Preparation method of self-supporting catalyst of boronized MoNi loaded foam nickel, catalyst and application

Abstract

The application discloses a preparation method of a boronized MoNi self-supporting catalyst loaded on foamed nickel, a catalyst and application; the preparation method comprises the following steps: reacting a nickel source and a molybdenum source in a solvent to obtain an Anderson-type MoNi polyoxometalate precursor; mixing the precursor with a boron source to obtain a mixture of the precursor and boron; uniformly mixing the mixture of the precursor and boron with a NaCl-KCl molten salt medium to obtain a precursor mixture; calcining the precursor mixture and a foamed nickel substrate under an inert atmosphere to make the precursor undergo a boronization reaction and be loaded on the foamed nickel; and washing and drying the calcination product to obtain the catalyst; the Anderson-type precursor is used to realize uniform dispersion of Mo and Ni elements at a molecular scale, the electronic structure is regulated through boronization treatment, the molten salt confined reaction and the foamed nickel self-supporting structure are combined, and as a result, the catalyst exhibits excellent bifunctional catalytic activity of oxygen evolution and hydrogen evolution and good stability under alkaline conditions.

Description

Technical Field

[0001] This invention relates to the fields of energy materials and electrocatalysis technology, specifically to a method for preparing a boronized MoNi-supported nickel foam self-supporting catalyst, the catalyst itself, and its applications. Background Technology

[0002] With the continuous growth of global energy consumption and the increasingly prominent environmental pollution and climate change problems caused by the use of fossil fuels, the development of green, clean, and sustainable energy conversion and storage technologies has become an important research direction in the energy field. Hydrogen energy, due to its high energy density, clean combustion products, and wide availability, is considered an important carrier for building a future low-carbon energy system. Electrolysis of water to produce hydrogen, as a green and efficient hydrogen production technology, mainly includes the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER). Its reaction efficiency largely depends on the activity, stability, and conductivity of the electrode catalytic materials. Currently, noble metal catalysts such as Pt, IrO2, and RuO2 exhibit excellent catalytic performance in water electrolysis, but their limited reserves, high prices, and inability to meet the needs of large-scale applications severely restrict industrial development. Therefore, the development of highly active, low-cost, and stable non-noble metal electrocatalysts has become an important research hotspot in the field of electrocatalytic water splitting. Transition metal-based catalytic materials, due to their abundant elemental reserves, tunable structure, and excellent electrochemical performance, are gradually becoming important candidate systems to replace noble metal catalysts.

[0003] Polyoxometalates (POMs) are a class of inorganic clusters with well-defined compositions and tunable structures, exhibiting rich redox activity, designable metal centers, and excellent electronic structure control, demonstrating unique advantages in the field of electrocatalysis. Anderson-type POMs, in particular, possess stable structures and uniform metal element distribution, making them ideal precursors for constructing multi-component catalytic materials. However, traditional POM materials still have several shortcomings: firstly, their intrinsic electronic conductivity is weak, hindering rapid electron transport during electrocatalysis; secondly, powder-type materials typically require binders to be loaded onto conductive substrates during electrode preparation, which can easily lead to active site shielding, charge transport obstruction, and catalyst layer detachment, thereby reducing catalytic activity and cycle stability; furthermore, POMs may undergo structural reconstruction under high-temperature treatment or electrochemical reaction conditions, and how to transform them into more active and structurally stable derived catalytic phases remains a key problem to be solved.

[0004] Boration treatment can effectively modulate the electronic structure of transition metal materials, improve their conductivity, and help form active sites that are conducive to reactant adsorption and intermediate transformation. Therefore, it has attracted widespread attention in the design of electrocatalytic materials. Nickel foam has a three-dimensional continuous porous framework, good conductivity, and a large specific surface area, which can be used as a self-supporting catalyst substrate, which is beneficial to the uniform distribution of active components, sufficient electrolyte wetting, and rapid release of gaseous products. However, the existing technology still lacks a self-supporting electrocatalytic material constructed by boration treatment and combining it with nickel foam, using Anderson-type MoNi polyoxometalate as a precursor, to achieve effective conversion of the precursor and a stable bond between the active phase and the conductive substrate, thereby further improving its catalytic activity and long-term stability in the water electrolysis reaction. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for preparing a boronized MoNi-supported nickel foam self-supporting catalyst, the catalyst itself, and its applications.

