Electrolysis water catalyst doped with heterojunction and preparation method and application thereof

Abstract

This invention relates to the field of oilfield chemistry technology, specifically to a doped and heterojunction synergistic water electrolysis catalyst, its preparation method, and its application. The latter includes: immersing copper foam in a ferric ion solution; then adding ammonium molybdate and hydrochloric acid to the ferric ion solution to form a mixed immersion solution; ultrasonically treating the copper foam in the mixed immersion solution and allowing it to stand to obtain MoO. x / Foamed copper material; with MoO x Using copper foam as the working electrode, platinum sheet as the counter electrode, and Ag / AgCl electrode as the reference electrode, electrodeposition is performed in the electrolyte to obtain a water electrolysis catalyst with synergistic doping and heterojunction. This invention induces the formation of unique broccoli-shaped nanoclusters through specific pretreatment steps, and, combined with molybdenum doping, oxygen vacancies, and the generation of crystalline / amorphous heterojunction interfaces, significantly improves catalyst activity and electron transport efficiency. Its self-supporting structure enhances stability, and the preparation process is simple, environmentally friendly, and easily scalable.

Description

Technical Field

[0001] This invention relates to the field of oilfield chemical technology, specifically to a doped and heterojunction synergistic electrolytic water catalyst, its preparation method, and its application. Background Technology

[0002] Anion exchange membrane electrolysis (AEMWE) technology has made significant progress in recent years, driven by the demands for clean energy and sustainable development. This technology combines the advantages of alkaline water electrolysis (AWE) and proton exchange membrane electrolysis (PEMWE), aiming to achieve low-cost, high-efficiency hydrogen production. With continuous innovation and optimization in membrane materials, catalysts, membrane electrode assembly (MEA) fabrication technologies, and electrolyzer design, AEMWE technology is gradually moving towards commercial application. To meet the industrialization requirements of AEMWE, HER catalysts need to focus on optimizing three core characteristics: First, by designing mass transfer enhancement structures through porous arrays, nano-hierarchical structures, or surface wettability regulation, to promote rapid bubble detachment and efficient reactant replenishment; second, by employing alloying, doping, or conductive substrate composite strategies to achieve a synergistic improvement in high conductivity and activity, enhancing intrinsic conductivity while maintaining a high density of active sites; and third, by optimizing mechanical stability through multi-scale coupling structures, enhancing the bonding force between the catalyst and the substrate, resisting mechanical failure caused by bubble impact under high current, thereby ensuring long-term operational reliability.

[0003] High current density (HCD) environments present new challenges for catalysts. Most non-noble metal HER catalysts, under HCD conditions, exhibit insufficient intrinsic activity and conductivity due to low intrinsic conductivity and high reaction barriers, resulting in limited electron transfer rates and difficulty in maintaining efficient reaction kinetics, leading to low activity and severe activity decay. Secondly, mass transfer is restricted; the rapid consumption of reactant ions and accumulation of H2 at high current densities can block active sites on the catalyst surface, and increased bubble retention and mass transfer resistance significantly reduce reaction efficiency. Furthermore, insufficient long-term durability is a concern. Under harsh electrolyte environments and repeated electrochemical cycles, catalysts are prone to structural evolution, escape of active elements, and decreased chemical stability, leading to rapid degradation of catalytic performance and making it difficult to meet the requirements for long-term stable operation in industrial applications. Therefore, the destructive forces generated by electrolyte convection and bubble collapse at high current densities place higher demands on the mechanical strength of catalysts. Designing catalyst structures that combine high activity and high mechanical stability to prevent catalyst detachment or failure during long-term operation is also a key issue for realizing the industrial application of HER catalysts.

[0004] Chinese patent document CN113856711A discloses a method for preparing a high-efficiency nickel-cobalt phosphide heterojunction catalyst. Using foamed cobalt-nickel as a substrate, the substrate is cut and placed in a dual-temperature zone tube furnace. A Co2P / Ni2P porous conductive framework is obtained through thermal phosphating with phosphoric acid powder, followed by a second phosphating with a cobalt-nickel salt solution to form a nanoporous structure. This catalyst significantly improves the exposure rate of active sites and reduces contact resistance through heterojunction interface design, exhibiting excellent hydrogen evolution performance in alkaline electrolytes. However, it does not mention stability data at high current densities, only operating at lower current densities, and does not provide data on operating cycles, failing to meet industrial operation requirements. Furthermore, the method is relatively complex, requiring 100°C nitrogen protection and an oil bath, making it difficult to scale up and mass-produce.

[0005] Chinese patent document CN109999861A discloses a nickel-cobalt bimetallic phosphide electrocatalyst, its synthesis method, and its applications. A NiCo-PBA precursor is obtained by aging a mixture of potassium cobalt cyanide and a nickel salt solution. This precursor is then treated with ammonia to form a hollow structure, followed by low-temperature phosphating to obtain the bimetallic phosphide. This catalyst exhibits a low hydrogen evolution overpotential under acidic conditions and excellent oxygen evolution reaction activity, and can simultaneously catalyze the entire water electrolysis reaction, making it suitable for high-efficiency water electrolysis devices. Its preparation process involves multiple stages, including electrochemical deposition, nitriding, and chemical vapor deposition. Each stage requires precise control of reaction conditions and parameters, such as voltage, temperature, and atmosphere flow rate, which may lead to a long preparation cycle and low yield. Furthermore, although the catalyst exhibits excellent performance in the hydrogen evolution reaction of water electrolysis, it is highly sensitive to minute changes in preparation conditions, increasing the difficulty of controlling these conditions in practical applications. Even small fluctuations in temperature or instability in atmosphere flow rate can affect the final performance of the catalyst, thus limiting its feasibility for large-scale industrial applications.

