elements are distributed in a gradient along the thickness direction. The platinum-enriched catalytic layer serves to provide hydrogen evolution active sites for the cathode.

[0056] Example 2: Preparation of integrated platinum-titanium alloy cathodes at different heat treatment temperatures

[0057] To control the degree of interdiffusion between platinum and titanium, Pt / Ti / Pt multilayer metal precursors were prepared according to the method in Example 1, and then heat-treated at different temperatures to obtain integrated platinum-titanium alloy cathodes with different degrees of interdiffusion.

[0058] Specifically, multiple Pt / Ti / Pt / Ti substrate samples with the same structure were placed in a nitrogen atmosphere and annealed at 400℃, 500℃, 550℃, 600℃, 650℃, and 700℃. After annealing, they were naturally cooled to room temperature to obtain integrated platinum-titanium alloy cathodes corresponding to different heat treatment temperatures.

[0059] like Figure 2 As shown, in the unannealed sample, the platinum layer, titanium interlayer, and titanium substrate still maintain relatively clear layered interfaces, while the platinum / titanium interface is relatively sharp. With increasing annealing temperature, platinum and titanium elements undergo gradually enhanced interdiffusion in the interface region, forming a continuous platinum-titanium interdiffusion layer. When the annealing temperature is within a suitable range, a platinum-enriched catalytic layer is retained on the electrode surface, while a continuous platinum-titanium gradient interdiffusion interface is formed internally, thus balancing hydrogen evolution activity, interfacial bonding strength, and electron transport capability.

[0060] If the annealing temperature is too low, the interdiffusion of platinum and titanium will be insufficient, the platinum / titanium interface will remain relatively sharp, and the interfacial bonding enhancement effect will be limited. If the annealing temperature is too high, it may lead to excessive diffusion of the surface metal layer, grain coarsening, or localized granulation, thereby affecting the exposure of active sites and the uniformity of the electrode surface. Therefore, the preferred annealing temperature is 500–700 °C, and more preferably 550–650 °C.

[0061] Example 3: Structural characterization of an integrated platinum-titanium alloy cathode

[0062] The integrated platinum-titanium alloy cathodes obtained in Examples 1 and 2 were structurally characterized to verify the formation of the platinum-titanium interdiffusion layer and the platinum-enriched catalyst layer.

[0063] The surface morphology of the electrode was observed using scanning electron microscopy, and the cross-sectional structure of the electrode was observed using transmission electron microscopy or a combination of focused ion beam cross-section preparation and transmission electron microscopy. The distribution of platinum and titanium elements along the cross-sectional direction was analyzed using high-angle annular dark-field scanning transmission electron microscopy, energy-dispersive X-ray spectroscopy, elemental surface distribution, and elemental line scanning.

[0064] like Figure 3 As shown, Figure 3 In this context, 'a' represents the unannealed sample. Figure 3 Sample b is annealed at 550℃. In the unannealed sample, there is a relatively obvious layered structure between the platinum and titanium layers, and the transition region between platinum and titanium at the interface is narrow. After heat treatment, platinum and titanium interdiffusion occur at the interface, forming a continuous platinum-titanium interdiffusion layer. In this platinum-titanium interdiffusion layer, the platinum and titanium elements exhibit a gradient along the thickness direction, while the outer surface of the electrode remains relatively platinum-enriched, forming a platinum-enriched catalytic layer. This structure is beneficial for enhancing the bonding between the catalytic layer and the titanium substrate and improving interfacial electron transport.

[0065] Example 4: Assembly of anion exchange membrane water electrolyzer

[0066] The integrated platinum-titanium alloy cathode prepared in Example 1 or Example 2 was used in an anion exchange membrane water electrolyzer for water electrolysis hydrogen production testing.

[0067] The anion exchange membrane water electrolyzer includes a cathode, an anode, and an anion exchange membrane disposed between the cathode and the anode. The cathode is an integrated platinum-titanium alloy cathode as described above, and the anode is a nickel-iron-based catalytic electrode, a nickel-iron-layered double hydroxide electrode, a nickel-iron phosphide electrode, a nickel-iron sulfide electrode, a nickel-molybdenum-based electrode, a cobalt-iron-based electrode, or other electrodes suitable for alkaline oxygen evolution reactions. The anion exchange membrane can be a commercially available anion exchange membrane or an anion exchange membrane activated by alkaline solution.