[0006] To achieve the above objectives, the present invention provides the following technical solution: This application provides a method for preparing a boronized MoNi-supported nickel foam self-supporting catalyst, comprising the following steps: S1. React nickel source and molybdenum source in a solvent to prepare Anderson-type MoNi polyoxometalate precursor; S2. The precursor is mixed with a boron source to obtain a mixture of the precursor and boron; S3. The mixture of the precursor and boron is mixed evenly with a molten salt medium to obtain a precursor mixture; S4. The precursor mixture and the nickel foam substrate are calcined under an inert atmosphere to cause the precursor to undergo a borylation reaction and be loaded onto the nickel foam. S5. The calcined product is washed and dried to obtain the boronized MoNi-supported nickel foam self-supporting catalyst.

[0007] Preferably, in step S1, the nickel source is nickel nitrate hydrate, and the molybdenum source is ammonium molybdate hydrate; The reaction includes: dissolving nickel nitrate hydrate and ammonium molybdate hydrate in boiling deionized water, reacting them at 80-90°C, centrifuging and drying to obtain the Anderson-type MoNi polyoxometalate precursor.

[0008] Preferably, in step S1, the molar ratio of nickel source to molybdenum source is 1:3 to 1:8, calculated as nickel and molybdenum elements.

[0009] Preferably, in step S2, the mass ratio of the precursor to the boron source is 2:1 to 2:5.

[0010] Preferably, in step S2, the boron source is at least one of boron powder, boric acid, sodium borohydride, and melamine borate.

[0011] Preferably, in step S3, the molten salt medium is a mixture of NaCl and KCl, and the molar ratio of NaCl to KCl is 1:1.

[0012] Preferably, in step S4, the calcination is carried out at 800~1000℃; the inert atmosphere is argon; and the heating rate is 5~20℃·min. -1 The heat preservation time is 0.5~3 hours.

[0013] Preferably, in step S5, the washing includes: ultrasonic washing with hot water to remove B2O3 and residual molten salt, followed by washing with deionized water and ethanol in sequence; the drying temperature is 60~100℃ and the time is 8~16h.

[0014] A boronized MoNi-supported nickel foam self-supporting catalyst was prepared by the above-described preparation method.

[0015] Application of a boronized MoNi-supported nickel foam self-supporting catalyst in water electrolysis.

[0016] Compared with the prior art, this application has the following beneficial effects: This invention proposes a method for preparing a boronized MoNi-supported nickel foam self-supporting catalyst, the catalyst itself, and its application. For the first time, an Anderson-type MoNi polyoxometalate is used as a precursor. The catalyst is prepared in situ by mixing it with a boron source and a molten salt medium and then calcining it with nickel foam under an inert atmosphere. The Anderson-type precursor achieves uniform dispersion of Mo and Ni elements at the molecular scale, providing a structural basis for the subsequent formation of a highly dispersed, multi-active-site borated MoNi catalytic phase. Boration effectively modulates the local electronic structure of the MoNi components, improves charge transport capabilities, and optimizes the adsorption and desorption behavior of key intermediates in the oxygen evolution and hydrogen evolution reactions. The molten salt medium, acting as a reaction medium and dispersant during calcination, not only lowers the reaction temperature and promotes uniform boration but also effectively prevents the aggregation of active particles, thus forming a nanostructure with abundant active interfaces. The nickel foam substrate provides a continuous conductive network and an open three-dimensional porous structure, enabling in-situ robust loading of active components without the need for external binders. This significantly promotes electrolyte wetting, ion diffusion, and rapid gas release, while avoiding problems such as binders obscuring active sites and increasing interfacial resistance. Through the above multi-element synergistic regulation and structural design, the resulting catalyst exhibits excellent dual-function catalytic activity for oxygen evolution and hydrogen evolution, rapid reaction kinetics, and outstanding long-term operational stability under alkaline conditions. Attached Figure Description

[0017] Figure 1 The image shows the XRD pattern of the boronized MoNi-supported nickel foam self-supporting catalyst synthesized in Example 1.

