MXene and high-entropy metal phosphide composite electrode material and preparation method and application thereof

Abstract

The invention discloses an MXene and high-entropy metal phosphide composite electrode material and a preparation method and application thereof.The MXene and high-entropy metal phosphide composite electrode material is characterized in that a three-dimensional porous substrate serves as a framework, MXene is loaded on the three-dimensional porous substrate, and five-element high-entropy metal phosphide CoNiZnFeMnP is loaded on the surface of the MXene; wherein MXene is Ti < 3 > C < 2 > T < x >, Al atoms between layers are removed through etching of a TiAlC < MAX > phase, and a surface functional group T < x > is introduced, so that MXene is obtained. The MX-coated CoNiZnFeMnP prepared by the invention has a relatively large specific surface area, a large number of active sites and abundant heterogeneous interfaces, and the composite electrode material has a unique multi-stage flower-shaped hierarchical structure, a remarkable high-entropy effect and a strong interface coupling effect, shows extremely high catalytic activity, excellent charge transfer capability and industrial-grade long-term stability, and has a good application prospect. The electrocatalyst can be used as an efficient bifunctional electrocatalyst, and is widely applied to hydrogen evolution, oxygen evolution and full hydrolysis reaction in the water electrolysis process. Meanwhile, the preparation method disclosed by the invention has the advantages of simplicity, convenience, low cost and easiness in large-scale production, effectively overcomes the bottleneck in the background technology, and provides a new idea for developing a high-performance difunctional electrocatalyst.

Description

Technical Field

[0001] This invention relates to the field of electrocatalytic materials technology, specifically to an MXene@high-entropy metal phosphide composite electrode material, its preparation method, and its applications. In particular, it relates to a composite material based on high-entropy metal phosphide and MXene, its preparation method, and the application of this material as a highly efficient bifunctional electrocatalyst in hydrogen evolution reaction, oxygen evolution reaction, and total hydrolysis reaction. Background Technology

[0002] With the increasing global energy demand and escalating environmental problems, the development of clean and sustainable energy has become a focus of research. Hydrogen energy, as an ideal energy source with high calorific value and zero carbon emissions, is mainly produced through water electrolysis. However, the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) kinetics in the water electrolysis process are slow, resulting in excessive energy consumption throughout the process. Currently, the most efficient HER and OER catalysts rely on precious metal materials such as platinum (Pt) and ruthenium (Ru) / iridium (Ir), respectively, but their high cost and scarcity severely restrict their large-scale commercial application. Therefore, developing high-performance, highly stable, and low-cost non-precious metal bifunctional electrocatalysts is key to promoting the development of water electrolysis technology.

[0003] Bimetallic LDHs, represented by CoFe LDH and NiFe LDH, have been extensively studied and analyzed in depth. However, their electrocatalytic OER performance is still affected by poor intrinsic activity, limited active sites, metal ion leaching, and phase separation. In recent years, transition metal phosphides (TMPs) have shown great potential in the field of electrocatalysis due to their metalloid conductivity and moderate hydrogen adsorption free energy. In particular, high-entropy metal phosphides (HEPs), as an emerging material, offer a broad platform for regulating electronic structure and optimizing the adsorption energy of reaction intermediates due to their unique "cocktail effect" and severe lattice distortion, and are expected to achieve both high activity and high stability.

[0004] However, existing high-entropy metal phosphide catalysts still face several serious challenges. Most research focuses on ternary to quaternary high-entropy systems, which, while showing some improvement in catalytic activity, often suffer from unsatisfactory stability under high current and long-term operation. Particularly in strongly alkaline OER environments, the dissolution and phase separation of metal elements are particularly prominent, leading to rapid performance degradation. Furthermore, designs utilizing component design to simultaneously optimize the bifunctional activity of HER and OER are rare. For example, manganese (Mn), due to its unique electronic structure, is considered to have the potential to optimize adsorption energy, but it is easily oxidized and dissolved under alkaline OER conditions, and is traditionally considered an unstable factor, thus limiting its application in highly efficient and stable catalysts. High-entropy metal phosphides (HEPs) are prone to aggregation and detachment during catalysis, especially when poorly bonded to conductive substrates, directly leading to a reduction in active surface area and decreased long-term stability. Simple physical mixing or loading methods result in high interfacial contact resistance between the catalyst and the substrate, hindering rapid electron transport and limiting reaction kinetics.

[0005] Therefore, there is an urgent need to develop a new technical solution that can prepare a catalyst with excellent HER and OER bifunctional activity as well as industrial-grade long-term operational stability through ingenious component design and structural engineering. Summary of the Invention

[0006] To overcome the technical problems of "high overpotential, poor catalytic stability, and insufficient active sites in the electrode material of the oxygen evolution reaction in water electrolysis" in the prior art, the present invention aims to provide an MXene@high-entropy metal phosphide composite electrode material, its preparation method, and its application. By constructing a synergistic interface structure between high-entropy metal phosphide and MXene, the electrocatalytic activity and long-term stability of the hydrogen evolution / oxygen evolution reaction are significantly improved, making it suitable for high-efficiency water electrolysis catalysts.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] This invention provides an MXene@high-entropy metal phosphide composite electrode material, which uses a three-dimensional porous substrate as a framework, with MXene loaded on the three-dimensional porous substrate, and pentagonal high-entropy metal phosphides CoNiZnFeMnP loaded on the surface of MXene.

[0009] Wherein, MXene is Ti3C2T x The Ti3AlC2 MAX phase was formed by etching to remove Al atoms between layers and introducing surface functional groups T. x It was obtained.

[0010] In a preferred embodiment, the microstructure of the composite electrode material is a flower-shaped structure combining nanometer and micrometer dimensions, with the flower-shaped structures uniformly anchored on a three-dimensional porous substrate; the flower-shaped structures have a size of 1~5 μm and are assembled from nanosheets with a thickness of 10~50 nm.

[0011] In a preferred embodiment, the three-dimensional porous substrate is one of nickel foam, copper foam, nickel mesh, carbon cloth, or carbonized wood.