[0068] like Figure 4 As shown, during assembly, the integrated platinum-titanium alloy cathode, anion exchange membrane, and anode are stacked sequentially and assembled into the electrolytic cell fixture. Cathode flow field plates and anode flow field plates are respectively installed on both sides of the electrolytic cell for electrolyte flow, gas discharge, and current collection. The electrolyte can be deionized water, pure water, low-concentration potassium hydroxide solution, sodium hydroxide solution, or other alkaline aqueous solutions.

[0069] During the test, a hydrogen evolution reaction occurs on the cathode side, producing hydrogen gas, while an oxygen evolution reaction occurs on the anode side, producing oxygen gas. Since the cathode of this invention is an integrated metal electrode without a carbon support or polymer binder, its platinum-enriched catalyst layer is directly connected to the titanium substrate through a platinum-titanium interdiffusion layer. This reduces the multi-level interfaces between particles, support, binder, and substrate in traditional catalyst coatings, which helps to lower interfacial contact resistance and improve high current density operating stability.

[0070] Example 5: Electrochemical performance testing of an integrated platinum-titanium alloy cathode

[0071] The anion exchange membrane water electrolyzer assembled in Example 4 was connected to an electrochemical workstation or electrolyzer testing system for polarization curve, constant current stability and electrochemical impedance testing.

[0072] First, the electrolytic cell was activated under set temperature and electrolyte flow rate conditions. Then, the cell voltage variation was tested under different current densities. The test current density range was 0.01–10 A. Preferably 0.1–5A Under the same test conditions, the integrated platinum-titanium alloy cathode of the present invention was compared with an unannealed Pt / Ti electrode, a conventional Pt / C coated cathode, or other comparative electrodes.

[0073] like Figure 5 As shown, compared with the control electrode that does not form a gradient interdiffusion interface, the integrated platinum-titanium alloy cathode of the present invention exhibits lower cell voltage or smaller cathode polarization loss at the same current density. This is because the platinum-enriched catalyst layer provides highly efficient hydrogen evolution active sites, the platinum-titanium interdiffusion layer provides continuous metal electron transport channels, and enhances the bonding strength between the catalyst layer and the titanium substrate.

[0074] Further constant current stability testing was conducted. The electrolytic cell was continuously operated under high current density, and the cell voltage change over time was recorded. Figure 6 As shown, under the same test conditions, an anion exchange membrane water electrolyzer was assembled using a platinum-titanium alloy integrated cathode with a gradient interdiffusion interface formed by heat treatment, an untreated Pt / Ti multilayer cathode, and a commercial Pt / C cathode, respectively, and the same NiFeS anode. The test temperature was 60 ℃, and the electrolyte was 0.1 M KOH.

[0075] like Figure 6 As shown in Figure a, within the tested current density range, the electrolytic cell using an integrated platinum-titanium alloy cathode exhibits the lowest cell voltage, followed by the untreated Pt / Ti multilayer cathode, while the electrolytic cell using a commercial Pt / C cathode has the highest cell voltage. This result indicates that the platinum-titanium gradient interdiffusion interface formed by heat treatment is beneficial for reducing cathode polarization losses and interfacial transport resistance.

[0076] like Figure 6 As shown in b, at current densities of 0.5 A cm⁻², 1.0 A cm⁻², and 2.0 A cm⁻², the cell voltage of the electrolytic cell with the integrated platinum-titanium alloy cathode is lower than that of the other two comparative electrolytic cells. Furthermore, its cell voltage advantage is maintained as the current density increases, indicating that the integrated cathode can adapt to ampere-level current densities.

[0077] like Figure 6 As shown in Figure c, under constant current density conditions of 60℃, 0.1M KOH, and 1.0 Acm⁻², the electrolyzer using an integrated platinum-titanium alloy cathode maintained a relatively stable cell voltage for over 5000 h with a voltage growth rate of 3.227 μV h⁻¹. In contrast, electrolyzers using untreated Pt / Ti multilayer cathodes and commercial Pt / C cathodes exhibited higher cell voltages or more significant performance changes within a shorter operating time. These results indicate that the platinum-titanium gradient interdiffusion interface can maintain the structural continuity and electron transport pathway between the catalyst layer and the titanium substrate during long-term hydrogen evolution.

[0078] The integrated platinum-titanium alloy cathode of the present invention exhibits small cell voltage decay or low voltage growth rate during long-term operation, indicating that it has good structural and electrochemical stability under high current density hydrogen evolution conditions.