[0018] Figure 2 This is a TEM image of the boronized MoNi-supported nickel foam self-supporting catalyst synthesized in Example 1.

[0019] Figure 3 The image shows the XRD pattern of the Anderson-type MoNi polyoxometalate synthesized in Example 1.

[0020] Figure 4 The image shows the LSV polarization curve of the boronized MoNi-supported nickel foam self-supporting catalyst synthesized in Example 1 during the oxygen evolution reaction at 1MKOH.

[0021] Figure 5 The LSV curve of the boronized MoNi-supported nickel foam self-supporting catalyst synthesized in Example 1 is shown in the hydrogen evolution reaction test. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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.

[0023] Furthermore, in this invention, an element referred to as fixed to or disposed on another element may be directly disposed on the other element, or there may be an intermediate element. When an element is considered to be connected to another element, it may be directly connected to the other element, or there may be an intermediate element present simultaneously. The terms vertical, horizontal, left, right, and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementation.

[0024] Example 1 See Figures 1-5 This application provides a method for preparing a boronized MoNi-supported nickel foam self-supporting catalyst, comprising the following steps: S1. React nickel and molybdenum sources in a solvent to prepare Anderson-type MoNi polyoxometalate precursors.

[0025] Specifically, an Anderson-type MoNi polyoxometalate precursor was prepared by reacting a nickel source and a molybdenum source in a solvent. This precursor achieved uniform dispersion of Mo and Ni elements at the molecular scale, providing a structural basis for the subsequent formation of a highly dispersed, multi-active-site borated MoNi catalytic phase.

[0026] S2. The precursor is mixed with a boron source to obtain a mixture of precursor and boron.

[0027] Specifically, the precursor obtained in step S1 is mixed with a boron source to obtain a mixture of precursor and boron. Thorough mixing ensures close contact and uniform dispersion of the precursor and boron source in the solid state, which is beneficial for the full reaction of boron with the metal components in the precursor during the subsequent high-temperature boration process.

[0028] S3. The mixture of the precursor and boron is mixed evenly with a molten salt medium to obtain a precursor mixture.

[0029] Specifically: The mixture of precursor and boron obtained in step S2 is mixed evenly with molten salt medium to obtain a precursor mixture; the molten salt medium acts as a reaction medium and dispersant in the subsequent calcination process, which can reduce the reaction temperature, promote the uniform boration reaction, and effectively prevent the agglomeration of active particles, which is conducive to the formation of nanostructures with rich active interfaces.

[0030] S4. The precursor mixture and the nickel foam substrate are calcined under an inert atmosphere to cause the precursor to undergo a boronization reaction and be loaded onto the nickel foam.

[0031] Specifically: The precursor mixture obtained in step S3 is calcined with the nickel foam substrate under an inert atmosphere to cause the precursor to undergo a boronization reaction and be loaded onto the nickel foam; under high temperature and inert atmosphere conditions, the Anderson-type MoNi polyoxometalate precursor undergoes a boronization conversion with a boron source to generate boronized MoNi active components. At the same time, these active components are loaded in situ onto the surface of the three-dimensional porous framework of the nickel foam, forming a firmly bonded catalytic interface; the nickel foam substrate provides a continuous conductive network and an open three-dimensional porous structure, which can achieve in-situ loading of active components without the need for external binders, which is beneficial for promoting electrolyte wetting, ion diffusion and rapid gas release.

[0032] S5. The calcined product is washed and dried to obtain the boronized MoNi-supported nickel foam self-supporting catalyst.

[0033] Specifically: the calcined product obtained in step S4 is washed and dried to obtain a boronized MoNi-supported nickel foam self-supporting catalyst; the purpose of washing is to remove impurities and residual molten salt generated during calcination, and the drying process brings the catalyst to a usable state.