[0012] In a preferred embodiment, the pentagonal high-entropy metal phosphide CoNiZnFeMnP exhibits a multi-level flower-like hierarchical structure, uniformly covering the surface and interlayer of the MXene / three-dimensional porous substrate, with equal atomic percentages of the five metal elements: cobalt, nickel, zinc, iron, and manganese.

[0013] In a preferred embodiment, the pentagonal high-entropy metal phosphide exhibits a polycrystalline structure, and the metallic conductivity of MXene synergistically enhances charge / mass transfer dynamics with the three-dimensional conductive framework.

[0014] This invention also provides a method for preparing MXene@high-entropy metal phosphide composite electrode material, comprising the following steps:

[0015] S1. Load MXene material onto a three-dimensional porous substrate to obtain an MXene-modified three-dimensional porous substrate; S2. Prepare a precursor solution containing cobalt salt, nickel salt, zinc salt, iron salt, manganese salt, and surfactant, and perform a hydrothermal reaction between the precursor solution and the MXene-modified three-dimensional porous substrate to grow MXene@CoNiZnFeMn-LDH, i.e., the precursor, in situ on the substrate; S3. Phosphate the precursor under a protective atmosphere to obtain MXene@CoNiZnFeMnP / substrate, i.e., the MXene@high-entropy metal phosphide composite electrode material.

[0016] Preferably, step S1 specifically includes:

[0017] Preparation of Ti3C2T x The material was dispersed in deionized water and ultrasonically treated to obtain a uniform colloidal suspension. A completely dried three-dimensional conductive substrate was then immersed in the colloidal suspension to form Ti3C2T. x The material is fully adsorbed and locked within a three-dimensional porous substrate, and is obtained after drying.

[0018] Furthermore, the aforementioned Ti3C2T x The material and preparation process are as follows: Ti3AlC2MAX phase powder is immersed in a mixed solution of HF or LiF+HCl and etched at 30-50°C for 24-48 hours with stirring to selectively remove the aluminum layer and simultaneously introduce functional groups such as -OH, -O, and -F (collectively referred to as T) onto the surface. xThus, multilayer Ti3C2T was obtained. x MXene was then repeatedly centrifuged and washed until the supernatant turned dark green and the pH was approximately 6 to remove residual acid and impurity ions. Finally, the resulting precipitate was freeze-dried to obtain loose Ti3C2T. x powder.

[0019] Furthermore, the concentration of the colloidal suspension is 0.5~5 mg / mL, and the sonication time is 0.5~4 h.

[0020] Furthermore, the three-dimensional conductive substrate undergoes pretreatment before use: foamed nickel, foamed copper, and nickel mesh are ultrasonically cleaned sequentially with hydrochloric acid, acetone, and ethanol to remove surface oxides and oil stains; carbon cloth is refluxed in nitric acid to increase its hydrophilicity; carbonized wood is thoroughly cleaned with deionized water and ethanol to unblock its natural pipe structure; the three-dimensional porous substrate is soaked in colloidal suspension for 2-12 hours, dried at 60-80 ℃ for 6-12 hours.

[0021] Preferably, in step S2, the cobalt salt, nickel salt, zinc salt, iron salt, and manganese salt are one of chloride salts, nitrate salts, or sulfate salts, the molar concentration ratio of each metal salt is 1:1:1:1:1, and the total metal ion concentration is 0.01~0.2 mol / L; the surfactant is one of polyvinylpyrrolidone, hexadecyltrimethylammonium bromide, and sodium citrate, and the amount added is 5%~20% of the total mass of the metal salts.

[0022] Preferably, in step S2, the hydrothermal reaction temperature is 120~180 ℃ and the reaction time is 8~16 h; after the reaction, the mixture is naturally cooled, washed with deionized water and ethanol, and vacuum dried at 60~80 ℃ to obtain the precursor.

[0023] Preferably, in step S3, sodium hypophosphite is added as the phosphorus source for phosphating, and the mass ratio of sodium hypophosphite to the precursor is 1:1 to 1:5; the phosphating temperature is 300 to 450 °C, the phosphating time is 1 to 6 h, and the protective atmosphere is argon or nitrogen.

[0024] Preferably, in step S3, the MXene@high-entropy metal phosphide composite electrode material obtained after phosphating is directly used as a self-supporting electrode for electrocatalytic hydrogen evolution and oxygen evolution reactions.

[0025] Furthermore, the MXene@high-entropy metal phosphide composite electrode material exhibits excellent activity and stability when used in electrocatalytic hydrogen evolution reaction, oxygen evolution reaction and total hydrolysis reaction.

[0026] Specifically, for HER, only a 79 mV overpotential is required to achieve 10 mA cm⁻¹. -2The current density; for OER, only a 210 mV overpotential is required to reach 50 mA cm⁻¹. -2 The current density is such that the complete hydrolysis reaction can be driven to 10 mA cm⁻¹ at a low voltage of 1.43 V. -2 The material also exhibits excellent long-term stability at a current density of 10 mA cm⁻¹. -2 HER continuous testing was performed for 120 hours at a current density of 50 mA cm⁻¹. -2 OER was continuously tested for 120 hours at a current density, and at 10 mA cm⁻¹. -2 After 70 hours of continuous full hydrolysis testing at the current density, the performance degradation was negligible. Kinetic tests showed that the composite electrode had the smallest Tafel slope and the smallest electrochemical impedance, confirming its rapid reaction kinetics.

[0027] The MXene@high-entropy metal phosphide composite electrode material prepared in this invention possesses a large specific surface area, numerous active sites, and abundant heterogeneous interfaces. This composite electrode material exhibits a unique multi-level flower-like hierarchical structure, significant high-entropy effect, and strong interfacial coupling, demonstrating extremely high catalytic activity, excellent charge transport capability, and industrial-grade long-term stability. It can serve as a highly efficient bifunctional electrocatalyst, widely applicable to hydrogen evolution, oxygen evolution, and total water splitting reactions in water electrolysis. Furthermore, the preparation method of this invention combines the advantages of simplicity, low cost, and ease of scalability, effectively overcoming the bottlenecks in the prior art and providing a new approach for the development of high-performance bifunctional electrocatalysts.

