Preparation methods and applications of ruthenium-doped nickel-iron-based heterostructure catalysts
By growing a nickel-iron-based heterostructure in situ on a nickel foam substrate and doping it with ruthenium, an RFN catalyst was formed, which solved the problem of insufficient activity and stability of existing electrocatalysts and achieved highly efficient electrocatalytic water splitting reaction performance.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- KUNMING UNIV OF SCI & TECH
- Filing Date
- 2025-01-21
- Publication Date
- 2026-05-26
AI Technical Summary
Existing non-precious metal electrocatalysts lack sufficient catalytic activity and durability in the electrocatalytic water splitting reaction, especially the oxygen evolution reaction and hydrogen evolution reaction performance of nickel-iron oxide-based materials under alkaline conditions, which need to be improved.
In situ, a nickel-iron-based heterostructure NiFe2O4-Ni(OH)2 was grown on a nickel foam substrate using a hydrothermal method, and a low amount of ruthenium was doped by impregnation to form a ruthenium-doped nickel-iron-based heterostructure catalyst (RFN), thereby adjusting the electronic structure and increasing the number of active sites.
It significantly improves the catalytic activity and stability of the catalyst, reduces the risk of ruthenium oxidation and dissolution, and enhances electrocatalytic performance, especially showing excellent catalytic performance in oxygen evolution and hydrogen evolution reactions.
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Abstract
Description
Technical Field
[0001] This invention relates to a method for preparing a low-loaded ruthenium-doped nickel-iron-based heterostructure catalyst and its application in the electrocatalytic water splitting reaction. Background Technology
[0002] Hydrogen is one of the most promising green energy sources for the future. Electrochemical water splitting is a highly attractive technology in the field of energy conversion because it can simultaneously produce H2 and O2 in a clean and safe manner without emitting carbon dioxide. Furthermore, although the theoretical voltage for electrocatalytic water splitting is 1.23V, the actual required battery voltage is often greater than 1.23V. Therefore, exploring bifunctional electrocatalysts with excellent HER and OER catalytic performance, while also possessing good stability and economic efficiency, is of great significance.
[0003] Transition metal-based electrocatalysts with three-dimensional orbitals have attracted considerable interest from researchers due to their similar properties to noble metal-based catalysts. Many transition metal-based electrocatalysts have been developed, including transition metal oxides / hydroxides, nitrides, carbides, and phosphides. Oxides or hydroxides of transition metal catalysts are among the most common OER catalysts, with nickel-based and iron-based electrocatalysts receiving widespread attention due to their abundant reserves, excellent catalytic activity, and low cost. Under alkaline conditions, nickel-iron oxide or nickel hydroxide exhibits excellent catalytic activity for the oxygen evolution reaction (OER) and has a strong ability to adsorb oxygen-containing intermediates. The readily formed Ni-O bonds of optimal strength between Ni atoms and water molecules facilitate the adsorption of intermediates, thereby accelerating the OER process. This makes nickel-iron-based materials excellent OER catalysts in alkaline solutions, while also promoting water dissociation in the hydrogen evolution reaction (HER).
[0004] However, compared with precious metal catalysts, these non-precious metal electrocatalysts are still insufficient in terms of electrocatalytic activity and durability in total water splitting, and need to be improved. Summary of the Invention
[0005] To at least partially address the problems of the prior art, the first aspect of the present invention discloses a method for preparing a ruthenium-doped nickel-iron-based heterostructure catalyst, comprising the following steps:
[0006] Oxalic acid and iron salt were dissolved in deionized water to obtain an iron precursor solution;
[0007] The nickel foam is placed in the iron precursor solution for a hydrothermal reaction to form a nickel-iron-based heterostructure on the nickel foam;
[0008] Nickel foam with a nickel-iron-based heterostructure was immersed in a ruthenium salt solution for reaction. After washing and drying, a ruthenium-doped nickel-iron-based heterostructure catalyst was obtained, wherein ruthenium is doped inside the lattice of the nickel-iron-based heterostructure.
[0009] Furthermore, the hydrothermal reaction is carried out at a temperature of 120–220°C for 6–12 hours. Preferably, the hydrothermal reaction is carried out at a temperature of 200°C for 7 hours.
[0010] Furthermore, the impregnation reaction time is 3-12 hours, preferably 5 hours.