[0034] Through the above steps, using Anderson-type MoNi polyoxometalate as a precursor, a self-supporting catalytic material with multi-element synergistic effect, good conductivity and structural stability was constructed through boronization conversion and in-situ loading.

[0035] In a preferred embodiment, in step S1, the nickel source is nickel nitrate hydrate, and the molybdenum source is ammonium molybdate hydrate; The reaction includes: dissolving nickel nitrate hydrate and ammonium molybdate hydrate in boiling deionized water, reacting them at 80-90°C, centrifuging and drying to obtain the Anderson-type MoNi polyoxometalate precursor.

[0036] In this embodiment, the nickel source is specifically nickel nitrate hydrate, preferably nickel nitrate hexahydrate; the molybdenum source is specifically ammonium molybdate hydrate, preferably ammonium molybdate tetrahydrate. During the reaction, the nickel nitrate hydrate and ammonium molybdate hydrate are first added to boiling deionized water and fully dissolved, and then the reaction system temperature is maintained between 80°C and 90°C for the reaction. After the reaction is completed, the solid product is separated by centrifugation and then dried to obtain the MoNi polyoxometalate precursor with an Anderson structure. This temperature and reaction conditions are conducive to the formation of a well-structured and highly crystalline Anderson-type precursor, laying the foundation for subsequent steps.

[0037] In a preferred embodiment, in step S1, the molar ratio of the nickel source to the molybdenum source is 1:3 to 1:8, calculated as nickel and molybdenum elements.

[0038] In this embodiment, the molar ratio of nickel source to molybdenum source, calculated as nickel and molybdenum elements, is controlled within the range of 1:3 to 1:8. Preferably, the molar ratio is 1:6. Within this range, the target Anderson-type polyoxometalate structure can be effectively formed, ensuring a uniform distribution and appropriate stoichiometry of Mo and Ni elements in the precursor, which is beneficial for the formation of the highly catalytically active MoNiB component during subsequent boration.

[0039] In a preferred embodiment, in step S2, the mass ratio of the precursor to the boron source is 2:1 to 2:5.

[0040] In this embodiment, the mass ratio of the precursor to the boron source is controlled within the range of 2:1 to 2:5. Within this mass ratio range, sufficient boron source can be provided to participate in the subsequent boration reaction, so that the metal components in the precursor can be fully converted into catalytically active boride phases. If the amount of boron source is too small, the boration reaction may be incomplete. If the amount of boron source is too large, it may cause waste of raw materials and increase the burden of subsequent washing to remove excess boron source.

[0041] In a preferred embodiment, in step S2, the boron source is at least one of boron powder, boric acid, sodium borohydride, and melamine borate.

[0042] In this embodiment, the boron source can be selected from at least one of boron powder, boric acid, sodium borohydride, and melamine borate; among the above boron sources, boron powder is preferred; boron powder can undergo a solid-phase reaction with the metal components in the precursor under high temperature conditions, effectively introducing boron elements into the material structure. At the same time, the by-reaction products of boron powder are relatively simple and easy to remove by subsequent washing; the mixing method can be grinding, and the grinding time is generally 10 to 60 minutes, preferably 30 minutes. Thorough grinding helps the components to achieve uniform dispersion and close contact in the solid state.

[0043] In a preferred embodiment, in step S3, the molten salt medium is a mixture of NaCl and KCl, and the molar ratio of NaCl to KCl is 1:1.

[0044] In this embodiment, the molten salt medium is specifically a mixture of NaCl and KCl, with a molar ratio of NaCl to KCl of 1:1. This NaCl-KCl mixed salt has a low eutectic point and can form a uniform liquid phase medium environment at the calcination temperature. This liquid phase medium serves as a reaction medium to promote the borylation reaction and as a dispersant to effectively isolate precursor particles and prevent them from agglomerating at high temperatures, thereby facilitating the formation of nanostructured active components with uniform particle size and high specific surface area.

[0045] In a preferred embodiment, in step S4, the calcination is carried out at 800~1000℃; the inert atmosphere is argon; and the heating rate is 5~20℃·min. -1 The heat preservation time is 0.5~3 hours.