[0028] Since the advent of MXene in 2011, transition metal carbides / nitrides (MXenes) have redefined electrocatalyst design, hydrophilic surface terminations (-O / -OH), and mechanoelasticity through their unparalleled conductivity. MXenes promote uniform dispersion of the active phase while enhancing charge / mass transfer efficiency. The strategic integration of MXenes with high-entropy metal phosphides leverages the novel two-dimensional (2D) structure of MXenes to promote active site proliferation and surface functional groups, thereby stabilizing the metal-phosphide interface. The synergistic effect between the high-entropy effect and substrate-activated electron transport creates a versatile architecture for high-performance HER / OER systems.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] This invention introduces manganese (Mn) into the Co-Ni-Zn-Fe phosphide system for the first time, constructing a unique MXene@pentabyte high-entropy metal phosphide composite structure on various universal three-dimensional conductive substrates. This design produces a significant synergistic enhancement effect: the introduction of Mn and the composite with MXene jointly regulate the electronic structure of the material, optimize the adsorption energy of reaction intermediates, and form a unique micron-nano combined flower-like hierarchical structure morphology. MXene can form a stable three-dimensional conductive network with different substrates, effectively preventing the shedding and aggregation of active materials, demonstrating the excellent universality of this preparation strategy; the high-entropy effect enhances the intrinsic chemical stability of the material.

[0031] This invention also discloses a method for preparing the aforementioned MXene@high-entropy metal phosphide composite electrode material. By selecting hexadecyltrimethylammonium bromide as a morphology directing agent and precisely controlling the molar ratio of five metal salts (cobalt, nickel, zinc, iron, and manganese), a precursor was successfully grown in situ on an MXene-modified three-dimensional porous framework. The target product was finally obtained through phosphating. This method has a clear process route and mild conditions, enabling the controllable preparation of MXene@penta-membered high-entropy metal phosphide catalysts.

[0032] The present invention also discloses the phase composition of the MXene@high-entropy metal phosphide composite electrode material prepared by the above method, which has high purity and good crystallinity.

[0033] This invention also discloses the MXene@high-entropy metal phosphide composite electrode material prepared by the above method, which can be directly used as a self-supporting electrode without the use of precious metal binders. It has high catalytic activity and good stability, and has broad commercial application prospects in the field of water electrolysis for hydrogen production. Attached Figure Description

[0034] Figure 1 The Ti3C2T prepared in Example 1 x X-ray diffraction pattern of the material;

[0035] Figure 2 The X-ray diffraction pattern of MX@CoNiZnFeMnP / NF prepared in Example 4;

[0036] Figure 3 The image shows the SEM image, angular annular dark field (HAADF) image, and TEM-coupled energy dispersive X-ray spectroscopy (EDS) elemental spectrum of the MX@CoNiZnFeMnP / NF catalyst prepared in Example 4.

[0037] Figure 4Linear sweep voltammetry curves, Tafel curves, Nyquist plots, stability curves of electrocatalyzed HER, and LSV curves before and after 120 hours of HER stability testing are shown for the MX@CoNiZnFeMnP / NF catalyst prepared in Example 4.

[0038] Figure 5 The linear sweep voltammetry curve, Tafel curve, Nyquist plot, stability curve of electrocatalytic OER, and LSV curves before and after 120-hour OER stability test of the MX@CoNiZnFeMnP / NF catalyst prepared in Example 4 are shown. Detailed Implementation

[0039] To facilitate understanding of the technical solution and scope of protection of this invention, the terms and expressions used in the specification and claims are hereby uniformly explained and interpreted.

[0040] General Principles: The summary of the invention and the detailed description of the embodiments of this invention should be understood in conjunction with each other. The detailed description of the embodiments is used to illustrate the technical solutions and should not be construed as limiting the overall scope of the invention.

[0041] Scope definition: The features of this invention expressed in the form of numerical ranges should be interpreted as including not only the endpoint values ​​of the range, but also explicitly disclosing every integer and fractional value within the range, as well as all subranges derived therefrom.

[0042] Open-ended claims: Unless the context explicitly excludes, the terms "comprising," "including," and similar expressions should be interpreted as open-ended, meaning they include the specified element but do not exclude other elements. This interpretation is consistent with the usual meaning in patent practice.

[0043] Combinations of technical features: Each of the technical features disclosed in this specification can be combined in a logically consistent manner. All such possible combinations should be considered as the technical content disclosed in this invention.

[0044] Experimental conventions: Unless otherwise specified, the equipment, raw materials and methods used in the following embodiments are conventionally selected in the art; the proportions and percentages are all weight ratios and weight percentages; and the "parts" are all parts by weight.

[0045] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0046] This invention provides a method for preparing MXene@high-entropy metal phosphide composite electrode material, comprising the following steps:

[0047] Step 1: Immerse Ti3AlC2 powder in a mixed solution of HCl and LiF, stir and react at a constant temperature to selectively remove the aluminum layer and simultaneously introduce functional groups such as -OH, -O, and -F (collectively referred to as T) onto the surface. x The resulting suspension was repeatedly centrifuged and washed until the pH reached neutral. The resulting sample was then freeze-dried to obtain Ti3C2T. x Material.

[0048] In step 1, the HCl+LiF mixed solution is LiF dissolved in 4.0-8.0 M HCl, and the ratio of Ti3AlC2 powder to HCl+LiF mixed solution is 1g:15-30 mL. The stirring and constant temperature reaction is carried out at 40-50 ℃ with continuous magnetic stirring for 24-48 h. The washing is done with deionized water until the pH of the supernatant is 6-7. The sample is freeze-dried at -60 ℃ for 24-48 h.

[0049] Step 2, place Ti3C2T x A stable colloidal suspension was obtained by dispersing the substrate in deionized water and then ultrasonically treating it. Three-dimensional porous substrates such as nickel foam (NF), copper foam (CF), nickel mesh (NN), carbon cloth (CC), and carbonized wood (CW) were pretreated and then immersed in the colloidal suspension. After drying, MXene-modified substrates were obtained.

[0050] In step 2, the colloidal suspension is prepared by adding 0.04-0.08 g of Ti3C2T... x The material is dispersed in 20-40 mL of deionized water and then sonicated for 1-3 hours to obtain a homogeneous and stable colloidal suspension.