[0011] Further, the molar concentration of the ruthenium salt solution is 0.0005 to 0.01 mM, preferably 0.001 to 0.008 mM, for example 0.005 mM.
[0012] Further, the molar concentration of oxalic acid in the iron precursor solution is 0.01-0.1M, preferably 0.02-0.08M, for example 0.06M; the molar concentration of iron salt in the iron precursor solution is 0.01-0.08M, preferably 0.02-0.05M, for example 0.03M.
[0013] Furthermore, the iron salt is ferric nitrate or ferric chloride, and the ruthenium salt is ruthenium chloride.
[0014] The second aspect of the present invention discloses the application of the ruthenium-doped nickel-iron-based heterostructure catalyst prepared by the above method in the electrocatalytic water splitting reaction.
[0015] The technical solution of the present invention has the following beneficial effects:
[0016] (1) Nickel-iron based heterostructures NiFe2O4-Ni(OH)2 were synthesized via a hydrothermal method using nickel foam as the substrate. The introduction of Fe can improve the catalytic activity and stability of nickel-based oxides and hydroxides. Under alkaline conditions, nickel-iron oxide and nickel hydroxide have a strong ability to adsorb oxygen-containing intermediates and exhibit excellent catalytic activity in the oxygen evolution reaction (OER), while also promoting the dissociation of water in the hydrogen evolution reaction (HER).
[0017] (2) In this invention, ruthenium is incorporated into the lattice of the nickel-iron-based heterostructure NiFe2O4-Ni(OH)2. On the one hand, this forms a strong electronic interaction between Ru and Ni and Fe, which can regulate the electronic structure of the electrochemical reaction intermediate and optimize its adsorption energy. On the other hand, the doped Ru atoms not only act as efficient active sites and work synergistically with the host material to promote electrocatalytic reactions, but also change the microstructure of the material, resulting in more lattice distortion in the nickel-iron-based heterostructure NiFe2O4-Ni(OH)2, exposing more active sites, thereby significantly improving the catalytic activity and stability of the catalyst.
[0018] (3) After ruthenium is incorporated into the lattice of the nickel-iron-based heterostructure NiFe2O4-Ni(OH)2, electrons are transferred from Fe and Ni to Ru, which reduces the oxidation state of Ru. This solves the serious problem that Ru active sites in noble metal catalysts are often oxidized to high valence states and dissolved into the electrolyte during long-term OER reactions, leading to reduced stability.
[0019] To more clearly illustrate the purpose, technical solution, and advantages of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Attached Figure Description
[0020] Figure 1 Here is the XRD pattern of the catalyst in the example;
[0021] Figure 2 In the figures: a is the Ru 3p XPS spectrum of the catalyst in the examples; b is the Fe 2p XPS spectrum of the catalysts in the examples and comparative examples; c is the Ni 2p XPS spectrum of the catalysts in the examples and comparative examples; d is the O 1s XPS spectrum of the catalysts in the examples and comparative examples.
[0022] Figure 3 In the image: a and b are SEM images of the catalyst in the example, and c and d are TEM images of it;
[0023] Figure 4 In the middle: a and b are SEM images of the catalysts in proportion, and c and d are TEM images of them;
[0024] Figure 5 In the image: a is a comparison of the HER linear sweep voltammetry (LSV) curves of the examples, comparative examples, and commercial Pt / C catalysts; b is a comparison of their Tafel slopes; c is a comparison of their double-layer capacitance (C0). dl (Comparison chart, d is the HER chronovoltage curve (CP) of the catalyst in the example;)
[0025] Figure 6 In the image: a is a comparison of the linear sweep voltammetry (LSV) curves of the OER for the examples, comparative examples, and commercial RuO2 catalysts; b is a comparison of their Tafel slopes; c is a comparison of their double-layer capacitance (C0). dl (Comparison chart, d is the OER chronovoltage curve (CP) of the catalyst in the example;)
[0026] Figure 7 In the diagram: a is a comparison of the total water splitting LSV of the example catalyst and the commercial catalyst; b is a Faraday efficiency (FE) diagram of the example catalyst.
