A bimetallic-vacancy type ZIF-8 composite material, a preparation method and application thereof

Abstract

The present application relates to the technical field of hydrogen evolution by water electrolysis, and particularly relates to a bimetallic@vacancy type ZIF-8 composite material, a preparation method and application. The bimetallic@vacancy type ZIF-8 composite material comprises vacancy type ZIF-8 and Ru and Pt atomic level active sites anchored on the surface of the vacancy type ZIF-8, the Ru and Pt are dispersed on the surface of the vacancy type ZIF-8 in the form of single atoms or double-atom near neighbors, and no metal crystal phase is formed. The present application utilizes the precise anchoring and spatial confinement effect of the metal coordination unsaturated vacancy on the vacancy type ZIF-8 on the Ru atoms and Pt atoms, so that the Ru sites and Pt sites are distributed in near-neighbor distribution on the atomic scale and form an interface electronic coupling effect, thereby simultaneously breaking through the kinetic bottleneck that a single metal site is difficult to consider water dissociation and hydrogen desorption, and solving the technical problems of low utilization rate of noble metal atoms, insufficient activity of single metal catalyst and slow alkaline HER kinetics in the prior art.

Description

Technical Field

[0001] This invention relates to the field of hydrogen evolution through water electrolysis, specifically to a bimetallic@vacancy type ZIF-8 composite material, its preparation method, and its application. Background Technology

[0002] Hydrogen energy, as a clean, efficient, and sustainable secondary energy source, holds significant strategic importance in building a new energy system. Electrolysis of water to produce hydrogen is considered one of the core technological pathways for achieving green hydrogen production due to its wide availability of raw materials, high hydrogen purity, and controllable process. However, the hydrogen evolution reaction (HER) in water splitting exhibits certain energy barriers both thermodynamically and kinetically, especially in alkaline electrolytes. The slow dissociation of water molecules restricts reaction kinetics, requiring a high overpotential and severely limiting energy conversion efficiency.

[0003] Currently, platinum (Pt)-based materials and ruthenium (Ru) are considered the best-performing HER catalysts, but their scarcity and high cost limit their large-scale application. In recent years, single-atom catalysts have become an important research direction for reducing the amount of precious metals used and improving catalytic performance due to their near 100% metal atom utilization and unique electronic structure modulation capabilities. However, single-atom catalysts generally suffer from problems such as easy migration and aggregation of metal atoms and insufficient stability. Furthermore, a single metal active site often cannot simultaneously handle multiple key steps in complex reaction processes, such as water molecule dissociation and hydrogen intermediate adsorption / desorption. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a bimetallic@vacancy-type ZIF-8 composite material, its preparation method, and its applications. The bimetallic@vacancy-type ZIF-8 composite material of this invention consists of vacancy-type ZIF-8 and Ru and Pt atomic-level active sites anchored on the surface of the vacancy-type ZIF-8. Ru and Pt are dispersed on the surface of the vacancy-type ZIF-8 in single-atom or diatomic near-neighbor forms, without forming a metallic crystalline phase. This invention achieves stable anchoring of noble metal atoms through rational carrier design and atomic-level structure control, and further introduces a bimetallic synergistic effect, optimizing the adsorption and desorption behavior of key intermediates in the hydrogen evolution reaction, thus solving a current technical challenge in the field of hydrogen production via water electrolysis.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: The first objective of this invention is to provide a bimetallic@vacancy-type ZIF-8 composite material comprising vacancy-type ZIF-8 and Ru and Pt atomic-level active sites anchored on the surface of the vacancy-type ZIF-8, wherein the Ru and Pt are dispersed on the surface of the vacancy-type ZIF-8 in a monoatomic or diatomic near-neighbor form and do not form a metallic crystalline phase.

[0006] A second objective of this invention is to provide a method for preparing the above-mentioned bimetallic@vacancy-type ZIF-8 composite material, comprising the following steps: S1. In the liquid phase, a soluble zinc salt undergoes a coordination reaction with 2-methylimidazole. During the reaction, the 2-methylimidazole is deprotonated and reacts with Zn in the soluble zinc salt. 2+ Coordination is performed to form a tetrahedral configuration and bridge it to form a three-dimensional porous ZIF-8 with a zeolite topology. Subsequently, the three-dimensional porous ZIF-8 is pyrolyzed at 350°C in air, causing some 2-methylimidazolium ligands to undergo dehydrogenation, breakage and slight carbonization, resulting in the reconstruction of the Zn-N coordination environment and the formation of a slightly defective organic framework that retains the main framework of ZIF-8, thus obtaining defective ZIF-8.

