A catalyst, a method for preparing the catalyst, and a battery

Abstract

The application provides a catalyst, a preparation method of the catalyst and a battery, and relates to the technical field of batteries. A specific technical scheme is as follows: the catalyst comprises a core, a protective layer and a passivation layer; the core comprises a plurality of transition metal carbides; the protective layer is coated outside the core, and the protective layer has conductivity; the passivation layer comprises hydrated oxyhydroxide, and the passivation layer is coated outside the protective layer; the catalyst has high catalytic activity, excellent structural stability, strong corrosion resistance, and low cost.

Description

Technical Field

[0001] This application relates to the field of battery technology, and more particularly to a catalyst, a method for preparing the catalyst, and a battery. Background Technology

[0002] Platinum, a precious metal, is commonly used as a catalyst in related technologies, but its cost is high. To save costs, some technologies also use non-precious metals (such as transition metals) as catalytic materials. However, when these catalysts are applied to batteries, under long-term operating conditions, the catalyst is constantly exposed to an acidic electrolyte environment, inevitably leading to complex structural evolution on the catalyst surface, including valence state changes and dissolution of active components. These microscale structural evolutions often result in a significant loss of active sites and a gradual deterioration of the electronic structure, ultimately causing a sharp decline in the catalyst's catalytic activity.

[0003] Therefore, how to design a catalyst that combines high catalytic activity, excellent structural stability, corrosion resistance, and low cost is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0004] This application provides a catalyst, a method for preparing the catalyst, and a battery. The catalyst has high catalytic activity, excellent structural stability, strong corrosion resistance, and low cost.

[0005] To achieve the above objectives, the embodiments of this application adopt the following technical solutions: In the first aspect, a catalyst is provided, which includes a core, a protective layer and a passivation layer. The core includes a variety of transition metal carbides, which are non-precious metal catalytic materials with a platinum-like electronic structure and good intrinsic catalytic activity. While ensuring the high catalytic activity of the catalyst, the cost of the catalyst can also be reduced compared to platinum catalysts.

[0006] The protective layer covers the outside of the core and is conductive, allowing electrons to be transferred between the core and the passivation layer. By covering the outside of the core, the core can be isolated from corrosive external environments (such as acidic electrolytes), protecting it from oxidation or agglomeration. This can inhibit the dissolution, migration, or agglomeration of metals in the core, significantly improving the catalyst's corrosion resistance and long-term stability.

[0007] The passivation layer comprises hydrated hydroxyoxides, which coat the exterior of the protective layer. It's important to note that the hydrated hydroxyoxides themselves are highly active electrocatalytic phases, stably providing high-valence metal active sites. Thus, the passivation layer acts as the main reaction interface, allowing the electrolyte to directly undergo adsorption, activation, and redox reactions at these active sites. The passivation layer absorbs the electrochemical reaction potential loss, reducing direct electrolyte erosion of the internal carbide lattice and minimizing the continuous oxidation of transition metal carbides into readily soluble oxides, effectively inhibiting further dissolution of metal ions from the core. The transition metal carbides in the core rapidly transfer electrons to the passivation layer, providing an electron source for the electrocatalytic reactions within the passivation layer.

[0008] In addition, hydrated hydroxyl oxides can anchor metals through lattice doping and interfacial bonding. Even if a small amount of metal on the surface undergoes a valence state change, it is difficult for it to detach from the matrix and enter the electrolyte, which can significantly reduce the dissolution rate of metal ions.

[0009] As can be seen from the above, the catalyst in this application embodiment maintains high catalytic activity while also possessing excellent structural stability and strong corrosion resistance, thereby achieving long-term stability in an electrochemical environment, and at a low cost.

[0010] In one possible implementation of the first aspect, the core comprises a molybdenum carbide / tungsten carbide heterostructure, which modulates the catalyst's antioxidant capacity. The heterostructure interface between Mo2C and WC can induce electron redistribution between the metals, regulate surface oxidation behavior, reduce the tendency of surface metal oxidation and dissolution, and enable the catalyst to maintain stable catalytic activity during long-term operation.

[0011] In one possible implementation of the first aspect, the protective layer comprises at least one of heteroatom-doped carbon materials, conductive polymer-derived carbon materials, graphene, carbon nanotubes, mesoporous carbon, amorphous carbon, boron nitride, carbon nitride, and transition metal nitrides.

[0012] The aforementioned materials all possess a continuous rigid framework structure, resistance to acid and alkali corrosion, adjustable conductivity, and high specific surface area. They can provide physical confinement, chemical protection, and electronic transport channels for the metal carbide core, thereby enabling the protective layer to have conductivity, chemical stability, and confinement function.

[0013] In one possible implementation of the first aspect, the mass ratio of molybdenum to tungsten in the catalyst is 1:1 to 1:20. It should be understood that in the Mo2C / WC heterostructure, WC provides high specific surface area and conductive support, while Mo2C provides the main active sites. When the mass ratio of molybdenum to tungsten in the catalyst is greater than 1:1, the content of Mo2C is too high and the content of WC is insufficient, resulting in WC failing to form a complete Mo2C / WC heterostructure interface with Mo2C, leading to reduced catalytic performance; simultaneously, it increases the degree of metal oxidation, reducing the heterostructure. When the mass ratio of molybdenum to tungsten in the catalyst is less than 1:20, the content of W is too high and the content of Mo is insufficient; excess W easily forms inert WO3 during calcination. x Species cover active sites and weaken the electronic coupling effect of heterostructures, thus reducing the catalytic performance of the catalyst.

[0014] Therefore, by having a suitable mass ratio of molybdenum to tungsten in the catalyst, it is possible to ensure that WC and Mo2C form a good Mo2C / WC heterointerface, reducing the degree of metal oxidation; and also to provide the catalyst with enough active sites to react with the electrolyte, which helps to improve the catalyst's catalytic performance.

[0015] In one possible implementation of the first aspect, the mass fraction of the molybdenum carbide / tungsten carbide heterostructure in the catalyst is 50% to 80%. It should be understood that when the mass fraction of the Mo2C / WC heterostructure is less than 50%, the content of the active component in catalyst 1 is too low, leading to a decrease in the catalyst's catalytic performance; when the mass fraction of the Mo2C / WC heterostructure is greater than 80%, it is difficult for the protective layer to uniformly coat the core, and the exposed metal sites of Mo2C and WC will preferentially oxidize and dissolve in an acidic environment, reducing the long-term stability of the catalyst.

[0016] Therefore, by having the mass fraction of Mo2C / WC heterostructure in the catalyst be 50%~80%, not only can the content of active components in the catalyst be guaranteed, thus ensuring the catalytic performance of the catalyst, but also the core can be coated as much as possible in the protective layer, reducing the oxidation and dissolution of metal by the acidic environment, thereby improving the long-term stability of the catalyst.