[0079] Example 6: Operational Testing under Fluctuating Power Input Conditions

[0080] To evaluate the adaptability of the integrated platinum-titanium alloy cathode of the present invention to the fluctuating power input of renewable energy, the anion exchange membrane water electrolyzer assembled in Example 4 was connected to a programmable DC power supply or an electrochemical testing system, and a fluctuating current program simulating solar energy, wind energy, or solar / wind energy coupling was input.

[0081] The fluctuating current program can include stepped current variations, periodic current cycles, random current fluctuations, low current holding, start-stop cycles, or combinations thereof. For example, the actual solar or wind power output curve can be normalized and converted into an electrolyzer current density curve, and then compressed into an accelerated fluctuation test program on a laboratory timescale. The current density can cycle between low-load and high-load regions to simulate the dynamic operating environment caused by fluctuations in renewable energy output.

[0082] During the test, the cell voltage, current density, and running time of the electrolytic cell were recorded. The results show that, compared with traditional coated platinum-based cathodes, the integrated platinum-titanium alloy cathode of this invention exhibits better cell voltage stability and structural retention under fluctuating power input conditions. This is because the present invention connects the platinum-enriched catalytic surface to the titanium substrate as a continuous metal interface through a platinum-titanium interdiffusion layer, making it less prone to catalytic layer cracking, peeling, or interface failure during repeated current changes and bubble generation / desorption processes.

[0083] Therefore, the integrated platinum-titanium alloy cathode of the present invention is not only suitable for hydrogen production by anion exchange membrane water electrolysis under constant current density, but also suitable for hydrogen production by water electrolysis driven by fluctuating renewable energy sources such as solar and wind power, either directly or indirectly.

[0084] Example 7: Comparative Example

[0085] To further illustrate the technical effects of the present invention, the following comparative examples are provided.

[0086] Comparative Example 1 is an unannealed Pt / Ti / Pt / Ti substrate electrode. This electrode has a layered structure of a platinum layer, a titanium interlayer, and a titanium substrate, but it has not undergone heat treatment to induce interdiffusion. Due to its relatively sharp platinum / titanium interface, the interfacial bonding enhancement effect is limited, and large interfacial resistance or insufficient structural stability may occur during high current density or long-term operation.

[0087] Comparative Example 2 is a commercially available Pt / C coated cathode. This electrode is prepared by mixing Pt / C catalyst, ionomer, and solvent to form a catalyst slurry, which is then coated onto a gas diffusion layer or a conductive substrate. This type of electrode contains multi-level interfaces between catalyst particles, carbon support, ionomer, and substrate, and is susceptible to bubble erosion, localized stress, and changes in interfacial contact during high current density operation.

[0088] The integrated platinum-titanium alloy cathode of this invention was compared with the comparative example described above under the same anion exchange membrane water electrolyzer conditions. The results show that the cathode of this invention exhibits comprehensive advantages in terms of electrolyzer cell voltage, interfacial impedance, long-term stability, and adaptability to fluctuating power supplies, indicating that the gradient platinum-titanium interdiffusion interface plays a crucial role in improving the structural stability of the integrated cathode and the operational stability of water electrolysis.

[0089] The technical means disclosed in this invention are not limited to those disclosed in the above embodiments, but also include technical solutions composed of any combination of the above technical features.

Claims

1. A platinum-titanium alloy integrated cathode with a gradient interdiffusion interface, characterized in that, The integrated platinum-titanium alloy cathode is a self-supporting metal cathode without carbon carrier and polymer binder, comprising a titanium substrate and a platinum-titanium alloy functional layer formed directly on the surface of the titanium substrate. The platinum-titanium alloy functional layer includes a platinum-titanium interdiffusion layer and a platinum enrichment catalyst layer in sequence along the direction away from the titanium substrate, and the platinum-titanium interdiffusion layer directly connects the titanium substrate and the platinum enrichment catalyst layer; In the platinum-titanium interdiffusion layer, platinum and titanium coexist, and along the thickness direction of the platinum enrichment catalytic layer pointing towards the titanium substrate, the atomic fraction of titanium increases overall, while the atomic fraction of platinum decreases overall, forming a continuous composition gradient. The platinum-titanium interdiffusion layer has a Pt–Ti coordination structure, and the platinum content of the platinum enrichment catalytic layer is higher than that of the adjacent platinum-titanium interdiffusion layer, which is used to catalyze the cathode hydrogen evolution reaction.

