A high-efficiency cathode catalytic electrode for proton exchange membrane electrolysis of water and a preparation method and application thereof

Abstract

This invention belongs to the field of electrochemical energy conversion and electrocatalytic materials technology, specifically relating to a method for preparing a highly efficient cathode catalytic electrode for proton exchange membrane (PEM) water electrolysis. The method includes the following steps: S1. Taking material from a supporting conductive porous substrate and pre-treating it with cleaning and surface activation; S2. Electrodepositing an MXene conductive layer; S3. Nitrogen-doped MXene support layer; S4. Electrodepositing molybdenum species to form sub-nanoclusters; S5. Electrodepositing platinum species to form single atoms. This invention also provides a highly efficient cathode catalytic electrode for PEM water electrolysis prepared by this method. This method is green, controllable, and scalable, constructing a multi-scale synergistic catalytic structure of Pt single atoms / Mo sub-nanoclusters in situ on a nitrogen-doped MXene support, thereby achieving a PEM water electrolysis cathode electrode with low noble metal loading, high activity, and high stability.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical energy conversion and electrocatalytic materials technology, specifically relating to a high-efficiency cathode catalytic electrode for proton exchange membrane water electrolysis, its preparation method, and its application. Background Technology

[0002] Hydrogen energy, as a clean and high-energy-density secondary energy source, holds significant strategic importance in achieving "dual carbon" goals and building a sustainable energy system. Proton exchange membrane (PEM) water electrolysis technology, due to its advantages such as high current density, fast response speed, high hydrogen purity, and compact system, is considered an important development direction for renewable energy hydrogen production, particularly suitable for distributed hydrogen production and hydrogen refueling stations for hydrogen fuel cell vehicles. However, PEM water electrolysis operates under highly acidic environments, high current densities, and high potential gradients, placing extremely stringent requirements on the catalytic activity, structural stability, and corrosion resistance of electrode materials, especially the hydrogen evolution reaction (HER) catalyst at the cathode.

[0003] Currently, platinum (Pt)-based catalysts are considered the most effective catalytic materials for HER under acidic conditions due to their near-zero hydrogen adsorption free energy. However, there are still significant limitations in the application of existing commercial Pt / C or Pt black catalysts in PEM water electrolysis: (1) High amount of precious metals and high cost: In traditional Pt nanoparticle catalysts, most Pt atoms are located inside the particles and cannot directly participate in the reaction, resulting in low atomic utilization, which seriously restricts the large-scale promotion of PEM water electrolysis.

[0004] (2) Insufficient stability under high current density: Under long-term operation or high load conditions, Pt nanoparticles are prone to agglomeration, dissolution-redeposition and carrier stripping, resulting in activity decay and shortened electrode life.

[0005] (3) Uncontrollable interface structure and electronic structure: In traditional supported Pt catalysts, the interaction between Pt and the support is weak, making it difficult to precisely control the electronic structure and reaction pathway of Pt.

[0006] To overcome the aforementioned bottlenecks, single-atom catalysts (SACs) have become a research hotspot in the field of electrocatalysis in recent years. Pt single atoms exhibit excellent mass-to-specific activity in electrocatalysis (HER) due to their maximum atomic utilization, unique electronic structure, and uniform active sites. However, Pt single atoms suffer from thermodynamic instability under acidic HER conditions: proton attacks easily disrupt the metal-support coordination bonds, leading to Pt atom migration and aggregation into nanoparticles. Simultaneously, the singular electronic structure of single-atom sites makes it difficult to simultaneously optimize the hydrogen adsorption-desorption kinetics during the HER process, limiting further improvement in intrinsic activity. Therefore, developing highly conductive support materials capable of stably anchoring Pt single atoms under acidic conditions and constructing a reasonable coordination environment and electronic structure regulation mechanism are crucial for realizing the practical application of Pt single atoms.

[0007] In recent years, MXene has emerged as a class of compounds with the general formula M n+1 X n T x (M is a transition metal, X is C / N, T) x Two-dimensional transition metal carbides / nitrides (MXenes) with surface functional groups have attracted widespread attention in the field of electrocatalysis due to their high conductivity, layered structure, abundant surface functional groups, and excellent acid-base stability. Compared with traditional carbon supports (such as carbon black and graphene), MXene's interlayer channels can accelerate proton / electron transport, and its surface functional groups can provide metal anchoring sites, showing great application potential in PEM water electrolysis cathodes. However, unmodified MXene as a support has two major drawbacks: First, the number and strength of anchoring sites are insufficient, and the coordination between its native surface functional groups (-OH, -F) and Pt atoms is weak, making it difficult to stabilize Pt single atoms under strong acid conditions; at the same time, the density of surface defect sites is low, limiting the loading and dispersion of Pt single atoms. Second, the ability to regulate electronic structure is limited. The density of electronic states near the Fermi level of pure MXene is low, and the electronic interaction with Pt single atoms is weak, making it impossible to effectively optimize the hydrogen adsorption free energy, thus limiting the improvement of the intrinsic activity of single-atom Pt.

[0008] The aforementioned problems can be systematically solved by modifying MXene with nitrogen doping. Nitrogen atoms have high electronegativity, and their introduction can form strong coordination sites such as pyridine nitrogen and pyrrole nitrogen in the MXene framework. These sites can form stable coordination bonds with platinum atoms with binding energies exceeding 3 eV, thereby achieving a firm anchorage of platinum single atoms. Simultaneously, nitrogen doping can effectively control the charge distribution of MXene, optimizing platinum through charge transfer between the metal and the support. dBy leveraging the central position of platinum, its adsorption strength for hydrogen can be precisely tuned. To further enhance performance, introducing a second metal, molybdenum, to construct a bimetallic synergistic system is an effective strategy. Molybdenum sub-nanoclusters possess both high dispersion and unique electronic coupling advantages. Through "Pt-Mo electronic interactions," the electronic structure of platinum can be further fine-tuned, and molybdenum itself can serve as an auxiliary active site to promote the adsorption and activation of water molecules. Ultimately, this forms a synergistic catalytic mechanism of "platinum single atoms dominating hydrogen adsorption, and molybdenum sub-nanoclusters assisting water activation," thereby overcoming the performance limitations of single-component catalysts.