[0006] Chinese patent document CN111841589A discloses a nickel-cobalt-tungsten phosphide catalyst, its preparation method, and its applications. The method first pretreats the surface of nickel-cobalt alloy foam using dielectric barrier discharge plasma (DPS) at a power of 50-100 W for 5-20 min to enhance its conductivity and specific surface area. The pretreated foam is then placed in a sodium tungstate solution with a pH of 4-7 and subjected to a hydrothermal reaction at 120-210 °C for 3-12 h to obtain a nickel-cobalt-tungsten oxide precursor. Finally, phosphating is performed in a tube furnace using red phosphorus as the phosphorus source at 450-750 °C under a nitrogen or argon atmosphere for 1-4 h to obtain an octahedral nickel-cobalt-tungsten phosphide catalyst. This method, combining plasma pretreatment with hydrothermal-phosphating, significantly improves the catalyst's hydrogen evolution performance and stability, avoids metal salt contamination, and shows promising prospects for industrial application. Non-precious metal catalysts have limited electron transport capabilities, and although their octahedral nickel-cobalt-tungsten phosphides are prepared through plasma pretreatment and hydrothermal reaction, the phosphating temperature is high, the energy consumption is large, and the requirements for the high temperature resistance of the equipment are strict, which increases the cost of industrial production.

[0007] Chinese patent document CN115466979A discloses a method for preparing a nickel-cobalt-phosphorus electrocatalyst for efficient water electrolysis and hydrogen evolution. Using a metal foam substrate as a pretreatment, followed by acid washing, acetone and ethanol cleaning, the substrate is used as the working electrode. Electrochemical cyclic voltammetric deposition is performed in a mixed electrolyte containing Ni²⁺, Co²⁺ and PO₄³⁻ to obtain a nickel-cobalt-phosphorus precursor. Subsequently, a low-temperature phosphating treatment is performed at below 400°C under an inert atmosphere, with sodium hypophosphite as the phosphorus source, ultimately yielding a highly active and stable nickel-cobalt-phosphorus electrocatalyst. This method, combining electrodeposition and low-temperature phosphating, significantly improves the catalyst's hydrogen evolution performance in alkaline electrolytes, exhibiting a low overpotential and good electrochemical stability. However, while this method combines electrochemical deposition and low-temperature phosphating to prepare the nickel-cobalt-phosphorus electrode, it lacks the specific element doping to regulate the hydrogen adsorption free energy, resulting in a slower hydrogen evolution reaction kinetics. Furthermore, the use of concentrated hydrofluoric acid for etching poses safety risks and environmental pollution problems.

[0008] Chinese patent document CN109037709A discloses a method for preparing a nickel-cobalt-phosphorus co-doped carbon-based catalyst. A hollow polyhedral structure is generated through a hydrothermal reaction of a ZIF-67 precursor with a nickel salt solution, followed by phosphating to obtain a functionalized material. When used as a positive electrode catalyst in zinc-air batteries, this catalyst exhibits a discharge voltage of 1.45V and a charge-discharge cycle life exceeding 2000 cycles. Furthermore, the preparation process is environmentally friendly and suitable for high-energy-density energy storage devices. However, the catalyst is in powder form and requires a binder to fix it to the electrode when used as a catalytic electrode. The use of a binder may weaken the electrode's conductivity, leading to the obscuring of active sites and thus reducing the catalyst's activity. Summary of the Invention

[0009] This invention provides a doped and heterojunction synergistic water electrolysis catalyst and its preparation method, which overcomes the shortcomings of the prior art and can effectively solve the problems of insufficient electron supply, limited mass transfer, and poor stability of existing water electrolysis hydrogen evolution catalysts under high current density.

[0010] One of the technical solutions of this invention is achieved through the following measures: a method for preparing a doped and heterojunction synergistic water electrolysis catalyst, comprising the following steps: Step 1: Immerse the copper foam in a ferric ion solution. Then, add ammonium molybdate and hydrochloric acid to the ferric ion solution to form a mixed immersion solution. After ultrasonic treatment in the mixed immersion solution and standing, MoO is obtained. x / Foamed copper material; Step two, using MoO x Using copper foam as the working electrode, platinum sheet as the counter electrode, and Ag / AgCl electrode as the reference electrode, electrodeposition was performed in the electrolyte to obtain a water electrolysis catalyst with doping and heterojunction synergy.

[0011] The following are further optimizations and / or improvements to one of the above-mentioned inventive technical solutions: The above-mentioned ferric ion solution is a Fe(NO3)3 solution, and the concentration of ferric ions in the ferric ion solution is 0.02 mol / L to 0.05 mol / L.

[0012] The concentration of ammonium molybdate in the above mixed soaking solution is 0.01 mol / L to 0.14 mol / L, and the concentration of hydrochloric acid is 0.3 mol / L to 0.6 mol / L.

[0013] The concentration of hydrochloric acid in the above mixed soaking solution is 0.4 mol / L to 0.56 mol / L.