[0046] In this embodiment, the calcination temperature is controlled within the range of 800℃ to 1000℃, preferably 900℃. Within this temperature range, the NaCl-KCl mixed molten salt can be fully melted to form a liquid phase medium, while the borylation reaction between the precursor and the boron source can proceed fully, transforming the metal component into a catalytically active boride phase. An argon atmosphere is used as the inert atmosphere to prevent oxidation of the material at high temperatures. The heating rate is controlled at 5℃·min. -1 up to 20℃·min -1 Within the range, preferably 10℃·min -1 The heat preservation time should be controlled within the range of 0.5h to 3h, preferably 1 hour. The appropriate heat preservation time can ensure that the boronization reaction is fully completed, while avoiding excessive growth of active particles due to prolonged high-temperature treatment.

[0047] In a preferred embodiment, step S5 includes: ultrasonic washing with hot water to remove B2O3 and residual molten salt, followed by washing with deionized water and ethanol in sequence; the drying temperature is 60~100℃ and the time is 8~16h.

[0048] In this embodiment, the washing process first involves ultrasonic washing with hot water, preferably at a temperature of 80°C, to fully dissolve and remove the B2O3 byproducts generated during calcination and the residual NaCl-KCl molten salt. Subsequently, the process involves washing with deionized water and ethanol in sequence to further remove residual soluble impurities and organic contaminants. The drying temperature is controlled within the range of 60°C to 100°C, preferably 80°C. The drying time is controlled within the range of 8 hours to 16 hours, preferably overnight. After the above washing and drying steps, a pure and dry boronized MoNi-supported nickel foam self-supporting catalyst can be obtained.

[0049] A boronized MoNi-supported nickel foam self-supporting catalyst was prepared by the above-described preparation method.

[0050] In this embodiment, the catalyst uses nickel foam as a three-dimensional conductive support framework. The MoNiB active component, formed by the boronization conversion of the Anderson-type MoNi polyoxometalate precursor, is uniformly and firmly loaded on the surface of the nickel foam. The open porous structure of the nickel foam facilitates rapid electrolyte wetting, timely desorption of gaseous products, and full exposure of active sites. The introduction of boron effectively regulates the electronic structure of the MoNi component, enhances the interfacial charge transport capacity, and optimizes the adsorption and desorption process of reaction intermediates. At the same time, since the catalyst can achieve integration of the active component and the substrate without the addition of an external binder, it avoids the problems of binders obscuring active sites and increasing interfacial resistance, thus exhibiting excellent electrocatalytic activity and structural stability.

[0051] Application of a boronized MoNi-supported nickel foam self-supporting catalyst in water electrolysis.

[0052] In this embodiment, the catalyst is particularly suitable for hydrogen evolution reaction, oxygen evolution reaction or overall water splitting process under alkaline conditions. In application, the catalyst can be used directly as a working electrode without additional electrode preparation processes such as slurrying and coating, simplifying the construction process of the water electrolysis device. Thanks to its multi-element synergistically regulated active components, good conductive network and stable self-supporting structure, the catalyst can achieve a high current density at a low overpotential and maintain a stable current output during long-term electrolysis, exhibiting excellent bifunctional catalytic activity and durability.

[0053] Example 2 Based on the foregoing, this embodiment, in conjunction with the accompanying drawings, further elaborates on the technical solution of this application: This technical solution constructs a boronized MoNi-supported nickel foam self-supporting catalyst. Using nickel foam as a three-dimensional conductive framework and Anderson-type MoNi polyoxometalate as a precursor, a robustly supported MoNi active layer is formed on the surface of the nickel foam through a molten salt-assisted in-situ boronization reaction. This preparation route achieves synergistic optimization of several key aspects, including uniform molecular-scale dispersion of the precursor, regulation of the electronic structure of boron, confined reaction in a molten salt medium, and binder-free self-supporting integration of the active components. This results in a catalytic material with high conductivity, abundant active sites, and excellent structural stability. The specific implementation methods of each step are described in detail below.

