High-valent ruthenium monatomic catalyst, preparation method and application thereof

Abstract

The application discloses a high-valence ruthenium monatomic catalyst and a preparation method and application thereof. A ruthenium monatomic is anchored on the surface of double-metal (nickel and M) phosphate porous hollow nanospheres MNiPi PHSs (M=Fe, Co, Mn or Cu), and the high-valence state and coordination environment of the ruthenium are controlled through the double transition metal, so that the bottleneck of the thermodynamic instability of the traditional high-valence ruthenium active site is effectively overcome. The catalyst exhibits high catalytic stability and high activity for hydrogen evolution and oxygen evolution reactions.

Description

Technical Field

[0001] This invention belongs to the field of metal catalyst technology, and relates to a high-valence ruthenium single-atom site catalyst, its preparation method, and its application. Background Technology

[0002] Water electrolysis technology, capable of storing intermittent renewable electricity, is central to the hydrogen economy. However, practical water electrolysis devices are currently limited by low catalytic efficiency, primarily due to the large overpotential caused by the slow kinetics of the oxygen evolution reaction (OER). From a techno-economic perspective, there is an urgent need to significantly reduce the use of precious metals while improving the catalytic activity and stability of OER. Therefore, there is a pressing need to develop an OER electrocatalyst with excellent activity and high precious metal utilization.

[0003] Ru, as the most reactive metal catalyst in the OER reaction, is less expensive than Ir and is considered the optimal choice for OER catalysis. The catalytic performance of Ru depends largely on its oxidation state; its higher oxidation state (Ru...)... 4+ ) compared to its lower valence state (Ru) 2+ Ruthenium species exhibit higher activity. However, high-valence ruthenium species are highly unstable under high voltages at the OER, and Ru... 4+ It is water-soluble, which causes rapid loss of Ru active species under operating conditions, leading to a rapid decline in catalyst performance. To solve this problem, researchers usually use low-valence (Ru valence state between 0 and 2) RuO x Clusters or particles anchored on the surface of a conductive support can effectively improve the overall stability of the catalyst, but this comes at the cost of high catalytic activity. On the other hand, limiting the operating voltage of Ru-based catalysts can also effectively suppress Ru... 4+ Excessive oxidation protects the highly active reaction sites of the catalyst, but excessively low current density (<10 mA·cm) -2 This greatly limits hydrogen production efficiency.

[0004] Therefore, a method was developed that combines high activity, high stability, and high current density (>1000 mA·cm). -2 High-valence ruthenium-based catalysts are crucial for the development of water electrolysis technology and will greatly promote the rapid development of hydrogen energy technology in my country. Summary of the Invention

[0005] The purpose of this invention is to provide a solution that combines high activity, high stability, and high current density (>1000 mA·cm). -2This paper describes a high-valence ruthenium single-atom catalyst, its preparation method, and its application. By effectively controlling the coordination environment and valence state of Ru single atoms on porous hollow nanospheres of MNi bimetallic phosphate (M=Fe,Co,Cu,Mn) (referred to as MNiPi PHSs), the thermodynamic instability of the high-valence Ru active site is effectively overcome. Furthermore, this method has the characteristics of universality and easy scale-up preparation.

[0006] To achieve the above-mentioned technical objectives, the present invention provides the following technical solution:

[0007] A high-valence ruthenium single-atom catalyst is disclosed, wherein high-valence ruthenium single atoms are anchored on the surface of bimetallic phosphate porous hollow nanospheres (MNiPi PHSs) via Ru-O bonds. The loading of Ru single atoms is 3.1–4.2 wt%, the Ru-O coordination number is (3.0–3.8) ± 0.5, and the valence state of Ru is +2.9–+5.1. In the bimetallic phosphate porous hollow nanospheres, M is one of Fe, Co, Cu, and Mn, and the molar ratio of Ni to M is 1:1 to 1:1.5.

[0008] In the above-mentioned high-valence ruthenium single-atom catalyst, Ni has a valence state of +2 to +3, and M has a valence state of +1 to +3; the particle size of the bimetallic phosphate porous hollow nanospheres is 50 to 150 nm.

