A porous nickel-based nitrogen-doped tungsten oxide loaded Ce-La composite catalyst, a preparation method and application thereof

Abstract

The application discloses a porous nickel-based Ce-La composite catalyst loaded with nitrogen-doped tungsten oxide and a preparation method and application thereof, and comprises the following steps: S1, tungsten source, nitrogen source and inorganic mixed salt are mixed to obtain mixed powder, the mixed powder is mixed with a porous nickel base, the base is completely wrapped by the mixed powder, pyrolysis is carried out at 550-650 DEG C under an oxygen-containing atmosphere, then reduction heat treatment is carried out under a mixed atmosphere containing hydrogen and inert gas, and after washing and drying, nitrogen-doped WO 3‑x loaded porous nickel is obtained; S2, the base treated in S1 is immersed in a mixed solution containing cerium salt and lanthanum salt, and after being taken out and dried, heat treatment is carried out under an inert atmosphere to obtain the composite catalyst. The composite catalyst takes the porous nickel as a self-supporting base, and has excellent hydrogen evolution and oxygen evolution performance and long-term stability in alkaline solution under the synergistic effect of nitrogen-doped WO 3‑x WO and Ce-La, and has good application prospect in the field of hydrogen production by water electrolysis.

Description

Technical Field

[0001] This invention relates to the fields of catalyst preparation and water electrolysis for hydrogen production, specifically to a porous nickel-based nitrogen-doped tungsten oxide supported Ce-La composite catalyst, its preparation method, and its application. Background Technology

[0002] Hydrogen energy, with its high energy density and clean combustion products, is considered a crucial component of the future energy system. Electrolysis of water is an important pathway for converting renewable energy into hydrogen energy, with alkaline water electrolysis technology showing promising industrial application prospects due to its lower equipment cost and milder operating conditions. However, both the hydrogen evolution reaction at the cathode and the oxygen evolution reaction at the anode in alkaline water electrolysis exhibit significant kinetic resistance, resulting in an actual operating voltage of the electrolyzer that is much higher than the theoretical decomposition voltage, leading to high energy consumption. Therefore, developing efficient and stable electrocatalysts is key to reducing reaction overpotential and improving energy conversion efficiency in alkaline water electrolysis for hydrogen production.

[0003] Currently, the best-performing hydrogen evolution and oxygen evolution catalysts are still mainly noble metals and their oxides, such as platinum-based materials for hydrogen evolution and oxides of iridium or ruthenium for oxygen evolution. However, noble metal resources are scarce and expensive, making it difficult to meet the needs of large-scale industrial applications. Therefore, the development of low-cost, high-activity non-noble metal electrocatalysts has become a research hotspot in this field.

[0004] Among non-precious metal catalysts, nickel-based materials have attracted widespread attention due to their abundant resources, low cost, and certain electrocatalytic activity in alkaline media. However, existing nickel-based catalysts still have the following shortcomings: First, their catalytic activity is limited, especially under high current density conditions, where the overpotentials for hydrogen evolution and oxygen evolution increase significantly, making it difficult to meet the low energy consumption requirements of industrial-grade water electrolysis. Second, most nickel-based catalysts only exhibit good activity for a single hydrogen or oxygen evolution reaction, making it difficult to achieve efficient hydrogen and oxygen evolution simultaneously on the same electrode. This necessitates the use of different catalysts for the entire water electrolysis system, increasing process complexity and cost. Third, nickel-based catalysts lack stability during long-term alkaline electrolysis, easily experiencing phenomena such as surface hydride formation, loss of active components, structural reconstruction, or agglomeration, leading to catalytic performance degradation and making it difficult to balance high activity and long-term stability.

[0005] While researchers have attempted to modify nickel-based catalysts through strategies such as elemental doping, heterostructure construction, and compositing with conductive substrates, the following limitations exist: single modification methods typically only improve one aspect of performance, making it difficult to simultaneously enhance the bifunctional catalytic activity for hydrogen evolution and oxygen evolution; the utilization rate of active sites decreases and the overpotential increases rapidly under high current densities in some catalysts; furthermore, the bonding strength between the active material and the substrate is insufficient, making it prone to detachment or deactivation under long-term bubble erosion and alkaline corrosion conditions, resulting in poor stability. Therefore, existing non-precious metal catalysts still struggle to simultaneously meet the requirements of low hydrogen evolution overpotential, low oxygen evolution overpotential, and long-term stable operation under alkaline conditions at high current densities.

[0006] Therefore, there is an urgent need for a catalyst that is low in cost, has a controllable preparation process, and exhibits excellent hydrogen evolution and oxygen evolution performance under alkaline conditions while remaining stable over a long period of time. Summary of the Invention

[0007] To address the technical problems of existing alkaline water electrolysis catalysts, such as high cost and limited resources due to reliance on precious metals, insufficient catalytic activity of non-precious metal catalysts, high hydrogen / oxygen evolution overpotentials at high current densities, difficulty in achieving dual-function catalytic performance for both hydrogen and oxygen evolution, and poor long-term alkaline stability, this invention provides a porous nickel-based nitrogen-doped tungsten oxide-supported Ce-La composite catalyst, its preparation method, and its application. This is achieved through nitrogen doping with WO3. 3-x The synergistic effect of oxygen vacancy regulation and Ce-La electronic structure significantly enhances the bifunctional catalytic activity of hydrogen evolution and oxygen evolution, as well as the long-term alkaline stability, while maintaining the porous nickel self-supporting structure. This results in a catalyst with advantages such as low overpotential at high current density, good stability, and low cost in alkaline water electrolysis for hydrogen production.