[0051] The three-dimensional porous substrate requires rigorous pretreatment before use to ensure its surface is clean and has excellent hydrophilicity / wettability:

[0052] Nickel foam (NF) and copper foam (CF): Soak in 3 M hydrochloric acid, acetone and anhydrous ethanol for 15-30 minutes each to thoroughly remove metal oxides and organic contaminants from the surface. Finally rinse with deionized water and vacuum dry.

[0053] Nickel mesh (NN): Processing method is the same as for nickel foam;

[0054] Carbon cloth (CC): Reflux treatment in concentrated nitric acid at 80-100℃ for 2-4 hours to introduce oxygen-containing functional groups and enhance its hydrophilicity, followed by washing with deionized water until neutral and drying.

[0055] Carbonized wood (CW): It is ultrasonically cleaned several times in anhydrous ethanol and deionized water to open up its natural micron-channel structure, which facilitates the penetration and adhesion of MXene suspension, and then vacuum dried.

[0056] The pretreated and completely dried three-dimensional conductive substrate is immersed in the above colloidal suspension for 1-4 hours to ensure that the MXene nanosheets can be fully and firmly adsorbed on the porous matrix surface and inside of the substrate.

[0057] After soaking, the MXene-loaded substrate is removed and dried at 60-80℃ for 6-12 hours to obtain a structurally stable MXene-modified substrate.

[0058] Step 3: Add cobalt salt, nickel salt, zinc salt, iron salt, manganese salt and surfactant to deionized water to obtain a mixed solution and stir evenly. Then, perform a hydrothermal reaction between the mixed solution and the MXene-modified substrate.

[0059] In step 3, cetyltrimethylammonium bromide, 0.5 mmol Co(NO3)2∙6H2O, 0.5 mmol Ni(NO3)2∙6H2O, 0.5 mmol Zn(NO3)2∙6H2O, 0.5 mmol Fe(NO3)2∙9H2O, and 0.5 mmol MnCl2∙6H2O were added to 40 mL of water and stirred until fully dissolved to obtain a mixed solution. The mixed solution was transferred to a high-pressure reactor with a polytetrafluoroethylene liner for hydrothermal reaction. MXene / substrate was used as a conductive substrate, and CoNiZnFeMn layered double hydroxide nanosheets were grown in situ on its surface.

[0060] In step 3, the hydrothermal reaction temperature and duration were 140 °C and 12 h, respectively. After the hydrothermal reaction was stopped, the mixture was cooled to room temperature, rinsed alternately with deionized water and anhydrous ethanol, and then vacuum dried to obtain the MX@CoNiZnFeMn-LDH precursor.

[0061] In step 3, a one-step hydrothermal method was used to synthesize the MX@CoNiZnFeMn-LDH precursor. This method helps to form a microstructure with a high specific surface area, thereby providing abundant active sites for the catalytic reaction and effectively improving the overall performance of the electrocatalytic material. During this reaction, MXene / substrate was used as a highly conductive substrate, and a CoNiZnFeMn layered double hydroxide (LDH) nanosheet catalytic layer was constructed on its surface through in-situ growth, forming a composite structure with abundant heterogeneous interfaces. This structure not only enhances the tight bonding between interfaces but also helps to reduce interfacial contact resistance, thereby improving the conductivity and structural stability of the material. Furthermore, Ti3C2T... x A significant interfacial synergistic coupling effect is generated between it and CoNiZnFeMn-LDH, which helps to promote electron transport and enhance the overall catalytic activity in the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) processes.

[0062] The MX@CoNiZnFeMn-LDH precursor material obtained in step 3 is characterized by CoNiZnFeMn layered double hydroxide (LDH) nanosheets on Ti3C2T x The nanosheets are grown uniformly on the substrate surface, with an average length of approximately 500 nm.

[0063] Step 4: Phosphorus (P) doping of the above material was performed using a non-metallic atom doping strategy. Specifically, NaH₂PO₂·H₂O was placed upstream of a ceramic boat, and the MX@CoNiZnFeMn-LDH / substrate prepared in step S3 was placed downstream of the boat. Phosphating was then carried out under a flowing inert atmosphere. This process successfully generated P-doped CoNiZnFeMn nanoflowers on the MXene-modified three-dimensional substrate, denoted as MX@CoNiZnFeMnP bifunctional electrocatalytic material.

[0064] In step 4, the p-doping strategy employed has multiple positive effects: firstly, it effectively improves the intrinsic conductivity of the composite material and promotes the exposure of more catalytic active sites; secondly, it further enhances the properties of Ti3C2T. x The heterointerfacial interaction between the catalyst and CoNiZnFeMn-LDH significantly enhances both the catalytic activity and structural stability of the electrocatalyst.

[0065] Unlike existing technologies, this invention constructs a heterostructure on an MXene-modified substrate by growing CoNiZnFeMn-LDH via a hydrothermal method. Non-metallic doping enhances the electronic interactions between the heterostructures. By constructing a heterostructure and doping, the electronic structure is adjusted and the catalytic activity is enhanced.

[0066] In step 4, the process conditions are as follows: under a nitrogen flow rate of 30 sccm, the temperature is increased to 350 ℃ at a rate of 2 ℃ / min, and then held at that temperature for 2 h.

[0067] After P doping, a large number of spherical micron-sized aggregates were uniformly loaded on the MXene / substrate. The aggregates were densely distributed and had good coverage, indicating that the material achieved efficient and uniform growth on the conductive substrate, providing a "macroscopically continuous reaction field" for electrocatalytic reactions. The individual aggregates were flower-like structures formed by stacked layers of nanosheets. The core advantage of this structure is that the "thin-layer characteristics" of the nanosheets greatly increase the specific surface area, exposing more electrocatalytic active sites. The "stereopores" of the three-dimensional flower-like assembly facilitate electrolyte penetration and rapid desorption of bubbles (H2 / O2), optimizing mass transfer efficiency.