[0009] The above-mentioned high-valence ruthenium single-atom catalyst was prepared by the following method:

[0010] 1) Nickel-based phosphate porous hollow nanospheres (denoted as NiPi PHSs) were prepared using a chemical co-precipitation method as a basic material;

[0011] 2) Disperse the NiPi PHSs obtained in step 1) in a solvent and slowly add a salt solution of metal M to it to obtain bimetallic phosphate porous hollow nanospheres (MNiPi PHSs) by ion exchange method.

[0012] 3) Disperse the MNiPi PHSs obtained in step 2) in a solvent and slowly add a ruthenium precursor solution to it to obtain the high-valence ruthenium single-atom catalyst (Ru SS / MNiPi PHSs) by ion exchange method.

[0013] Further, in step 1), the nickel salt and phosphate precursors are dissolved in solvents respectively, and the nickel salt solution is slowly added dropwise to the phosphate precursor solution while being stirred thoroughly; then the reaction system is allowed to cool naturally, aged at low temperature, the precipitate is collected by centrifugation, washed, and dried to obtain nickel-based phosphate hollow porous nanospheres.

[0014] Furthermore, the molar ratio of the nickel salt and phosphate precursor in step 1) above is 1:(1-3), for example 1:1, 1:2 or 1:3; the nickel salt includes, but is not limited to, nickel chloride, nickel nitrate, nickel sulfate, nickel acetylacetonate, etc.; the phosphate precursor includes, but is not limited to, disodium hydrogen phosphate, sodium dihydrogen phosphate, dipotassium hydrogen phosphate, potassium dihydrogen phosphate, potassium phosphate, sodium phosphate, potassium pyrophosphate, sodium pyrophosphate, etc.

[0015] Preferably, in step 1), a 0.01M PBS solution with pH 7.2–7.4 (containing 0.135M NaCl and 0.003M KCl) is prepared as the phosphate precursor solution. The nickel salt solution is slowly added dropwise to the phosphate precursor solution. After stirring at room temperature for a period of time, the resulting suspension is aged in a refrigerator at 4°C for 12 hours. The product is collected by centrifugation, washed, and vacuum dried.

[0016] Further, in step 2), a salt solution of metal M of a certain concentration is first prepared and stirred thoroughly at a certain temperature. Then, a certain amount of nickel-based phosphate porous hollow nanospheres obtained in step 1) are redispersed in a solvent, and the salt solution of metal M is slowly added dropwise. The reaction system is then allowed to cool naturally, and the resulting bimetallic phosphate hollow porous nanospheres are collected by centrifugation, washed, and dried in a vacuum drying oven.

[0017] Furthermore, the salt of metal M mentioned in step 2) includes, but is not limited to, ferric sulfate, ferrous ammonium sulfate, ferric nitrate, ferric chloride, ferrous chloride, cobalt sulfate, cobalt nitrate, cobalt chloride, manganese sulfate, manganese nitrate, manganese chloride, copper sulfate, copper nitrate, copper chloride, ferric acetylacetone, cobalt acetylacetone, manganese acetylacetone, copper acetylacetone, etc.

[0018] Further, in step 3), a ruthenium precursor solution of a certain concentration is first prepared. The ruthenium precursor includes, but is not limited to, ruthenium chloride, ruthenium acetylacetone, ruthenium oxide, and ruthenium nitrate, and is stirred thoroughly at a certain temperature. Next, a certain amount of bimetallic phosphate hollow porous nanospheres obtained in step 2) are ultrasonically dispersed in a solvent, and the ruthenium precursor solution is slowly added dropwise and ultrasonically mixed. The reaction system is then allowed to cool naturally, stirred at room temperature, and the resulting high-valence ruthenium single-atom catalyst is collected by centrifugation, washed, and dried in a vacuum drying oven.

[0019] Furthermore, the solvents mentioned in steps 1), 2), and 3) include, but are not limited to, water, ethanol, methanol, oleylamine, cyclohexane, etc.

[0020] This invention also provides the application of the above-mentioned high-valence ruthenium single-atom-site catalyst as a catalyst for water electrolysis reaction.

[0021] More preferably, the water electrolysis reaction includes the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER).

[0022] The beneficial effects of this invention are as follows:

[0023] This invention anchors ruthenium single atoms onto the surface of bimetallic (nickel and M) porous hollow phosphate nanospheres MNiPiPHSs (M = Fe, Co, Mn, or Cu), resulting in a highly stable and active catalyst. By controlling the high valence state of ruthenium through bimetallic modulation, this invention overcomes the thermodynamic instability of the high-valence ruthenium active sites, thereby leveraging the characteristics of single-atom site catalysts, enhancing the interaction between the substrate and the active sites, and significantly improving the catalytic performance of the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER).