[0014] The molar concentration ratio of the above-mentioned ferric ions and ammonium molybdate in the mixed soaking solution is (4 to 1): (1 to 4).

[0015] The molar ratio of the trivalent iron ions and ammonium molybdate in the mixed soaking solution is 2:1.5 to 2.5:1.

[0016] The above-mentioned copper foam was soaked in a ferric ion solution for 12 to 18 minutes at a temperature of 15°C to 35°C; the copper foam was ultrasonically treated in a mixed soaking solution for 3 to 15 minutes, and then left to stand for 3 to 15 minutes after ultrasonic treatment.

[0017] The electrolyte is a mixture of divalent cobalt ions, divalent nickel ions, sodium acetate, and sodium hypophosphite; wherein the concentration of divalent cobalt ions is 0.072 mol / L to 0.085 mol / L, the concentration of divalent nickel ions is 0.02 mol / L to 0.07 mol / L, the concentration of sodium acetate is 0.1 mol / L to 0.4 mol / L, and the concentration of sodium hypophosphite is 0.1 mol / L to 0.4 mol / L.

[0018] The electrodeposition time is 10 min to 25 min.

[0019] The second technical solution of the present invention is achieved through the following measures: a method for preparing a doped and heterojunction synergistic water electrolysis catalyst to obtain a doped and heterojunction synergistic water electrolysis catalyst.

[0020] The third technical solution of the present invention is achieved through the following measures: the application of a doped and heterojunction synergistic water electrolysis catalyst in water electrolysis.

[0021] This invention provides a doped and heterojunction synergistic water electrolysis catalyst and its preparation method. Through specific pretreatment steps, a unique broccoli-shaped nanocluster structure is induced to form. Combined with molybdenum doping, oxygen defects, and the generation of crystalline / amorphous heterojunction interfaces, the catalyst activity and electron transport efficiency are significantly improved. Its self-supporting structure enhances stability. The preparation process is simple, environmentally friendly, and easy to scale up, meeting the industrial-grade hydrogen evolution requirements of water electrolysis. Attached Figure Description

[0022] Appendix Figure 1 These are TEM images of the catalysts prepared in Example 11 and Comparative Example 1 of the present invention.

[0023] Appendix Figure 2 The images show the XRD patterns of the catalysts prepared in Example 11 and Comparative Example 1 of this invention.

[0024] Appendix Figure 3 The images show the ESR diagrams of the catalysts prepared in Example 11 and Comparative Example 1 of this invention.

[0025] Appendix Figure 4 SEM images of the catalysts prepared in Example 11 and Comparative Examples 1 to 4 of this invention.

[0026] Appendix Figure 5 This is a stability diagram of the three-electrode system of the catalyst prepared in Example 11 of the present invention.

[0027] Appendix Figure 6 The HER polarization curves are for the catalysts prepared in Example 11 and Comparative Examples 1, 2, and 12 of this invention. Detailed Implementation

[0028] This invention is not limited to the following embodiments, and specific implementation methods can be determined according to the technical solutions and actual conditions of this invention. Unless otherwise specified, all chemical reagents and chemicals mentioned in this invention are well-known and commonly used chemical reagents and chemicals in the prior art; unless otherwise specified, all percentages in this invention are mass percentages; unless otherwise specified, all solutions in this invention are aqueous solutions with water as the solvent, for example, hydrochloric acid solution is an aqueous solution of hydrochloric acid; room temperature in this invention generally refers to a temperature between 15°C and 25°C, generally defined as 25°C.

[0029] The present invention will be further described below with reference to embodiments: Example 1: The preparation method of the doped and heterojunction synergistic water electrolysis catalyst includes the following steps: Step 1: Immerse the copper foam in a ferric ion solution. Then, add ammonium molybdate and hydrochloric acid to the ferric ion solution to form a mixed immersion solution. After ultrasonic treatment in the mixed immersion solution and standing, MoO is obtained. x / Foamed copper material; Step two, using MoO x Using copper foam as the working electrode, platinum sheet as the counter electrode, and Ag / AgCl electrode as the reference electrode, electrodeposition was performed in the electrolyte to obtain a water electrolysis catalyst with doping and heterojunction synergy.

[0030] Example 2: As an optimization of the above example, the ferric ion solution is a Fe(NO3)3 solution, and the concentration of ferric ions in the ferric ion solution is 0.02 mol / L to 0.05 mol / L.

[0031] Example 3: As an optimization of the above example, the concentration of ammonium molybdate in the mixed soaking solution is 0.01 mol / L to 0.14 mol / L, and the concentration of hydrochloric acid is 0.3 mol / L to 0.6 mol / L.

[0032] Example 4: As an optimization of Example 3 above, the concentration of hydrochloric acid in the mixed soaking solution is 0.4 mol / L to 0.56 mol / L.

[0033] Example 5: As an optimization of the above example, the molar concentration ratio of ferric ions and ammonium molybdate in the mixed soaking solution is (4 to 1): (1 to 4).

[0034] Example 6: As an optimization of Example 4 above, the molar ratio of ferric ions to ammonium molybdate in the mixed soaking solution is 2:1.5 to 2.5:1.

[0035] Example 7: As an optimization of the above example, the soaking time of copper foam in ferric ion solution is 12 min to 18 min, and the soaking temperature is 15°C to 35°C; the ultrasonic treatment time of copper foam in mixed soaking solution is 3 min to 15 min, and it is left to stand for 3 min to 15 min after ultrasonic treatment.