[0009] However, existing techniques for constructing Pt single-atom and Mo species-synergistic structures generally rely on soluble metal salt precursors (such as chloroplatinic acid and molybdate) and are coupled with complex processes such as strong chemical reduction, organic ligand protection, or high-temperature heat treatment. This methodological approach suffers from a series of inherent and interrelated limitations: (1) Low atom economy and waste of resources: In liquid phase reaction, a large number of metal precursors are lost due to physical adsorption competition, ineffective reduction or formation of inactive precipitates. The actual efficiency of conversion into stable active sites is extremely low, resulting in serious waste of precious metal resources, which is contrary to the fundamental goal of reducing catalyst cost.

[0010] (2) Complex process and environmentally unfriendly: The multi-step impregnation, reduction, washing and post-treatment process is lengthy and relies on strong reducing agents (such as NaBH4), organic stabilizers or high-temperature calcination, which not only increases the complexity of the process and energy consumption, but also easily introduces impurities and generates waste liquid containing heavy metals, resulting in a significant environmental burden.

[0011] (3) Poor scalability and engineering bottlenecks: Traditional processes based on solution immersion and coating are difficult to guarantee a uniform, dense and strongly adhered catalytic layer on a large-area conductive substrate. The batch repeatability is poor and the compatibility with the continuous, roll-to-roll membrane electrode industrial production mode is low.

[0012] (4) Insufficient precision in microstructure control: In mixed precursor solutions, the reduction potentials and nucleation kinetics of different metal ions vary, making it difficult to separate their deposition processes in time and space.

[0013] Therefore, simultaneously achieving the precise construction and positioning of Pt as isolated single atoms and Mo as sub-nano clusters at the same carrier interface, while avoiding the formation of random alloy particles, is a control challenge that is almost insurmountable with existing technologies. To solve this problem, there is an urgent need to research and develop a highly efficient cathode catalytic electrode for proton exchange membrane water electrolysis and its preparation method. Summary of the Invention

[0014] To address the problems of low precious metal utilization, difficulty in precisely controlling the catalytic layer structure and electronic structure, and complex preparation process in existing PEM water electrolysis cathode catalysts, which are not conducive to large-area and continuous preparation, especially the key technical bottleneck of simultaneously and controllably constructing a Pt single-atom and Mo sub-nanocluster synergistic active structure on the same support interface, this invention aims to provide a method for preparing a highly efficient cathode catalytic electrode for proton exchange membrane water electrolysis. This method is green, controllable, and scalable, and constructs a multi-scale synergistic catalytic structure of Pt single atoms / Mo sub-nanoclusters in situ on a nitrogen-doped MXene support, thereby achieving a PEM water electrolysis cathode electrode with low precious metal loading, high activity, and high stability.

[0015] The technical solution of this invention is as follows: A method for preparing a high-efficiency cathode catalytic electrode for proton exchange membrane water electrolysis includes the following steps: S1. Taken from a supporting conductive porous substrate, and subjected to cleaning and surface activation pretreatment; S2. Electrodeposition of MXene conductive layer: In MXene dispersion, a constant voltage or constant current electrodeposition method is used to deposit MXene on the surface of the self-supporting conductive porous substrate obtained in step S1 and vacuum dry it to construct a continuous MXene conductive layer, thereby obtaining a self-supporting conductive porous substrate containing the MXene conductive layer. S3. Nitrogen-doped MXene support layer: The self-supporting conductive porous substrate containing the MXene conductive layer obtained in step S2 is subjected to plasma treatment under a nitrogen-containing atmosphere to obtain a self-supporting conductive porous substrate containing an N-MXene support layer; S4. Electrodeposition of molybdenum species to form sub-nano clusters: Using the self-supporting conductive porous substrate containing the N-MXene support layer obtained in step S3 as the working electrode, and Mo foil as the counter electrode or sacrificial anode, in the electrolyte, the potential, current density or deposition charge is controlled by cyclic voltammetry and an external electric field to obtain a self-supporting conductive porous substrate containing the Mo / N-MXene layer. S5. Electrodeposition of platinum species to form single atoms: Using the self-supporting conductive porous substrate containing the Mo / N-MXene layer obtained in step S4 as the working electrode, and Pt foil as the counter electrode or sacrificial anode, a highly efficient cathode catalytic electrode for proton exchange membrane electrolysis of water is obtained in the electrolyte by low overpotential controlled electrodeposition.

[0016] Preferably, the self-supporting conductive porous substrate of the present invention is selected from carbon paper, carbon cloth, titanium mesh, and nickel foam. The cleaning and surface activation pretreatment specifically involves: ultrasonic cleaning in ethanol for 10–20 min, ultrasonic cleaning in 0.5–2 M HCl for 10–20 min, ultrasonic cleaning in deionized water for 10–20 min, followed by radio frequency plasma activation for 5–20 min in a N2 / H2 mixed atmosphere with a volume ratio of 90:10 and a power of 150–300 W. The cleaning and surface activation treatment of the self-supporting conductive porous substrate in this invention can improve its wettability, interfacial activity, and electron transport capability, providing a foundation for the uniform deposition and stable bonding of subsequent materials.