[0017] In one possible implementation of the first aspect, the passivation layer has the chemical structural formula MC-(OH)x, where M represents a transition metal element. This passivation layer can be formed in situ by the reconstruction of a transition metal carbide during electrochemical activation. The surface of transition metal carbides contains numerous dangling bonds and defect sites, making them highly susceptible to oxidation and dissociation into metal ions. The hydrated hydroxyl oxides formed after in-situ reconstruction fill these surface defect sites and end-cap active bonds, thereby reducing easily soluble and unstable active sites at their source. Furthermore, MC-(OH)x itself is a highly active electrocatalytic phase, stably providing high-valence metal active sites and enhancing the catalytic activity of the catalyst.

[0018] In one possible implementation of the first aspect, the thickness of the protective layer is 2 nm to 5 nm, enabling it to physically confine and chemically protect the core, reducing the dissolution of metal ions from the core. Furthermore, it avoids the problem of excessive mass transfer resistance between reactants and products caused by an excessively thick protective layer, thus ensuring the electrocatalytic efficiency of the catalyst.

[0019] In one possible implementation of the first aspect, the passivation layer thickness is 1 nm to 3 nm. It is understandable that when the passivation layer thickness is too small, it is difficult to effectively protect the transition metal center, and the active sites of the transition metal center are continuously exposed to the corrosive environment, making the metal easily oxidized and dissolved. When the passivation layer thickness is too large, it significantly increases mass transfer resistance and contact resistance, leading to a decrease in catalytic activity.

[0020] By using a passivation layer with a thickness of 1nm to 3nm, the transition metal center can be effectively protected, preventing the active sites of the transition metal center from being continuously exposed to the corrosive environment. At the same time, it can reduce mass transfer resistance and contact resistance, thus ensuring the catalytic activity of the catalyst.

[0021] Secondly, a method for preparing a catalyst is provided, the method comprising: First, provide transition metal sources and carbon and nitrogen sources; Then, the transition metal source and the carbon-nitrogen source are processed to obtain an intermediate material, which includes a core and a protective layer. The protective layer covers the core and is conductive. The core includes a transition metal carbide. Finally, the intermediate material was placed in an acidic electrolyte for cyclic voltammetry scanning, which allowed the surface of the intermediate material to be reconstructed in situ to form a passivation layer, thus obtaining the catalyst.

[0022] Understandably, the beneficial effects of the catalyst prepared by this method can be found in the first aspect and any possible implementation thereof, and will not be repeated here.

[0023] Furthermore, by placing the intermediate material in an acidic electrolyte for cyclic voltammetry scanning, a stable passivation layer is formed through electrochemically driven dynamic surface reconstruction, effectively suppressing metal dissolution from the catalyst. The carbon substrate undergoes structural evolution during electrochemical cycling, forming robust MOC bonds with the transition metal center. Even after multiple cycles, the catalyst maintains its intact core-shell structure.

[0024] In one possible implementation of the second aspect, the protective layer comprises at least one selected from heteroatom-doped carbon materials, conductive polymer-derived carbon materials, graphene, carbon nanotubes, mesoporous carbon, amorphous carbon, boron nitride, carbon nitride, and transition metal nitrides. The beneficial effects of the protective layer can be referred to in the description of the beneficial effects of the protective layer in the first aspect of the technical solution, and will not be repeated here.

[0025] In one possible implementation of the second aspect, the transition metal source includes molybdenum and tungsten sources, and the carbon-nitrogen source includes dopamine. Molybdenum and tungsten sources are low-cost and readily available. Dopamine can serve as both a carbon-nitrogen source and a chelating agent. The catechol groups of dopamine have the ability to chelate and adsorb metal ions, and can fully coordinate with Mo / W oxygen anions. In high-temperature environments, it can promote the dispersion of metal oxide nanoparticles and stabilize them as metal centers, preventing the migration or aggregation of metal oxide nanoparticles.

[0026] In one possible implementation of the second aspect, the molybdenum source includes at least one of ammonium paramolybdate, ammonium phosphomolybdate, ammonium tetrathiomolybdate, phosphomolybdic acid, sodium molybdate, and sodium phosphomolybdate, wherein the molybdenum source is low in cost and readily available.

[0027] In one possible implementation of the second aspect, the tungsten source includes at least one of ammonium paratungstate, ammonium phosphotungstate, and sodium tungstate, which are low in cost and readily available.

[0028] In one possible implementation of the second aspect, the method for processing the transition metal source and the carbon-nitrogen source includes: First, the molybdenum source is divided into a first part and a second part. The first part is subjected to hydrothermal treatment to obtain molybdenum oxide nanotubes. Then, the molybdenum oxide nanotubes, the second part, the tungsten source, and dopamine were mixed and reacted to obtain the molybdenum / tungsten-polydopamine precursor; Finally, the molybdenum / tungsten-polydopamine precursor was sintered at high temperature to obtain an intermediate material, which was a Mo2C / WC@NC composite material.

[0029] By first preparing molybdenum oxide nanotubes, and then mixing and reacting them with the second part, a tungsten source, and dopamine, molybdenum and tungsten can be uniformly anchored on the surface or within the pores of the molybdenum oxide nanotubes, avoiding agglomeration between the molybdenum and tungsten sources. The nitrogen-doped carbon layer forms in situ during high-temperature carbonization, physically confining the internal metal nanoparticles, inhibiting their migration and agglomeration, and ensuring high-density exposure of active sites.

[0030] In one possible implementation of the second aspect, the ratio of the molybdenum mass in the molybdenum oxide nanotubes to the molybdenum mass in the second part is 2 / 7 to 2. This ratio modulates the carbonization behavior of different molybdenum sources and the intermetallic electron distribution in the reaction system.

[0031] When the ratio A of the molybdenum mass in the molybdenum oxide nanotubes to the molybdenum mass in the second part exceeds 2, the molybdenum oxide nanotube template is excessive and prone to accumulation, causing blockage of the mesoporous structure and making it difficult to form a complete Mo2C / WC heterostructure interface in the reaction system. When the ratio A of the molybdenum mass in the molybdenum oxide nanotubes to the molybdenum mass in the second part is less than 2 / 7, the confined structure in the reaction system cannot be continuously constructed, and the number of nucleation sites after the decomposition of the molybdenum oxide nanotube template is insufficient, resulting in uneven formation of the Mo2C / WC heterostructure.

[0032] When the ratio A of the molybdenum mass in the molybdenum oxide nanotubes to the molybdenum mass in the second part is in the range of 2 / 7 to 2, the catalyst can generate a confined structure and a uniform Mo2C / WC heterostructure, resulting in less activity decay after long-term cycling. Therefore, the catalyst exhibits enhanced catalytic activity and excellent catalytic performance.

[0033] In one possible implementation of the second aspect, the molybdenum / tungsten-polydopamine precursor is placed in an inert gas and kept there for a first preset time; the temperature of the inert gas is 700℃~1000℃, and the first preset time is 2h~5h. This allows the Mo / W-PDA precursor to undergo carbonization pyrolysis, balances the degree of carbonization, ensures the formation of a uniform Mo2C / WC heterostructure, and avoids thermal deactivation of the catalyst due to excessively high temperatures.

[0034] Thirdly, a battery is provided, the battery including a catalyst layer comprising the catalyst described in the first aspect; and / or, the catalyst layer comprising a catalyst prepared by the preparation method described in the second aspect.