2. The integrated platinum-titanium alloy cathode with a gradient interdiffusion interface according to claim 1, characterized in that, The titanium substrate is one or more of the following: titanium sheet, titanium foil, titanium mesh, titanium felt, titanium foam, titanium fiber felt, titanium microporous plate, titanium array substrate, or titanium substrate with micro / nano structures on its surface; the platinum-titanium interdiffusion layer and the titanium substrate are a continuous metal interface, and the platinum-titanium interdiffusion layer and the platinum enrichment catalyst layer are a continuous transition interface.

3. The integrated platinum-titanium alloy cathode according to claim 1, characterized in that, The thickness of the platinum-enriched catalyst layer is The thickness of the platinum-titanium interdiffusion layer is The total platinum loading in the platinum-titanium alloy functional layer is .

4. A method for preparing an integrated platinum-titanium alloy cathode with a gradient interdiffusion interface, based on the integrated platinum-titanium alloy cathode with a gradient interdiffusion interface as described in any one of claims 1-3, characterized in that, Includes the following steps: Step S1: Provide a titanium substrate and clean, dry or pre-treat the titanium substrate. Step S2: Deposit a multilayer metal precursor containing a platinum layer and a titanium layer on the surface of the titanium substrate; Step S3: The multilayer metal precursor is heat-treated to allow interfacial interdiffusion of platinum and titanium elements, forming a platinum-titanium alloy functional layer including a platinum-titanium interdiffusion layer and a platinum enrichment catalyst layer on the surface of the titanium substrate, thereby obtaining the integrated platinum-titanium alloy cathode.

5. The method for preparing an integrated platinum-titanium alloy cathode with a gradient interdiffusion interface according to claim 4, characterized in that, In step S1, the surface pretreatment includes one or more of the following: mechanical polishing, chemical cleaning, acid pickling, alkaline cleaning, plasma treatment, etching, anodizing, sandblasting, annealing pretreatment, or micro / nano arraying treatment; in step S2, the deposition method is magnetron sputtering, electron beam evaporation, thermal evaporation, atomic layer deposition, pulsed laser deposition, electrodeposition, electroless plating, or a combination thereof; in step S2, the thickness of the platinum-containing layer is... The thickness of a single titanium layer is In step S2, the multilayer metal precursor is one of Pt / Ti, Ti / Pt, Pt / Ti / Pt, Ti / Pt / Ti / Pt, or a multi-period Pt / Ti alternating layer structure.

6. The method for preparing an integrated platinum-titanium alloy cathode with a gradient interdiffusion interface according to claim 5, characterized in that, In step S2, the multilayer metal precursor is a Pt / Ti / Pt structure, specifically, a first platinum layer, a titanium intermediate layer, and a second platinum layer are sequentially deposited on the surface of a titanium substrate; the thickness of the first platinum layer is 5-50 nm, the thickness of the titanium intermediate layer is 0.5-10 nm, and the thickness of the second platinum layer is 5-80 nm.

7. The method for preparing an integrated platinum-titanium alloy cathode with a gradient interdiffusion interface according to claim 6, characterized in that, The first platinum layer has a thickness of 25 nm, the titanium interlayer has a thickness of 1.5 nm, and the second platinum layer has a thickness of 15 nm.

8. The method for preparing an integrated platinum-titanium alloy cathode with a gradient interdiffusion interface according to claim 4, characterized in that, In step S3, the heat treatment temperature is 300-900 ℃; in step S3, the heat treatment time is 1 min-10 h; in step S3, the heat treatment atmosphere is nitrogen, argon, helium, hydrogen, hydrogen-argon mixture, hydrogen-nitrogen mixture, vacuum, or a combination thereof.

9. An anion exchange membrane water electrolyzer, characterized in that, The anion exchange membrane water electrolyzer is suitable for 0.01-10 A. The current density range includes a cathode, an anode, and an anion exchange membrane disposed between the cathode and the anode, wherein the cathode is an integrated platinum-titanium alloy cathode as described in any one of claims 1-3; the anode is a nickel-iron-based catalytic electrode, a nickel-iron layered double hydroxide electrode, a nickel-iron phosphide electrode, a nickel-iron sulfide electrode, a nickel-molybdenum-based electrode, a cobalt-iron-based electrode, a noble metal oxide electrode, or a composite electrode thereof; the electrolyte of the anion exchange membrane water electrolyzer is deionized water, pure water, potassium hydroxide aqueous solution, sodium hydroxide aqueous solution, carbonate aqueous solution, low-concentration alkaline aqueous solution, or a combination thereof.

10. The application of the integrated platinum-titanium alloy cathode as described in claim 1 or 2 in fluctuating renewable electricity-driven water electrolysis for hydrogen production.

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