[0027] Figure 8 This is a chronovoltage curve (CP) of the total water splitting of the catalyst in the example;
[0028] Figure 9 This is a comparison chart of the oxygen vacancy content of the catalysts in the examples and comparative examples;
[0029] Figure 10 This is a comparison diagram of the hydrophilic contact angles of the catalyst and pure nickel foam in the examples. Detailed Implementation
[0030] Numerous specific details are set forth in the following description to provide a thorough understanding of the invention; however, the invention may also be implemented using other variations or substitutions. Therefore, other possible implementations that can be discerned by those skilled in the art based on the embodiments described herein are all within the scope of protection of this invention.
[0031] This invention discloses a method for obtaining an RFN catalyst (ruthenium-doped nickel-iron-based heterostructure catalyst) by first growing an FN heterostructure (nickel-iron-based heterostructure) in situ on a nickel foam substrate using a hydrothermal method, and then doping it with a low amount of the noble metal ruthenium using an impregnation method. The method includes the following steps:
[0032] The surface of the nickel foam is cleaned. Specifically, the nickel foam can be ultrasonically cleaned by sequentially placing it in acetone, hydrochloric acid solution, and deionized water. Acetone can prevent organic impurities from remaining on the surface of the nickel foam, while hydrochloric acid solution can remove its surface oxides.
[0033] An iron salt, such as ferric nitrate, and oxalic acid are dissolved in deionized water to obtain an iron precursor solution. The molar concentration of oxalic acid in the iron precursor solution is 0.01–0.1 M, preferably 0.02–0.08 M, for example 0.06 M; the molar concentration of the iron salt is 0.01–0.08 M, preferably 0.02–0.05 M, for example 0.03 M.
[0034] After surface cleaning, nickel foam is placed in an iron precursor solution for hydrothermal reaction to obtain an FN heterostructure. The hydrothermal reaction temperature can be 120–220℃, and the time can be 6–12 h.
[0035] Ruthenium salt is dissolved in deionized water to obtain a ruthenium salt solution. The molar concentration of the ruthenium salt solution is 0.0005–0.01 mM, preferably 0.001–0.008 mM, for example 0.005 mM.
[0036] Nickel foam forming an FN heterostructure was impregnated in a ruthenium salt solution, and after washing and drying, an RFN heterostructure catalyst was obtained. The impregnation time could be 3-12 hours.
[0037] The following is a detailed description with reference to embodiments and comparative examples.
[0038] Example (RFN catalyst)
[0039] (1) A 2.5cm*3cm nickel foam was ultrasonically cleaned sequentially in acetone, 6.0M hydrochloric acid solution, and deionized water for 30 minutes each, and then dried to obtain a clean nickel foam substrate. The nickel foam had a thickness of 1.6mm and a pore size of 110ppi.
[0040] (2) First, add 225 mg of oxalic acid and 485 mg of Fe(NO3)3·9H2O to 40 mL of deionized water and stir for 300 s at room temperature. Then, transfer the homogeneous solution to a Teflon high-pressure reactor (the molar concentration of oxalic acid in the solution is 0.06 M and the molar concentration of Fe(NO3)3 is 0.03 M).
[0041] (3) Place the cleaned nickel foam horizontally at the bottom of the inner liner of the Teflon high-pressure reactor, then place the reactor in a forced-air drying oven, set the temperature to 200℃, and keep it at that temperature for 7 hours.
[0042] (4) The product obtained after the reaction was completed was washed three times with deionized water and anhydrous ethanol, and then placed in a vacuum drying oven at 60°C for 6 hours.
[0043] (5) The nickel foam with FN heterostructure formed in step (4) was placed in 30 mL of aqueous solution containing 24 mg RuCl3·xH2O (the molar concentration of RuCl3 in the solution was 0.005 mM), and after soaking for 5 h, it was rinsed three times with deionized water and anhydrous ethanol in sequence, and then placed in a vacuum drying oven at 60 °C for 6 h to obtain the RFN catalyst.
[0044] Comparative example (NF catalyst)
[0045] The difference between the comparative example and the embodiment is that step (5) of the embodiment is not included, i.e., no ruthenium doping is introduced.
[0046] Morphology, dimensions and phase analysis of the examples and comparative examples
[0047] Figure 1 The X-ray diffraction (XRD) patterns verified the crystal structure and composition of the RFN catalyst in the examples. A series of strong diffraction peaks at 18.6°, 33.1°, 38.3°, and 51.6° were attributed to Ni(OH)₂ (PDF#73-1520), and a series of strong diffraction peaks at 17.6°, 30.1°, 35.6°, 44.3°, and 62.7° were attributed to NiFe₂O₄ (PDF#44-1485). Notably, no Ru diffraction peaks were observed in the patterns.