[0035] Understandably, the beneficial effects of this battery can be seen in the first aspect and any possible implementation thereof, as well as the beneficial effects of the catalyst, which will not be repeated here. Attached Figure Description

[0036] Figure 1 Microscopic images of the catalysts provided in some embodiments of this application under a transmission electron microscope; Figure 2 Partial microstructure of the catalysts provided in some embodiments of this application under a high-resolution transmission electron microscope Figure 1 ; Figure 3 Partial microstructure of the catalysts provided in some embodiments of this application under a high-resolution transmission electron microscope Figure 2 ; Figure 4 for Figure 3 Enlarged view of the circled part at point C; Figure 5 for Figure 3 Enlarged view of the circled area at point D; Figure 6 Microscopic morphology images of intermediate substances provided in some embodiments of this application under a transmission electron microscope; Figure 7 O 1s XPS comparison spectra of catalysts prepared for the activation group and control group provided in some embodiments of this application Figure 1 ; Figure 8 O 1s XPS comparison spectra of catalysts prepared for the activation group and control group provided in some embodiments of this application Figure 2 .

[0037] Figure label: 1. Catalyst; 2. Passivation layer. Detailed Implementation

[0038] Hereinafter, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this embodiment, unless otherwise stated, "a plurality of" means two or more.

[0039] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.

[0040] In the description of the embodiments of this application, "and / or" is merely a way of describing the relationship between related objects, indicating that there can be three relationships. For example, A and / or B can represent three situations: A exists alone, A and B exist simultaneously, and B exists alone.

[0041] The battery comprises electrodes, an electrolyte, and a catalyst layer, with the catalyst layer disposed on the surface of the electrodes. The catalyst layer includes a catalyst, which promotes oxidation and reduction reactions. The long-term stability of the catalyst is one of the important indicators for evaluating its practical application potential. The aforementioned battery can be a fuel cell or a flow battery; the fuel cell can be a hydrogen fuel cell (e.g., a proton exchange membrane battery).

[0042] Unless otherwise specified, the battery described in this application is a hydrogen fuel cell, which does not imply any limitation on this application.

[0043] In the electrochemical reactions of hydrogen fuel cells, the main reactions involved are the hydrogen oxidation reaction (HOR) at the anode and the oxygen reduction reaction (ORR) at the cathode. The main role of the catalyst is to promote the occurrence of hydrogen oxidation and oxygen reduction reactions, thereby generating electrical energy.

[0044] Platinum, a precious metal, is commonly used as a catalyst in related technologies, but its cost is high. To save costs, some technologies also use non-precious metals (such as transition metals) as catalytic materials. However, when these catalysts are applied to batteries, under long-term operating conditions, the catalyst is constantly exposed to an acidic electrolyte environment, inevitably leading to complex structural evolution on the catalyst surface, including valence state changes and dissolution of active components. These microscopic structural evolutions often result in a significant loss of active sites and a gradual deterioration of the electronic structure, ultimately causing a sharp decline in the catalyst's catalytic performance.

[0045] Transition metal carbides, as an important class of non-noble metal catalytic materials, have become a research hotspot due to their unique platinum-like electronic structure and excellent intrinsic catalytic activity. However, under strongly acidic conditions, the surface of carbide-based catalysts is prone to electrochemical oxidation, leading to the transformation of the active phase into higher valence oxides. The corrosion behavior of carbon supports under acidic potential alternation conditions further exacerbates the destruction of the catalyst structure, exposing the transition metals coated inside the carbon layer to a corrosive environment, resulting in significant dissolution losses of metal ions.

[0046] Therefore, how to design a catalyst that combines high catalytic activity, excellent structural stability, corrosion resistance, and low cost is a technical problem that urgently needs to be solved in this field.

[0047] Please see Figure 1 and Figure 2 , Figure 1 Microscopic images of catalyst 1 provided in some embodiments of this application under a transmission electron microscope; Figure 2 Partial microstructure of catalyst 1 provided in some embodiments of this application under a high-resolution transmission electron microscope Figure 1 To address the aforementioned problems, this application provides a catalyst 1, which includes a core, a protective layer, and a passivation layer 2. The catalyst 1 exhibits a capsule-like microstructure under a transmission electron microscope, with a maximum particle size of approximately 100 nm.

[0048] The core includes various transition metal carbides, which are non-precious metal catalytic materials with platinum-like electronic structures and good intrinsic catalytic activity. While ensuring the high catalytic activity of catalyst 1, the cost of catalyst 1 can also be reduced compared to platinum catalysts.

[0049] For example, the transition metal in catalyst 1 may include molybdenum (Mo) and tungsten (W). Alternatively, the transition metal in catalyst 1 may be one or more of group IVB, VB, and VIB transition metals such as Ti, Zr, V, Nb, and Cr, or binary or multi-component combinations of the above metals with Mo and / or W. Different transition metals can achieve differentiated catalytic performance and passivation behavior through electronic structure modulation.

[0050] Taking Mo and W as transition metals as examples, catalyst 1 includes two transition metal carbides, molybdenum carbide (Mo2C) and tungsten carbide (WC), and Mo2C and WC form a Mo2C / WC heterostructure. This bimetallic heterostructure regulates the antioxidant capacity of catalyst 1. The hetero interface between Mo2C and WC can induce the redistribution of electrons between the metals, regulate the surface oxidation behavior, reduce the tendency of surface metal oxidation and dissolution, and enable the catalyst to maintain stable catalytic activity during long-term operation.

[0051] It should be noted that the " / " in the molybdenum carbide / tungsten carbide heterostructure (i.e., Mo2C / WC heterostructure) indicates "loaded on"; Mo2C / WC means Mo2C is loaded on the surface of WC. The same understanding applies to Mo2C / WC in the following description, and therefore will not be repeated. The transition metal carbides in catalyst 1 are metal nanoparticles.

[0052] See Figures 3-5 , Figure 3 Partial microstructure of catalyst 1 provided in some embodiments of this application under a high-resolution transmission electron microscope Figure 2 ; Figure 4 for Figure 3 Enlarged view of the circled part at point C; Figure 5 for Figure 3 Enlarged view of the circled part at point D; the image shows clear heterogeneous interface lattice fringes, where the 0.21 nm lattice fringes correspond to the (100) crystal plane of Mo2C and the 0.13 nm lattice fringes correspond to the (110) crystal plane of WC.

[0053] The protective layer covers the outside of the core, and the protective layer and the core together form a core-shell structure. The active center of the bimetallic carbide is composed of Mo2C and WC nanocrystals.

[0054] For example, the protective layer may include at least one of heteroatom-doped carbon materials, conductive polymer-derived carbon, graphene, carbon nanotubes, mesoporous carbon, amorphous carbon, boron nitride, carbon nitride, and transition metal nitrides. The heteroatom-doped carbon material may be nitrogen-doped carbon, with nitrogen atoms distributed in the carbon framework as dopant to construct defect sites and conductive channels; alternatively, the heteroatom-doped carbon material may be heteroatom-doped carbon such as boron, phosphorus, or sulfur. The conductive polymer-derived carbon material may be carbon material derived from conductive polymers such as polypyrrole, polyaniline, or polythiophene.