[0024] XAFS and DFT verification confirmed that the stability of the high-valence ruthenium single-atom catalyst of this invention originates from the suitable valence state, coordination number, and geometry of the ruthenium single atom. For the optimal Ru SS / FeNiPi PHSs catalyst, the current density reaches 10 mA·cm⁻¹. -2 The overpotentials for OER and HER at that time were 201 mV and 49 mV, respectively. Furthermore, without IR correction, this catalyst achieved an industrial-grade 1000 mA·cm⁻¹ in a self-made alkaline anion exchange membrane electrolyzer (AEMWE). -2 and 2000mA·cm -2 The operating voltages with current densities of 1.64V and 1.78V are respectively. These performance parameters are those of commercial Pt / C / / RuO2 (347mA·cm⁻¹). -2 It is 5.7 times more potent than other bifunctional AEMWEs monolithic water splitting catalysts reported to date, and has already surpassed them. Attached Figure Description

[0025] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the following drawings are provided for illustration.

[0026] Figure 1 SEM, TEM, and STEM images of Ru SS / FeNiPi PHSs prepared in Example 1 include: SEM image of Ru SS / FeNiPi PHSs (a); TEM image of Ru SS / FeNiPi PHSs (b); HAADF-STEM image of Ru SS / FeNiPi PHSs (c) and distribution map of corresponding Fe, Ni, P, O, and Ru elements (d); spherical aberration corrected STEM image of Ru SS / FeNiPi PHSs (e) and intensity curve of the corresponding region (f).

[0027] Figure 2Photographs of the batch preparation of NiPi PHSs, including photographs of preparation in four 500 mL beakers (a) and one 2500 mL beaker (b); and an optical photograph (c) of Ru SS / FeNiPi PHSs prepared on a large scale.

[0028] Figure 3 From left to right are the aberration-corrected STEM image, HAADF-STEM image, and elemental distribution map of Ru SS / MNiPi PHSs (M = Co, Mn, Cu), where: ac represents Ru SS / CoNiPi PHSs, df represents Ru SS / MnNiPi PHSs, and gi represents Ru SS / CuNiPi PHSs.

[0029] Figure 4 The following is a comparison of polarization curves and overpotentials obtained from the electrochemical tests in Example 5, including: a. OER polarization curves of different catalysts; b. Ru SS / MNiPi PHSs (M=Fe,Co,Mn,Cu) at 10 mA·cm⁻¹. -2 and 100mA·cm -2 c. Comparison of OER overpotentials; d. HER polarization curves of different catalysts; e. Ru SS / MNiPi PHSs (M=Fe,Co,Mn,Cu) at 10 mA·cm⁻¹ -2 and 100mA·cm -2 Comparison of HER overpotentials at different current densities; and comparison of e.Ru SS / FeNiPi PHSs electrodes at different current densities (500, 1000, 2000, 3000 and 4000 mA·cm⁻¹). -2 The graph shows the change of electric potential over time.

[0030] Figure 5 Including: OER Tafel curves (a) for NiPi PHSs, FeNiPi PHSs, Ru SS / FeNiPi PHSs and commercial RuO2; OER polarization curves (b) and corresponding Tafel slope curves (c) for Ru SS / CoNiPi PHSs, Ru SS / CuNiPi PHSs and Ru SS / MnNiPi PHSs.

[0031] Figure 6 Including: HER Tafel curves (a) of NiPi PHSs, FeNiPi PHSs, Ru SS / FeNiPi PHSs and commercial Pt / C; HER polarization curves (b) and corresponding Tafel slope curves (c) of Ru SS / CoNiPi PHSs, Ru SS / CuNiPi PHSs and Ru SS / MnNiPi PHSs.

[0032] Figure 7 For FeNiPi PHSs, Ru SS / FeNiPi PHSs and commercial RuO2, 150 mA·cm -2 The constant potential curve under current density.