[0017] Preferably, step S2 of the present invention specifically involves: using the self-supporting conductive porous substrate obtained in step S1 as the working electrode, and in a 0.2–1.0 mg / mL MXene dispersion, applying a constant voltage of 1–3 V or a constant current density of 0.5–10 mA / cm². 2 Electrodeposition was performed for 5–25 min, followed by electrode drying for 0.5–2 h, and then vacuum drying at 50–70 °C for 1–3 h to form a continuous MXene conductive layer, resulting in a self-supporting conductive porous substrate containing the MXene conductive layer. This process allows for the construction of a continuous and dense MXene conductive layer on the substrate surface, achieving large-area uniform coverage.

[0018] Preferably, step S3 of the present invention specifically involves: performing plasma-assisted heat treatment on the self-supporting conductive porous substrate containing the MXene conductive layer obtained in step S2 under a N2 atmosphere. The specific conditions are: power 200–450 W, temperature 220–380 °C, and time 10–30 min, to form a self-supporting conductive porous substrate containing an N-MXene support layer. Plasma treatment of the self-supporting conductive porous substrate containing the MXene conductive layer under a nitrogen-containing atmosphere introduces nitrogen elements into the MXene surface and edge sites, forming a nitrogen-doped MXene support layer with abundant atomic-level coordination sites and a confined structure.

[0019] Preferably, step S4 of the present invention specifically involves: using a self-supporting conductive porous substrate containing an N-MXene support layer as the working electrode and a Mo foil as the counter electrode, in a 0.3–0.7 M H₂SO₄ electrolyte, adjusting the cyclic voltammetry conditions to: a potential window of -0.75–0.25 V vs. RHE, a scan rate of 50–200 mV / s, and 800–2500 cycles, to form a self-supporting conductive porous substrate containing a Mo / N-MXene layer. In this step, using the self-supporting conductive porous substrate containing an N-MXene support layer as the working electrode and the Mo foil as the counter electrode, in an electrolyte without the addition of a soluble molybdenum salt precursor, controlled electrochemical deposition causes the Mo foil to undergo anodic dissolution, and molybdenum species are deposited in situ on the support surface. By adjusting the deposition parameters, the molybdenum species are stably anchored on the support surface in the form of sub-nanoclusters.

[0020] Preferably, step S5 of the present invention specifically involves: using a self-supporting conductive porous substrate containing a Mo / N-MXene layer as the working electrode and a Pt foil as the counter electrode, low overpotential constant potential deposition is performed in a 0.3–0.7 M H₂SO₄ electrolyte. The deposition conditions are: deposition potential -0.08–0.10 V vs. RHE, and current density 0.03–1.5 mA / cm². 2 The process takes 5–30 min to form a PtMo / N-MXene structure, resulting in a highly efficient cathode catalytic electrode for proton exchange membrane water electrolysis. In this step, a self-supporting conductive porous substrate of the Mo / N-MXene layer is used as the working electrode, and a Pt foil is used as the counter electrode. Without the addition of additional platinum salt precursors, the platinum species generated by the slow dissolution of the Pt foil are preferentially captured by nitrogen coordination sites and Mo subnanoclusters through low overpotential controlled electrodeposition, thus existing stably as isolated single atoms.

[0021] Preferably, the method of the present invention further includes step S6, which specifically involves: heat-treating the high-efficiency cathode catalytic electrode for proton exchange membrane electrolysis of water obtained in step S5 at 180–320 °C for 20–60 min in an inert atmosphere of Ar or N2 or a reducing atmosphere containing 5–10% H2.

[0022] This invention also provides a high-efficiency cathode catalytic electrode for proton exchange membrane water electrolysis prepared by the method described above. Preferably, this invention also provides the application of the high-efficiency cathode catalytic electrode for proton exchange membrane water electrolysis in membrane electrode assemblies or proton exchange membrane water electrolyzers. Preferably, the high-efficiency cathode catalytic electrode for proton exchange membrane water electrolysis described in this invention is used as a cathode catalytic electrode.

[0023] In this invention, the Mo sub-nanocluster deposition step and the Pt single-atom deposition step are performed sequentially, forming a stepped electrodeposition process. This allows for independent control of the nucleation and growth behavior of different metal species, ultimately resulting in a PEM electrolytic water splitting cathode catalytic electrode with synergistic control of Pt single atoms and Mo sub-nanoclusters. This invention abandons the traditional "salt precursor + chemical reduction" paradigm and innovatively proposes a stepped electrodeposition strategy using metal foil as an in-situ consumption source. The core of this method lies in directly using Mo and Pt foils as metal sources. In a solution containing only the supporting electrolyte, controlled dissolution of the anode metal foil and directional deposition on the cathode (i.e., functionalized support) surface are driven sequentially through stepwise and precisely controlled electrochemical parameters. This design achieves atomic-level short-range transfer of "dissolution-deposition," thereby sequentially constructing Mo sub-nanoclusters and Pt single atoms in situ on a nitrogen-doped MXene support. This method fundamentally solves four major shortcomings of existing technologies: (1) near 100% metal atom utilization rate, eliminating precursor waste; (2) extremely simple and green process, requiring no external reducing agent, organic ligand, or high-temperature treatment; (3) potential for large-area, continuous preparation, and high compatibility with existing electrochemical engineering equipment; (4) with the independent adjustability of electrochemical parameters (potential, current, and time, etc.), the nucleation and growth kinetics of Mo and Pt can be optimized separately, ultimately achieving precise and reproducible construction of the multi-scale synergistic active center of "Pt single atom / Mo sub-nano cluster". This not only provides a disruptive preparation path for developing high-performance, low-cost PEM water electrolysis cathodes, but also has significant implications for promoting the industrialization of atom manufacturing technology for energy electrocatalytic materials.