[0048] Figure 2 These are the XPS spectra of the catalysts in the examples and comparative examples. Specifically, Figure 2a shows the Ru 3p XPS spectrum of the RFN catalyst in Example, where the two peaks at 462.3 and 484.9 eV correspond to Ru 4+ The two peaks at 464.7 and 487.9 eV correspond to Ru 3+ . Figure 2 The XPS spectrum of Fe 2p in b can be divided into two peaks, corresponding to Fe... 3+ 2p 3 / 2 and Fe 3+ 2p 1 / 2 track. Figure 2 c shows the Ni 2p XPS spectrum, where the two peaks correspond to Ni... 2+ 2p 3 / 2 and Ni 2+ 2p 1 / 2 The orbit has two remaining peaks, which are satellite peaks. Figure 2 d shows the O1s XPS spectrum, where three peaks are attributed to hydroxyl (OH), unsaturated oxygen, and lattice oxygen (MO). Figure 2 The test results show that RFN heterostructures (ruthenium-doped nickel-iron-based heterostructures) were grown in situ on the surface of nickel foam through hydrothermal and impregnation processes.
[0049] Figure 3 a and b are field emission scanning electron microscope (FE-SEM) images of the RFN catalyst in the example, showing that the RFN heterostructure grown in situ on nickel foam forms uniform three-dimensional nanosheets. Figure 3 c and d are transmission electron microscopy (TEM) images, confirming the nanosheet structure and size of the RFN catalyst in the examples, wherein... Figure 3 High-resolution transmission electron microscopy (HRTEM) images show two different lattice fringes with lattice spacings of 0.108 nm and 0.104 nm, respectively, corresponding to the (001) crystal plane of Ni(OH)2 and the (111) crystal plane of NiFe2O4.
[0050] Figure 4 a and b are field emission scanning electron microscopy (FE-SEM) images of the comparative FN catalysts. It can be seen that the FN heterostructure in the comparative example is also a three-dimensional nanosheet shape, indicating that the introduction of Ru did not affect the morphology of the FN heterostructure. Figure 4 c and d are transmission electron microscopy (TEM) images of the comparative FN catalysts, in which... Figure 4 The high-resolution transmission electron microscope (HRTEM) images of d show two different lattice stripes with lattice spacing of 0.108 nm and 0.104 nm, corresponding to the (001) crystal plane of Ni(OH)2 and the (111) crystal plane of NiFe2O4, respectively.
[0051] Based on the above analysis, on the one hand, Figure 2 The XPS spectrum of a proves that Ru was successfully introduced, while Figure 3 No obvious Ru phase was observed in the SEM and TEM images, and Figure 1 The XRD pattern does not show any Ru diffraction peaks; on the other hand... Figure 1 The negative shift of the NiFe2O4 and Ni(OH)2 peaks in the XRD pattern compared to the corresponding diffraction peaks on the standard card is sufficient to prove that Ru is incorporated into the NiFe2O4-Ni(OH)2 heterostructure lattice.
[0052] Because ruthenium (Ru) and nickel (Ni) atoms have similar physical properties and radii, ruthenium atoms can effectively penetrate and replace nickel atom sites. The unique three-dimensional plate-like configuration of the NiFe2O4-Ni(OH)2 heterostructure provides conditions for Ru to be incorporated into the crystal lattice. Therefore, nickel substitution can be achieved by immersing the NiFe2O4-Ni(OH)2 heterostructure in a ruthenium solution. Ru atoms can be incorporated into the crystal lattice of NiFe2O4 and Ni(OH)2 without significantly changing the structure of the matrix material.
[0053] Electrocatalytic performance tests of examples and comparative examples
[0054] The three-electrode system was tested in a 1 mol / L KOH solution saturated with N2; the reference electrode was an Ag / AgCl electrode, and the counter electrode was a Pt sheet electrode.
[0055] The water splitting test conditions were as follows: the test was conducted in a 1 mol / L KOH solution saturated with N2; the reference electrode and the counter electrode were both catalysts prepared in the examples.