[0055] The aforementioned materials all possess a continuous rigid framework structure, resistance to acid and alkali corrosion, adjustable conductivity, and high specific surface area. They can provide physical confinement, chemical protection, and electron transport channels for the metal carbide core, thereby enabling the protective layer to have conductivity, chemical stability, and confinement function.

[0056] The conductive protective layer allows for electron transfer between the core and the passivation layer. By encasing the core, the protective layer isolates it from corrosive external environments (such as acidic electrolytes), protecting it from oxidation or agglomeration. This inhibits the dissolution, migration, or agglomeration of metals within the core, significantly improving the corrosion resistance and long-term stability of catalyst 1.

[0057] Passivation layer 2 comprises hydrated hydroxy oxide and is coated on the outside of the protective layer. This passivation layer 2 is an amorphous passivation layer 2 with the chemical structural formula MC-(OH)x, where M represents a transition metal element (Mo or W).

[0058] The passivation layer 2 can be formed by in-situ reconstruction of transition metal carbides during electrochemical activation. The surface of transition metal carbides has a large number of dangling bonds and defect sites, which are easily oxidized and dissociated into metal ions; while the hydrated hydroxyl oxides formed after in-situ reconstruction fill the surface defect sites and end active bond breaks, thereby reducing the unstable active sites that are easily dissolved from the source.

[0059] Hydrated hydroxyl oxides are themselves highly active electrocatalytic phases, providing stable high-valence metal active sites and enhancing the catalytic activity of catalyst 1. In this way, passivation layer 2 acts as the main reaction interface, allowing the electrolyte to directly undergo adsorption, activation, and redox reactions at the active sites of passivation layer 2. Passivation layer 2 absorbs the electrochemical reaction potential loss, reducing direct erosion of the internal carbide lattice by the electrolyte and minimizing the continuous oxidation of transition metal carbides into easily soluble oxides, effectively inhibiting further dissolution of metal ions. The transition metal carbides in the core rapidly transfer electrons to passivation layer 2, providing an electron source for the electrocatalytic reaction in passivation layer 2 and reducing the dissolution of metal ions from the core.

[0060] In addition, hydrated hydroxyl oxides can anchor metals through lattice doping and interfacial bonding. Even if a small amount of metal on the surface undergoes a valence state change, it is difficult for it to detach from the matrix and enter the electrolyte, which can significantly reduce the dissolution rate of metal ions.

[0061] As can be seen from the above, the catalyst 1 in this embodiment of the application maintains high catalytic activity while also possessing excellent structural stability and strong corrosion resistance, thereby achieving long-term stability in an electrochemical environment, and at a low cost.

[0062] In some embodiments, the thickness of the protective layer is 2nm to 5nm, for example, the thickness of the protective layer can be 2nm, 3nm, 4nm, or 5nm. By using a protective layer thickness of 2nm to 5nm, the protective layer can achieve its physical confinement function and chemical protection of the core, reducing the dissolution of metal ions from the core; and it can avoid the reaction of excessively thick protective layers (e.g., H+) that could lead to the formation of reactive substances. + This addresses the issues of excessive mass transfer resistance of the reaction products and ensures the electrocatalytic efficiency of catalyst 1.

[0063] The thickness of passivation layer 2 is 1 nm to 3 nm; for example, the thickness of passivation layer 2 can be 1 nm, 1.5 nm, 2 nm, 2.5 nm, or 3 nm. Understandably, when the thickness of passivation layer 2 is too small, it is difficult to effectively protect the transition metal center, and the active sites of the transition metal center are continuously exposed to the corrosive environment, making the metal easily oxidized and dissolved. When the thickness of passivation layer 2 is too large, it significantly increases mass transfer resistance and contact resistance, leading to a decrease in catalytic activity.

[0064] With a passivation layer 2 having a thickness of 1nm~3nm, it can effectively protect the transition metal center, preventing the active sites of the transition metal center from being continuously exposed to the corrosive environment, and can also reduce mass transfer resistance and contact resistance, thus ensuring the catalytic activity of catalyst 1.

[0065] It should be noted that there are interfacial interpenetration and bonding transition regions between the core, protective layer, and passivation layer 2, without obvious boundaries. Different layers exhibit different bright and dark areas under high-resolution transmission electron microscopy (HRTEM). By measuring the dimensions of different areas, the thickness of the protective layer and the thickness of passivation layer 2 can be obtained.

[0066] In some embodiments, the mass ratio of molybdenum to tungsten in catalyst 1 is 1:1 to 1:20. For example, the mass ratio of molybdenum to tungsten in catalyst 1 can be 1:1, 1:2, 1:4, 1:6, 1:8, 1:10, 1:12, 1:14, 1:16, 1:18, or 1:20.

[0067] It should be understood that in the Mo2C / WC heterostructure, WC provides high specific surface area and conductive support, while Mo2C provides the main active sites. When the mass ratio of molybdenum to tungsten in catalyst 1 is greater than 1:1, the Mo2C content is too high and the WC content is insufficient, resulting in WC being unable to form a complete Mo2C / WC heterostructure interface with Mo2C, leading to a decrease in the catalytic performance of catalyst 1; at the same time, it increases the degree of metal oxidation, reducing the heterostructure. When the mass ratio of molybdenum to tungsten in catalyst 1 is less than 1:20, the W content is too high and the Mo content is insufficient; excess W easily forms inert WO3 during calcination. x The species, by covering the active sites and weakening the electronic coupling effect of the heterostructure, reduce the catalytic performance of catalyst 1.

[0068] Therefore, by having a suitable mass ratio of molybdenum to tungsten in catalyst 1, it is possible to ensure that WC and Mo2C form a good Mo2C / WC heterointerface, reducing the degree of metal oxidation; and it can also provide the catalyst with enough active sites to react with the electrolyte, which helps to improve the catalytic performance of catalyst 1.

[0069] In some embodiments, the mass fraction of the Mo2C / WC heterostructure in catalyst 1 is 50% to 80%. For example, the mass fraction of the Mo2C / WC heterostructure in catalyst 1 can be 50%, 50%, 50%, 50%, 50%, 50%, 80%.

[0070] It should be understood that when the mass fraction of the Mo2C / WC heterostructure is less than 50%, the content of the active component in catalyst 1 is too low, which leads to a decrease in the catalytic performance of catalyst 1. When the mass fraction of the Mo2C / WC heterostructure is greater than 80%, it is easy for the protective layer to be difficult to uniformly coat the core. The exposed metal sites of Mo2C and WC will preferentially oxidize and dissolve in the acidic environment, reducing the long-term stability of catalyst 1.

[0071] Therefore, by having the mass fraction of Mo2C / WC heterostructure in catalyst 1 be 50%~80%, not only can the content of active components in catalyst 1 be guaranteed, thus ensuring the catalytic performance of catalyst 1, but also the core can be coated as much as possible within the protective layer, reducing the oxidation and dissolution of metal by the acidic environment, thereby improving the long-term stability of catalyst 1.

[0072] Please see Figure 2 This application also provides a method for preparing catalyst 1, the method comprising: First, a transition metal source and a carbon and nitrogen source are provided.