[0033] Figure 8 The electrocatalytic performance test results for Example 5 include: a. polarization curves of Ru SS / FeNiPi PHSs and commercial Pt / C / / RuO2 electrodes; b. Faradaic efficiency of Ru SS / FeNiPi PHSs and commercial Pt / C / / RuO2 electrodes at 1.5, 1.6, 1.7, and 1.8 V; c. performance of AEMWE assembled using Ru SS / FeNiPi PHSs as a catalyst at different temperatures; d. polarization curves of AEMWEs assembled using Ru SS / FeNiPi PHSs and commercial Pt / / RuO2 as catalysts at 80 °C; e. performance of AEMWE assembled using Ru SS / FeNiPi PHSs at 1000 mA·cm⁻¹. -2 and 2000mA·cm -2 Stability at current density. Detailed Implementation

[0034] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0035] Example 1

[0036] Preparation of NiPi PHSs:

[0037] First, 355.5 mg NaCl, 9 mg KCl, 10.8 mg KH₂PO₄, and 81.5 mg K₂HPO₄ were dissolved in 45 mL of deionized water to form a 0.01 M PBS solution with a pH of 7.2–7.4. Next, freshly prepared NiSO₄·6H₂O solution (157.7 mg, 2 mL) was slowly added dropwise to the PBS solution, and the mixture was stirred at room temperature for 20 minutes. The resulting suspension was then aged at 4 °C for 12 hours. The product was collected by centrifugation, washed several times with deionized water, and dried in a vacuum oven at 80 °C for 12 hours.

[0038] Preparation of FeNiPi PHSs:

[0039] First, 55.6 mg of FeSO4·7H2O was dissolved in 10 mL of deionized water. Then, 50 mg of NiPi PHSs was dispersed in 40 mL of deionized water, and the solution was sonicated for 10 minutes. Next, the FeSO4·7H2O aqueous solution was added dropwise to the dispersed NiPi PHSs, and the reaction was stirred at room temperature for 6 hours. The resulting product was collected by centrifugation, washed several times with deionized water, and dried under vacuum for 12 hours to obtain FeNiPi PHSs.

[0040] Preparation of Ru SS / FeNiPi PHSs:

[0041] First, 100 mg of the FeNiPi PHSs prepared above was ultrasonically dispersed in 10 mL of deionized water. Then, 830 μL of a 10 mg / mL RuCl3·3H2O solution was slowly added dropwise to the FeNiPi PHSs ultrasonic dispersion. The mixture was ultrasonicated for 30 minutes and then stirred at room temperature for 12 hours. After the reaction was completed, Ru SS / FeNiPi PHSs were obtained by centrifugation, washing, and drying.

[0042] Example 2

[0043] Preparation of NiPi PHSs:

[0044] First, 355.5 mg NaCl, 9 mg KCl, 10.8 mg KH₂PO₄, and 81.5 mg K₂HPO₄ were dissolved in 45 mL of deionized water to form a 0.01 M PBS solution with a pH of 7.2–7.4. Next, freshly prepared NiSO₄·6H₂O solution (157.7 mg, 2 mL) was slowly added dropwise to the PBS solution, and the mixture was stirred at room temperature for 20 minutes. The resulting suspension was then aged at 4 °C for 12 hours. The product was collected by centrifugation, washed several times with deionized water, and dried in a vacuum oven at 80 °C for 12 hours.

[0045] Preparation of CoNiPi PHSs:

[0046] First, 56.2 mg of CoSO4·7H2O was dissolved in 10 mL of deionized water. Then, 50 mg of NiPi PHSs was dispersed in 40 mL of deionized water, and the solution was sonicated for 10 minutes. Next, the CoSO4·7H2O aqueous solution was added dropwise to the dispersed NiPi PHSs, and the reaction was stirred at room temperature for 6 hours. The resulting product was collected by centrifugation, washed several times with deionized water, and dried under vacuum for 12 hours to obtain CoNiPi PHSs.

[0047] Preparation of Ru SS / CoNiPi PHSs:

[0048] First, 100 mg of the CoNiPi PHSs prepared above was ultrasonically dispersed in 10 mL of deionized water. Then, 830 μL of a 10 mg / mL RuCl3·3H2O solution was slowly added dropwise to the CoNiPi PHSs ultrasonic dispersion. The mixture was ultrasonicated for 30 minutes and then stirred at room temperature for 12 hours. After the reaction was completed, Ru SS / CoNiPi PHSs were obtained by centrifugation, washing, and drying.