[0007] S2. Load defective ZIF-8 onto a conductive substrate to form an electrode sheet loaded with defective ZIF-8.

[0008] S3. Using a standard three-electrode system, a carbon rod is used as the counter electrode, an Hg / HgO electrode is used as the reference electrode, and an electrode sheet loaded with defective ZIF-8 is used as the working electrode. Electrochemical etching is performed in an alkaline electrolyte to selectively extract Zn species from the defective ZIF-8 framework. At the same time, the organic framework undergoes local collapse and reconstruction, resulting in a nitrogen-containing carbon substrate rich in defects, and metal vacancies are formed in situ to form vacancy-type ZIF-8, thus obtaining a vacancy-type ZIF-8 carrier electrode.

[0009] S4. Using a vacancy-type ZIF-8 carrier electrode as the working electrode, electrodeposition is performed in an electrolyte containing noble metal ions, so that the noble metal is anchored in an atomically dispersed state on the metal vacancy sites in the vacancy-type ZIF-8 to obtain a bimetallic@vacancy-type ZIF-8 composite material; wherein the noble metal ions are Ru ions and Pt ions.

[0010] Preferably, the molar ratio of soluble zinc salt to 2-methylimidazole is 1:10~80, more preferably 1:30~60, and even more preferably 1:47.67.

[0011] Preferably, the particle size of the three-dimensional porous ZIF-8 is 50 nm to 800 nm, more preferably 100 nm to 500 nm, and even more preferably 180 nm to 300 nm. In this embodiment of the invention, the particle size of the three-dimensional porous ZIF-8 is approximately 220 nm. The particle size of the three-dimensional porous ZIF-8 affects the specific surface area and pore size of the vacancy-type ZIF-8. A higher specific surface area and a suitable pore size are beneficial for subsequent noble metal deposition.

[0012] Preferably, in the electrode sheet loaded with defective ZIF-8, the loading of defective ZIF-8 is 0.5 mg / cm³. 2~2.0mg / cm 2 More preferably, 1.0 mg / cm³ 2 .

[0013] Preferably, electrochemical etching is performed using pulsed potential activation, wherein the pulsed potential activation is performed by alternating short cathode pulses and short anode pulses, wherein the cathode potential is -2.0V to -0.8V and the anode potential is +0.8V to +2.0V, the duration of each pulse is 0.1s to 5s, the number of pulses is 50 times / cycle to 1000 times / cycle, and the activation cycle is 1 to 10 times.

[0014] Preferably, the electrodeposition is a sequential bimetallic deposition: Ru is deposited first and then Pt is deposited to obtain Ru-Pt@vacancy type ZIF-8 or Pt is deposited first and then Ru is deposited to obtain Pt-Ru@vacancy type ZIF-8.

[0015] Preferably, the sequential bimetallic deposition is performed using a chronoamperometry or a chronopotentialometry method, with a deposition potential of -2.0V to -0.5V, a single deposition time of 10s to 10000s, and a total deposition time of 100s to 50000s.

[0016] Preferably, the electrodeposition is a bimetallic co-deposition: co-deposition is performed in an electrolyte containing both Ru ion precursors and Pt ion precursors to obtain RuPt@vacancy type ZIF-8.

[0017] Preferably, the bimetallic co-deposition is performed using a chronoamperometry method, with a deposition potential of -2.0V to -0.5V, a deposition time of 10s / cycle to 10000s / cycle, and repeated for 1 to 10 cycles.

[0018] Preferably, defective ZIF-8, binder and dispersant are mixed and coated onto a conductive substrate, and dried to obtain an electrode sheet loaded with defective ZIF-8; wherein, the ratio of defective ZIF-8, binder and dispersant is 1mg:1µL~10µL:0.2mL~2mL, more preferably 1mg:2µL~5µL:0.5mL~1.0mL, and more preferably 1mg:2µL:0.5mL.