[0036] Example 8: As an optimization of the above example, the electrolyte is a mixture of divalent cobalt ions, divalent nickel ions, sodium acetate and sodium hypophosphite; wherein the concentration of divalent cobalt ions is 0.072 mol / L to 0.085 mol / L, the concentration of divalent nickel ions is 0.02 mol / L to 0.07 mol / L, the concentration of sodium acetate is 0.1 mol / L to 0.4 mol / L, and the concentration of sodium hypophosphite is 0.1 to 0.4 mol / L.

[0037] Example 9: As an optimization of the above example, the electrodeposition time is 10 min to 25 min.

[0038] Example 10: Application of the doped and heterojunction synergistic water electrolysis catalyst in water electrolysis.

[0039] This invention, through the synergistic effects of doping, morphology control, defect engineering, and phase engineering, yields a highly efficient, stable, and noble metal-free cathode catalytic electrode that can be directly used in anion exchange membrane electrolyzers. Firstly, this invention incorporates MoO₂ into NiCoP through specific pretreatment steps. x This invention not only improves HER kinetics by adjusting the catalyst's adsorption energy for H* through Mo doping, but also generates a large number of oxygen vacancies and crystalline / amorphous heterogeneous interfaces on the catalyst surface, further enhancing HER activity. Secondly, this invention can induce the formation of broccoli-shaped nanoclusters on the surface of copper foam, providing more active sites for the electrocatalytic reaction, facilitating better electrolyte penetration into the material, promoting rapid product removal, reducing mass transfer resistance, and increasing the reaction rate. Furthermore, through the synergistic regulation of molybdenum doping and oxygen defects, a NiCoP-Ni(Co) structure with crystalline / amorphous heterogeneous interfaces is constructed on a copper foam substrate. y (PO4) z / MoO x / Copper foam composite material. This structure significantly enhances the intrinsic activity of the material by optimizing electronic interactions and adjusting oxygen defect concentration through molybdenum doping; the synergistic effect between crystalline and amorphous components further improves HER kinetics, achieving lower overpotential, higher electrochemical active surface area, and charge transfer efficiency, providing a new strategy for the design of highly efficient electrocatalytic hydrogen evolution materials. Furthermore, as a self-supporting catalyst, it is prepared through in-situ growth, which allows for strong electronic interactions between the catalyst and the matrix. This interaction not only enhances the bonding force between the catalyst and the matrix but also significantly improves the stability of the entire catalyst system. Specifically, MoO... x The rough and conductive surface provided by the copper foam substrate firmly supports the active components and modulates the electronic interaction between NiCoP and phosphate, thereby ensuring the high efficiency and durability of the catalyst under various operating conditions. Finally, this invention uses a chemical solution-electrodeposition method to prepare the catalyst, which is simple and easy to scale up. It requires no additional processing and can be assembled into an anion exchange membrane electrolyzer as a cathode catalytic electrode simply through mechanical stacking.

[0040] Example 11: The preparation process of this doped and heterojunction synergistic water electrolysis catalyst is as follows: (1) Clean the foamed copper successively with hydrochloric acid and deionized water, and then ultrasonically clean it with deionized water and ethanol for a period of time to remove impurities such as organic matter and oxides on the surface. Then dry it in a vacuum drying oven at 60°C. o Dry at C for 6 hours.

[0041] (2) Cut the cleaned and dried foam copper into 2×2cm pieces. 2 The copper foam was immersed in a 0.04 mol / L Fe(NO3)3·9H2O solution at room temperature for 15 min. Ammonium molybdate and hydrochloric acid were then added to form a mixed immersion solution. The concentration of ammonium molybdate in the mixed immersion solution was 0.02 mol / L (i.e., the molar ratio of ammonium molybdate to Fe(NO3)3·9H2O in the mixed immersion solution was 2:1), and the concentration of hydrochloric acid was 0.48 mol / L. The mixture was ultrasonically treated for 10 min, allowed to stand for 5 min, and then the reacted copper foam was removed, washed with deionized water, and dried to obtain MoO2. x / Foamed copper.

[0042] (3) Prepare the electrolyte with the following composition: 0.078 mol / L CoCl2·6H2O, 0.05 mol / L NiSO4·6H2O, 0.3 mol / L CH3COONa, and 0.3 mol / L NaH2PO2·H2O; with MoO xUsing copper foam as the working electrode, a platinum sheet as the counter electrode, and an Ag / AgCl electrode as the reference electrode, electrodeposition was performed for 15 minutes. The electrodepositor was then flipped over and subjected to the same conditions for another 3 minutes, followed by drying. The catalyst prepared in this example is designated as S1.

[0043] Example 12: The difference from Example 11 is that the molar concentration of hydrochloric acid in the mixed soaking solution in step (2) is 0.52 mol / L. The catalyst prepared in this example is designated as S2.

[0044] Example 13: The difference from Example 11 is that the molar concentration of hydrochloric acid in the mixed soaking solution in step (2) is 0.56 mol / L. The catalyst prepared in this example is designated as S3.

[0045] Example 14: The difference from Example 11 is that the molar concentration of hydrochloric acid in the mixed soaking solution in step (2) is 0.58 mol / L. The catalyst prepared in this example is designated as S4.

[0046] Example 15: The difference from Example 11 is that the molar concentration of hydrochloric acid in the mixed soaking solution in step (2) is 0.44 mol / L. The catalyst prepared in this example is designated as S5.