[0049] Example 3

[0050] Preparation of NiPi PHSs:

[0051] First, 355.5 mg NaCl, 9 mg KCl, 10.8 mg KH₂PO₄, and 81.5 mg K₂HPO₄ were dissolved in 45 mL of deionized water to form a 0.01 M PBS solution with a pH of 7.2–7.4. Next, freshly prepared NiSO₄·6H₂O solution (157.7 mg, 2 mL) was slowly added dropwise to the PBS solution, and the mixture was stirred at room temperature for 20 minutes. The resulting suspension was then aged at 4 °C for 12 hours. The product was collected by centrifugation, washed several times with deionized water, and dried in a vacuum oven at 80 °C for 12 hours.

[0052] Preparation of MnNiPi PHSs:

[0053] First, 48.2 mg of MnSO4·H2O was dissolved in 10 mL of deionized water. Then, 50 mg of NiPi PHSs was dispersed in 40 mL of deionized water, and the solution was sonicated for 10 minutes. Next, the MnSO4·H2O aqueous solution was added dropwise to the dispersed NiPi PHSs, and the reaction was stirred at room temperature for 6 hours. The resulting product was collected by centrifugation, washed several times with deionized water, and dried under vacuum for 12 hours to obtain MnNiPi PHSs.

[0054] Preparation of Ru SS / MnNiPi PHSs:

[0055] First, 100 mg of the prepared MnNiPi PHSs was ultrasonically dispersed in 10 mL of deionized water. Then, 830 μL of a 10 mg / mL RuCl3·3H2O solution was slowly added dropwise to the MnNiPi PHSs ultrasonic dispersion. The mixture was ultrasonicated for 30 minutes and then stirred at room temperature for 12 hours. After the reaction was complete, Ru SS / MnNiPi PHSs were obtained by centrifugation, washing, and drying.

[0056] Example 4

[0057] Preparation of NiPi PHSs:

[0058] First, 355.5 mg NaCl, 9 mg KCl, 10.8 mg KH₂PO₄, and 81.5 mg K₂HPO₄ were dissolved in 45 mL of deionized water to form a 0.01 M PBS solution with a pH of 7.2–7.4. Next, freshly prepared NiSO₄·6H₂O solution (157.7 mg, 2 mL) was slowly added dropwise to the PBS solution, and the mixture was stirred at room temperature for 20 minutes. The resulting suspension was then aged at 4 °C for 12 hours. The product was collected by centrifugation, washed several times with deionized water, and dried in a vacuum oven at 80 °C for 12 hours.

[0059] Preparation of CuNiPi PHSs

[0060] First, 49.9 mg of CuSO4·5H2O was dissolved in 10 mL of deionized water. Then, 50 mg of NiPi PHSs was dispersed in 40 mL of deionized water, and the solution was sonicated for 10 minutes. Next, the CuSO4·5H2O aqueous solution was added dropwise to the dispersed NiPi PHSs, and the reaction was stirred at room temperature for 6 hours. The resulting product was collected by centrifugation, washed several times with deionized water, and dried under vacuum for 12 hours to obtain MnNiPi PHSs.

[0061] Preparation of Ru SS / CuNiPi PHSs

[0062] First, 100 mg of the above-prepared CuNiPi PHSs was ultrasonically dispersed in 10 mL of deionized water. Then, 830 μL of a 10 mg / mL RuCl3·3H2O solution was slowly added dropwise to the CuNiPi PHSs ultrasonic dispersion. The mixture was ultrasonicated for 30 minutes and then stirred at room temperature for 12 hours. After the reaction was complete, Ru SS / CuNiPi PHSs were obtained by centrifugation, washing, and drying.

[0063] Example 5

[0064] Characterization methods:

[0065] X-ray diffraction patterns were obtained using a Shimadzu XRD-7000 diffractometer, with a target source of Cu Kα, a scanning range of 10–80°, and a scanning rate of 3° / min. -1The accelerating voltage was 40 kV and the current was 80 mA. The morphology and structure of the prepared materials were tested and analyzed by field emission scanning electron microscopy (FESEM, JEOL, JSM-7800F) with an accelerating voltage of 10 kV. High-resolution transmission electron microscopy (TEM) and aberration-corrected HAADF-STEM results were obtained by JEOL JEM-2100 and FEI Tecnai G2 F20 S-Twin HRTEM, respectively, with operating voltages of 200 and 300 kV. The chemical states of the obtained samples were obtained by X-ray photoelectron spectroscopy (XPS) using an Escalab 250xi X-ray photoelectron spectroscopy system. All binding energies were corrected using the C1s peak at 284.8 eV in air contaminants. Nitrogen isothermal adsorption / desorption (BET) was obtained using a Quadrasorb evo 2QDS-MP-30 analyzer. Fourier transform infrared (FTIR) spectra were obtained using a SHIMADZU Pretige-21 infrared spectrometer. The Ru metal content in Ru SS / MNiPi (M = Fe, Co, Mn, Cu) was determined using inductively coupled plasma atomic emission spectrometry on a PerkinElmer Optima 7300DV.