[0019] Preferably, the conductive substrate is selected from nickel foam, carbon paper, carbon cloth or titanium mesh.

[0020] Preferably, the adhesive is selected from perfluorosulfonic acid resin solution (Nafion) or polyvinylidene fluoride (PVDF).

[0021] Preferably, the dispersant is selected from isopropanol, ethanol or N-methyl-2-pyrrolidone (NMP).

[0022] A third objective of this invention is to provide the application of the above-mentioned bimetallic@vacancy-type ZIF-8 composite material in the preparation of a hydrogen evolution reaction electrode for water electrolysis under alkaline conditions.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The present invention provides a bimetallic@vacancy-type ZIF-8 composite material, which consists of vacancy-type ZIF-8 and Ru and Pt atomic-level active sites anchored on the surface of the vacancy-type ZIF-8. The Ru and Pt are dispersed on the surface of the vacancy-type ZIF-8 in the form of single atoms or biatomic near-neighbors, and no metallic crystalline phase that can be detected by X-ray diffraction is formed. The bimetallic@vacancy-type ZIF-8 composite material of this invention utilizes the precise anchoring and spatial confinement effect of metal-coordinated unsaturated vacancies on vacancy-type ZIF-8 to Ru and Pt atoms, enabling Ru and Pt sites to be distributed in close proximity at the atomic scale and forming interfacial electronic coupling. Specifically, Ru sites preferentially lower the dissociation energy barrier of water molecules to promote the Volmer step, while Pt sites optimize the adsorption-desorption balance of hydrogen intermediates to accelerate the Heyrovsky / Tafel step. The two work together to construct a tandem catalytic pathway, simultaneously overcoming the kinetic bottleneck that a single metal site cannot simultaneously address water dissociation and hydrogen desorption. This significantly reduces the overpotential and Tafel slope of the alkaline water electrolysis hydrogen evolution reaction, solving the technical problems of low utilization of noble metal atoms, insufficient activity of single metal catalysts, and slow alkaline HER kinetics in the prior art.

[0024] 2. This invention also provides a method for preparing a bimetallic@vacancy-type ZIF-8 composite material. A soluble zinc salt and 2-methylimidazole undergo a coordination reaction in the liquid phase to generate a tetrahedral configuration, which is then bridged to form a three-dimensional porous ZIF-8 with a zeolite topology. Subsequently, the mixture is pyrolyzed at 350°C in air, causing some of the 2-methylimidazole ligands to undergo dehydrogenation, breakage, and slight carbonization, leading to a reconstruction of the Zn-N coordination environment and the formation of slightly defective organic frameworks that retain the main ZIF-8 framework, thus obtaining defective ZIF-8. The defective ZIF-8 is then loaded onto a conductive substrate to obtain an electrode sheet loaded with defective ZIF-8. A standard three-electrode system is used. Using a defect-loaded ZIF-8 electrode as the working electrode, electrochemical etching is performed in an alkaline electrolyte to selectively extract Zn species from the defective ZIF-8 framework. Simultaneously, the organic framework undergoes local collapse and reconstruction, resulting in a defect-rich nitrogen-containing carbon substrate. Metal vacancies are formed in situ, creating vacancy-type ZIF-8, thus obtaining a vacancy-type ZIF-8 support electrode. Then, using this vacancy-type ZIF-8 support electrode as the working electrode, electrodeposition is performed in an electrolyte containing noble metal ions. This allows the noble metal to be anchored at the metal vacancy sites in the vacancy-type ZIF-8 in an atomically dispersed state, yielding a bimetallic@vacancy-type ZIF-8 composite material. This invention employs an in-situ construction strategy combining electrochemical etching and electrodeposition. The process is mild, simple, and allows for real-time monitoring and precise adjustment of deposition potential and time. It eliminates the need for complex post-processing steps, exhibiting high controllability and good repeatability, making it suitable for large-scale preparation. Attached Figure Description

[0025] Figure 1 This is a field emission scanning electron microscope image of ZIF-8.

[0026] Figure 2 X-ray diffraction patterns of ZIF-8, defective ZIF-8, and standard ZIF-8.