[0073] Then, the transition metal source and the carbon-nitrogen source are processed to obtain an intermediate material, which includes a core and a protective layer. The protective layer covers the core and includes at least one of the following: heteroatom-doped carbon material, conductive polymer-derived carbon material, graphene, carbon nanotubes, mesoporous carbon, amorphous carbon, boron nitride, carbon nitride, and transition metal nitride. The core includes a transition metal carbide.

[0074] Finally, the intermediate material was placed in an acidic electrolyte for cyclic voltammetry scanning, allowing in-situ reconstruction of the intermediate material's surface to form passivation layer 2, thus obtaining catalyst 1. The chemical structural formula of the formed passivation layer 2 is MC-(OH)x, where M represents a transition metal element.

[0075] The acidic electrolyte mentioned above can be a 0.5 mol / L to 1 mol / L dilute hydrochloric acid (HCl) or dilute sulfuric acid (H2SO4) solution. For example, the concentration of the acidic electrolyte can be 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, or 1 mol / L.

[0076] In acidic electrolytes, the potential range for cyclic voltammetry scanning is -0.1V vs. RHE to 1.0V vs. RHE, the scan rate is 50mV / s to 100mV / s, and the number of cycles is 500 to 2000. It should be noted that RHE refers to the Reversible Hydrogen Electrode (RHE), -0.1V vs. RHE means a potential 0.1V lower than the RHE potential, and 1.0V vs. RHE means a potential 0.1V higher than the RHE potential.

[0077] For example, the potentials for cyclic voltammetry scanning are -0.1V vs. RHE, 0.1V vs. RHE, 0.2V vs. RHE, 0.5V vs. RHE, 0.8V vs. RHE, or 1.0V vs. RHE; the scan rate can be 50mV / s, 60mV / s, 70mV / s, 80mV / s, 90mV / s, or 100mV / s; and the number of cycles can be 500, 800, 1000, 1200, 1500, 1800, or 2000.

[0078] By placing the intermediate material in an acidic electrolyte for cyclic voltammetry scanning, a stable passivation layer is formed through electrochemically driven dynamic surface reconstruction, effectively suppressing metal dissolution from the catalyst. The carbon substrate undergoes structural evolution during electrochemical cycling, forming robust MOC bonds with the transition metal center. Even after multiple cycles, the catalyst maintains its intact core-shell structure.

[0079] In some embodiments, the transition metal source described above may include a molybdenum source and a tungsten source. The molybdenum source may include at least one of ammonium paramolybdate, ammonium phosphomolybdate, ammonium tetrathiomolybdate, phosphomolybdic acid, sodium molybdate, and sodium phosphomolybdate; the tungsten source may include at least one of ammonium paratungstate, ammonium phosphomolybdate, and sodium tungstate. The molybdenum source and tungsten source described above are low in cost and readily available.

[0080] In some embodiments, the carbon-nitrogen source may include dopamine, for example, dopamine hydrochloride. Dopamine can serve as both a carbon-nitrogen source and a chelating agent. The catechol groups of dopamine have the ability to chelate and adsorb metal ions, and can fully coordinate with Mo / W oxygen anions. In high-temperature environments, it can promote the dispersion of metal oxide nanoparticles and stabilize them as metal centers, preventing the migration or aggregation of metal oxide nanoparticles.

[0081] In some embodiments, the method for processing the transition metal source and the carbon-nitrogen source includes: First, the molybdenum source is divided into two parts, namely the first part and the second part. The first part of the molybdenum source is subjected to hydrothermal treatment to obtain molybdenum oxide nanotubes. This is because molybdenum oxide has an anisotropic crystal structure, and the Mo-O-Mo bond energy is high, so it grows preferentially to form one-dimensional nanoribbons. The high specific surface area nanoribbons reduce the surface energy by curling, forming hollow tubular structures, thus obtaining molybdenum oxide nanotubes.

[0082] For example, the first portion of the molybdenum source can be added to a solvent, which can be deionized water, distilled water, ultrapure water, or a mixture of deionized water and anhydrous ethanol. After the molybdenum source is uniformly dispersed in the solvent, the entire solution can be transferred to an autoclave for hydrothermal treatment. The hydrothermal treatment process is as follows: the solution is reacted at a constant temperature of 120℃~200℃ for 6h~24h. For example, the hydrothermal treatment temperature can be 120℃, 130℃, 140℃, 150℃, 160℃, 170℃, 180℃, 190℃, or 200℃, and the hydrothermal treatment time can be 6h, 8h, 10h, 12h, 14h, 16h, 18h, 20h, 22h, or 24h.

[0083] The aforementioned autoclave is used to provide a closed high-temperature and high-pressure reaction environment. The filling degree is controlled at 60%~80% (e.g., 60%, 65%, 70%, 75% or 80%). At a reaction temperature of 120℃~200℃, the self-generated pressure is 1MPa~3MPa (e.g., 1MPa, 2MPa or 3MPa), and no external pressurization is required.

[0084] Molybdenum oxide solid is obtained by separating the hydrothermally treated solution. After washing, the obtained molybdenum oxide solid is placed in a vacuum drying oven and dried at a constant temperature under vacuum conditions. The drying temperature is 60℃~100℃, and the drying time is 6h~12h. The dried molybdenum oxide solid is then ground to obtain molybdenum oxide nanotubes. For example, the drying temperature can be 60℃, 70℃, 80℃, 90℃, or 100℃, and the drying time can be 6h, 8h, 10h, or 12h.

[0085] Then, the prepared molybdenum oxide nanotubes were mixed and reacted with the molybdenum source, tungsten source, and dopamine from the second part to obtain the molybdenum / tungsten-polydopamine precursor. It should be noted that the " / " in molybdenum / tungsten (Mo / W) indicates "loaded on", and Mo / W means that Mo is loaded on W. The same understanding should be applied to Mo / W in the following description, so it will not be repeated.

[0086] By first preparing molybdenum oxide nanotubes, and then mixing and reacting the molybdenum oxide nanotubes with the second part, tungsten source and dopamine, molybdenum and tungsten can be uniformly anchored on the surface or in the pores of the molybdenum oxide nanotubes, avoiding the aggregation of molybdenum source and tungsten source.

[0087] Finally, the molybdenum / tungsten-polydopamine precursor was sintered at high temperature to obtain an intermediate material, which was a Mo2C / WC@NC composite material.

[0088] It should be noted that the "@" in Mo2C / WC@NC usually indicates "encased in"; Mo2C / WC@NC means that the Mo2C / WC heterostructure is encased within a nitrogen-doped carbon layer, that is, the Mo2C / WC heterostructure is encased within a protective layer. The same understanding should be applied to Mo2C / WC@NC in the following description, and therefore it will not be elaborated further.

[0089] The nitrogen-doped carbon layer forms in situ during the high-temperature carbonization process, which physically confines the internal metal nanoparticles, inhibits their migration and aggregation, and ensures high-density exposure of active sites.