[0008] Specifically, the following technical solutions are provided: The first aspect of this invention provides a method for preparing a porous nickel-based nitrogen-doped tungsten oxide supported Ce-La composite catalyst, comprising the following steps: S1. A porous nickel substrate is mixed with a mixed powder containing a tungsten source, a nitrogen source, and an inorganic salt, so that the substrate is completely coated with the mixed powder. The mixture is then pyrolyzed at 550-650 °C (e.g., 550 °C, 560 °C, 570 °C, 580 °C, 590 °C, 600 °C, 610 °C, 620 °C, 630 °C, 640 °C, 650 °C, etc.) in an oxygen-containing atmosphere. Afterward, a reduction heat treatment is performed in a mixed atmosphere containing hydrogen and an inert gas. Following washing and drying, nitrogen-doped WO3 is obtained. 3-x Loaded porous nickel; S2, The nitrogen-doped WO 3-xThe supported porous nickel was impregnated in a mixed solution containing cerium salt and lanthanum salt, removed and dried, and then subjected to a second heat treatment under an inert atmosphere to obtain the porous nickel-based nitrogen-doped tungsten oxide supported Ce-La composite catalyst.

[0009] In this invention, the pyrolysis temperature under an oxygen-containing atmosphere is controlled within the range of 550-650 °C to ensure sufficient decomposition of the tungsten source, partial nitrogen doping, moderate oxidation of porous nickel, and the formation of a strong interface with the tungsten species. Simultaneously, excessive grain growth and substrate sintering are avoided, thus facilitating the subsequent reduction heat treatment stage where WO3 is partially reduced to WO in an H2 / inert atmosphere. 3-x It efficiently introduces oxygen vacancies to provide the structural basis. If the pyrolysis temperature is too low (<550 ℃), the tungsten and nitrogen sources decompose insufficiently, the mass transfer and confinement effect of the inorganic salt medium is insufficient, and the mixed powder is difficult to form a uniform coating and complete interface structure (Ni-OW) with the porous nickel substrate. The generated tungsten oxide precursor has a low degree of crystallization, which makes it difficult to generate oxygen vacancies uniformly and efficiently in subsequent reduction heat treatment, and the nitrogen doping amount is also insufficient. However, if the temperature is too high (>650 ℃), the nitrogen source is easily over-oxidized and burned off, and the tungsten oxide grains grow excessively. Subsequent reduction heat treatment is difficult to achieve the desired WO3 structure. 3-x Effective and stable introduction of oxygen vacancies into the crystal lattice ultimately leads to a reduction in active sites, an increase in interfacial resistance, and a decrease in hydrogen evolution and oxygen evolution performance.

[0010] Furthermore, in step S1, the porous nickel substrate includes one of nickel mesh and nickel foam.

[0011] Further, in step S1, the tungsten source includes one or more of ammonium metatungstate, ammonium tungstate, ammonium paratungstate, sodium tungstate, potassium tungstate, and tungsten chloride; in some preferred embodiments of the present invention, ammonium metatungstate is used as the tungsten source.

[0012] Further, in step S1, the nitrogen source includes one or more of urea, melamine, and ammonium chloride; in some preferred embodiments of the present invention, urea is used as the nitrogen source.

[0013] Furthermore, in step S1, the inorganic salt is NaCl and / or KCl, which is easily removed by washing with water.

[0014] Furthermore, in step S1, the molar ratio of the tungsten source (W) to the nitrogen source (N) is 1:(1-5), for example, 1:1, 1:2, 1:3, 1:4, 1:5, etc. The feeding ratio of the two is controlled within the above range to ensure effective nitrogen doping while avoiding excessive nitrogen source from damaging the catalytic performance.

[0015] Furthermore, in step S1, the ratio of the sum of the masses of the tungsten source and the nitrogen source to the mass of the inorganic salt is 1:(1-10), for example, 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, etc., so as to control the amount of inorganic salt added within a suitable range, so as to provide a suitable molten salt mass transfer and confined environment, while ensuring that the inorganic salt can be completely removed in subsequent washing.

[0016] Furthermore, in step S1, the oxygen-containing atmosphere is air, or it may be a mixture of oxygen and an inert gas.

[0017] Furthermore, in step S1, the heat treatment time in the pyrolysis step is preferably 1-5 h, so as to ensure that the tungsten source is fully decomposed, nitrogen doping is effectively carried out and a good interface structure is formed, while avoiding problems such as excessive grain growth, nitrogen species burn-off and excessive oxidation sintering of porous nickel substrate caused by excessive heat treatment time.

[0018] This invention controls the pyrolysis temperature and holding time, for example, holding at 550-650 ℃ for 1-5 h, so that the tungsten source can react fully, achieving effective nitrogen doping and the construction of the interface structure, while suppressing grain coarsening and substrate damage, providing a substrate material with a complete structure and abundant active sites for subsequent reduction to introduce oxygen vacancies and Ce-La loading.