[0068] The three-dimensional conductive substrate described in this invention can be selected from, but is not limited to, porous materials with high specific surface area and excellent conductivity, such as nickel foam (NF), copper foam (CF), nickel mesh (NN), carbon cloth (CC), or carbonized wood (CW). These substrates provide a stable supporting framework and efficient electron transport channels for the high-entropy metal phosphide active material of this invention. Those skilled in the art will understand that any conductive substrate capable of achieving the above-described functions is applicable to this invention.

[0069] The following examples and comparative examples all use nickel foam (NF) as a representative substrate to demonstrate in detail the preparation process, material characteristics, and catalytic performance of the present invention. It should be understood that this is not intended to limit the invention. Given that the core of the method of the present invention lies in "in-situ hydrothermal growth and phosphating on an MXene-modified three-dimensional substrate," and that other substrates can obtain suitable hydrophilicity and surface properties through pretreatment methods known in the art (such as acid washing, oxidation, etc.), those skilled in the art, after reading this specification, can apply the method to other substrates such as copper foam, nickel mesh, carbon cloth, and carbonized wood without any inventive effort, and are expected to obtain similar beneficial effects.

[0070] The present invention will now be described in more detail with reference to more specific embodiments.

[0071] The following examples and comparative examples use nickel foam (NF) as a three-dimensional conductive substrate to prepare MX@CoNiZnFeMnP / NF composite materials. The specific steps are as follows:

[0072] Example 1

[0073] 1 g of Ti3AlC2 powder was slowly added to 20 mL of 40% HF solution in multiple additions, and the reaction was carried out at 40 °C for 36 h with continuous magnetic stirring during the reaction. After the reaction was completed, the supernatant was washed with deionized water until the pH of the supernatant was 6-7. The obtained product was then freeze-dried at -60 °C for 48 h to obtain Ti3C2T. x Material.

[0074] 0.06 g of Ti3C2T x Dissolved in 20 mL of deionized water, then sonicated for 2 h, a stable colloidal suspension was obtained. The dried nickel foam (NF) was immersed in the colloidal suspension for 3 h, and dried to obtain the MXene / substrate precursor. At 25 °C, 0.1 g of hexadecyltrimethylammonium bromide, 0.2 mmol Co(NO3)2∙6H2O (0.0582 g), 0.2 mmol Ni(NO3)2∙6H2O (0.0581 g), 0.2 mmol Zn(NO3)2∙6H2O (0.0592 g), 0.2 mmol Fe(NO3)2∙9H2O (0.080 g), and 0.2 mmol MnCl2∙6H2O (0.0396 g) were weighed and dissolved in 30 mL of deionized water. The solution was then placed in a hydrothermal reactor, and the dried MXene / substrate was cut to a 1 cm diameter. 2 The substrate was placed in a hydrothermal reactor at a heating rate of 5 °C / min, a reaction temperature of 120 °C, and a reaction time of 12 h. After the reaction, the substrate was removed, washed, and dried for 24 h. Then, it was calcined and phosphated in a tube furnace under a nitrogen atmosphere, wherein the mass ratio of the precursor to sodium hypophosphite was 1:2. First, the temperature was raised to 350 °C at a heating rate of 2 °C / min and held for 2 h to finally obtain the MX@CoNiZnFeMnP / NF composite material.

[0075] Example 2

[0076] 1 g of Ti3AlC2 powder was slowly added to 20 mL of 40% HF solution in multiple additions, and the reaction was carried out at 40 °C for 36 h with continuous magnetic stirring during the reaction. After the reaction was completed, the supernatant was washed with deionized water until the pH of the supernatant was 6-7. The resulting product was then freeze-dried at -60 °C for 48 h to obtain Ti3C2T. x Material.

[0077] 0.06 g of Ti3C2T xDissolved in 20 mL of deionized water, then sonicated for 2 h, a stable colloidal suspension was obtained. The dried nickel foam (NF) was immersed in the colloidal suspension for 3 h, and dried to obtain the MXene / substrate precursor. At 25 °C, 0.1 g of hexadecyltrimethylammonium bromide, 0.3 mmol Co(NO3)2∙6H2O (0.0873 g), 0.3 mmol Ni(NO3)2∙6H2O (0.0872 g), 0.3 mmol Zn(NO3)2∙6H2O (0.0893 g), 0.3 mmol Fe(NO3)2∙9H2O (0.121 g), and 0.3 mmol MnCl2∙6H2O (0.0593 g) were weighed and dissolved in 30 mL of deionized water. The solution was then placed in a hydrothermal reactor, and the dried MXene / substrate was cut to a 1 cm diameter. 2 The substrate was placed in a hydrothermal reactor, heated at a rate of 2 °C / min, at a reaction temperature of 100 °C, and for 24 h. After the reaction, the substrate was removed, washed, and dried for 24 h. Then, it was calcined and phosphated in a tube furnace under a nitrogen atmosphere, wherein the mass ratio of the precursor to sodium hypophosphite was 1:5. First, the heating rate was 2 °C / min, and the temperature was raised to 350 °C and held for 2 h to finally obtain the MX@CoNiZnFeMnP / NF composite material.

[0078] Example 3

[0079] 1 g of Ti3AlC2 powder was slowly added to 20 mL of 40% HF solution in multiple additions, and the reaction was carried out at 40 °C for 36 h with continuous magnetic stirring during the reaction. After the reaction was completed, the supernatant was washed with deionized water until the pH of the supernatant was 6-7. The resulting product was then freeze-dried at -60 °C for 48 h to obtain Ti3C2T. x Material.

[0080] 0.06 g of Ti3C2T xDissolved in 20 mL of deionized water, then sonicated for 2 h, a stable colloidal suspension was obtained. The dried nickel foam (NF) was immersed in the colloidal suspension for 3 h, and dried to obtain the MXene / substrate precursor. At 25 °C, 0.1 g of hexadecyltrimethylammonium bromide, 0.4 mmol Co(NO3)2∙6H2O (0.1164 g), 0.4 mmol Ni(NO3)2∙6H2O (0.1163 g), 0.4 mmol Zn(NO3)2∙6H2O (0.1189 g), 0.4 mmol Fe(NO3)2∙9H2O (0.1616 g), and 0.4 mmol MnCl2∙6H2O (0.0791 g) were weighed and dissolved in 30 mL of deionized water. The solution was then placed in a hydrothermal reactor, and the dried MXene / substrate was cut to a 1 cm diameter. 2 The substrate was placed in a hydrothermal reactor, heated at a rate of 5 °C / min, at a reaction temperature of 120 °C, and for 12 h. After the reaction, the substrate was removed, washed, and dried for 24 h. Then, it was calcined and phosphated in a tube furnace under a nitrogen atmosphere, wherein the mass ratio of the precursor to sodium hypophosphite was 1:3. First, the heating rate was 2 °C / min, and the temperature was raised to 350 °C and held for 2 h to finally obtain the MX@CoNiZnFeMnP / NF composite material.