[0066] Figure 1 The images show SEM, TEM, EDS-mapping, and spherical aberration electron microscopy (SEM) images of Ru SS / FeNiPi PHSs. SEM and TEM images show that the FeNi phosphate support has a hollow porous nanosphere morphology. EDS-mapping images show that Ru, Fe, Ni, P, and O are uniformly distributed on the nanospheres. Spherical aberration electron microscopy confirms that Ru is uniformly dispersed on the surface of the FeNi phosphate support in the form of single atoms.

[0067] Figure 2 Optical images of Ru SS / FeNiPi PHSs were obtained for both batch and large-scale preparation of NiPi PHSs. The results indicate that the methods for preparing NiPi PHSs precursors and Ru SS / FeNiPi PHSs are easily scalable and can be readily mass-produced.

[0068] Figure 3Aberration-corrected STEM images, HAADF-STEM images, and elemental distribution maps of Ru SS / CoNiPi PHSs, Ru SS / MnNiPi PHSs, and Ru SS / CuNiPi PHSs are shown. The morphology of the CoNi, MnNi, and CuNiPi phosphate supports is hollow porous nanospheres. EDS-mapping images show that Ru, M (M = Co, Mn, Cu), Ni, P, and O are uniformly distributed on the nanospheres. Aberration-corrected STEM images confirm that Ru is uniformly dispersed on the surface of the MNi phosphate support in the form of single atoms. These results indicate that the preparation method of this invention has universality.

[0069] Electrochemical testing

[0070] A classic three-electrode system was used, with the prepared sample as the working electrode, a graphite rod as the counter electrode, and an Hg / HgO electrode as the reference electrode. Electrochemical tests were performed on a CHI760E electrochemical analyzer (CH Instruments, Shanghai). Working electrode preparation: 5 mg of prepared Ru SS / MNiPi PHSs (M = Fe, Co, Mn, Cu), 2 mg of Ketjen black, and 10 μL of 5 wt.% Nafion solution were dispersed in 990 μL of isopropanol / water (volume ratio 1:1) mixed solution and subjected to ultrasonic treatment for at least 30 minutes to obtain a homogeneous slurry. Linear sweep spectroscopy (LSV) was performed in 1 M KOH electrolyte at a scan rate of 2 mV·s. -1 The tests were conducted under the following conditions: Electrochemical impedance spectroscopy (EIS) was performed at an AC voltage of 5 mV and a frequency range of 100,000 to 0.01 Hz.

[0071] Figure 4 The HER and OER polarization curves of NiPi PHSs, FeNiPi PHSs, and Ru SS / FeNiPi PHSs are shown (see Figure 4 In (a) and (c), Ru SS / MNiPi PHSs (M=Fe,Co,Mn,Cu) at a current density of 10 mA·cm -2 and 100mA·cm -2 Comparison of HER and OER overpotentials (see) Figure 4 (b and d) and Ru SS / FeNiPi PHSs were tested at current densities of 500, 1000, 2000, 3000 and 4000 mA·cm⁻¹. -2 Stability at 10 mA·cm⁻¹. Ru SS / FeNiPi PHSs at 10 mA·cm⁻¹ -2At current densities of 500, 1000, 2000, 3000, and 4000 mA·cm⁻¹, it exhibited the lowest overpotentials for both HER and OER (OER: 204.2 mV; HER: 49 mV), outperforming noble metals Pt / C and RuO₂. Furthermore, at current densities of 500, 1000, 2000, 3000, and 4000 mA·cm⁻¹, it showed the lowest overpotentials for both HER and OER (OER: 204.2 mV; HER: 49 mV), outperforming noble metals Pt / C and RuO₂. -2 They exhibit excellent stability at various current densities.