[0027] Figure 3 X-ray diffraction patterns of vacancy-type ZIF-8, bimetallic@vacancy-type ZIF-8 composite materials of Examples 1 to 3, and monometallic@vacancy-type ZIF-8 composite materials of Comparative Examples 1 to 2.

[0028] Figure 4 This is a high-angle annular dark-field scanning transmission electron microscope image of Ru-Pt@vacancy type ZIF-8, with the inset being a magnified view of a portion within the red box.

[0029] Figure 5 Energy dispersive X-ray spectroscopy analysis of Ru-Pt@vacancy type ZIF-8.

[0030] Figure 6This is a high-angle annular dark-field scanning transmission electron microscope image of Pt-Ru@vacancy type ZIF-8, with the inset being a magnified view of a portion within the red box.

[0031] Figure 7 Energy dispersive X-ray spectroscopy analysis of Pt element in Pt-Ru@vacancy type ZIF-8.

[0032] Figure 8 Energy dispersive X-ray spectroscopy analysis of Ru in Pt-Ru@vacancy type ZIF-8.

[0033] Figure 9 This is a high-angle annular dark-field scanning transmission electron microscope image of RuPt@vacancy-type ZIF-8, with the inset being a magnified view of a portion within the red box.

[0034] Figure 10 Energy dispersive X-ray spectroscopy analysis of Pt element in RuPt@vacancy type ZIF-8.

[0035] Figure 11 Energy dispersive X-ray spectroscopy analysis of Ru element in RuPt@vacancy type ZIF-8.

[0036] Figure 12 The diagram shows the molar loading of electrodeposited noble metals in the bimetallic@vacancy-type ZIF-8 composite materials of Examples 1 to 3 and the monometallic@vacancy-type ZIF-8 composite materials of Comparative Examples 1 to 2.

[0037] Figure 13 Raman spectra of defective ZIF-8, vacancy-type ZIF-8, bimetallic@vacancy-type ZIF-8 composites of Examples 1 to 3, and monometallic@vacancy-type ZIF-8 composites of Comparative Examples 1 to 2.

[0038] Figure 14 The images show the ultraviolet photoelectron spectra of defect-type ZIF-8 and vacancy-type ZIE-8.

[0039] Figure 15 The images show the ultraviolet photoelectron spectra of the bimetallic@vacancy-type ZIF-8 composite materials of Examples 1 to 3 and the monometallic@vacancy-type ZIF-8 composite materials of Comparative Examples 1 to 2.

[0040] Figure 16 Linear scanning voltammetry plots of vacancy-type ZIF-8, bimetallic@vacancy-type ZIF-8 composite materials of Examples 1 to 3, and monometallic@vacancy-type ZIF-8 composite materials of Comparative Examples 1 to 2.

[0041] Figure 17Tafel polarization curves for vacancy-type ZIF-8, bimetallic@vacancy-type ZIF-8 composite materials of Examples 1 to 3, and monometallic@vacancy-type ZIF-8 composite materials of Comparative Examples 1 to 2.

[0042] Figure 18 The bimetallic@vacancy-type ZIF-8 composite materials of Examples 1-3 and the monometallic@vacancy-type ZIF-8 composite materials of Comparative Examples 1-2 are shown at 10 mA / cm 2 The results of the constant current electrolysis stability test are shown in the figure.

[0043] Figure 19 The reported Ru and Pt doped catalysts, the bimetallic@vacancy ZIF-8 composites of Examples 1-3, and the monometallic@vacancy ZIF-8 composites of Comparative Examples 1-2 were compared at 10 mA / cm². 2 Overpotential and Tafel slope plot. Detailed Implementation

[0044] The technical solution of the present invention will be clearly and completely described below with reference to the data in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0045] It should be noted that the technical terms used in this invention are for the purpose of describing specific embodiments only and are not intended to limit the scope of protection of this invention. Unless otherwise specified, all raw materials, reagents, instruments and equipment used in the following embodiments of this invention can be purchased commercially or prepared by existing methods. 2-Methylimidazole is denoted as H-MIM, and the 5% perfluorinated resin solution is denoted as Nafion.

[0046] Metal-organic frameworks (MOFs) exhibit unique advantages in constructing single-atom and diatomic catalysts due to their strong structural designability, large specific surface area, and well-defined coordination environment. Among them, ZIF-8, as a typical Zn-based MOF material, can form abundant metal vacancies and defect structures after etching or demetallization treatment, providing an ideal platform for anchoring noble metal atoms and controlling interfacial electrons.