[0056] Figure 5 Figure a is a comparison of the linear sweep voltammetry (LSV) curves of the example catalyst, the comparative catalyst, and the commercial Pt / C catalyst. It can be seen that the RFN catalyst of the example exhibits significantly enhanced HER activity, showing the lowest overpotential; specifically, the RFN catalyst at 10 mA cm⁻¹... -2 The HER overpotential is 15mV at 100mA cm⁻¹. -2 The HER overpotential is 124 mV, and the catalytic activity is significantly better than that of FN and commercial Pt / C. Figure 5 b. Comparison of the Tafel slopes of the three catalysts shows that the RFN catalyst exhibits the lowest Tafel slope (59.66 mV dec) at high current densities. -1 This indicates that the RFN catalyst has faster reaction kinetics. Figure 5 c is the double-layer capacitance used to evaluate the electrochemical surface area (ECSA). dl (Comparison chart, C of RFN catalyst) dlIt is 17.95mFcm -2 The concentration was significantly higher than that of other samples, indicating that it can provide more active sites during the OER process. Figure 5 d is the chronovoltage curve (CP) of the RFN catalyst at 100 mA cm⁻¹. -2 The RFN catalyst operated continuously for over 532 hours at industrial-grade current densities with almost no degradation in catalytic activity.
[0057] Figure 6 Figure a is a comparison of linear sweep voltammetry (LSV) curves for the example catalyst, comparative catalyst, and commercial Ru₂O catalyst. The OER performance of the RFN catalyst is significantly better than that of the FN and commercial Ru₂O catalysts. Specifically, at 10 mA / cm²... -2 The OER overpotential of the RFN catalyst is 248 mV at 100 mA / cm². -2 The OER overpotential of the RFN catalyst was 308 mV, showing the lowest overpotential. Figure 6 b is a comparison of the Tafel slopes of the three catalysts. The RFN catalyst exhibits the lowest Tafel slope (24.54 mV dec) at high current densities. -1 This indicates that the RFN catalyst has faster reaction kinetics. Figure 6 c is the double-layer capacitance of the three components (C0). dl (Comparison chart, C of RFN catalyst) dl It is 17.95mF cm -2 The concentration was higher than that of the comparative FN catalyst, indicating that it can provide more active sites in the OER process. Figure 6 d is the chronovoltage curve (CP) of the RFN catalyst in the example, at 100 mA / cm². -2 The RFN catalyst operated continuously for over 3940 hours at industrial-grade current densities with almost no degradation in catalytic activity.
[0058] Figure 7 a is a comparison graph of the total water splitting LSV of the RFN catalyst in the example and the commercial catalyst. The RFN catalyst in the example only requires 1.498V and 1.665V respectively to achieve 10mA cm⁻¹. -2 and 100mA cm -2 Its current density is far superior to that of commercial catalysts. Figure 7 b) The Faraday efficiency (FE) of the RFN catalyst was calculated by testing with a hydrogen production efficiency testing system. By comparing the theoretical and actual gas production at different times, the volume ratio of H2 to O2 was measured to be 2:1. The calculated FE of the RFN catalyst for overall water splitting was close to 100%, demonstrating its excellent catalytic activity. Figure 8This is a chronovoltage curve (CP) of the RFN catalyst in the example, at 100 mA cm⁻¹. -2 The RFN catalyst operated continuously for over 540 hours at the specified current density, and its catalytic activity showed almost no decline.
[0059] Oxygen vacancy content test in examples and comparative examples
[0060] from Figure 2 The O1s XPS spectra of d show that the unsaturated oxygen intensity in the RFN catalyst of the examples is higher than that in the comparative FN catalyst. Since unsaturated oxygen is correlated with oxygen vacancies, this suggests that the RFN catalyst may be more oxygen-vacancy-rich. To further confirm the presence of oxygen vacancies, electron paramagnetic resonance (EPR) technology was used to test the RFN and FN catalysts.
[0061] Figure 9 At g = 2.003, a strong signal corresponding to oxygen vacancies was observed in both the RFN and FN catalysts. Importantly, the EPR signal of the RFN catalyst was stronger than that of the FN catalyst, indicating a greater abundance of oxygen vacancies in the RFN catalyst, consistent with the XPS results. Abundant oxygen vacancies can enhance the conductivity of the electrocatalyst, facilitating the adsorption and dissociation of water and electrochemical reaction intermediates, thereby optimizing the binding strength of reaction intermediates and improving the electrocatalytic performance of the RFN catalyst.