[0024] Due to the adoption of the above technical solution, the beneficial effects of the present invention are as follows: 1. Revolutionary Atom Economy and Green Process: This invention utilizes metal foil as a self-consumable source and leverages an in-situ conversion mechanism of "anodic dissolution-cathode deposition" to achieve near 100% direct transfer of metal atoms from the source to the active site, completely avoiding the enormous waste of soluble salt precursors in traditional wet chemical processes. Furthermore, the entire process requires no strong chemical reducing agents, organic ligands, or high-temperature calcination, using only an aqueous supporting electrolyte, making the process extremely simple and environmentally friendly.

[0025] 2. Atomic-level precise control of active center structure: The innovative step-by-step electrodeposition strategy of this invention allows for independent and precise control of the electrochemical parameters (such as potential, current, and waveform) of the two deposition steps, thereby optimizing the nucleation and growth kinetics of Mo and Pt respectively. This enables the controllable synthesis of multi-scale, heterogeneous active centers—"Mo sub-nanoclusters" and "Pt single atoms"—on the same support, solving the problem of disordered alloying caused by metal co-deposition in traditional methods.

[0026] 3. Superior Electrocatalytic Performance: The "Pt single atom / Mo sub-nano cluster / N-MXene" synergistic system constructed in this invention combines the atomic utilization limit of Pt single atoms, the unique electronic control capability of Mo clusters, and the strong anchoring effect and high conductivity of nitrogen-doped MXene supports. This electrode exhibits a significantly reduced hydrogen evolution overpotential, extremely high specific activity, and excellent long-term operational stability under acidic conditions, achieving high performance with low noble metal loading.

[0027] 4. Outstanding potential for engineering and large-scale fabrication: The core process of this invention is a fully electrochemical deposition process, which features universal equipment, mild conditions, and easily scaled-up parameters. This method is naturally suitable for large-area, continuous electrode production (such as roll-to-roll technology), and the prepared electrode itself is an integrated gas diffusion electrode that can be directly used for thermo-press packaging of membrane electrode assemblies. It perfectly integrates with existing PEM electrolytic cell production processes and has a clear path from laboratory to industrialization.

[0028] 5. Broad technical applicability: The "metal foil source stepped electrodeposition" methodology established in this invention is not limited to the Pt-Mo system, but can be extended to combinations of other noble metals (such as Ir, Ru) and transition metals (such as Ni, Co, Fe), providing a universal technical platform for the customized construction of multi-element atomic-level precision catalytic materials on various conductive supports. Attached Figure Description

[0029] Figure 1 A schematic diagram of the stepped electrodeposition reaction of this invention.

[0030] Figure 2 The image shows the HAADF-STEM image of the cathode material obtained in Example 1.

[0031] Figure 3 The image shows the HAADF-STEM image of the Mo sub-nanocluster / N-MXene cathode material obtained in Comparative Example 1.

[0032] Figure 4 The image shows the HAADF-STEM image of the Pt single-atom / N-MXene cathode material obtained in Comparative Example 2.

[0033] Figure 5 The graphs show the electrochemical HER performance of Example 1 and Comparative Examples 1-3. Detailed Implementation

[0034] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] The raw materials and instruments used in this invention are all commercially available products or can be obtained using conventional techniques in the field. In the following embodiments, unless otherwise specified, the reference electrode is a saturated Hg / Hg2SO4 electrode, and all potentials are converted to the reversible hydrogen electrode (RHE) scale.

[0036] The specific method for preparing MXene dispersion is as follows: (1) Accurately weigh 1 g of LiF powder and slowly add it to 20 mL of 9 M hydrochloric acid solution. Stir continuously for 30 min at room temperature until LiF is completely dissolved to form a homogeneous and clear etching solution. (2) Take 1 g of Ti3AlC2 MAX phase powder (purity 99 wt.%, particle size 400 mesh) and slowly add it to the etching solution placed in the polytetrafluoroethylene reactor. After sealing the reactor, transfer it to a constant temperature magnetic stirrer. Set the temperature to 35 ℃ and the stirring speed to 500 rpm. Maintain continuous and stable stirring and react at a constant temperature for 24 h. After the reaction is completed, wait for the reaction system to cool naturally to room temperature. Transfer the reaction solution to a 50 mL centrifuge tube and centrifuge at 8000 rpm for 10 min to separate the solid and liquid. Discard the upper waste liquid and retain the black precipitate at the bottom. Wash the precipitate with deionized water and anhydrous ethanol until neutral. Dry the precipitate in a vacuum drying oven at 60 ℃ for 4 h to obtain multilayer Ti3AlC2T x MXene solid powder; (3) The dried multilayer Ti3AlC2T x MXene solid powder was added to deionized water at a concentration of 1 mg / mL and subjected to ultrasonic treatment in an ice-water bath. The ultrasonic parameters were set as follows: power 180 W, ultrasonic frequency 40 kHz, ultrasonic treatment for 10 min each time, with a 2 min interval, and the total ultrasonic treatment time was controlled to be 30 min. After ultrasonic treatment, the dispersion was transferred to a centrifuge tube and centrifuged at 3000 rpm for 15 min. The uniformly dispersed colloidal solution in the upper layer was taken as the MXene dispersion. Example 1