[0090] In some embodiments, the steps of reacting molybdenum oxide nanotubes with the molybdenum source, tungsten source, and dopamine in the second part are as follows: Step 1: Mix the molybdenum oxide nanotubes, the molybdenum source from the second part, and the tungsten source in an ethanol solution, and stir magnetically for 20 to 40 minutes to form a homogeneous Mo / W precursor solution. For example, the stirring time can be 20, 30, or 40 minutes.

[0091] Step 2: Add concentrated ammonia dropwise to the Mo / W precursor solution to adjust the pH to 8-9. Under these alkaline conditions, add dopamine hydrochloride to the Mo / W precursor solution and continue stirring.

[0092] Dopamine undergoes cross-linking polymerization under alkaline conditions to form a three-dimensional network of carbonaceous frameworks. The catechol groups of dopamine have the ability to chelate and adsorb metal ions, and through coordination bonds, they undergo strong chemisorption with the Mo / W precursor, so that dopamine is fully coordinated with the Mo / W oxygen anions, confining the MoO3 nanotubes and Mo / W precursors within a nanoscale space. This prevents the internal metal particles from migrating, agglomerating, and growing at high temperatures, thereby stabilizing the ultrasmall nanocrystalline structure.

[0093] Step 3: Add 30-50 ml of anhydrous ethanol to the mixed solution obtained in Step 2. Anhydrous ethanol can induce the self-polymerization reaction of dopamine. Then, stir continuously at room temperature for 10-14 hours to allow the self-polymerization reaction of dopamine to proceed fully, and finally obtain the molybdenum / tungsten-polydopamine (Mo / W-PDA) precursor precipitate.

[0094] Step 4: Centrifuge the Mo / W-PDA precursor precipitate to collect the precipitate, and wash it three times with deionized water and ethanol to thoroughly remove residual ions and impurities. Finally, dry the washed Mo / W-PDA precursor in a vacuum drying oven at 50℃~90℃ for 8h~16h. For example, the drying temperature in the vacuum drying oven can be set to 50℃, 60℃, 70℃, 80℃, or 90℃, and the drying time can be 8h, 10h, 12h, 14h, 15h, or 16h.

[0095] For example, the Mo / W-PDA precursor precipitate can be centrifuged using a centrifuge. The centrifuge speed can be set to 7500 rpm to 8500 rpm, and the centrifugation time can be 8 min to 15 min. For instance, the centrifuge speed can be set to 7500 rpm, 7800 rpm, 8000 rpm, 8300 rpm, or 8500 rpm, and the centrifugation time can be 8 min, 10 min, 12 min, 14 min, or 15 min.

[0096] In some embodiments, the method for high-temperature sintering of the Mo / W-PDA precursor includes: heating the Mo / W-PDA precursor to a first preset temperature in an inert gas at a heating rate of 2°C / min to 5°C / min, and maintaining the temperature at the first preset temperature for a first preset duration. The first preset temperature is 700°C to 1000°C, and the first preset duration is 2 hours to 5 hours. For example, the first preset temperature can be 700°C, 800°C, 900°C, or 1000°C, and the first preset duration can be 2 hours, 3 hours, 4 hours, or 5 hours.

[0097] The high-temperature sintering method described above can cause the Mo / W-PDA precursor to undergo carbonization and pyrolysis, and can balance the degree of carbonization, ensuring the formation of a uniform Mo2C / WC heterostructure, and avoiding thermal deactivation of catalyst 1 due to excessively high temperature.

[0098] For example, the Mo / W-PDA precursor can be placed in a tube furnace for high-temperature sintering, causing the Mo / W-PDA precursor to undergo carbonization and pyrolysis; the inert gas can be nitrogen, and the flow rate of the inert gas is 100 sccm.

[0099] After high-temperature sintering, an intermediate substance is obtained, and the intermediate substance is naturally cooled to room temperature.

[0100] In some embodiments, the ratio A of the molybdenum mass in the molybdenum oxide nanotube to the molybdenum mass in the second part is 2 / 7 to 2 (e.g., 2 / 7, 1 / 3, 2 / 5, 2 / 3, 1 or 2).

[0101] It should be noted that molybdenum oxide nanotubes act as a dynamic self-sacrificing template for confinement during the preparation of catalyst 1. The layered structure of molybdenum oxide nanotubes forms a topological match with the (100) crystal plane of the target metal phase Mo and the (110) crystal plane of W, which, along with the directional relaxation of lattice stress during induced epitaxial growth, significantly suppresses lattice distortion caused by high-temperature phase transformation. During carbonization, molybdenum oxide nanotubes gradually decompose through a controllable redox reaction, and with the help of in-situ ion exchange and diffusion kinetics, a high proportion of active sites are exposed on the atomic surfaces of the bimetallic Mo and W atoms. Among them, (100) and (110) are the Miller indices of the crystal, representing the ratio of the coprime integers of the reciprocals of the intercepts of the crystal planes on the three crystal axes (a, b, c) in the crystal coordinate system, and are used to determine the spatial orientation of the crystal planes.

[0102] The ratio A of the molybdenum mass in the molybdenum oxide nanotubes to the molybdenum mass in the second part regulates the carbonization behavior of different molybdenum sources and the intermetallic electron distribution in the reaction system. When the ratio A exceeds 2, the molybdenum oxide nanotube template is excessive, easily accumulating and causing blockage of the mesoporous structure, making it difficult to form a complete Mo2C / WC heterostructure interface in the reaction system. When the ratio A is less than 2 / 7, the confined structure cannot be continuously constructed in the reaction system, and the number of nucleation sites after the decomposition of the molybdenum oxide nanotube template is insufficient, resulting in uneven formation of the Mo2C / WC heterostructure.

[0103] To verify the effect of the ratio A of the molybdenum mass in the molybdenum oxide nanotubes to the molybdenum mass in the second part on the performance of catalyst 1, an electrochemical test experiment can be carried out on the prepared catalyst 1.

[0104] The test method used in this experiment was the accelerated decay method. The test parameters and procedures are as follows: Electrochemical tests were conducted at room temperature using a standard three-electrode system. A rotating disk electrode coated with the catalyst sample was used as the working electrode, a platinum wire as the counter electrode, and an Ag / AgCl electrode as the reference electrode. All three electrodes (working electrode, counter electrode, and reference electrode) were in contact with the electrolyte. Before the test, 30 mL of 1 mol / L HCl solution was added to the electrolyte. Hydrogen gas was then passed through the electrolyte for 30 min using a hydrogen generator to remove oxygen and saturate the electrolyte with hydrogen.

[0105] First, linear sweep voltammetry (LSV) was performed at 1600 rpm, with a potential range of -0.2V to 0.2V (vs. Ag / AgCl).

[0106] Then, cyclic voltammetry (CV) was performed in the potential range of -0.2V to 0.3V, with the rotation speed at 0 rpm during the cycle and a total of 1000 cycles. After the CV cycle was completed, the rotation speed was adjusted to 1600 rpm, and LSV testing was performed in the potential range of -0.2V to 0.2V (vs. Ag / AgCl).