[0054] Step S1 involves the preparation of Anderson-type MoNi polyoxometalate precursors. The nickel source is nickel nitrate hydrate, typically nickel nitrate hexahydrate; the molybdenum source is ammonium molybdate hydrate, typically ammonium molybdate tetrahydrate. The molar ratio of nickel to molybdenum is controlled within the range of 1:3 to 1:8. A suitable molar ratio is crucial for forming well-structured Anderson-type polyoxometalates. If the ratio deviates from this range, other impurities may be generated or the precursor structure may be incomplete, thus affecting the quality of the active phase formation during subsequent boration. Specifically, when the molar ratio of nickel to molybdenum is 1:6, the precursor... The precursor has the most regular structure. In the specific operation, the weighed nickel nitrate hexahydrate and ammonium molybdate tetrahydrate are added to boiling deionized water to dissolve them completely. Then, the system temperature is maintained between 80°C and 90°C for the reaction. Within this temperature range, the condensation reaction between molybdate ions and nickel ions in the aqueous solution can proceed fully, gradually constructing the structural unit unique to Anderson-type clusters, where the central heteroatom is surrounded by six molybdenum-oxygen octahedra. After the reaction is completed, the product is centrifuged and dried to obtain a solid powdered Anderson-type MoNi polyoxometalate precursor.

[0055] Figure 3 The X-ray diffraction pattern of the precursor prepared under the above conditions is shown. It can be seen that the precursor exhibits strong and sharp characteristic diffraction peaks in the low-angle region, with clear peak positions and symmetrical peak shapes, indicating that the product has good crystallinity and a regular crystal structure, which is consistent with the typical diffraction characteristics of Anderson-type polyoxometalates. This highly ordered structure means that Mo and Ni elements have achieved uniform distribution and fixed stoichiometry at the molecular scale in the precursor, avoiding random mixing or segregation of the two metal elements, and laying an important structural foundation for the formation of a homogeneous active phase in the subsequent borylation process.

[0056] Step S2 involves mixing the precursor with a boron source to obtain a mixture of the precursor and boron. The boron source can be selected from at least one of boron powder, boric acid, sodium borohydride, and melamine borate. Boron powder is preferred due to its simple composition, ability to directly undergo solid-phase boration with the metal component at high temperatures, and relatively simple and easily removed byproducts. The mass ratio of the precursor to the boron source is controlled between 2:1 and 2:5, providing sufficient boron atoms for complete boration of the system. Insufficient boron source will prevent the metal component from being completely converted into an active borated phase, resulting in low activity of the remaining unboronized component. Excessive boron source can lead to oxidation at high temperatures, forming a B2O3 glass phase, which increases the burden of subsequent washing and removal and may also encapsulate some active sites. The mixing process can be achieved through grinding, with a grinding time of 10 to 60 minutes, and a more thorough grinding time of 30 minutes. Through solid-phase grinding, the precursor powder and boron source powder are dispersed and in close contact under mechanical force, forming a macroscopically uniform mixture of precursor and boron. This close contact shortens the diffusion distance of boron atoms into the metal component during subsequent high-temperature reactions, facilitating a more complete and uniform boronization reaction.

[0057] Step S3 introduces a molten salt medium, which is used to uniformly mix the precursor and boron mixture to obtain a precursor mixture. The molten salt medium is a mixture of NaCl and KCl in a molar ratio of 1:1. This eutectic ratio mixed salt has a low eutectic point and can completely melt at the calcination temperature to form a uniform liquid phase medium environment. This liquid phase medium plays multiple roles in this technical solution: as a reaction medium, it promotes the mass transfer and interfacial reaction between the boron source and the precursor; as a dispersant, it encapsulates the precursor particles in liquid phase form, using the spatial isolation effect of the liquid phase to inhibit the mutual contact and fusion growth of nanoparticles at high temperatures; it provides a confined reaction environment, allowing the borylation reaction to take place in the liquid phase micro-region, which helps to form a product with uniform particle size and good crystallinity. During operation, the pre-ground NaCl-KCl mixed salt is combined with the aforementioned precursor and boron mixture and ground thoroughly again to achieve uniform blending of the three phase components in the solid state, thus obtaining the precursor mixture.