[0037] A method for preparing a high-efficiency cathode catalytic electrode for proton exchange membrane water electrolysis includes the following steps: S1. Take carbon paper (2 cm × 2 cm) and ultrasonically clean it for 15 min each time with ethanol, 1 M HCl solution and deionized water. The ultrasonic power is 150 W and the frequency is 40 kHz each time. After cleaning, vacuum dry it at 80 ℃ for 2 h. After drying, treat it with 150 W radio frequency plasma for 20 min under N2 / H2 (90:10, v / v, purity ≥99.99%) atmosphere, with gas flow rate controlled at 50 sccm and chamber pressure at 0.1 MPa, to achieve surface activation and improve hydrophilicity, so as to ensure uniform adhesion of the subsequent MXene layer. S2. Electrodeposition of MXene conductive layer: Using the carbon paper obtained in step S1 as the working electrode, a saturated Hg / Hg2SO4 electrode as the reference electrode, and a platinum sheet as the counter electrode, a three-electrode system is constructed; in 60 mL of 0.2 mg / mL MXene dispersion, electrodeposition is performed at a constant voltage of 3 V (relative to the reference electrode SCE) for 25 min. During the electrodeposition process, the electrolyte temperature is controlled at 25 ℃ and the stirring rate is 300 r / min. After deposition, the electrode is air-dried at room temperature for 2 h and then vacuum-dried at 50 ℃ and 0.08 MPa for 3 h to form a uniform, continuous, and highly conductive MXene conductive layer, thus obtaining carbon paper containing the MXene conductive layer; S3. Nitrogen-doped MXene support layer regulation: Under a N2 atmosphere, with a gas flow rate of 80 sccm and a heating rate of 5 ℃ / min, the carbon paper with the MXene conductive layer obtained in step S2 is subjected to plasma-assisted heat treatment. The specific conditions are: power 200 W, temperature 380 ℃, time 10 min. Nitrogen element is introduced to form carbon paper with an N-MXene support layer containing atomic-level coordination sites and confined structures, thereby optimizing the electronic structure and metal anchoring ability. S4. Electrodeposition of molybdenum species to form sub-nano clusters: A three-electrode system was constructed using carbon paper with an N-MXene support layer as the working electrode, Mo foil with a purity ≥99.95%, a thickness of 0.1 mm, and an area consistent with the working electrode as the counter electrode, and a saturated calomel electrode (SCE) as the reference electrode. In 55 mL of 0.3 M H2SO4 electrolyte, the cyclic voltammetry conditions were adjusted as follows: potential window -0.45 to 0.25 V vs. RHE, scan rate 200 mV / s, and 1500 cycles, to induce controlled dissolution of the Mo foil and in-situ deposition of molybdenum species on the working electrode surface. By adjusting the parameters, the molybdenum species were stably anchored on the N-MXene surface in the form of sub-nano clusters with a particle size distribution of 0.3 to 0.5 nm, forming carbon paper with a Mo / N-MXene layer. S5. Electrodeposition of Platinum Species to Single Atoms: A three-electrode system was constructed using carbon paper containing a Mo / N-MXene layer as the working electrode, a Pt foil with a purity ≥99.99%, a thickness of 0.1 mm, and an area consistent with the working electrode as the counter electrode, and a saturated calomel electrode (SCE) as the reference electrode. Electrodeposition was performed in 50 mL of 0.3 M H₂SO₄ electrolyte using a low overpotential constant potential deposition method. The deposition conditions were: deposition potential 0.10 V vs. RHE, current density 0.03 mA / cm². 2 With an electrode spacing of 1 cm and a time of 30 min, the Pt foil was slowly dissolved. The resulting platinum species were preferentially captured by the nitrogen coordination sites of N-MXene and the Mo sub-nano clusters, and existed stably in an atomically dispersed form, forming a PtMo / N-MXene structure, thus obtaining a highly efficient cathode catalytic electrode for proton exchange membrane water electrolysis. S6. The high-efficiency cathode catalytic electrode for proton exchange membrane water electrolysis obtained in step S5 was heat-treated at 180 °C for 60 min under a reducing atmosphere containing 10% H2, with a gas flow rate of 60 sccm and a heating rate of 5 °C / min. Then, it was cooled to room temperature at a rate of 3 °C / min to enhance the coordination between Pt single atoms, Mo sub-nano clusters, and N-MXene, thereby improving the stability of the electrode structure and obtaining the cathode material. The obtained cathode material was characterized by atomic resolution high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), confirming that the Pt single atoms were atomically dispersed and the Mo exhibited a sub-nano cluster morphology. Figure 1 As shown. HER testing was performed in 0.5 M H₂SO₄, and the electrode operated at 10 mA / cm⁻¹. 2 The overpotential at that time was 11.6 mV, 100 mA / cm. 2 The overpotential at that time was 48.9 mV, such as Figure 5 As shown. Example 2