[0047] Example 16: The difference from Example 11 is that the molar concentration of hydrochloric acid in the mixed soaking solution in step (2) is 0.4 mol / L. The catalyst prepared in this example is designated as S6.

[0048] Example 17: The difference from Example 11 is that the molar concentration of hydrochloric acid in the mixed soaking solution in step (2) is 0.36 mol / L. The catalyst prepared in this example is designated as S7.

[0049] Example 18: The difference from Example 11 is that in step (2), the molar ratio of Fe(NO3)3 in the Fe(NO3)3·9H2O solution to ammonium molybdate in the mixed soaking solution is 2:1.5. The catalyst prepared in this example is designated as S8.

[0050] Example 19: The difference from Example 11 is that in step (2), the molar ratio of Fe(NO3)3 in the Fe(NO3)3·9H2O solution to ammonium molybdate in the mixed soaking solution is 2:2. The catalyst prepared in this example is denoted as S9.

[0051] Example 20: The difference from Example 11 is that in step (2), the molar ratio of Fe(NO3)3 in the Fe(NO3)3·9H2O solution to ammonium molybdate in the mixed soaking solution is 2:3.5. The catalyst prepared in this example is denoted as S10.

[0052] Example 21: The difference from Example 11 is that in step (2), the molar ratio of Fe(NO3)3 in the Fe(NO3)3·9H2O solution to ammonium molybdate in the mixed soaking solution is 2.5:1. The catalyst prepared in this example is denoted as S11.

[0053] Example 22: The difference from Example 11 is that in step (2), the molar ratio of Fe(NO3)3 in the Fe(NO3)3·9H2O solution to ammonium molybdate in the mixed soaking solution is 3:1. The catalyst prepared in this example is designated as S12.

[0054] Example 23: The difference from Example 11 is that in step (2), the molar ratio of Fe(NO3)3 in the Fe(NO3)3·9H2O solution to ammonium molybdate in the mixed soaking solution is 3.5:1. The catalyst prepared in this example is designated as S13.

[0055] Example 24: The difference from Example 11 is that in step (2), the molar ratio of Fe(NO3)3 in the Fe(NO3)3·9H2O solution to ammonium molybdate in the mixed soaking solution is 4:1, and the catalyst prepared in this example is denoted as S14.

[0056] Example 25: The difference from Example 11 is that in step (2), the ultrasonic treatment lasts for 3 minutes, followed by standing for 15 minutes. The catalyst prepared in this example is designated as S15.

[0057] Example 26: The difference from Example 11 is that in step (2), the ultrasonic treatment lasts for 15 minutes, followed by standing for 3 minutes. The catalyst prepared in this example is designated as S16.

[0058] Example 27: The difference from Example 11 is that the electrolyte in step (3) is 0.072 mol / L CoCl2·6H2O, 0.07 mol / L NiSO4·6H2O, 0.1 mol / L CH3COONa, and 0.4 mol / L NaH2PO2·H2O. The catalyst prepared in this example is designated as S17.

[0059] Example 28: The difference from Example 11 is that the electrolyte in step (3) is 0.085 mol / L CoCl2·6H2O, 0.02 mol / L NiSO4·6H2O, 0.4 mol / L CH3COONa, and 0.1 mol / L NaH2PO2·H2O. The catalyst prepared in this example is designated as S18.

[0060] Comparative Example 1: The difference from Example 11 is that step (2) is omitted, and the copper foam obtained in step (1) is directly used in step (3). The catalyst prepared in this comparative example is denoted as D1.

[0061] Comparative Example 2: The difference from Example 11 is that step (3) is not performed. The catalyst prepared in this comparative example is denoted as D2.

[0062] Comparative Example 3: The difference from Example 11 is that in step (2), the mixed soaking solution was replaced with an ammonium molybdate solution of the same molar concentration, i.e., hydrochloric acid was not added. The catalyst prepared in this comparative example is denoted as D3.

[0063] Comparative Example 4: The difference from Example 11 is that, in step (2), soaking in 0.04 mol / L Fe(NO3)3·9H2O solution is not performed. The catalyst prepared in this comparative example is designated as D4.

[0064] Comparative Example 5: The difference from Example 11 is that in step (2), the 0.48 mol / L hydrochloric acid in the mixed soaking solution was replaced with 0.48 mol / L sulfuric acid. The catalyst prepared in this comparative example is designated as D5.

[0065] Comparative Example 6: The difference from Example 11 is that in step (2), the 0.48 mol / L hydrochloric acid in the mixed soaking solution was replaced with 0.48 mol / L nitric acid. The catalyst prepared in this comparative example is designated as D6.

[0066] Comparative Example 7: The difference from Example 11 is that in step (2), the 0.48 mol / L hydrochloric acid in the mixed soaking solution was replaced with 0.48 mol / L phosphoric acid. The catalyst prepared in this comparative example is designated as D7.

[0067] Comparative Example 8: The difference from Example 11 is that in step (2), ammonium molybdate in the mixed soaking solution was replaced with ZnO of the same molar concentration. The catalyst prepared in this comparative example is denoted as D8.

[0068] Comparative Example 9: The difference from Example 11 is that in step (2), ammonium molybdate in the mixed soaking solution was replaced with TiCl4 of the same molar concentration. The catalyst prepared in this comparative example is designated as D9.