[0058] Step S4 is the crucial high-temperature calcination step, where the precursor mixture and the nickel foam substrate are calcined together in an inert atmosphere to complete the boration reaction and in-situ loading of the active components. The calcination temperature is controlled within the range of 800℃ to 1000℃. The lower limit of this temperature range must ensure that the NaCl-KCl mixed salt can completely melt to form a liquid medium environment sufficient to drive the boration reaction, while the upper limit must avoid excessive sintering and growth of active particles due to excessive temperature, thereby reducing the specific surface area and the number of active sites. Among these, 900℃ is the preferred temperature for balancing the sufficiency of the reaction and the dispersibility of the product. An argon atmosphere is used as the inert atmosphere to prevent the metal and boron components from being oxidized at high temperatures, ensuring that the boration reaction proceeds smoothly in an inert environment. The heating rate is controlled at 5℃·min. -1 up to 20℃·min -1 A suitable heating rate is 10℃·min. -1 This ensures heating efficiency while avoiding excessively rapid heating that could lead to large temperature differences within the system. The holding time is controlled between 0.5 and 3 hours, with 1 hour being the preferred holding time, which is sufficient to allow the borylation reaction to be fully completed and the active component to crystallize and stabilize.

[0059] During this calcination process, the following synergistic changes occurred: the original clustered structure of the Anderson-type MoNi polyoxometalate precursor underwent deconstruction and recombination at high temperature, reacting with boron atoms provided by the boron source to generate a catalytically active borated MoNi phase; the molten salt liquid medium encapsulated and dispersed the reaction products, preventing their aggregation; simultaneously, the newly generated borated MoNi active components were deposited and bonded in situ on the surface of the three-dimensional porous framework of the nickel foam, forming a firmly attached active layer; in this process, the nickel foam not only served as an inert substrate, but its nickel element may also participate in the chemical bonding at the interface to a certain extent, enhancing the bonding force between the active layer and the substrate.

[0060] Figure 1 The X-ray diffraction pattern of the calcined product is shown; and... Figure 3 Compared with the diffraction pattern of the precursor shown, the peak position and peak shape distribution have changed significantly, and characteristic diffraction peaks corresponding to the boronized MoNi phase have appeared, confirming that the phase structure of the precursor has undergone the expected transformation during the boronization and loading process, and the target active component has been successfully generated. Figure 2 Transmission electron microscopy images of the product are shown. At low magnification, the sample exhibits a loose aggregate structure formed by interconnected nanoscale particles, with a relatively continuous overall distribution. At high magnification, clear lattice fringes can be observed in local areas, indicating that the formed boroide MoNi active component possesses certain crystal characteristics. This loosely aggregated nanoscale microstructure is conducive to exposing more surface active regions, providing abundant active sites for electrocatalytic reactions. At the same time, the gaps between particles facilitate the penetration of electrolyte and the escape of gaseous products.

[0061] Step S5 involves washing and drying the calcined product to remove impurities and obtain the final catalyst. First, ultrasonic washing with hot water (preferably 80°C) is performed. With ultrasonic assistance, the hot water effectively penetrates the product, fully dissolving and removing the B2O3 byproduct generated during calcination, as well as residual NaCl-KCl molten salt. B2O3 is an oxidation product that may form from excess boron at high temperatures; it has a certain degree of adhesion, and if not thoroughly removed, it will cover active sites and reduce catalytic performance. Removal of residual molten salt ensures the purity of the catalyst surface. Subsequently, washing is performed sequentially with deionized water and ethanol. Deionized water further cleans residual water-soluble impurities, while ethanol washing helps remove organic contaminants and utilizes its volatility to promote subsequent drying. The drying temperature is controlled within the range of 60°C to 100°C, preferably 80°C, and the drying time is generally controlled within 8 to 16 hours, typically overnight drying. After the above treatment, a pure and dry borated MoNi-supported nickel foam self-supporting catalyst is obtained.