[0047] Based on this, this invention addresses the problems of slow hydrogen evolution reaction kinetics, low utilization efficiency of precious metals, and difficulty in precisely controlling the catalytic interface structure during alkaline water electrolysis for hydrogen production. It proposes a bimetallic@vacancy-type ZIF-8 composite material, which uses a combination of electrochemical etching and electrodeposition to construct a bimetallic synergistic catalytic interface in situ on vacancy-type ZIF-8 for efficient water electrolysis for hydrogen production.

[0048] First, defective ZIF-8 is obtained by pyrolysis of three-dimensional porous ZIF-8. Then, electrochemical etching is performed to selectively extract Zn species from the defective ZIF-8 framework. While maintaining the basic integrity of the original framework structure, a large number of stable metal vacancies and defect structures are introduced, providing a clear site basis for the subsequent precise anchoring of noble metal atoms.

[0049] Then, Ru and Pt atoms were introduced in situ onto the vacancy-type ZIF-8 surface using electrodeposition. Compared with traditional impregnation, chemical reduction, or high-temperature calcination methods, the electrodeposition process can be carried out directly under electrochemical conditions, offering significant advantages such as real-time monitoring of the deposition process and highly controllable deposition locations. By adjusting the types of metal ions, deposition potential, and time in the electrodeposition electrolyte, the precise construction of noble metal atoms at metal vacancy sites was achieved, avoiding disordered growth and aggregation of metal atoms, thereby stably obtaining highly dispersed single-atom or diatomic active structures.

[0050] Finally, by controlling the deposition sequence of noble metal ions, bimetallic catalytic sites with different interfacial electronic structures were constructed. When Ru and Pt atoms are deposited sequentially at the metal vacancy sites of the vacancy-type ZIF-8 in a specific order, significant electronic coupling occurs between them, altering the local electron distribution and thus synergistically controlling the dissociation of water molecules and the adsorption or desorption of hydrogen intermediates during the hydrogen evolution reaction. This bimetallic synergistic effect effectively lowers the energy barrier of the hydrogen evolution reaction, enabling the bimetallic@vacancy-type ZIF-8 composite material to achieve a high current density at a lower overpotential and exhibiting a smaller Tafel slope, reflecting excellent reaction kinetics.

[0051] Furthermore, the process conditions of this invention are mild and the operation is simple, requiring no complex post-processing steps, making it suitable for large-scale preparation. The prepared bimetallic@vacancy-type ZIF-8 composite material exhibits excellent catalytic activity and long-term stability in alkaline water electrolysis hydrogen production systems, showing promising prospects for practical applications.

[0052] To enable those skilled in the art to more clearly understand the technical solution of the present invention, the following will provide a detailed description in conjunction with specific embodiments: Example 1 A method for preparing a bimetallic@vacancy-type ZIF-8 composite material includes the following steps: S1. According to the molar ratio of Zn(NO3)2·6H2O and H-MIM of 1:47.67, 0.863g of Zn(NO3)2·6H2O was weighed and dissolved in 8mL of deionized water to obtain a zinc salt solution; 11.350g of H-MIM was dissolved in 80mL of deionized water to obtain an H-MIM solution; under room temperature conditions, the zinc salt solution was added dropwise to the H-MIM solution and ultrasonically dispersed for 5min, followed by continuous stirring at room temperature for 8h to obtain a white product; the white product was centrifuged three times with methanol at 10000rpm for 10min each time to obtain a white separated product, which was then vacuum dried at 60℃ for 24h and ground to obtain a three-dimensional porous ZIF-8 with an average particle size of 220nm, denoted as ZIF-8.

[0053] S2. Grind ZIF-8 into powder in an agate grinding bowl for 15 minutes and place it in a quartz boat. Then place the quartz boat in a tube furnace and heat it to 350°C at a heating rate of 10°C / min in an air atmosphere. Pyrolyze it at 350°C for 0.5 hours. After pyrolysis, allow it to cool naturally to room temperature to obtain defective ZIF-8.