[0019] Further, in step S1, the volume fraction of hydrogen in the mixed atmosphere is 5%-10%, and the inert gas is nitrogen and / or argon. For example, the mixed atmosphere is formed by 5% hydrogen and 95% helium by volume fraction, or by 10% hydrogen and 90% helium.

[0020] Furthermore, in step S1, the temperature of the reduction heat treatment is preferably 400-550 ℃, and the time is preferably 1-3 h, for example, the reduction heat treatment is performed by holding at 450 ℃ for 2 h.

[0021] This invention achieves moderate reduction by controlling the volume fraction of hydrogen in the mixed atmosphere within the range of 5%-10% and by controlling the temperature and holding time of the reduction heat treatment. This introduces an appropriate amount of oxygen vacancies and forms tungsten ions in various valence states. The reversible valence state change enables rapid electron transfer, thereby lowering the reaction energy barrier and improving catalytic activity. Simultaneously, it avoids excessive reduction leading to WO3. 3-x The framework and nitrogen-doped structure are disrupted to balance catalytic activity and stability.

[0022] Further, in step S1, the washing is hot water washing, preferably deionized water at 60-100 °C. Through multiple washings, the nitrogen-doped WO3 is formed without damaging it. 3-x Under the premise of porous nickel structure, efficient removal of residual nitrogen-doped WO3 3-xInorganic salts (NaCl / KCl) and unreacted / decomposed residues in the loaded porous nickel.

[0023] Further, in step S2, the cerium salt includes one or more of cerium nitrate, cerium chloride, cerium sulfate, and cerium acetate.

[0024] Further, in step S2, the lanthanum salt includes one or more of lanthanum nitrate, lanthanum chloride, lanthanum sulfate, and lanthanum acetate.

[0025] Further, in step S2, the molar ratio of cerium ions to lanthanum ions in the mixed solution is preferably (1-2):1, and the total metal ion concentration is preferably 0.05-2 mol / L, such as 0.1 mol / L, 0.5 mol / L, 1 mol / L, etc.

[0026] Furthermore, in step S2, the mixed solution also contains a complexing agent, and in some preferred embodiments, the complexing agent is citric acid.

[0027] In this invention, cerium ions and lanthanum ions are introduced simultaneously. Through their division of labor and cooperation in electronic and lattice structures, combined with nitrogen-doped WO3, the cerium ions and lanthanum ions are utilized. 3-x Multiple synergistic active structures are constructed on the surface; and further, by controlling the amount of cerium ions added to be slightly more than that of lanthanum ions, on the one hand, the amount of cerium ions added is ensured to be slightly more than that of lanthanum ions. 3+ / Ce 4+ The variable valence pair provides ample oxygen vacancies and electron transfer centers, while also supplying an appropriate amount of La 3+ Inducing lattice distortion to stabilize Ce 3+ And enhance Ce-La and nitrogen-doped WO 3-x Interfacial electronic coupling between them, thereby synergistically optimizing the interaction between H2O and H2O. + This invention also addresses the adsorption and desorption of oxygen-containing intermediates, thereby lowering the energy barriers for hydrogen evolution and oxygen evolution reactions. Furthermore, by controlling the total concentration of metal ions in the mixed solution, for example, within the range of 0.05-2 mol / L, the invention ensures the stability of the impregnation solution in porous nickel and nitrogen-doped WO3. 3-x The surface has suitable permeability and adsorption capacity, which allows Ce-La to be loaded in a highly dispersed state, avoiding problems such as insufficient single loading and uneven impregnation at low concentrations, as well as excessive viscosity, pore blockage and local agglomeration at high concentrations.

[0028] Furthermore, in step S2, the impregnation time is 6-24 hours to ensure nitrogen-doped WO3. 3-x The loaded porous nickel fully adsorbs cerium and lanthanum ions and achieves a suitable loading amount.

[0029] Further, in step S2, the temperature of the second heat treatment is preferably 400-600 °C, and the time is preferably 2-4 h, for example, holding at 500 °C for 3 h. Under an inert atmosphere and at the above temperature and holding time, cerium salt and lanthanum salt can be fully decomposed and transformed into highly dispersed Ce-La composite oxides, which, together with nitrogen-doped WO3, can form a composite oxide. 3-x Form a strong interface bond and retain an appropriate amount of Ce. 3+ It also creates oxygen vacancies, thereby ensuring the full utilization of the Ce-La synergistic effect, enhancing hydrogen evolution and oxygen evolution activity, as well as long-term alkaline stability.

[0030] The second aspect of the present invention provides a porous nickel-based nitrogen-doped tungsten oxide supported Ce-La composite catalyst, which is prepared by the preparation method described in the first aspect.

[0031] The third aspect of this invention provides the application of the porous nickel-based nitrogen-doped tungsten oxide supported Ce-La composite catalyst described in the second aspect in alkaline water electrolysis for hydrogen evolution and / or oxygen evolution reactions.

[0032] Furthermore, in 1 M KOH at -300 mA·cm -2 At current density, the absolute value of the hydrogen evolution overpotential is less than 100 mV; in 1 M KOH at 300 mA·cm⁻¹ -2 At the current density, the absolute value of the oxygen evolution overpotential is less than 300 mV.