[0081] Example 4

[0082] 1 g of Ti3AlC2 powder was slowly added to 20 mL of 40% HF solution in multiple additions, and the reaction was carried out at 40 °C for 36 h with continuous magnetic stirring during the reaction. After the reaction was completed, the supernatant was washed with deionized water until the pH of the supernatant was 6-7. The obtained product was then freeze-dried at -60 °C for 48 h to obtain Ti3C2T. x Material.

[0083] 0.06 g of Ti3C2T xDissolved in 20 mL of deionized water, then sonicated for 2 h, a stable colloidal suspension was obtained. The dried nickel foam (NF) was immersed in the colloidal suspension for 3 h, and dried to obtain the MXene / substrate precursor. At 25 °C, 0.1 g of hexadecyltrimethylammonium bromide, 0.5 mmol Co(NO3)2∙6H2O (0.1455 g), 0.5 mmol Ni(NO3)2∙6H2O (0.1453 g), 0.5 mmol Zn(NO3)2∙6H2O (0.1487 g), 0.5 mmol Fe(NO3)2∙9H2O (0.2020 g), and 0.5 mmol MnCl2∙6H2O (0.0989 g) were dissolved in 30 mL of deionized water. The solution was then placed in a hydrothermal reactor, and the dried MXene / substrate was cut to a 1 cm diameter. 2 The substrate was placed in a hydrothermal reactor, heated at a rate of 5 °C / min, at a reaction temperature of 120 °C, and for 24 h. After the reaction, the substrate was removed, washed, and dried for 24 h. Then, it was calcined and phosphated in a tube furnace under a nitrogen atmosphere, wherein the mass ratio of the precursor to sodium hypophosphite was 1:5. First, the heating rate was 2 °C / min, and the temperature was raised to 350 °C and held for 2 h to finally obtain the MX@CoNiZnFeMnP / NF composite material.

[0084] Comparative Example 1

[0085] The nickel foam was cut into cubes with sides of 1 cm to ensure an area of ​​1 square centimeter. Then, to thoroughly remove impurities or oxides from its surface, it was washed sequentially with 3.0 M HCl, acetone, anhydrous ethanol, and deionized water to prepare nickel foam electrodes for HER and OER testing.

[0086] Comparative Example 2

[0087] 5 mg of Pt / C was dispersed in Nafion solution (5 wt.%, 20 μL) and ethanol (200 μL), and sonicated for 30 min. The dispersion was then pipetted into a 1 cm volume. 2 The NF substrate coated with the electrocatalyst was vacuum dried at 60 °C to obtain a Pt / C electrode for the HER control sample.

[0088] Comparative Example 3

[0089] 5 mg RuO2 was dispersed in Nafion solution (5 wt.%, 20 μL) and ethanol (200 μL), and sonicated for 30 min. The solution was then pipetted into a 1 cm volume. 2 The NF substrate coated with the electrocatalyst was vacuum dried at 60 °C to obtain a RuO2 electrode for use as a control sample in OER.

[0090] Comparative Example 4

[0091] This comparative example provides a method for preparing a binary phosphide catalyst. In this method, except that the metal salt solution contains only cobalt salt and zinc salt, the rest is the same as in Example 1, and a binary phosphide catalyst is obtained.

[0092] Comparative Example 5

[0093] This comparative example provides a method for preparing a ternary phosphide catalyst. In the preparation method, except that the metal salt solution contains only cobalt salt, nickel salt and zinc salt, the rest is the same as in Example 1, and a ternary phosphide catalyst is obtained.

[0094] Comparative Example 6

[0095] This comparative example provides a method for preparing a quaternary phosphide catalyst. In this method, except that the metal salt solution contains only cobalt salt, nickel salt, zinc salt and iron salt, the rest is the same as in Example 1, and a quaternary phosphide catalyst is obtained.

[0096] Comparative Example 7

[0097] This comparative example provides a method for preparing a five-membered phosphide catalyst, wherein the preparation method does not involve adding Ti3C2T. x Except for the above, the rest are the same as in Example 1, and a five-membered phosphide catalyst is obtained.

[0098] All electrochemical measurements were performed in 1.0 M KOH solution (pH=13.7) using a typical three-electrode system on a Gamry electrochemical workstation (Interface 1000). A saturated calomel electrode (SCE) was used as the reference electrode, and a graphite rod as the counter electrode. Measurements were performed using linear sweep voltammetry (LSV) at 5 mV s⁻¹. -1 The electrochemical properties of the catalyst during the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) were investigated using scan rates. At 10 5 Electrochemical impedance spectroscopy (EIS) was recorded at different overpotentials within a frequency range up to 0.01 Hz, with an AC voltage of 5 mV applied. Based on the solution resistance in the EIS data, the potential, after 80% iR compensation, was obtained through E... RHE =E （SCE） The equation +0.0591 × pH + 0.242 V is converted to the reversible hydrogen electrode (RHE) potential. For the study of the oxygen evolution reaction, the overpotential (η) is expressed by the formula η(V) = E. RHE -1.23 V is calculated. Furthermore, the overpotential (η) studied for the hydrogen evolution reaction is given by the formula η(V) = -E. RHEThe reaction kinetics mechanism was obtained and studied using the Tafel equation: η = blog|j| + a, where b is the Tafel slope and j is the current density.