[0069] Comparative Example 10: The difference from Example 11 is that in step (2), ammonium molybdate in the mixed soaking solution was replaced with MnSO4 of the same molar concentration. The catalyst prepared in this comparative example is denoted as D10.

[0070] Comparative Example 11: The difference from Example 11 is that in step (2), the 0.04 mol / L Fe(NO3)3·9H2O solution soaking was not performed, and 0.48 mol / L hydrochloric acid was used to replace the mixed soaking solution. The catalyst prepared in this comparative example is denoted as D11.

[0071] Comparative Example 12: A commercially available 20% Pt / C electrode, purchased from Shanghai Hans Chemical Co., Ltd. It is designated as D12.

[0072] Test Example 1: Figure 1 TEM images of the catalysts prepared in Example 11 and Comparative Example 1 are shown, where (a) is catalyst S1 and (b) is catalyst D1. Figure (a) shows that catalyst S1 prepared in Example 11 has a clearly defined layered amorphous / crystalline heterostructure with interplanar spacings of 0.203 nm, 0.212 nm, and 0.230 nm, respectively, and belongs to NiCoP and NiP4O, respectively. 11 The presence of Mo and Co3(PO3)2 indicates that Mo doping leads to the formation of a layered amorphous / crystalline heterostructure. In contrast, catalyst D1 prepared in Comparative Example 1 in Figure (b) does not exhibit a similar layered structure.

[0073] Test Example 2: Figure 2 The images show the XRD patterns of catalysts S1 and D1 prepared in Example 11 and Comparative Example 1. Figure 2 Strong diffraction peaks were observed at three angles of 43.47°, 50.55° and 74.23° for all samples. These peaks correspond to the characteristic peaks of the copper Cu substrate (PDF#04-0836). Catalysts S1 and D1 both showed broad diffraction features centered at 21.75°, but the latter had a higher peak intensity, indicating that D1 had higher crystallinity. This suggests that Mo doping promoted structural amorphization.

[0074] Test Example 3: Figure 3 The ESR spectra of catalysts S1 and D1 prepared in Example 11 and Comparative Example 1 are shown. A comparison of catalyst S1 (red curve) and catalyst D1 (blue curve) reveals a distinct signal peak at a g-factor of 2.003. This peak indicates the presence of oxygen vacancies in both catalysts, resulting from unpaired electrons on the catalyst surface. Catalyst S1 exhibits a higher ESR signal intensity, reflecting a higher unpaired electron density, i.e., more oxygen vacancies. These oxygen vacancies significantly influence the electronic structure of the catalysts; these defects not only increase the specific surface area but also provide more active sites, enhancing their adsorption capacity for reaction intermediates and thus accelerating the electrocatalytic process.

[0075] Test Example 4: The catalysts prepared in Example 11, Comparative Example 1, Comparative Example 2, Comparative Example 3, and Comparative Example 4 were observed by scanning transmission electron microscopy (SEM), and the results are as follows: Figure 4 As shown. From Figure 4As can be seen, catalyst S1 synthesized in Example 11 exhibits a unique broccoli-shaped nanocluster structure. This three-dimensional porous morphology facilitates electrolyte permeation and bubble escape, thereby synergistically improving mass transfer efficiency and accessibility of active sites, providing a structural basis for efficient electrocatalytic hydrogen evolution reaction. SEM images of catalyst D1 show that the material without molybdenum doping treatment has a relatively dense structure, lacking the abundant pore space of catalyst S1, which is not conducive to electrolyte permeation and bubble escape, resulting in insufficient exposure of its active sites and affecting catalytic performance. Catalyst D2 did not undergo an electrodeposition step, and its microstructure differs significantly from catalyst S1. It lacks effective bonding between the active component and the substrate, failing to form structural features conducive to catalytic reaction, and exhibits an extremely high overpotential, indicating poor catalytic performance. In the SEM image of Comparative Example 3 (D3), the catalyst exhibits a single morphology. Due to the absence of hydrochloric acid, significant agglomeration occurs, with large and unevenly distributed particles. This indicates that the metal ion hydrolysis and precipitation process was not effectively regulated, the active components were poorly dispersed, and the surface lacked porous structure and nanocluster characteristics, which hindered electrolyte permeation and bubble escape, resulting in poor catalytic performance and high overpotential. In Comparative Example 4 (D4), the catalyst exhibited a relatively thin nanosheet structure. Although this structure increased surface roughness to some extent, compared to catalyst S1, its overall morphology lacked hierarchy and pore structure. This meant that bubbles generated at high current densities could cover the entire catalyst surface, hindering sufficient contact between the electrolyte and the catalyst, thus limiting its catalytic performance. In contrast, catalyst S1's broccoli-shaped nanocluster structure exhibited a clear hierarchical characteristic, with both large and small pores present. This hierarchical pore structure effectively promoted electrolyte permeation and bubble escape under high current density conditions, thereby improving mass transfer efficiency and the accessibility of active sites.

[0076] Test Example 5: Evaluation of Electrocatalytic Performance The HER performance of the catalyst materials prepared in Examples 11 to 26 and Comparative Examples 1 to 12 was tested using a Shanghai Chenhua 760e electrochemical workstation and a 680C current amplifier at a high current density of 1000 mA·cm⁻². The test conditions were as follows: the catalyst materials prepared in the above examples and comparative examples were used as the working electrode (size: 2cm × 2cm), the Hg / HgO electrode was used as the reference electrode, the graphite rod was used as the counter electrode, the electrolyte was a 1.0 mol / L KOH aqueous solution, and the test temperature was 35°C. The test results are shown in Tables 1 and 2.