[0072] Figure 5 The OER Tafel curves for NiPi PHSs, FeNiPi PHSs, Ru SS / FeNiPi PHSs, and the commercial catalyst RuO2 are shown. The OER polarization curves and corresponding Tafel slope curves for Ru SS / CoNiPi PHSs, Ru SS / CuNiPi PHSs, and Ru SS / MnNiPi PHSs are also shown. Ru SS / FeNiPi PHSs exhibits the smallest Tafel slope (45.6 mV dec) compared to NiPi PHSs, FeNiPi PHSs, and the commercial RuO2 catalyst. -1 This indicates its rapid OER reaction kinetics. In contrast, other catalysts of the present invention, Ru SS / CoNiPi PHSs, Ru SS / CuNiPi PHSs, and Ru SS / MnNiPi PHSs, also exhibit good catalytic performance for OER.

[0073] Figure 6 HER Tafel curves for NiPi PHSs, FeNiPi PHSs, Ru SS / FeNiPi PHSs, and the commercial catalyst Pt / C are shown. HER polarization curves and corresponding Tafel slope curves for Ru SS / CoNiPi PHSs, Ru SS / CuNiPi PHSs, and Ru SS / MnNiPi PHSs are also shown. Ru SS / FeNiPi PHSs exhibits the smallest Tafel slope (39.1 mV dec) compared to NiPi PHSs and FeNiPi PHSs. -1 Its value is very close to Pt / C (32.7 mV dec). -1 The results indicate that Ru SS / FeNiPiPHSs exhibit excellent HER performance. In contrast, other catalysts of this invention, Ru SS / CoNiPi PHSs, Ru SS / CuNiPi PHSs, and Ru SS / MnNiPi PHSs, also demonstrate good catalytic performance for HER.

[0074] Figure 7 For FeNiPi PHSs, Ru SS / FeNiPi PHSs and commercial RuO2, 150 mA·cm -2The galvanostatic curves at current density demonstrate that Ru SS / FeNiPi PHSs exhibit excellent stability.

[0075] Fabrication of membrane electrodes

[0076] 30 mg of Ru SS / FeNiPi PHSs powder, 12 mg of Ketjen Black, and 240 μL of Nafion solution were dispersed in 6 mL of ethanol. The mixture was sonicated for 1 hour to obtain a homogeneous slurry, which was then sprayed onto the surface of carbon paper as the anode and cathode of the membrane electrode, with a loading of 2.5 mg·cm⁻¹. -2 Next, an anion exchange membrane (X37-50 grade T) was sandwiched between the cathode and anode, and a membrane electrode assembly (MEA) was fabricated by hot pressing. A flowing 1M KOH solution was used as the electrolyte, and the temperature of the electrolyte was controlled by a constant-temperature heating chamber.

[0077] Figure 8 The polarization curves of Ru SS / FeNiPi PHSs and commercial Pt / C / / RuO2 electrodes are shown. The Faradaic efficiencies of the Ru SS / FeNiPi PHSs and commercial Pt / C / / RuO2 electrodes at 1.5, 1.6, 1.7, and 1.8 V are also shown. The performance of an alkaline anion exchange membrane electrolyzer (AEMWE) assembled using Ru SS / FeNiPi PHSs as a catalyst at different temperatures is also presented. The polarization curves of AEMWEs assembled using Ru SS / FeNiPi PHSs and commercial Pt / / RuO2 as catalysts at 80 °C are also shown. Finally, the performance of the AEMWE assembled using Ru SS / FeNiPi PHSs at 1000 mA cm⁻¹ is also presented. -2 and 2000mA cm -2 The stability at current densities was demonstrated. This indicates that the two-electrode electrolyzer assembled with the RuSS / FeNiPi PHSs bifunctional catalyst exhibits superior catalytic performance and Faradaic efficiency compared to a commercially available two-electrode electrolyzer assembled with noble metals Pt / C / / RuO2. The AEMWEs assembled with RuSS / FeNiPi PHSs require only 1.78 V to reach 2000 mA·cm⁻¹. -2 The current density is 5.7 times that of commercially available Pt / / RuO2-based AEMWEs. AEMWEs assembled from Ru SS / FeNiPiPHSs exhibit current densities at 1000 and 2000 mA·cm⁻¹. -2 No significant current density decay was observed during long-term operation at the specified current density, indicating that it has excellent stability.