[0062] The boronized MoNi-supported nickel foam self-supporting catalyst prepared through the above steps has the following structural features: with nickel foam as a three-dimensional conductive support framework, the boronized MoNi active components generated through in-situ reaction are uniformly and firmly loaded on the framework in nanoscale particles. The active components form direct electrical contact and mechanical bonding with the substrate, without the need for binders, thereby reducing interfacial resistance and avoiding the shielding of active sites by binders; the introduction of boron modulates the electronic structure of the MoNi components and optimizes the adsorption energy of catalytic reaction intermediates.

[0063] Figure 4 and Figure 5 Linear sweep voltammetry curves of the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) of the catalyst in a 1.0 MkOH alkaline solution are shown. A three-electrode system was used, with the prepared catalyst directly as the working electrode, and the electrode area was 0.5 × 0.5 cm². In the OER reaction, a current of 10 mA·cm⁻¹ was achieved. -2 The overpotential required for the current density is only 220 mV; in the hydrogen evolution reaction, the overpotential at the same current density is only 65 mV. These performance data are superior to most non-noble metal catalysts reported to date, confirming that the prepared catalyst has excellent bifunctional electrocatalytic activity and good reaction kinetics. At the same time, the self-supporting structure of nickel foam gives the catalyst the convenience of avoiding secondary slurry coating in practical use, and it can be used directly as a working electrode. Moreover, the structure remains intact after long-term operation, showing good stability.

[0064] Based on the above technical solution, the parameters of each step can be flexibly adjusted within a given range. For example, in step S2, sodium borohydride can be used instead of boron powder as the boron source, and the mass ratio of the precursor to the boron source can be adjusted to 2:1. Sodium borohydride decomposes at high temperature to provide boron atoms, and the released hydrogen can further enhance the reducing atmosphere of the system. The resulting catalyst also exhibits good oxygen evolution and hydrogen evolution activities. As another example, in step S4, the calcination temperature can be adjusted to 800℃, and the holding time can be extended to 3 hours. Under these conditions, the lower calcination temperature combined with the longer holding time can still ensure that the borylation reaction is fully completed, and the resulting catalyst has a solid active component loading and excellent catalytic performance.

[0065] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0066] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for preparing a boronized MoNi-supported nickel foam self-supporting catalyst, characterized in that, Includes the following steps: S1. React nickel source and molybdenum source in a solvent to prepare Anderson-type MoNi polyoxometalate precursor; S2. The precursor is mixed with a boron source to obtain a mixture of the precursor and boron; S3. The mixture of the precursor and boron is mixed evenly with a molten salt medium to obtain a precursor mixture; S4. The precursor mixture and the nickel foam substrate are calcined under an inert atmosphere to cause the precursor to undergo a borylation reaction and be loaded onto the nickel foam. S5. The calcined product is washed and dried to obtain the boronized MoNi-supported nickel foam self-supporting catalyst; In step S1, the nickel source is nickel nitrate hydrate, and the molybdenum source is ammonium molybdate hydrate; The reaction of nickel and molybdenum sources in a solvent includes: dissolving nickel nitrate hydrate and ammonium molybdate hydrate in boiling deionized water, reacting them at 80-90°C, centrifuging and drying to obtain the Anderson-type MoNi polyoxometalate precursor; In step S2, the mass ratio of the precursor to the boron source is 2:1 to 2:5; In step S4, the calcination is carried out at 800~1000℃; the inert atmosphere is argon; and the heating rate is 5~20℃·min. -1 The heat preservation time is 0.5~3 hours; In step S1, the molar ratio of nickel source to molybdenum source is 1:6, calculated as nickel and molybdenum elements. In step S2, the boron source is boron powder or sodium borohydride; In step S3, the molten salt medium is a mixture of NaCl and KCl, and the molar ratio of NaCl to KCl is 1:1; In step S5, the washing includes: ultrasonic washing with hot water to remove B2O3 and residual molten salt, followed by washing with deionized water and ethanol in sequence; the drying temperature is 60~100℃ and the time is 8~16h.

2. A boronized MoNi-supported nickel foam self-supporting catalyst, characterized in that, It is prepared by the preparation method described in claim 1.

3. The application of the boronized MoNi-supported nickel foam self-supporting catalyst according to claim 2 in water electrolysis.

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