[0054] S3. Following the ratio of defective ZIF-8, Nafion, and isopropanol of 1 mg: 2 µL: 0.5 mL, place 0.25 mg of defective ZIF-8, 0.5 µL of Nafion, and 0.125 mL of isopropanol in a centrifuge tube and sonicate for 1 hour. Then, use a pipette to aspirate and evenly drop the solution onto a 0.5 cm... 2 ×0.5cm 2 On a nickel foam mesh, the electrode sheet of load defect type ZIF-8 is dried at 60°C for 24 hours in a vacuum environment.

[0055] S4. A standard three-electrode system is used, with a carbon rod as the counter electrode, an Hg / HgO electrode as the reference electrode, and a ZIF-8 electrode plate with a loading defect as the working electrode. The working electrode is activated by pulse potential in a 1 mol / L potassium hydroxide solution. A short pulse of cathode potential (cathode potential = -1.5V, t = 1s) is followed immediately by a short pulse of anode potential (anode potential = +1.5V, t = 1s) 120 times. This 120-times cycle constitutes one activation period. One activation period lasts 240s, and five activation periods are performed, for a total pulse potential activation time of 1200s. This process is used to activate Zn... 2+ The organic ligand on 2-methylimidazole is etched out to form a metal vacancy, resulting in a vacancy-type ZIF-8 carrier electrode, denoted as vacancy-type ZIF-8.

[0056] S5. Continue using the above three-electrode system to perform electrodeposition in a mixed solution consisting of 30 mL of deionized water, 0.3 mL of 1 mol / L HCl solution and 9 µL of 0.1 mol / L RuCl3 aqueous solution; wherein, the electrodeposition is performed using the chronoamperometry method, with the initial voltage set at -1.5 V, the deposition time being 2000 s as one cycle, and the cycle being repeated for 3 cycles.

[0057] Then, electrodeposition was carried out in a mixed solution consisting of 30 mL of deionized water, 0.3 mL of 1 mol / L HCl solution, and 9 µL of 0.1 mol / L H2PtCl6 aqueous solution. The electrodeposition was performed using a chronoamperometry method, with an initial voltage of -1.5 V and a deposition time of 2000 s per cycle, repeated for 3 cycles to keep the total electrodeposition time at 12000 s. This allowed Ru ions and Pt ions to be deposited sequentially on the metal vacancies of the vacancy-type ZIF-8, resulting in a bimetallic@vacancy-type ZIF-8 composite material, named Ru-Pt@vacancy-type ZIF-8.

[0058] In this embodiment of the invention, the loading amount of defective ZIF-8 in the electrode sheet is approximately 0.25 mg.

[0059] Example 2 A method for preparing a bimetallic@vacancy-type ZIF-8 composite material is the same as S1~S4 in Example 1, except that in S5, Pt is first deposited on the vacancy-type ZIF-8, and then Ru is deposited. The method includes the following steps: The above three-electrode system was continued, and electrodeposition was carried out in a mixed solution consisting of 30 mL of deionized water, 0.3 mL of 1 mol / L HCl solution and 9 µL of 0.1 mol / L H2PtCl6 aqueous solution. The electrodeposition was performed using the chronoamperometry method, with an initial voltage of -1.5 V and a deposition time of 2000 s per cycle, repeated for 3 cycles, so that the total electrodeposition time was kept at 12000 s.

[0060] Then, electrodeposition was carried out in a mixed solution consisting of 30 mL of deionized water, 0.3 mL of 1 mol / L HCl solution, and 9 µL of 0.1 mol / L RuCl3 aqueous solution. The electrodeposition was performed using a chronoamperometry method, with an initial voltage of -1.5 V and a deposition time of 2000 s per cycle, repeated for 3 cycles. This allowed Pt ions and Ru ions to be deposited sequentially on the vacancies of the vacancy-type ZIF-8, resulting in a bimetallic@vacancy-type ZIF-8 composite material, named Pt-Ru@vacancy-type ZIF-8.