[0038] A method for preparing a high-efficiency cathode catalytic electrode for proton exchange membrane water electrolysis includes the following steps: S1. Take carbon cloth (10 cm × 10 cm) and ultrasonically clean it for 10 min each time with ethanol, 0.5 M HCl solution and deionized water. The ultrasonic power is 150 W and the frequency is 40 kHz each time. After cleaning, vacuum dry it at 80 ℃ for 2 h. After drying, treat it with 200 W radio frequency plasma for 15 min in a N2 / H2 (90:10, v / v, purity ≥99.99%) mixed atmosphere, with the gas flow rate controlled at 50 sccm and the chamber pressure at 0.1 MPa, in order to achieve surface activation and improve hydrophilicity, and ensure the uniform adhesion of the subsequent MXene layer. S2. Electrodeposition of MXene conductive layer: Using the carbon cloth obtained in step S1 as the working electrode, a saturated Hg / Hg2SO4 electrode as the reference electrode, and a platinum sheet as the counter electrode, a three-electrode system is constructed; in 50 mL of 1.0 mg / mL MXene dispersion, electrodeposition is performed at a constant voltage (relative to the reference electrode SCE) of 1.2 V for 5 min. During the electrodeposition process, the electrolyte temperature is controlled at 25 ℃ and the stirring rate is 300 r / min. After deposition, the electrode is air-dried at room temperature for 0.5 h and then vacuum-dried at 70 ℃ and 0.08 MPa for 1 h to form a uniform, continuous, and highly conductive MXene conductive layer, thus obtaining carbon cloth containing the MXene conductive layer; S3. Nitrogen-doped MXene support layer regulation: Under an N2 atmosphere, with a gas flow rate of 80 sccm and a heating rate of 5 ℃ / min, the carbon cloth with the MXene conductive layer obtained in step S2 is subjected to plasma-assisted heat treatment. The specific conditions are: power 450 W, temperature 220 ℃, time 30 min. Nitrogen element is introduced to form a carbon cloth with an N-MXene support layer containing atomic-level coordination sites and confined structures, thereby optimizing the electronic structure and metal anchoring ability. S4. Electrodeposition of molybdenum species to form sub-nano clusters: A three-electrode system was constructed using carbon cloth with an N-MXene support layer as the working electrode, Mo foil with a purity ≥99.95%, a thickness of 0.1 mm, and an area consistent with the working electrode as the counter electrode, and a saturated calomel electrode (SCE) as the reference electrode. In 50 mL of 0.7 M H2SO4 electrolyte, the cyclic voltammetry conditions were adjusted as follows: potential window -0.75 V to -0.45 V vs. RHE (equivalent to -0.99 V to -0.69 V relative to SCE), scan rate 200 mV / s, and 800 cycles, to induce controlled dissolution of the Mo foil and in-situ deposition of molybdenum species on the working electrode surface. By adjusting the parameters, the molybdenum species were stably anchored on the N-MXene surface in the form of sub-nano clusters with a particle size distribution of 0.4–0.9 nm, forming a carbon cloth containing a Mo / N-MXene layer. S5. Electrodeposition of Platinum Species to Single Atoms: A three-electrode system was constructed using carbon cloth containing a Mo / N-MXene layer as the working electrode, a Pt foil with a purity ≥99.99%, a thickness of 0.1 mm, and an area consistent with the working electrode as the counter electrode, and a saturated calomel electrode (SCE) as the reference electrode. Electrodeposition was performed in 50 mL of 0.7 M H₂SO₄ electrolyte using a low overpotential constant potential deposition method. The deposition conditions were: deposition potential -0.08 V vs. RHE (equivalent to -0.32 V relative to SCE), and current density 1.5 mA / cm². 2With an electrode spacing of 1 cm and a time of 5 min, the Pt foil was allowed to slowly dissolve. The resulting platinum species were preferentially captured by the nitrogen coordination sites of N-MXene and the Mo sub-nano clusters, existing stably in an atomically dispersed form to form a PtMo / N-MXene structure, thus obtaining a highly efficient cathode catalytic electrode for proton exchange membrane water electrolysis. S6. The high-efficiency cathode catalytic electrode for proton exchange membrane electrolysis of water obtained in step S5 was heat-treated at 320 ℃ for 20 min under an Ar inert atmosphere with a gas flow rate of 60 sccm and a heating rate of 5 ℃ / min. Then, it was cooled to room temperature at a rate of 3 ℃ / min to enhance the coordination between Pt single atoms and Mo sub-nano clusters and N-MXene, improve the stability of the electrode structure, and obtain the cathode material. Example 3