[0062] Hydrophilicity test of the example
[0063] Figure 10 In this study, the surface properties of the RFN catalyst were revealed by measuring the contact angles at the solid-liquid and solid-gas interfaces between the RFN catalyst and the pure nickel foam (NF) substrate. These properties are closely related to the improved catalytic performance at high current densities. The contact angle of the pure nickel foam was 115.63°, indicating that it is a hydrophobic material. In contrast, the contact angle of the RFN catalyst was 0°, indicating that the RFN catalyst is superhydrophilic. The strong wettability of the RFN catalyst facilitates the contact between the solution and the material surface, thereby accelerating the reaction kinetics and improving the electrocatalytic efficiency.
[0064] In summary, the RFN catalyst of this invention, when applied to the electrocatalytic total water splitting reaction, demonstrates excellent OER catalytic performance due to the inherent properties of nickel-iron oxides and hydroxides. The strong electronic effect between Ru and Fe / Ni modulates the electronic structure of the active sites, optimizing the adsorption energy for reaction intermediates. Electrons are transferred from Fe and Ni to Ru, inhibiting excessive Ru oxidation and improving the catalyst's catalytic activity and stability. The superhydrophilicity of the RFN catalyst allows for good contact with the electrolyte, accelerating reaction kinetics and enhancing electrocatalytic efficiency. Abundant oxygen vacancies enhance the electrocatalyst's conductivity, facilitating the adsorption and dissociation of water and other electrochemical reaction intermediates, thereby optimizing the binding strength of these intermediates. These combined advantages improve the electrocatalytic performance of the RFN catalyst.
[0065] Although the present invention has been described above through specific embodiments, it should be understood that any equivalent changes made by those skilled in the art in accordance with the present invention without departing from the scope of the present invention should be covered by the protection scope of the present invention.
Claims
1. A method for preparing a ruthenium-doped nickel-iron-based heterostructure catalyst, comprising the following steps: Oxalic acid and iron salts are dissolved in water to obtain an iron precursor solution; The nickel foam is placed in the iron precursor solution for a hydrothermal reaction to form a nickel-iron-based heterostructure on the nickel foam; Nickel foam with a nickel-iron-based heterostructure is impregnated in a ruthenium salt solution to obtain a ruthenium-doped nickel-iron-based heterostructure catalyst; wherein, ruthenium is doped inside the lattice of the nickel-iron-based heterostructure, and the nickel-iron-based heterostructure is NiFe2O4-Ni(OH)2.
2. The method for preparing the ruthenium-doped nickel-iron-based heterostructure catalyst according to claim 1; wherein, The hydrothermal reaction is carried out at a temperature of 120–220°C for 6–12 hours.
3. The method for preparing the ruthenium-doped nickel-iron-based heterostructure catalyst according to claim 2; wherein, The hydrothermal reaction was carried out at a temperature of 200°C for 7 hours.
4. The method for preparing the ruthenium-doped nickel-iron-based heterostructure catalyst according to claim 1; wherein, The impregnation reaction takes 3 to 12 hours.
5. The method for preparing the ruthenium-doped nickel-iron-based heterostructure catalyst according to claim 4; wherein, The impregnation reaction takes 5 hours.
6. The method for preparing the ruthenium-doped nickel-iron-based heterostructure catalyst according to claim 1; wherein, The molar concentration of the ruthenium salt solution is 0.0005–0.01 mM.
7. The method for preparing the ruthenium-doped nickel-iron-based heterostructure catalyst according to claim 1; wherein, The molar concentration of oxalic acid in the iron precursor solution is 0.01–0.1 M, and the molar concentration of iron salt is 0.01–0.08 M.
8. The method for preparing the ruthenium-doped nickel-iron-based heterostructure catalyst according to claim 1; wherein, The iron salt is ferric nitrate or ferric chloride.
9. The method for preparing the ruthenium-doped nickel-iron-based heterostructure catalyst according to claim 1; wherein, The ruthenium salt is ruthenium chloride.
10. The application of the ruthenium-doped nickel-iron-based heterostructure catalyst obtained by the preparation method of any one of claims 1-9 in the electrocatalytic water splitting reaction.