[0099] 1) Morphology and structure

[0100] Figure 1 The Ti3C2T prepared in Example 1 x The X-ray diffraction pattern of the material, based on Figure 1 The XRD pattern of Ti3C2T x The XRD pattern of the material was compared with that of the Ti3AlC2MAX phase. Ti3AlC2MAX exhibits characteristic crystal plane peaks at 9.5° and 39°. Selective etching with HF and subsequent Li... + After embedding / stripping, Ti3C2T x The (002) peak shifted to 6.6°, accompanied by the disappearance of the Al-related peak at 39°. This peak shift reflects the effects of Al layer elimination, functional group incorporation, and Li... + The increased interlayer spacing due to embedding.

[0101] Figure 2 The X-ray diffraction pattern of MX@CoNiZnFeMnP / NF prepared in Example 4 is shown below. Figure 2 The X-ray diffraction (XRD) pattern shows that the high-entropy metal phosphide MX@CoNiZnFeMnP / NF crystal structure exists in the Co2P crystal morphology without phase separation.

[0102] Depend on Figure 3 Scanning electron microscopy (SEM) images show that the MX@CoNiZnFeMnP prepared in Example 4 uniformly supports a large number of spherical micron-sized aggregates, which are densely distributed and have good coverage. This indicates that the material achieves efficient and uniform growth on a conductive substrate, providing a "macroscopically continuous reaction field" for electrocatalytic reactions. Individual aggregates are flower-like structures formed by stacked layers of nanosheets. The core advantage of this structure is that the "thin-layer characteristic" of the nanosheets significantly increases the specific surface area, exposing more electrocatalytic active sites. Figure 3 High-angle annular dark-field (HAADF) images and TEM-coupled energy-dispersive X-ray spectroscopy (EDS) elemental maps show that the nine elements Mn, Fe, Co, Ni, Zn, Ti, C, O, and P are uniformly distributed in MX@CoNiZnFeMnP / NF.

[0103] 2) HER performance testing and analysis of water electrolysis

[0104] Figure 4Figure a shows the IR-corrected LSV curves. Clearly, the overpotential of the MX@CoNiZnFeMnP / NF prepared in Example 4 is 73 mV @ 10 mA cm⁻¹. -2 The values ​​were lower than those of MX@CoNiZnFeP / NF (74 mV), MX@CoNiZnP / NF (80 mV), MX@CoZnP / NF (88 mV), CoNiZnFeMnP / NF (96 mV), and NF (302 mV), indicating better HER catalytic activity. Figure 4 As shown in b, with MX@CoNiZnFeP / NF (106 mV dec -1 ), MX@CoNiZnP / NF (114 mV dec -1 ), MX@CoZnP / NF (127 mV dec -1 ), CoNiZnFeP / NF (95 mV dec -1 ) and NF (139 mV dec -1 Compared to MX@CoNiZnFeMnP / NF, MX@CoNiZnFeMnP / NF has a smaller Tafel slope value (88 mV dec). -1 This indicates that MX@CoNiZnFeMnP / NF has more favorable HER kinetics.

[0105] Table 1 Comparison of electrocatalytic hydrogen evolution parameters between the embodiments of the present invention and the comparative examples.

[0106] Example / Hydrogen Evolution Parameters <![CDATA[η 10 (mV vs. RHE)]]> <![CDATA[Tafel shope (mV dec -1 )]]> <![CDATA[R ct (Oh)]]> Example 4 73 88 1.96 Comparative Example 1 302 143 4.63 Comparative Example 2 17 27 0.48 Comparative Example 4 88 127 3.94 Comparative Example 5 80 114 3.57 Comparative Example 6 74 106 3.57 Comparative Example 7 96 95 2.49

[0107] Electrochemical impedance spectroscopy (EIS) was used as the detection method to reveal the interfacial charge transfer behavior of the electrocatalyst. The corresponding Nyquist plot is shown below. Figure 4 As shown in c, the diameter of the semicircle on the X-axis represents the interface charge transfer resistance (R). ct The semicircular diameter of MX@CoNiZnFeMnP / NF (1.96 Ω) is significantly smaller than that of MX@CoNiZnFeP / NF (3.57 Ω), MX@CoNiZnP / NF (3.57 Ω), and MX@CoZnP / NF (3.57 Ω), indicating that MX@CoNiZnFeMnP / NF has a lower charge transfer resistance and a faster charge transfer capability at the electrode-electrolyte interface during the HER process.

[0108] At 10 mA cm −2 After continuous testing at the specified current density, the catalyst exhibited negligible degradation. Stability characterization after 120 hours showed that the potential shift in the LSV polarization curve was negligible. Figure 4As shown in the inset in section d, the initial potential retention rate of the MX@CoNiZnFeMnP / NF electrode after 120 h of operation was 90.1%, indicating that the MX@CoNiZnFeMnP / NF electrocatalyst has good HER stability under alkaline conditions.

[0109] 3) Electrolysis water OER performance testing and analysis

[0110] Figure 5 Figure a shows the IR-corrected LSV curves. Clearly, the overpotential of the MX@CoNiZnFeMnP / NF prepared in Example 4 is 210 mV @ 50 mA cm⁻¹. -2 The values ​​were significantly lower than those of MX@CoNiZnFeP / NF (240 mV), MX@CoNiZnP / NF (320 mV), MX@CoZnP / NF (330 mV), CoNiZnFeMnP / NF (240 mV), and RuO2 / NF (350 mV), indicating better HER catalytic activity. Figure 5 As shown in b, MX@CoNiZnFeMnP / NF has a smaller Tafel slope value (22 mV dec). -1 This indicates that MX@CoNiZnFeMnP / NF has more favorable OER kinetics.

[0111] Table 2 Comparison of electrocatalytic oxygen evolution parameters between the embodiments of the present invention and the comparative examples.

[0112] Example / Oxygen Evolution Parameters <![CDATA[Η 50 (mV vs. RHE)]]> <![CDATA[Tafel shope (mV dec -1 )]]> <![CDATA[R ct (Oh)]]> Example 4 210 22 0.50 Comparative Example 3 350 126 2.90 Comparative Example 4 330 93 2.60 Comparative Example 5 320 72 1.96 Comparative Example 6 240 61 1.54 Comparative Example 7 240 34 1.24

[0113] Electrochemical impedance spectroscopy (EIS) was used as the detection method to reveal the interfacial charge transfer behavior of the electrocatalyst. The corresponding Nyquist plot is shown below. Figure 5 As shown in c, the diameter of the semicircle on the X-axis represents the interface charge transfer resistance (R). ct The semicircular diameter (0.5 Ω) of MX@CoNiZnFeMnP / NF is significantly smaller than that of other comparative examples, indicating that MX@CoNiZnFeMnP / NF has lower charge transfer resistance and faster charge transfer capability at the electrode-electrolyte interface during the OER process.