[0039] A method for preparing a high-efficiency cathode catalytic electrode for proton exchange membrane water electrolysis includes the following steps: S1. Take nickel foam (8 cm × 8 cm) and ultrasonically clean it for 20 min each time with ethanol, 2 M HCl solution and deionized water. The ultrasonic power is 150 W and the frequency is 40 kHz each time. After cleaning, vacuum dry it at 80 ℃ for 2 h. After drying, treat it with 300 W radio frequency plasma for 5 min under N2 / H2 (90:10, v / v, purity ≥99.99%) atmosphere, with gas flow rate controlled at 50 sccm and chamber pressure at 0.1 MPa, to achieve surface activation and improve hydrophilicity, so as to ensure uniform adhesion of the subsequent MXene layer. S2. Electrodeposition of the MXene conductive layer: A three-electrode system is constructed using the nickel foam obtained in step S1 as the working electrode, a saturated Hg / Hg2SO4 electrode as the reference electrode, and a platinum sheet as the counter electrode; a constant current density of 0.5 mA / cm² is applied in 55 mL of MXene dispersion with a concentration of 0.6 mg / mL. 2 Electrodeposition was performed for 25 min, during which the electrolyte temperature was controlled at 25 ℃ and the stirring rate at 300 r / min. After deposition, the electrode was air-dried at room temperature for 1.5 h and then vacuum-dried at 60 ℃ and 0.08 MPa for 2 h to form a uniform, continuous, and highly conductive MXene conductive layer, thus obtaining nickel foam containing the MXene conductive layer. S3. Nitrogen-doped MXene support layer regulation: Under an N2 atmosphere, with a gas flow rate of 80 sccm and a heating rate of 5 ℃ / min, the nickel foam containing the MXene conductive layer obtained in step S2 is subjected to plasma-assisted heat treatment. The specific conditions are: power 350 W, temperature 300 ℃, time 20 min. Nitrogen is introduced to form nickel foam with an N-MXene support layer containing atomic-level coordination sites and confined structures, thereby optimizing the electronic structure and metal anchoring ability. S4. Electrodeposition of Molybdenum Species to Form Sub-Nano Clusters: A three-electrode system was constructed using nickel foam containing an N-MXene support layer as the working electrode, Mo foil with a purity ≥99.95%, a thickness of 0.1 mm, and an area consistent with the working electrode as the counter electrode, and a saturated calomel electrode (SCE) as the reference electrode. In 55 mL of 0.5 M H₂SO₄ electrolyte, the cyclic voltammetry conditions were adjusted as follows: potential window -0.15 V to 0.15 V vs. RHE (equivalent to -0.39 V to -0.09 V relative to SCE), scan rate 150 mV / s, 2500 cycles. During electrodeposition, the electrolyte temperature was controlled at 25 ℃, the stirring rate at 300 r / min, and the electrode spacing at 1 cm, allowing for controlled dissolution of the Mo foil and in-situ deposition of molybdenum species on the working electrode surface. The molybdenum species were distributed in a particle size range of 0.4–0.9 μm by adjusting the parameters. Sub-nano clusters of nm are stably anchored on the N-MXene surface to form nickel foam containing a Mo / N-MXene layer; S5. Electrodeposition of Platinum Species to Single Atoms: A three-electrode system was constructed using nickel foam containing a Mo / N-MXene layer as the working electrode, a Pt foil with a purity ≥99.99%, a thickness of 0.1 mm, and an area consistent with the working electrode as the counter electrode, and a saturated calomel electrode (SCE) as the reference electrode. Electrodeposition was performed in 55 mL of 0.5 M H₂SO₄ electrolyte using a low overpotential constant potential deposition method. The deposition conditions were: deposition potential 0.02 V vs. RHE (equivalent to -0.22 V relative to SCE), and current density 0.83 mA / cm². 2 With an electrode spacing of 1 cm and a time of 18 min, the Pt foil was slowly dissolved. The resulting platinum species were preferentially captured by the nitrogen coordination sites of N-MXene and the Mo sub-nano clusters, and existed stably in an atomically dispersed form, forming a PtMo / N-MXene structure, thus obtaining a highly efficient cathode catalytic electrode for proton exchange membrane water electrolysis.

[0040] Comparative Example 1 The difference from Example 1 is that step S5 is omitted, while the remaining steps and parameters are the same as in Example 1, and the final Mo sub-nano cluster / N-MXene cathode material (denoted as Mo NC / N-MXene) is obtained.

[0041] HAADF-STEM characterization confirmed that Mo species are uniformly distributed on the N-MXene surface in the form of sub-nano clusters, such as... Figure 3 As shown. HER testing was performed in 0.5 M H₂SO₄, and the electrode operated at 10 mA / cm⁻¹. 2 The overpotential at that time was 529.0 mV, 100 mA / cm. 2 The overpotential at that time was 713.6 mV, specifically as follows: Figure 5 As shown.

[0042] Comparative Example 2 The difference from Example 1 is that step S4 is omitted, while the remaining steps and parameters are the same as in Example 1, and the final Pt single atom / N-MXene cathode material (denoted as Pt SA / N-MXene) is obtained.

[0043] HAADF-STEM characterization confirmed that Pt species are uniformly dispersed in single-atom form on the N-MXene surface, such as... Figure 4 As shown. HER testing was performed in 0.5 M H₂SO₄, and the electrode operated at 10 mA / cm⁻¹. 2 The overpotential at that time was 99.2 mV, 100 mA / cm. 2 The overpotential at that time was 297.8 mV, specifically as follows: Figure 5 As shown.

[0044] Comparative Example 3 The difference from Example 1 is that steps S4 and S5 are omitted; the remaining steps and parameters are the same as in Example 1, ultimately yielding an N-MXene cathode material, which serves as a reference. HER testing was performed in 0.5 M H2SO4, and the electrode achieved a speed of 10 mA / cm². 2 The overpotential at that time was 632.6 mV, specifically as follows: Figure 5 As shown.

[0045] In summary, the high-efficiency cathode catalytic electrode prepared by the method of the present invention exhibits a significantly reduced hydrogen evolution overpotential, extremely high specific activity, and excellent long-term operational stability under acidic conditions, achieving high performance under low noble metal loading.

[0046] It is worth noting that the preparation method of the PEM water electrolysis cathode based on the synergistic regulation of nitrogen-doped MXene by step-deposition of Pt single atoms / Mo sub-nano clusters described in this invention is not limited to the specific process parameters shown in the above embodiments, nor is it limited to the Pt-Mo metal combination. Without departing from the core technical concept of this invention, those skilled in the art can optimize and adjust process conditions such as plasma activation parameters (power, temperature, time, atmosphere, etc.), MXene dispersion concentration and electrodeposition voltage / current, nitrogen plasma doping temperature and power, potential window / scan rate / number of cycles / pulse parameters of step-deposition, and post-processing conditions (temperature, atmosphere, time, etc.) according to different substrate materials, electrolyte composition, deposition methods (constant voltage, constant current, cyclic voltammetry, pulse electrodeposition, etc.) and application requirements. They can also try to introduce other two-dimensional carrier materials (such as graphene, MoS2, etc.) or extend to other metal combinations (such as single atom / sub-nano cluster systems of Ni, Co, Fe, Cu, Ir, etc.) to further improve the PEM water electrolysis activity, long-term stability, corrosion resistance and feasibility of large-scale preparation of the electrode. The above adjustments are all reasonable extensions of the present invention and should also be included within the scope of protection of this patent.