[0061] Example 3 A method for preparing a bimetallic@vacancy-type ZIF-8 composite material is the same as S1~S4 in Example 1, except that in S5, Pt and Ru are deposited simultaneously on vacancy-type ZIF-8, including the following steps: Continuing with the aforementioned three-electrode system, electrodeposition was performed in a mixed solution consisting of 30 mL of deionized water, 0.3 mL of 1 mol / L HCl solution, 4.5 µL of 0.11 mol / L H₂PtCl₆ aqueous solution, and 4.5 µL of 0.11 mol / L RuCl₃ aqueous solution. Electrodeposition was performed using a chronoamperometry method, with an initial voltage of -1.5 V and a deposition time of 2000 s per cycle, repeated for 6 cycles to maintain a total electrodeposition time of 12000 s. This resulted in the deposition of Pt and Ru ions together on the vacancy-type ZIF-8 site, named RuPt@vacancy-type ZIF-8.

[0062] Comparative Example 1 A method for preparing a single-metal@vacancy-type ZIF-8 composite material is the same as S1~S4 in Example 1, except that in S5, only Ru is deposited on the vacancy-type ZIF-8, including the following steps: Continuing with the aforementioned three-electrode system, electrodeposition was performed in a mixed solution consisting of 30 mL of deionized water, 0.3 mL of 1 mol / L HCl solution, and 9 µL of 0.11 mol / L RuCl3 aqueous solution. The electrodeposition was performed using a chronoamperometry method, with an initial voltage of -1.5 V and a deposition time of 2000 s per cycle. This was repeated for six cycles to maintain a total electrodeposition time of 12000 s, thereby depositing Ru ions onto the vacancies in the vacancy-type ZIF-8 material, completing the electrochemical atomic exchange between Zn and Ru on the ZIF-8 material, and obtaining Ru@vacancy-type ZIF-8.

[0063] Comparative Example 2 A method for preparing a single-metal@vacancy-type ZIF-8 composite material is the same as S1~S4 in Example 1, except that in S5, only Ru is deposited on the vacancy-type ZIF-8, including the following steps: Continuing with the aforementioned three-electrode system, electrodeposition was performed in a mixed solution consisting of 30 mL of deionized water, 0.3 mL of 11 mol / L HCl solution, and 9 µL of 0.1 mol / L H2PtCl6 aqueous solution. Electrodeposition was conducted using a chronoamperometry method, with an initial voltage of -1.5 V and a deposition time of 2000 s per cycle. This was repeated for six cycles to maintain a total electrodeposition time of 12000 s, thereby depositing Pt ions onto the vacancies in the vacancy-type ZIF-8 material, completing the electrochemical atomic exchange between Zn and Pt on the ZIF-8 material, and obtaining Pt@vacancy-type ZIF-8.

[0064] To characterize the hydrogen evolution performance of the vacancy-type ZIF-8, the bimetallic@vacancy-type ZIF-8 composite materials of Examples 1-3, and the monometallic@vacancy-type ZIF-8 composite materials of Comparative Examples 1-2 in the hydrogen evolution reaction of water electrolysis, electrochemical tests were performed using a standard three-electrode test system. A carbon rod was used as the counter electrode, and an Hg / HgO electrode was used as the reference electrode. Electrode sheets using vacancy-type ZIF-8, the bimetallic@vacancy-type ZIF-8 composite materials of Examples 1-3, and the monometallic@vacancy-type ZIF-8 composite materials of Comparative Examples 1-2 as catalysts were used as working electrodes. The electrolyte was a 1 mol / L KOH aqueous solution.

[0065] Hydrogen evolution activity was tested using linear sweep voltammetry (LSV) on an electrochemical workstation. The scanning potential was performed relative to the reversible hydrogen electrode (RHE) within the range of -0.5V to 0V to obtain the overpotential required for electrode plates using different catalysts at the same current density, thereby comparing their hydrogen evolution reaction activities. The obtained polarization curves were analyzed during the scanning process to evaluate the differences in electrocatalytic performance of the catalysts.

[0066] In addition, to investigate the structural and reaction stability of the catalyst under long-term electrolysis conditions, at 10 mA / cm 2 Chronopotentiometry was used to test the electrochemical stability of each catalyst under current density conditions, and the changes in electrode potential over time were continuously recorded during the reaction. Through long-term testing, the electrochemical stability and durability of different catalysts in the continuous hydrogen evolution reaction were evaluated.

[0067] Depend on Figure 1 It was found that the ZIF-8 prepared by this invention has a regular hexahedral morphology and an average particle size of 220 nm.