[0107] Electrochemical testing experiment one can include multiple examples and multiple comparative examples. The ratio A of the molybdenum mass in the molybdenum oxide nanotubes in the multiple examples and multiple comparative examples to the molybdenum mass in Part II is different. The test results of ratio A and catalyst 1 in the multiple examples and multiple comparative examples are shown in Table 1: Table 1. Ratio A and Test Results

[0108] It should be noted that the presence of confined structures and the existence of Mo2C / WC heterostructures in Table 1 refer to the presence of confined structures and Mo2C / WC heterostructures in catalyst 1. The presence of confined structures in catalyst 1 means that catalyst 1 includes molybdenum oxide nanotubes, and the physical confinement space provided by the molybdenum oxide nanotubes has been successfully constructed, preventing agglomeration or migration of metal particles.

[0109] As shown in Table 1, when the ratio A of the molybdenum mass in the molybdenum oxide nanotubes to the molybdenum mass in the second part is in the range of 2 / 7 to 2, catalyst 1 possesses both a confined structure and a Mo2C / WC heterostructure, and the exchange current density during the cycling process is greater than 1.75 mA·cm⁻¹. -2 After 1000 cycles, the activity decay was less than 16%. In particular, catalyst 1 in Example 1 exhibited an exchange current density of 2.6 mA·cm⁻¹ during the cycling process. -2After 1000 cycles, the activity decay was only 11.1%, indicating that the catalytic activity of catalyst 1 was improved and its catalytic performance was excellent.

[0110] In Comparative Examples 1-3, the ratio A was not within the range of 2 / 7 to 2 (MoO3 nanotubes were not added in Comparative Example 3). During electrochemical cycling, it was difficult to simultaneously increase the exchange current density and reduce the activity decay of catalyst 1. For example, in Comparative Example 1, the ratio A was too low (below 2 / 7). Although a Mo2C / WC heterostructure existed in catalyst 1, it lacked a confined structure, leading to easy agglomeration of metal particles. After 1000 cycles, the activity decayed by 17%, indicating poor activity retention of catalyst 1. In Comparative Example 2, the ratio A was too high (above 2). Although a confined structure existed in catalyst 1, the Mo2C / WC heterostructure was absent, resulting in a low exchange current density during cycling, only 1.21 mA·cm⁻¹. -2 After 1000 cycles, the activity decreased by more than 20%, and the performance of catalyst 1 declined.

[0111] Therefore, when the ratio A of the molybdenum mass in the molybdenum oxide nanotube to the molybdenum mass in the second part is in the range of 2 / 7 to 2, catalyst 1 has both confined structure and heterostructure, thus enhancing the catalytic activity and exhibiting excellent catalytic performance.

[0112] This application also provides a catalyst 1, which can be prepared by the above-described preparation method. The catalyst 1 has a similar composition and structure to the catalyst 1 in the above embodiments, and the beneficial effects of the catalyst 1 can be referred to the beneficial effects of the catalyst 1 in the above embodiments, which will not be repeated here.

[0113] In some embodiments, in order to verify the effect of the mass ratio of Mo to W in catalyst 1 on the electronic coupling effect and catalytic activity of the heterostructure interface, an electrochemical test experiment two can be carried out on catalyst 1 prepared according to the above preparation method. The test method, test parameters and test process of electrochemical test experiment two can be designed with reference to electrochemical test experiment one in the above embodiments, and will not be repeated here.

[0114] The test experiments can include multiple examples and multiple comparative examples, with different Mo and W mass ratios. During the preparation of catalyst 1, the ratio A of the molybdenum mass in the molybdenum oxide nanotubes to the molybdenum mass in the second part is always 1. The test results of catalyst 1 in the multiple examples and multiple comparative examples are shown in Table 2: Table 2. Mass ratio of Mo and W in catalyst 1 and test results of catalyst 1

[0115] As shown in Table 2, in Examples 4-8, the mass ratio of Mo to W was between 1:1 and 1:20, and the content of heterostructure was between 50% and 80%, with an exchange current density greater than 1.9 mA·cm. -2 After 1000 cycles, the activity decay was less than 22%. This indicates that catalyst 1 in Examples 4-6 forms an effective heterogeneous interface and exhibits good performance.

[0116] In Comparative Examples 4 and 5, the Mo to W mass ratio was in the range of 1:1 to 1:20, but the heterostructure content was not in the range of 50% to 80%, and the exchange current density was less than 1.9 mA·cm. -2 After 1000 cycles, the activity decayed by more than 25%. This indicates that catalyst 1 in Comparative Examples 4 and 5 has insufficient active sites or the metal sites are oxidized and dissolved in an acidic environment, leading to a decline in the performance of catalyst 1.

[0117] In Comparative Examples 6 and 7, the heterostructure content ranged from 50% to 80%, but the Mo to W mass ratio was not in the range of 1:1 to 1:20, and the exchange current density was less than 1.6 mA·cm. -2 After 1000 cycles, the activity decayed by more than 30%. This indicates that catalyst 1 in Comparative Examples 6 and 7 has insufficient active sites and weakened interfacial coupling, and WC cannot form a good heterostructure with Mo2C, resulting in a decline in the performance of catalyst 1.

[0118] In some embodiments, in order to verify the stability changes of catalyst 1 in the long-term operation process of this application embodiment, the activity retention rate and metal dissolution amount of catalyst 1 in Example 1 after different number of cycles were recorded, and the recorded data are shown in Table 3: Table 3. Activity retention and metal dissolution of catalyst 1 after different number of cycles.

[0119] As shown in Table 3, catalyst 1 exhibited significant metal dissolution during the initial cycling phase (0-1000 cycles). After 1000 cycles, the dissolution concentrations of Mo and W in the electrolyte were detected to be 35.31 μg / L and 17.03 μg / L, respectively, corresponding to an initial activity loss of approximately 11.1% (for example, see Table 1, where catalyst 1 in Example 1 showed an 11.1% decrease in catalytic activity after 1000 cycles). This is because, during the initial cycling phase, exposed components not fully covered by the protective layer or metal sites with weak structural stability preferentially dissolved from the surface of catalyst 1. As the number of cycles increased, the metal dissolution rate and concentration decreased, and the activity decay rate slowed significantly. After undergoing initial surface reconstruction, an effective passivation layer 2 formed on the surface of catalyst 1, inhibiting further metal dissolution.

[0120] Therefore, the Mo2C / WC@NC catalyst 1 provided by this invention exhibits excellent electrochemical stability in the hydrogenation reaction. After 10,000 accelerated decay cycles, the activity retention rate of catalyst 1 can reach 73%, which is higher than the activity retention rate of 71% of traditional platinum catalysts, and there is very little or no dissolution of Mo or W.

[0121] In some embodiments, to verify the effect of electrochemical driving (cyclic voltammetry) on the formation of the surface passivation layer 2 and the stability of the catalyst 1, the intermediate material (Mo2C / WC@NC composite material) prepared in Example 1 can be divided into two groups for comparative experiments: an activation group and a control group. See [reference] Figure 6 , Figure 6 Microscopic morphology images of intermediate substances provided in some embodiments of this application under a transmission electron microscope; from Figure 6 As can be seen, the Mo2C / WC@NC composite material has not undergone chemical activation, and its surface does not have a passivation layer 2.