[0033] The beneficial effects of this invention are: 1. This invention provides a process route for preparing composite catalysts using a dry powder mixing and encapsulation pyrolysis combined with a two-step heat treatment. Specifically: First, a porous nickel substrate is directly mixed with a mixed powder containing a tungsten source, a nitrogen source, and inorganic salts, so that the substrate is uniformly encapsulated by the mixed powders. No solvent is required, making the operation simple and the process reproducible. Second, pyrolysis and reduction are carried out continuously in the same reaction system, eliminating the need for intermediate cooling, removal, and secondary loading, which can effectively reduce energy consumption and shorten the production cycle. Furthermore, the inorganic salts play a role in physical isolation and spatial confinement during pyrolysis, effectively inhibiting the high-temperature sintering and agglomeration of active components. Combined with subsequent washing, the salts can be completely removed without introducing metallic impurities. In addition, this invention utilizes the nitrogen-doped WO3 obtained from the above pyrolysis and reduction process. 3-x The loaded porous nickel was impregnated in a mixed solution containing cerium and lanthanum salts, and then gently calcined under an inert atmosphere to fully decompose the cerium and lanthanum precursors and form Ce-La composite oxides. During this process, the nitrogen-doped WO3 rich in oxygen vacancies constructed by the first reduction heat treatment was also processed. 3-x The carrier provides numerous anchoring points for the second step of Ce-La species, enabling Ce... 3+ / Ce 4+ La 3+ with WO 3-xOxygen vacancies on the surface form stable Ce-OW interfacial bonds, achieving firm anchoring and uniform dispersion of the active components and preventing aggregation and detachment during subsequent reactions. This enables the preparation of a composite catalyst that balances high catalytic activity and basic stability. The above preparation method is simple to operate, highly controllable, and conducive to large-scale preparation.

[0034] 2. The composite catalyst prepared by this invention exhibits a hierarchical synergistic characteristic in its structure and composition, with clearly defined electron and oxygen species transfer channels formed between the functional components. Specifically: nitrogen-doped WO3 3-x In this process, the introduction of nitrogen can partially reduce W 6+ Restore to W 5+ The formation of an intermediate energy level within the WO3 band gap effectively reduces the band gap width and improves electron mobility. Simultaneously, the presence of oxygen vacancies further enhances carrier concentration and active site density. Ce-La composite oxides cover WO3... 3-x On the surface, the incorporation of La can increase the oxygen vacancy concentration in the CeO2-based support and promote the migration of surface oxygen species. 3+ / Ce 4+ The redox pair provides a reversible oxygen storage-release capacity, in conjunction with the underlying WO3 layer. 3-x Oxygen vacancies form a synergistic oxygen species supply-transfer network. Furthermore, the three-dimensional interconnected pore structure of the porous nickel substrate not only provides a high specific surface area loading interface but also promotes increased carrier concentration through electronic interactions between Ni and W, facilitating rapid charge transfer in electrocatalytic reactions. This is achieved through porous nickel-nitrogen doping of WO3. 3-x The hierarchical integration of -Ce-La enables the catalyst to achieve a synergistic balance between active site density, electron conduction efficiency, and oxygen species regulation capability, thereby significantly improving the intrinsic activity, charge transfer efficiency, and long-term stability of the catalyst. Furthermore, the strong interfacial bonding of each component effectively prevents the loss of active components during the reaction process.

[0035] 3. The composite catalyst provided by this invention can be directly used as a self-supporting electrode in alkaline water electrolysis for hydrogen evolution and / or oxygen evolution reactions without the need for additional binders or conductive coatings, simplifying the electrode preparation process. An integrated conductive network is formed between the porous nickel substrate and the active layer, significantly reducing interfacial contact resistance. It maintains excellent electrocatalytic performance and durability even at high current densities, effectively reducing overpotential and energy consumption in water electrolysis for hydrogen production, and has broad application prospects in the field of green hydrogen energy. Attached Figure Description

[0036] Figure 1 The image shows the SEM image of the composite catalyst prepared in Example 1, with a scale bar of 500 μm. Figure 2 This is a SEM image of a local surface of the composite catalyst prepared in Example 1, with a scale bar of 50 μm; Figure 3 EDS diagram of the composite catalyst prepared in Example 1; Figure 4 The distribution of each element in the EDS diagram of the composite catalyst prepared in Example 1; Figure 5 Comparison of hydrogen evolution performance of the composite catalysts prepared in Examples 1 and 2 and Comparative Examples 1-3; Figure 6 Comparison of oxygen evolution performance of the composite catalysts prepared in Examples 1 and 2 and Comparative Examples 1-3; Figure 7 The hydrogen evolution stability test diagram of the composite catalyst prepared in Example 1; Figure 8 A comparison of the hydrogen evolution performance of the composite catalyst prepared in Example 1 before and after stability testing; Figure 9 The oxygen evolution stability test diagram of the composite catalyst prepared in Example 1; Figure 10 A comparison of the oxygen evolution performance of the composite catalyst prepared in Example 1 before and after the stability test; The above Figure 5 and Figure 6 In the above, Sample 1 corresponds to the composite catalyst prepared in Example 1, Sample 2 corresponds to the composite catalyst prepared in Example 2, Sample 3 corresponds to the composite catalyst prepared in Example 1, Sample 4 corresponds to the composite catalyst prepared in Example 2, and Sample 5 corresponds to the composite catalyst prepared in Example 3. Detailed Implementation

[0037] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0038] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The terms “comprising” or “including” used in this invention may also be replaced with the closed form “is” or “consisting of”.