[0114] At 50 mA cm −2 After continuous testing at the specified current density, the catalyst exhibited negligible degradation. Stability characterization after 120 hours showed that the potential change in the LSV polarization curve was negligible. Figure 5As shown in the inset in section d, the initial potential retention rate of the MX@CoNiZnFeMnP / NF electrode after 120 h of operation was 99.6%, indicating that the MX@CoNiZnFeMnP / NF electrocatalyst has good OER stability under alkaline conditions.

[0115] Those skilled in the art should understand that the specific embodiments described above are merely illustrative of the principles and core concepts of the present invention, intended to aid in understanding the invention, and should not be construed as limiting the scope of protection of the present invention. The scope of protection of the present invention is defined by the appended claims and their legal equivalents. For those skilled in the art, any modifications, substitutions, or improvements made to the above embodiments without departing from the principles and spirit of the present invention should be included within the scope of protection of the present invention.

Claims

1. An MXene@high-entropy metal phosphide composite electrode material, characterized in that, A three-dimensional porous substrate serves as the framework, on which MXene is loaded. The surface of the MXene is loaded with a pentagonal high-entropy metal phosphide, CoNiZnFeMnP; wherein the MXene is Ti3C2T. x .

2. The MXene@high-entropy metal phosphide composite electrode material according to claim 1, characterized in that, The composite electrode material has a microstructure that combines nanometer and micrometer dimensions, with the flower-shaped structures uniformly anchored on a three-dimensional porous substrate.

3. The MXene@high-entropy metal phosphide composite electrode material according to claim 1 or 2, characterized in that, The three-dimensional porous substrate is one of the following: nickel foam, copper foam, nickel mesh, carbon cloth, and carbonized wood.

4. A method for preparing an MXene@high-entropy metal phosphide composite electrode material, characterized in that, Includes the following steps: S1. Load MXene material onto a three-dimensional porous substrate to obtain an MXene-modified three-dimensional porous substrate; S2. Prepare a precursor solution containing cobalt salt, nickel salt, zinc salt, iron salt, manganese salt, and surfactant, and perform a hydrothermal reaction between the precursor solution and the MXene-modified three-dimensional porous substrate to grow MXene@CoNiZnFeMn-LDH, i.e., the precursor, in situ on the substrate; S3. Phosphate the precursor under a protective atmosphere to obtain the MXene@high-entropy metal phosphide composite electrode material.

5. The method for preparing an MXene@high-entropy metal phosphide composite electrode material according to claim 4, characterized in that, Step S1 is as follows: Preparation of Ti3C2T x The material was dispersed in deionized water and ultrasonically treated to obtain a uniform colloidal suspension. A completely dried three-dimensional conductive substrate was then immersed in the colloidal suspension to form Ti3C2T. x The material is fully adsorbed and locked in a three-dimensional porous substrate, and then dried to obtain the final product; the concentration of the colloidal suspension is 0.5~5 mg / mL, and the ultrasonic time is 0.5~4 h.

6. The method for preparing an MXene@high-entropy metal phosphide composite electrode material according to claim 5, characterized in that, The Ti3C2T x The preparation process of the material is as follows: Ti3AlC2MAX phase powder was immersed in HF or LiF+HCl solution and etched at 30~50 °C for 24~48 hours with stirring to selectively remove the aluminum layer and simultaneously introduce -OH, -O, and -F functional groups on the surface. The mixture was then centrifuged and washed until the pH of the supernatant was approximately 6. The resulting precipitate was then freeze-dried to obtain Ti3C2T x powder.

7. The method for preparing an MXene@high-entropy metal phosphide composite electrode material according to claim 5, characterized in that, The three-dimensional conductive substrate is pretreated before use: foamed nickel, foamed copper and nickel mesh need to be ultrasonically cleaned with hydrochloric acid, acetone and ethanol in sequence to remove surface oxides and oil stains; carbon cloth needs to be refluxed in nitric acid to increase its hydrophilicity; carbonized wood needs to be thoroughly cleaned with deionized water and ethanol to unclog the natural pipe structure; the three-dimensional porous substrate is soaked in colloidal suspension for 2-12 h, dried at 60-80 ℃ for 6-12 h.

8. The method for preparing an MXene@high-entropy metal phosphide composite electrode material according to claim 4, characterized in that, In step S2, the cobalt salt, nickel salt, zinc salt, iron salt, and manganese salt are one of chloride salts, nitrate salts, or sulfate salts, and the molar concentration ratio of each metal salt is 1:1:1:1:1, with a total metal ion concentration of 0.01~0.2 mol / L; the surfactant is one of polyvinylpyrrolidone, hexadecyltrimethylammonium bromide, and sodium citrate, and the amount added is 5%~20% of the total mass of the metal salts. In step S2, the hydrothermal reaction temperature is 120~180 ℃ and the reaction time is 8~16 h; after the reaction, the mixture is naturally cooled, washed with deionized water and ethanol, and vacuum dried at 60~80 ℃ to obtain the precursor.

9. The method for preparing an MXene@high-entropy metal phosphide composite electrode material according to claim 4, characterized in that, In step S3, sodium hypophosphite is added as the phosphorus source for phosphating, and the mass ratio of sodium hypophosphite to the precursor is 1:1 to 1:5; the phosphating temperature is 300 to 450 °C, the phosphating time is 1 to 6 h, and the protective atmosphere is argon or nitrogen.

10. The application of the MXene@high-entropy metal phosphide composite electrode material according to any one of claims 1 to 3, characterized in that, The MXene@high-entropy metal phosphide composite electrode material is used for electrocatalytic hydrogen evolution reaction, oxygen evolution reaction and total hydrolysis reaction.

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