[0077] The test results from S1 to S7 show that different hydrochloric acid concentrations have a significant impact on the HER performance of the catalyst. When the hydrochloric acid concentration is 0.48 mol / L (S1), the catalyst has the lowest overpotential at 1000 mA·cm⁻², which is only 213 mV. Hydrochloric acid mainly plays a role in regulating the acid-base environment of the reaction system during pretreatment, influencing the reaction pathway and doping uniformity of the molybdenum doping process by controlling the hydrolysis-precipitation equilibrium of metal ions in the precursor solution. A suitable hydrochloric acid concentration helps maintain the reaction system within the optimal acidity range, promoting effective binding between metal ions and dopant.

[0078] The test results from S1 and S8 to S14 show that the molar ratio of Fe to Mo also has a significant impact on catalytic performance. When the Fe:Mo ratio is 2:1 (S1), the material exhibits optimal HER activity. Deviations from this value all lead to an increase in overpotential, indicating that an appropriate doping ratio helps optimize the electronic structure and hydrogen adsorption energy of the material.

[0079] The results from S1, S15, and S16 indicate that the combination of ultrasound and settling time in the molybdenum doping treatment also affects the catalytic performance. The combination of "10 minutes of ultrasound + 5 minutes of settling" used in Example 11 showed the best results, with an overpotential of 213 mV. Figure 2 SEM morphology observation revealed that catalyst S1 exhibited a uniform broccoli-like nanocluster structure. This three-dimensional porous morphology facilitates electrolyte permeation and bubble escape, synergistically improving mass transfer efficiency and accessibility of active sites.

[0080] Comparative Example 1 (D1), without molybdenum doping, had an overpotential of 383 mV, significantly higher than S1, indicating that molybdenum doping plays a crucial role in enhancing HER activity. Comparative Example 2 (D2), without electrodeposition, had an extremely high overpotential (565 mV), demonstrating that the introduction of the NiCoP active layer is key to achieving efficient HER. Comparative Example 3 (D3), without hydrochloric acid, had an overpotential of 335 mV, further illustrating the influence of an acidic environment on the control of material composition and morphology during molybdenum doping. Comparative Example 4 (D4), using only ammonium molybdate without iron, had an overpotential of 324 mV, indicating that Fe-Mo synergistic doping plays a positive role in optimizing the material's electronic structure and catalytic performance. In Comparative Example 5 (D5), sulfuric acid (0.48 mol / L) was used instead of hydrochloric acid for pretreatment, and the results showed an overpotential of 389 mV at a high current density of 1000 mA·cm⁻². In Comparative Example 6 (D6), nitric acid (0.48 mol / L) was used instead of hydrochloric acid, resulting in an overpotential of 401 mV. In Comparative Example 7 (D7), phosphoric acid (0.48 mol / L) was used instead of hydrochloric acid, further increasing the overpotential to 422 mV. These data indicate that sulfuric acid, nitric acid, and phosphoric acid are all less effective than hydrochloric acid. Sulfuric acid performs slightly better than nitric acid and phosphoric acid, but still significantly worse than the hydrochloric acid-treated sample (overpotential 213 mV), highlighting the irreplaceable importance of hydrochloric acid in pretreatment. In Comparative Example 8 (D8), ZnO was used instead of ammonium molybdate for doping, increasing the overpotential to 431 mV. This shows that the introduction of ZnO cannot effectively optimize the electronic structure and active sites of the catalyst, and cannot replace the key role of ammonium molybdate in improving catalytic performance. In Comparative Example 9 (D9), TiCl4 was used for doping, resulting in an overpotential of 428 mV, significantly higher than S1, indicating that the doping effect of TiCl4 is inferior to that of ammonium molybdate. Comparative Example 10 (D10) used MnSO4 instead of ammonium molybdate, with an overpotential of 436 mV, which also failed to achieve the optimization effect of ammonium molybdate doping. Comparative Example 11 (D11) used only hydrochloric acid without metal doping during the molybdenum doping process. The test results showed that its overpotential at a high current density of 1000 mA·cm⁻² was 331 mV, which was higher than that of S1, further demonstrating that molybdenum doping has a positive effect on optimizing the electronic structure and catalytic performance of materials.

[0081] In summary, this invention successfully prepared a catalytic material with low overpotential at a high current density of 1000 mA·cm⁻² by optimizing parameters such as hydrochloric acid concentration, Fe:Mo ratio, and ultrasonic settling time. Its superior performance stems from the synergistic effect of multiple factors, including electronic structure modulation introduced by molybdenum doping, the formation of oxygen vacancy defects, the mass transfer advantages of the three-dimensional porous morphology, and the strong electronic coupling between the active component and the substrate. These characteristics collectively promote the efficient hydrogen evolution reaction of the material at high current densities, demonstrating promising prospects for industrial applications.

[0082] Test Example 6: HER polarization curve testing and stability assessment of the three-electrode system: Figure 5 The results of stability tests on the S1 catalyst prepared in Example 11 under a three-electrode system are presented. After long-term constant current density operation, the material still maintains a stable hydrogen evolution potential, exhibiting excellent electrochemical durability, indicating that the catalyst has good resistance to degradation under high current density conditions.