[0039] The nickel mesh used in the following examples and comparative examples were all pretreated as follows: Cut the nickel mesh (approximately 300 μm aperture) into 2 cm × 2 cm pieces, and ultrasonically clean it for 15 min each with acetone, dilute hydrochloric acid (2 mol / L), anhydrous ethanol, and deionized water to remove surface grease, oxide layer, and impurities. Then, place the cleaned nickel mesh in an oven at 60-80 ℃ to dry for later use.

[0040] Example 1 This embodiment relates to the preparation of a porous nickel-based nitrogen-doped tungsten oxide supported Ce-La composite catalyst, and the specific operation is as follows: (1) Weigh 2.0 g of ammonium metatungstate, 0.5 g of melamine and 7.5 g of sodium chloride and grind them in an agate mortar for 25 min until they are mixed evenly to obtain a mixed powder. Place the prepared mixed powder in an alumina crucible, then embed the pretreated nickel mesh into the mixed powder and press it lightly so that the powder completely fills and covers the entire surface of the substrate, ensuring that the substrate is completely wrapped by the mixed powder. Place the alumina crucible containing the sample in a tube furnace and heat it to 600 ℃ at 3 ℃ / min in an air atmosphere, hold it for 3 h, and carry out oxygen-containing atmosphere pyrolysis at an air flow rate of 100 mL / min.

[0041] After pyrolysis, residual oxygen in the furnace was removed by purging with Ar for 15 min. Then, the atmosphere was switched to a mixed atmosphere of 5% H2 / 95% Ar (volume ratio), and the temperature was increased to 450 ℃ at 3 ℃ / min and held for 2 h at a gas flow rate of 80 mL / min for reduction heat treatment. After cooling to room temperature in the furnace, the sample was removed and ultrasonically washed three times with 70-80 ℃ hot water for 15 min each time, followed by washing twice with anhydrous ethanol. The sample was then vacuum dried at 70 ℃ for 8 h to obtain nitrogen-doped WO3. 3-x Loaded porous nickel.

[0042] (2) Dissolve 1 g Ce(NO3)3, 0.65 g La(NO3)3, and 0.029 g citric acid in 10 mL of deionized water to obtain a mixed solution. The nitrogen-doped WO3 obtained in step (1) is then... 3-x The loaded porous nickel was immersed in a mixed solution at room temperature for 12 hours. After immersion, excess solution was absorbed from the surface with filter paper and dried in an oven at 60-80 ℃ for 8 hours.

[0043] The dried sample was placed in an alumina crucible and transferred to a tube furnace. Under an Ar atmosphere, the temperature was increased to 500 °C at 3 °C / min and held for 3 h for a second heat treatment. The Ar flow rate was 60 mL / min. After the heat treatment was completed, the sample was cooled to room temperature with the furnace to obtain a porous nickel-based nitrogen-doped tungsten oxide supported Ce-La composite catalyst.

[0044] a. Sample characterization The porous nickel-based nitrogen-doped tungsten oxide-supported Ce-La composite catalyst prepared in this embodiment and its local surface SEM images are shown below. Figure 1 , 2 As shown in the figure, the composite catalyst retains the complete woven nickel mesh skeleton morphology. The mesh holes of the interwoven nickel mesh can be clearly seen. The surface of the nickel wire is no longer smooth, and the whole is uniformly coated with a layer of active material without the accumulation of large particles. The active material is tightly bonded to the nickel substrate. Figure 2 ).

[0045] Furthermore, the porous nickel-based nitrogen-doped tungsten oxide-supported Ce-La composite catalyst prepared in this embodiment was characterized by EDS energy dispersive spectroscopy, and the results are as follows: Figure 3 As shown in the figure, the EDS spectrum reveals the presence of Ni, O, W, Ce, La, and N elements in the sample. Ni exhibits the strongest signal intensity, indicating its origin from the nickel mesh matrix. A strong O signal suggests that the active components primarily exist in oxide form. The detection of characteristic peaks for W, Ce, and La confirms the successful loading of W, Ce, and La rare earth components onto the nickel mesh matrix surface. The detection of characteristic signals for N and C confirms nitrogen and carbon doping in the material. Additionally, trace Al signals observed in localized areas of the sample are presumably derived from trace dust detached from the corundum crucible used in heat treatment or impurities introduced by components of the EDS testing system.

[0046] b. Hydrogen evolution and oxygen evolution catalytic activity test The catalytic performance of the composite catalyst prepared in this embodiment was tested using a three-electrode system in 1 M KOH electrolyte. The working electrode was the prepared composite catalyst, the reference electrode was Hg / HgO, and the counter electrode was a Pt sheet electrode. Linear sweep voltammetry was used with a scan rate of 5 mV / s, and IR compensation was performed. Test results are as follows: Figure 5 As shown in sample 3, at -300 mA·cm -2 At the given current density, the hydrogen evolution overpotential is -80.11 mV; For example Figure 6 As shown in sample 3, at 300 mA·cm -2 At the current density, the oxygen evolution overpotential is 267.31 mV.