Claims

1. A method for preparing a high-efficiency cathode catalytic electrode for proton exchange membrane water electrolysis, characterized in that, Includes the following steps: S1. Taken from a supporting conductive porous substrate, and subjected to cleaning and surface activation pretreatment; S2. Electrodeposition of MXene conductive layer: In MXene dispersion, a constant voltage or constant current electrodeposition method is used to deposit MXene on the surface of the self-supporting conductive porous substrate obtained in step S1 and vacuum dry it to construct a continuous MXene conductive layer, thereby obtaining a self-supporting conductive porous substrate containing the MXene conductive layer. S3. Nitrogen-doped MXene support layer: The self-supporting conductive porous substrate containing the MXene conductive layer obtained in step S2 is subjected to plasma treatment under a nitrogen-containing atmosphere to obtain a self-supporting conductive porous substrate containing an N-MXene support layer; S4. Electrodeposition of molybdenum species to form sub-nano clusters: Using the self-supporting conductive porous substrate containing the N-MXene support layer obtained in step S3 as the working electrode, and Mo foil as the counter electrode or sacrificial anode, in the electrolyte, the potential, current density or deposition charge is controlled by cyclic voltammetry and an external electric field to obtain a self-supporting conductive porous substrate containing the Mo / N-MXene layer. S5. Electrodeposition of platinum species to form single atoms: Using the self-supporting conductive porous substrate containing the Mo / N-MXene layer obtained in step S4 as the working electrode, and Pt foil as the counter electrode or sacrificial anode, a highly efficient cathode catalytic electrode for proton exchange membrane electrolysis of water is obtained in the electrolyte by low overpotential controlled electrodeposition.

2. The method for preparing the high-efficiency cathode catalytic electrode for proton exchange membrane water electrolysis as described in claim 1, characterized in that: The self-supporting conductive porous substrate is selected from one of carbon paper, carbon cloth, titanium mesh, and nickel foam; the cleaning and surface activation pretreatment specifically includes: ultrasonic cleaning in ethanol for 10-20 min, ultrasonic cleaning in 0.5-2 M HCl for 10-20 min, ultrasonic cleaning in deionized water for 10-20 min, and then radio frequency plasma activation for 5-20 min in a N2 / H2 mixed atmosphere with a volume ratio of 90:10 and a power of 150-300W.

3. The method for preparing the high-efficiency cathode catalytic electrode for proton exchange membrane water electrolysis as described in claim 1, characterized in that: Step S2 specifically involves using the self-supporting conductive porous substrate obtained in step S1 as the working electrode, and in a 0.2–1.0 mg / mL MXene dispersion, applying a constant voltage of 1–3 V or a constant current density of 0.5–10 mA / cm². 2 Electrodeposition was performed for 5–25 min. After deposition, the electrode was air-dried for 0.5–2 h and then vacuum-dried at 50–70 °C for 1–3 h to form a continuous MXene conductive layer, thus obtaining a self-supporting conductive porous substrate containing the MXene conductive layer.

4. The method for preparing the high-efficiency cathode catalytic electrode for proton exchange membrane water electrolysis as described in claim 1, characterized in that: Step S3 specifically involves: under an N2 atmosphere, performing plasma-assisted heat treatment on the self-supporting conductive porous substrate containing an MXene conductive layer obtained in step S2, with the following conditions: power 200–450 W, temperature 220–380 °C, and time 10–30 min, to form a self-supporting conductive porous substrate containing an N-MXene carrier layer.

5. The method for preparing the high-efficiency cathode catalytic electrode for proton exchange membrane water electrolysis as described in claim 1, characterized in that: Step S4 specifically involves: using a self-supporting conductive porous substrate containing an N-MXene carrier layer as the working electrode and a Mo foil as the counter electrode, in a 0.3–0.7 M H₂SO₄ electrolyte, adjusting the cyclic voltammetry conditions as follows: potential window -0.75–0.25 V vs. RHE, scan rate 50–200 mV / s, and 800–2500 cycles to form a self-supporting conductive porous substrate containing a Mo / N-MXene layer.

6. The method for preparing the high-efficiency cathode catalytic electrode for proton exchange membrane water electrolysis as described in claim 1, characterized in that: Step S5 specifically involves: using a self-supporting conductive porous substrate containing a Mo / N-MXene layer as the working electrode and a Pt foil as the counter electrode, low overpotential constant potential deposition is performed in a 0.3–0.7 M H₂SO₄ electrolyte. The deposition conditions are: deposition potential -0.08–0.10 V vs. RHE, and current density 0.03–1.5 mA / cm². 2 The process takes 5–30 min to form a PtMo / N-MXene structure, resulting in a highly efficient cathode catalytic electrode for proton exchange membrane water electrolysis.

7. The method for preparing the high-efficiency cathode catalytic electrode for proton exchange membrane water electrolysis as described in claim 1, characterized in that: The process also includes step S6, which involves heat-treating the high-efficiency cathode catalytic electrode for proton exchange membrane electrolysis of water obtained in step S5 at 180–320 °C for 20–60 min in an inert atmosphere of Ar or N2 or a reducing atmosphere containing 5–10% H2.

8. The high-efficiency cathode catalytic electrode for proton exchange membrane electrolysis of water prepared by the method for preparing the high-efficiency cathode catalytic electrode for proton exchange membrane electrolysis of water as described in any one of claims 1-7.

9. The application of the high-efficiency cathode catalytic electrode for proton exchange membrane water electrolysis as described in claim 8 in a membrane electrode assembly or a proton exchange membrane water electrolyzer.

10. The application as described in claim 9, characterized in that: The high-efficiency cathode catalytic electrode used for proton exchange membrane electrolysis of water serves as the cathode catalytic electrode.

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