[0083] Test Example 7: Figure 6 The HER polarization curves for different samples show that the catalyst S1 in Example 11 has an overpotential of only 213 mV at a high current density of 1000 mA·cm⁻², which is significantly lower than that of the commercial Pt / C in Comparative Example 12 (270 mV) and other comparative examples, demonstrating excellent hydrogen evolution reaction activity. This superior performance is mainly due to the interaction between NiCoP and MoO. x Synergistic effect between them, MoO x Not only does it provide high conductivity and abundant active sites as a substrate, but it also optimizes the electronic structure of NiCoP through interfacial electronic interactions, reducing the hydrogen adsorption free energy and thus significantly improving the overall performance of the catalyst. This synergistic effect allows the catalyst to maintain a low overpotential even at a high current density of 1000 mA·cm⁻². As shown in Table 1, the molar ratio of Fe(NO₃)₃ to ammonium molybdate, the hydrochloric acid concentration, and the molybdenum doping treatment time all have a significant impact on the catalytic performance. Among them, S1 has the best overall parameters and achieves the lowest overpotential. These electrochemical test results indicate that S1 (NiCoP-Ni(Co)) obtained by rationally controlling the precursor preparation conditions... y (PO4) z / MoO x Copper foam material has excellent catalytic activity and stability, and has the potential to be applied to industrial-grade anion exchange membrane water electrolysis systems.

[0084] In summary, this invention induces the formation of a unique broccoli-shaped nanocluster structure through specific steps, and, combined with molybdenum doping, oxygen vacancies, and the generation of crystalline / amorphous heterostructures, significantly improves the electrochemical performance of the catalyst. The obtained catalyst possesses a three-dimensional structure that effectively reduces mass transfer resistance, and the self-supporting catalyst prepared by in-situ growth strengthens the bond between the catalyst and the matrix, enabling it to meet the challenges of high current density and long-term operation in industrial applications, ensuring high efficiency and reliability under various operating conditions.

[0085] The above technical features constitute various embodiments of the present invention, which have strong adaptability and implementation effect. Unnecessary technical features can be added or removed according to actual needs to meet the needs of different situations.

Claims

1. A method for preparing a doped and heterojunction synergistic water electrolysis catalyst, characterized in that... Includes the following steps: Step 1: Immerse the copper foam in a ferric ion solution. Then, add ammonium molybdate and hydrochloric acid to the ferric ion solution to form a mixed immersion solution. After ultrasonic treatment in the mixed immersion solution and standing, MoO is obtained. x / Foamed copper material; Step two, using MoO x Using copper foam as the working electrode, platinum sheet as the counter electrode, and Ag / AgCl electrode as the reference electrode, electrodeposition was performed in the electrolyte to obtain a water electrolysis catalyst with doping and heterojunction synergy.

2. The method for preparing the doped and heterojunction synergistic water electrolysis catalyst according to claim 1, characterized in that... The ferric ion solution is a Fe(NO3)3 solution, and the concentration of ferric ions in the ferric ion solution is 0.02 mol / L to 0.05 mol / L.

3. The method for preparing the doped and heterojunction synergistic water electrolysis catalyst according to claim 1 or 2, characterized in that... The concentration of ammonium molybdate in the mixed soaking solution is 0.01 mol / L to 0.14 mol / L, and the concentration of hydrochloric acid is 0.3 mol / L to 0.6 mol / L.

4. The method for preparing the doped and heterojunction synergistic water electrolysis catalyst according to claim 3, characterized in that... The concentration of hydrochloric acid in the mixed soaking solution ranges from 0.4 mol / L to 0.56 mol / L.

5. The method for preparing the doped and heterojunction synergistic water electrolysis catalyst according to claim 2, characterized in that... The molar ratio of ferric ions to ammonium molybdate in the mixed soaking solution is (4 to 1): (1 to 4).

6. The method for preparing the doped and heterojunction synergistic water electrolysis catalyst according to claim 5, characterized in that... The molar ratio of ferric ions to ammonium molybdate in the mixed soaking solution is 2:1.5 to 2.5:

1.

7. The method for preparing the doped and heterojunction synergistic water electrolysis catalyst according to any one of claims 1 to 6, characterized in that... The soaking time of copper foam in ferric ion solution is 12 min to 18 min, and the soaking temperature is 15℃ to 35℃; the ultrasonic treatment time of copper foam in mixed soaking solution is 3 min to 15 min, and it is left to stand for 3 min to 15 min after ultrasonic treatment.

8. The method for preparing the doped and heterojunction synergistic water electrolysis catalyst according to any one of claims 1 to 7, characterized in that... The electrolyte is a mixture of divalent cobalt ions, divalent nickel ions, sodium acetate, and sodium hypophosphite; wherein the concentration of divalent cobalt ions is 0.072 mol / L to 0.085 mol / L, the concentration of divalent nickel ions is 0.02 mol / L to 0.07 mol / L, the concentration of sodium acetate is 0.1 mol / L to 0.4 mol / L, and the concentration of sodium hypophosphite is 0.1 mol / L to 0.4 mol / L. Or / and, the electrodeposition time is 10 min to 25 min.

9. A water electrolysis catalyst prepared by a method for preparing a doped and heterojunction synergistic water electrolysis catalyst according to any one of claims 1 to 8.

10. The application of a doped and heterojunction synergistic water electrolysis catalyst according to claim 9 in water electrolysis.

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