[0047] c. Stability test of hydrogen evolution catalytic activity The stability of the hydrogen evolution catalytic activity of the composite catalyst prepared in this embodiment was tested using the same method as in step b, and the results are as follows. Figure 7 As shown, at -500mA·cm -2After 500 hours of continuous operation at high current density, the working electrode potential of the composite catalyst did not show a significant negative drift, and the potential curve remained stable overall without significant increase or abrupt decay. This indicates that under high current hydrogen evolution conditions, the active component of the composite catalyst is firmly bonded to the nickel mesh matrix, exhibits strong resistance to bubble erosion and corrosion passivation, and possesses excellent long-term electrochemical stability for hydrogen evolution, maintaining stable catalytic activity for a long period.

[0048] Linear sweep voltammetry (LSV) curves of hydrogen evolution of the catalyst were collected before long-term stability testing and after 500-h chronopotential stability testing, with a scan rate of 5 mV / s and a reversible hydrogen electrode (RHE) as the reference. The hydrogen evolution polarization performance before and after the stability test was compared, and the values ​​were recorded at -300 mA·cm⁻¹. -2 The hydrogen evolution overpotential corresponding to the current density was used to obtain a comparison curve of hydrogen evolution performance before and after the stability test, as shown in the figure. Figure 8 As shown in the figure. It can be seen from the figure that the composite catalyst prepared in this embodiment has a performance of -300 mA·cm⁻¹. -2 Under current density conditions, the hydrogen evolution overpotential before the stability test was -80.11 mV; after 500 h of high-current hydrogen evolution stability testing, the hydrogen evolution overpotential was -84.69 mV. After long-term electrolysis testing, the catalyst's hydrogen evolution overpotential only increased slightly by 4.58 mV, and the polarization curves almost overlapped. These test results indicate that after prolonged high-current hydrogen evolution operation, the intrinsic hydrogen evolution catalytic activity of the catalyst hardly decreased, further confirming that this porous nickel-based nitrogen-doped tungsten oxide-supported Ce-La composite catalyst possesses excellent electrochemical stability and can maintain good hydrogen evolution catalytic activity under high-current electrolysis conditions.

[0049] d. Stability test of oxygen evolution catalytic activity The stability of the hydrogen evolution catalytic activity of the composite catalyst prepared in this embodiment was tested using the same method as in step b, and the results are as follows. Figure 9 As shown, at 500mA·cm -2 After 500 hours of continuous operation at high current density, the working electrode potential of the catalyst did not show a significant positive drift, and the potential curve remained stable overall, without any significant increase or abrupt decay. Minor fluctuations were observed in the electrolysis process curve, which are normal test noise caused by oxygen bubble disturbances. This indicates that under high current oxygen evolution conditions, the active component of this composite catalyst is firmly bonded to the nickel mesh matrix, can withstand the erosion of a large number of oxygen bubbles, has strong resistance to oxidation and corrosion, and possesses excellent long-term electrochemical stability for oxygen evolution, maintaining stable oxygen evolution catalytic activity over a long period.

[0050] Linear sweep voltammetry (LSV) curves of the catalyst were collected before the long-term oxygen evolution stability test and after the 500-h chronopotential stability test. The scan rate was set to 5 mV / s, and the potential was compared with the reversible hydrogen electrode (RHE). The oxygen evolution polarization performance before and after the stability test was compared, and the values ​​were recorded at 300 mA·cm⁻¹. -2 The oxygen evolution overpotential corresponding to the flux density was used to obtain a comparison curve of oxygen evolution performance before and after the stability test, as shown in the figure. Figure 10 As shown in the figure. It can be seen from the figure that at 300 mA·cm -2 At the given current density, the oxygen evolution overpotential of the catalyst before the stability test was 267.31 mV; after 500 h of high-current oxygen evolution stability testing, the overpotential was 264.27 mV. The overpotential decreased slightly by 3.04 mV after long-term electrolysis, and the polarization curves before and after the stability test essentially overlapped. This indicates that after long-term operation under high-current oxygen evolution conditions, the catalyst's oxygen evolution catalytic activity did not decrease, and even underwent slight activation, further verifying that the composite catalyst possesses excellent electrochemical stability for oxygen evolution.

[0051] In summary, the composite catalyst prepared in this embodiment has a strong bond between the active component and the nickel mesh matrix, can withstand bubble erosion under high current conditions, has excellent corrosion resistance, high hydrogen evolution and oxygen evolution catalytic activity, and good long-term operational stability, making it suitable for hydrogen production applications under high current conditions through water splitting.

[0052] Example 2 This embodiment relates to the preparation of a porous nickel-based nitrogen-doped tungsten oxide supported Ce-La composite catalyst, which differs from Example 1 only in that: In step (1), the mixed powder consists of 2.0 g of ammonium metatungstate, 1 g of melamine and 7 g of sodium chloride; the pyrolysis temperature is 550 ℃ and the holding time is 5 h; the reduction heat treatment is carried out in a mixed atmosphere of 10% H2 / 90% Ar (volume ratio), and the rest of the operations are the same.