[0122] The intermediate substance of the activated group was subjected to 1000 cycles of cyclic voltammetry scanning in dilute hydrochloric acid solution; the intermediate substance of the control group was immersed in dilute hydrochloric acid solution without applying potential cycling. The amount and concentration of the dilute hydrochloric acid solution in the control group were the same as those in the activated group, and the immersion time in the dilute hydrochloric acid solution was also the same. The test results of the activated group and the control group are shown in Table 4: Table 4. Treatment methods and test results for the activation group and experimental group.

[0123] Although both groups of samples exhibited high oxidation states, they differed fundamentally in their microchemical environments. (Refer to Table 4.) Figure 7 and Figure 8 , Figure 7 O1s XPS comparison spectra of catalyst 1 prepared for the activation group and control group provided in some embodiments of this application Figure 1 ; Figure 8 O1s XPS comparison spectra of catalyst 1 prepared for the activation group and control group provided in some embodiments of this application Figure 2 ; Figure 7 and Figure 8 The horizontal axis represents the binding energy (in eV), and the vertical axis represents the intensity (au is used to represent relative intensity). As can be seen from the figure, the characteristic peak of structural water appears at 535.9 eV in the O 1s spectrum of the activated group, and the π-π* satellite peak appears at 292.2 eV in the C 1s spectrum.

[0124] Figure 2 Catalyst 1 in the text is the chemically activated catalyst 1. Figure 2The microstructure diagram of catalyst 1 also confirms that an amorphous passivation layer 2 is formed on the surface of catalyst 1, which includes MC-(OH)x.

[0125] The control group did not exhibit structural water characteristic peaks or π-π* satellite peaks, failing to form a functional passivation layer 2. The activated catalyst 1 showed only an 11.1% activity decay after 1000 cycles, while the control group catalyst 1 showed a significant 36.1% activity decay. These results indicate that electrochemical driving (cyclic voltammetry) is a necessary condition for the formation of the functional passivation layer 2. Under electrochemical polarization conditions, the MC-(OH)x composite framework is formed in situ. MC-(OH)x provides reaction kinetics while simultaneously endowing catalyst 1 with protective capabilities against acidic media erosion, thus enhancing the long-term stability of catalyst 1.

[0126] In some embodiments, to study the adaptability of catalyst 1 under different acidic environments, the performance of catalyst 1 prepared in Example 1 was tested in dilute hydrochloric acid of different concentrations. The concentration of dilute hydrochloric acid and the test results are shown in Table 5. Table 5. Test results of dilute hydrochloric acid concentration and current density.

[0127] As shown in Table 5, the exchange current density can reach 2.60 mA·cm under 1 mol / L dilute hydrochloric acid conditions. -2 When the concentration of dilute hydrochloric acid increased to 2 mol / L and 3 mol / L, although the overall exchange current density decreased slightly, it gradually stabilized, and the electrode reaction kinetics were not significantly restricted. The results show that catalyst 1 in this embodiment can maintain good catalytic performance in acidic environments of different concentrations, exhibiting good acid adaptability, making the catalyst suitable for acidic hydroxide reactions.

[0128] This application also provides a battery, which includes an electrolyte, electrodes, and a catalyst layer disposed on the surface of the electrodes. The catalyst layer includes a catalyst 1, which is the catalyst 1 in any of the above embodiments.

[0129] Understandably, the beneficial effects that the battery can achieve are comparable to the beneficial effects of catalyst 1 in any of the above embodiments, and will not be repeated here. Furthermore, when catalyst 1 is applied to a battery, it helps to improve battery performance and ensure battery lifespan.

[0130] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as the combination of these technical features does not contradict each other, it should be considered within the scope of this specification. The above embodiments only illustrate several implementation methods of this application, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of this application. It should be noted that for those skilled in the art, several modifications and improvements can be made without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

[0131] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A catalyst, characterized in that, include: The core consists of various transition metal carbides; A protective layer, covering the core, is conductive; A passivation layer, comprising hydrated hydroxyoxide, is applied to the exterior of the protective layer.

2. The catalyst according to claim 1, characterized in that, The core comprises a molybdenum carbide / tungsten carbide heterostructure; and / or the protective layer comprises at least one of heteroatom-doped carbon materials, conductive polymer-derived carbon materials, graphene, carbon nanotubes, mesoporous carbon, amorphous carbon, boron nitride, carbon nitride, and transition metal nitrides.

3. The catalyst according to claim 2, characterized in that, The mass ratio of molybdenum to tungsten in the catalyst is 1:1 to 1:20; and / or, the mass fraction of the molybdenum carbide / tungsten carbide heterostructure in the catalyst is 50% to 80%.

4. The catalyst according to any one of claims 1-3, characterized in that, The catalyst also satisfies at least one of the following conditions: (1) The chemical structural formula of the passivation layer is MC-(OH)x, where M represents a transition metal element; (2) The thickness of the protective layer is 2nm~5nm; (3) The thickness of the passivation layer is 1nm~3nm.

5. A method for preparing a catalyst, characterized in that, include: Provides transition metal and carbon / nitrogen sources; The transition metal source and the carbon-nitrogen source are processed to obtain an intermediate substance, which includes a core and a protective layer. The protective layer covers the core and is conductive. The core includes a transition metal carbide. The intermediate substance was placed in an acidic electrolyte and subjected to cyclic voltammetry scanning to reconstruct a passivation layer on the surface of the intermediate substance in situ, thereby obtaining the catalyst.

6. The preparation method according to claim 5, characterized in that, The transition metal source includes a molybdenum source and a tungsten source, and the carbon and nitrogen source includes dopamine.

7. The preparation method according to claim 6, characterized in that, The molybdenum source includes at least one of ammonium paramolybdate, ammonium phosphomolybdate, ammonium tetrathiomolybdate, phosphomolybdic acid, sodium molybdate, and sodium phosphomolybdate; and / or, the tungsten source includes at least one of ammonium paratungstate, ammonium phosphomolybdate, and sodium tungstate.

8. The preparation method according to claim 6 or 7, characterized in that, The method for processing the transition metal source and the carbon-nitrogen source includes: The molybdenum source is divided into a first part and a second part. The first part is subjected to hydrothermal treatment to obtain molybdenum oxide nanotubes. The molybdenum oxide nanotubes, the second part, the tungsten source, and the dopamine are mixed and reacted to obtain a molybdenum / tungsten-polydopamine precursor. The molybdenum / tungsten-polydopamine precursor was subjected to high-temperature sintering to obtain the intermediate material, which is a Mo2C / WC@NC composite material.

9. The preparation method according to claim 8, characterized in that, The ratio of the mass of molybdenum in the molybdenum oxide nanotubes to the mass of molybdenum in the second portion is 2 / 7 to 2; and / or, The method for high-temperature sintering of the molybdenum / tungsten-polydopamine precursor includes: The molybdenum / tungsten-polydopamine precursor is placed in an inert gas and kept in the inert gas for a first preset time; the temperature of the inert gas is 700℃~1000℃, and the first preset time is 2h~5h.

10. A battery, characterized in that, include: A catalyst layer comprising the catalyst according to any one of claims 1-4; and / or, the catalyst layer comprising a catalyst prepared by the preparation method according to any one of claims 5-9.

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