[0078] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made to it in form and detail without departing from the scope defined by the claims of the present invention.

Claims

1. A high-valence ruthenium single-atom catalyst, wherein high-valence ruthenium single atoms are anchored on the surface of a bimetallic phosphate porous hollow nanosphere via Ru-O bonds, wherein the loading of Ru single atoms is 3.1~4.2 wt%, the Ru-O coordination number is (3.0~3.8)±0.5, and the valence state of Ru is +2.9~+5.1; the bimetal in the bimetallic phosphate porous hollow nanosphere is Ni and M, wherein M is selected from Fe, Co, Cu, Mn, and the molar ratio of Ni to M is 1:1~1:1.

5.

2. The high-valence ruthenium single-atom catalyst as described in claim 1, characterized in that, The bimetallic phosphate porous hollow nanospheres have a particle size of 50~150 nm; Ni has a valence state of +2~+3, and M has a valence state of +1~+3.

3. A method for preparing the high-valence ruthenium single-atom catalyst according to claim 1 or 2, comprising the following steps: 1) Nickel-based phosphate porous hollow nanospheres were prepared as basic materials using a chemical co-precipitation method; 2) Disperse the nickel-based phosphate porous hollow nanospheres obtained in step 1) in a solvent, and slowly add a salt solution of metal M to it to obtain bimetallic phosphate porous hollow nanospheres by ion exchange method; 3) Disperse the bimetallic phosphate porous hollow nanospheres obtained in step 2) in a solvent, and slowly add a ruthenium precursor solution to it to obtain the high-valence ruthenium single-atom catalyst by ion exchange method.

4. The preparation method according to claim 3, characterized in that, Step 1) First, prepare nickel salt solution and phosphate precursor solution separately. Then, slowly add nickel salt solution to phosphate precursor solution and stir thoroughly. After the reaction system is naturally cooled, age at low temperature, collect the precipitate by centrifugation, wash and dry to obtain nickel-based phosphate hollow porous nanospheres.

5. The preparation method according to claim 4, characterized in that, In step 1), the nickel salt and phosphate precursor are mixed in a molar ratio of 1:(1~3), wherein the nickel salt is selected from one or more of nickel chloride, nickel nitrate, nickel sulfate, and nickel acetylacetone; and the phosphate precursor is selected from one or more of disodium hydrogen phosphate, sodium dihydrogen phosphate, dipotassium hydrogen phosphate, potassium dihydrogen phosphate, potassium phosphate, sodium phosphate, potassium pyrophosphate, and sodium pyrophosphate.

6. The preparation method according to claim 4, characterized in that, Step 1) Prepare a 0.01 M PBS solution with pH 7.2-7.4 as the phosphate precursor solution, which contains 0.135 M NaCl and 0.003 M KCl. Slowly add the nickel salt solution to the phosphate precursor solution. After stirring at room temperature for a period of time, age the resulting suspension in a refrigerator at 4 °C for 12 hours. Collect the product by centrifugation, wash, and vacuum dry.

7. The preparation method according to claim 3, characterized in that, The salt of metal M mentioned in step 2) is selected from one or more of the following: ferric sulfate, ferrous ammonium sulfate, ferric nitrate, ferric chloride, ferrous chloride, cobalt sulfate, cobalt nitrate, cobalt chloride, manganese sulfate, manganese nitrate, manganese chloride, copper sulfate, copper nitrate, copper chloride, ferric acetylacetone, cobalt acetylacetone, manganese acetylacetone, and copper acetylacetone.

8. The preparation method according to claim 3, characterized in that, In step 3), the ruthenium precursor in the ruthenium precursor solution is selected from one or more of ruthenium chloride, ruthenium acetylacetone, and ruthenium nitrate. The ruthenium precursor solution is added dropwise to the dispersion of bimetallic phosphate porous hollow nanospheres for ultrasonic mixing. After the reaction system is naturally cooled, the reaction is stirred at room temperature. Finally, the product is collected by centrifugation, washed, and vacuum dried.

9. The application of the high-valence ruthenium single-atom catalyst according to claim 1 or 2 in water electrolysis reaction.

10. The application as described in claim 9, characterized in that, The water electrolysis reaction includes an oxygen evolution reaction and a hydrogen evolution reaction.

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