[0053] In step (2), the amount of La(NO3)3 added was increased to 1 g, and the rest of the operation was the same, so as to prepare the corresponding porous nickel-based nitrogen-doped tungsten oxide supported Ce-La composite catalyst.

[0054] The catalytic performance of the composite catalyst prepared in this embodiment was tested using the same method as in Example 1, and the results are as follows: Figure 5 As shown in sample 4, at -300 mA·cm -2 At the given current density, the hydrogen evolution overpotential is -95.07 mV; For example Figure 6 As shown in sample 4, at 300 mA·cm -2 At the current density, the oxygen evolution overpotential is 295.33 mV.

[0055] Comparative Example 1 This comparative example relates to the preparation of a porous nickel-based nitrogen-doped tungsten oxide-supported Ce-La composite catalyst. The only difference from Example 1 is that the composite catalyst is prepared by direct one-pot pyrolysis, as detailed below: 2.0 g of ammonium metatungstate, 0.5 g of melamine, 1 g of Ce(NO3)3, 0.65 g of La(NO3)3, 0.029 g of citric acid, and 7.5 g of sodium chloride were weighed and ground in an agate mortar for 25 min until uniformly mixed to obtain a mixed powder. The prepared mixed powder was placed in an alumina crucible, and a pretreated nickel mesh was embedded in the mixed powder. The mesh was gently pressed to ensure that the powder completely filled and covered the entire surface of the substrate, ensuring that the substrate was completely wrapped by the mixed powder. The alumina crucible containing the sample was placed in a tube furnace and heated to 600 ℃ at 3 ℃ / min under an air atmosphere, held at that temperature for 3 h, and subjected to oxygen-containing atmosphere pyrolysis at an air flow rate of 100 mL / min. After cooling to room temperature with the furnace, the sample was removed and ultrasonically washed three times with hot water at 70-80 ℃ for 15 min each time, followed by washing twice with anhydrous ethanol, and vacuum dried at 70 ℃ for 8 h to obtain a porous nickel-based nitrogen-doped tungsten oxide-supported Ce-La composite catalyst.

[0056] The catalytic performance of the composite catalyst prepared in this comparative example was tested using the same method as in Example 1. The test results are as follows: Figure 5 As shown in sample 1, at -300 mA·cm -2 At the given current density, the hydrogen evolution overpotential is -268.00 mV; For example Figure 6 As shown in sample 1, at 300 mA·cm -2 At the current density, the oxygen evolution overpotential is 450.45 mV.

[0057] Comparative Example 2 This comparative example relates to the preparation of a porous nickel-based nitrogen-doped tungsten oxide supported Ce-Y composite catalyst. The only difference from Example 1 is that iridium acetate is used instead of La(NO3)3 in equal molar amounts. All other operations are the same, and the corresponding porous nickel-based nitrogen-doped tungsten oxide supported Ce-Y composite catalyst is prepared.

[0058] The catalytic performance of the composite catalyst prepared in this comparative example was tested using the same method as in Example 1. The test results are as follows: Figure 5 As shown in sample 2, at -300 mA·cm -2 At the given current density, the hydrogen evolution overpotential is -110.39 mV; For example Figure 6 As shown in sample 2, at 300 mA·cm -2 At the current density, the oxygen evolution overpotential is 325.29 mV.

[0059] Comparative Example 3 This comparative example relates to the preparation of a porous nickel-based nitrogen-doped tungsten oxide supported Ce-La composite catalyst. The only difference from Example 1 is that step (1) does not include the reduction heat treatment step, while the other operations are the same, and the corresponding porous nickel-based nitrogen-doped tungsten oxide supported Ce-La composite catalyst is prepared.

[0060] The catalytic performance of the composite catalyst prepared in this comparative example was tested using the same method as in Example 1. The test results are as follows: Figure 5 As shown in sample 5, at -300 mA·cm -2 At the given current density, the hydrogen evolution overpotential is -125.23 mV; For example Figure 6 As shown in sample 5, at 300 mA·cm -2 At the current density, the oxygen evolution overpotential is 369.05 mV.

[0061] The hydrogen evolution and oxygen evolution catalytic activity data of the composite catalysts prepared in the above embodiments and comparative examples are summarized in Table 1 below: Table 1

[0062] As shown in Table 1, this invention utilizes a step-by-step process involving the pyrolysis of mixed powder in an oxygen-containing atmosphere, reduction heat treatment in a hydrogen / inert atmosphere, and secondary heat treatment in an inert atmosphere after impregnation with rare earth solution. This process sequentially constructs nitrogen-doped WO3 on a porous nickel substrate. 3-x A porous nickel-based nitrogen-doped tungsten oxide-supported Ce-La composite catalyst was obtained by combining an active layer with a Ce-La oxide modification layer. Compared with Comparative Example 1 prepared by one-pot pyrolysis, Example 1, using the above-described stepwise process, reduced the hydrogen evolution overpotential from -268.00 mV to -80.11 mV and the oxygen evolution overpotential from 450.45 mV to 267.31 mV, resulting in a more than 3-fold increase in catalytic activity. Therefore, the stepwise construction of the active layer and rare earth modification layer provided by this invention can effectively avoid mutual interference between components at high temperatures, ensuring the nitrogen-doped WO3... 3-x Sufficient formation and exposure of the active phase and Ce-La synergistic sites.

[0063] Furthermore, as shown in Example 1 and Comparative Examples 2 and 3, the reduction heat treatment combined with the Ce-La dual rare earth synergy is key to improving catalytic performance. In Comparative Example 3, after omitting the reduction heat treatment, the hydrogen evolution overpotential was -125.23 mV and the oxygen evolution overpotential was 369.05 mV, indicating a significant deterioration in performance compared to Example 1. This also demonstrates that hydrogen / inert atmosphere reduction is crucial for introducing oxygen vacancies and regulating WO3. 3-xElectronic structure is indispensable; in Comparative Example 2, after replacing La with Y, the hydrogen evolution overpotential was -110.39 mV and the oxygen evolution overpotential was 325.29 mV, both of which were inferior to those in Example 1, indicating that the specific electronic structure of La in the Ce-La dual rare earth combination plays an irreplaceable role in enhancing interfacial synergy.

[0064] In summary, the porous nickel-based nitrogen-doped tungsten oxide-supported Ce-La composite catalyst prepared by this invention, through the synergistic effect of process and materials, possesses both high hydrogen / oxygen evolution activity and long-term stability, making it suitable for high-current whole-water splitting hydrogen production applications and showing significant industrial application prospects.

[0065] The above-described embodiments are merely preferred embodiments provided to fully illustrate the present invention, and the scope of protection of the present invention is not limited thereto. Equivalent substitutions or modifications made by those skilled in the art based on the present invention are all within the scope of protection of the present invention. The scope of protection of the present invention is defined by the claims.

Claims

1. A method for preparing a porous nickel-based nitrogen-doped tungsten oxide-supported Ce-La composite catalyst, characterized in that, Includes the following steps: S1. A porous nickel substrate is mixed with a mixed powder containing a tungsten source, a nitrogen source, and an inorganic salt, so that the substrate is completely coated with the mixed powder. The mixture is then pyrolyzed at 550-650 °C in an oxygen-containing atmosphere. Following this, a reduction heat treatment is performed in a mixed atmosphere containing hydrogen and an inert gas. After washing and drying, nitrogen-doped WO3 is obtained. 3-x Loaded porous nickel; S2, The nitrogen-doped WO 3-x The supported porous nickel was impregnated in a mixed solution containing cerium salt and lanthanum salt, removed and dried, and then subjected to a second heat treatment under an inert atmosphere to obtain the porous nickel-based nitrogen-doped tungsten oxide supported Ce-La composite catalyst.

2. The preparation method according to claim 1, characterized in that, In step S1, the porous nickel substrate includes one of nickel mesh and nickel foam; And / or, the tungsten source includes one or more of ammonium metatungstate, ammonium tungstate, ammonium paratungstate, sodium tungstate, potassium tungstate, and tungsten chloride; And / or, the nitrogen source includes one or more of urea, melamine, and ammonium chloride; And / or, the inorganic salt is NaCl and / or KCl.

3. The preparation method according to claim 1 or 2, characterized in that, In step S1, the molar ratio of the tungsten source (W) to the nitrogen source (N) is 1:(1-5). And / or, the ratio of the sum of the masses of the tungsten source and the nitrogen source to the mass of the inorganic salt is 1:(1-10).

4. The preparation method according to claim 1, characterized in that, In step S1, the oxygen-containing atmosphere is air; And / or, in the pyrolysis step: the heat preservation time is 1-5 h.

5. The preparation method according to claim 1, characterized in that, In step S1, the volume fraction of hydrogen in the mixed atmosphere is 5%-10%, and the inert gas is nitrogen and / or argon. And / or, the reduction heat treatment is performed at a temperature of 400-550 °C for a time of 1-3 h; And / or, the washing is hot water washing.

6. The preparation method according to claim 1, characterized in that, In step S2, the cerium salt includes one or more of cerium nitrate, cerium chloride, cerium sulfate, and cerium acetate; And / or, the lanthanum salt includes one or more of lanthanum nitrate, lanthanum chloride, lanthanum sulfate, and lanthanum acetate; And / or, the molar ratio of cerium ions to lanthanum ions in the mixed solution is (1-2):1, and the total metal ion concentration is 0.05-2 mol / L; And / or, the mixed solution may further contain a complexing agent.

7. The preparation method according to claim 1, characterized in that, In step S2, the soaking time is 6-24 hours; And / or, the inert atmosphere is nitrogen and / or argon; And / or, the second heat treatment is performed at a temperature of 400-600 °C for 2-4 h.

8. A porous nickel-based nitrogen-doped tungsten oxide-supported Ce-La composite catalyst, characterized in that, It is prepared by the preparation method described in any one of claims 1-7.

9. The application of the porous nickel-based nitrogen-doped tungsten oxide supported Ce-La composite catalyst according to claim 8 in alkaline water electrolysis for hydrogen evolution and / or oxygen evolution reactions.

10. The application according to claim 9, characterized in that, In 1 M KOH at -300 mA·cm -2 At the current density, the absolute value of the hydrogen evolution overpotential is less than 100 mV; In 1 M KOH at 300 mA·cm -2 At the current density, the absolute value of the oxygen evolution overpotential is less than 300 mV.

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