[0068] observe Figure 2 The results show that the ZIF-8 prepared by this invention has the same peak position as the standard ZIF-8 in each crystal plane diffraction, indicating that the three-dimensional porous ZIF-8 of this invention was successfully synthesized; although the peak shape of the defective ZIF-8 is slightly broadened, the peak position has not changed, indicating that its structure is still intact.

[0069] Depend on Figure 3The results showed that almost all the crystal diffraction peaks of the defective ZIF-8 disappeared after electrochemical etching, proving that the metal-organic framework in ZIF-8 collapsed. The peaks at 15°, 28° and 54° were all attributed to carbon peaks, and no Ru or Pt crystal peaks were found. This proved that the electrodeposited metal existed in a highly dispersed non-static or atomically dispersed state, indicating that the noble metal and the carbon substrate formed a stable interfacial interaction, which effectively suppressed its aggregation and crystallization behavior in the electrochemical reaction.

[0070] observe Figure 4 and Figure 5 It was found that Ru-Pt@vacancy type ZIF-8 only has continuous carbon lattice fringes, and Ru atoms and Pt atoms are uniformly distributed on the nitrogen-containing carbon substrate of vacancy type ZIF-8 without forming continuous lattice fringes or obvious clusters.

[0071] observe Figure 6 , Figure 7 and Figure 8 It was found that Pt-Ru@vacancy type ZIF-8 only has continuous carbon lattice fringes, and Ru and Pt atoms are uniformly distributed on the nitrogen-containing carbon substrate of vacancy type ZIF-8 without forming continuous lattice fringes or obvious clusters.

[0072] observe Figure 9 , Figure 10 and Figure 11 It was found that RuPt@vacancy type ZIF-8 only has continuous carbon lattice fringes, and Ru and Pt atoms are uniformly distributed on the nitrogen-containing carbon substrate of vacancy type ZIF-8 without forming continuous lattice fringes or obvious clusters.

[0073] In summary, vacancy-type ZIF-8 can effectively inhibit the migration and aggregation of noble metal atoms, which is beneficial for constructing stable atomic-level noble metal active sites.

[0074] Depend on Figure 12 The results showed that both Ru@vacancy-type ZIF-8 and Pt@vacancy-type ZIF-8 exhibited high metal loading, while in Ru-Pt@vacancy-type ZIF-8 and Pt-Ru@vacancy-type ZIF-8, the loading of later-deposited metals was significantly limited, indicating that the first-deposited metal preferentially occupies vacancy sites and inhibits further anchoring of later metals through metal-ligand or metal-metal interactions. In RuPt@vacancy-type ZIF-8, the loading of Ru and Pt was more similar, suggesting that co-deposition helps alleviate site competition.

[0075] Depend on Figure 13 The intensity ratio I of defective carbon D bands to graphitized carbon G bands was obtained. D / I G A higher value indicates a higher degree of defect and electronic disorder in the carbon substrate. The ratio of the 2D diffraction peak of π-conjugated carbon to the G band of graphitized carbon is also higher. 2D / I G This demonstrates the extent to which the introduction of charge doping states modulates the electronic structure of the carrier. In vacancy-type ZIF-8, I D / I G A ratio as high as 2.15 indicates the highest degree of defect. After electrodeposition, noble metal fills the vacancies, and this value decreases to varying degrees. 2D / I G The ratios also changed to varying degrees; the most significant change was observed in Ru-Pt@vacancy type ZIF-8, while the lowest was observed in I. D / I G The ratio with higher I 2D / I G This indicates that it is most effective at electronically controlling the carbon substrate, while also reducing the degree of defects in the carbon framework.

[0076] Depend on Figure 14 and Figure 15 The results showed that as the degree of defects increased due to pyrolysis and electrochemical etching in air, the Fermi level decreased from 5.3 eV (3D porous ZIF-8) to 5.0 eV (defect-type ZIF-8). This decrease indicates that the chemical defects introduced by air pyrolysis effectively modulated the electronic structure of the carbon substrate, increasing the surface electronic disorder. After electrodeposition of the vacancy-type ZIF-8 support electrode in an electrolyte containing noble metal ions, its Fermi level further decreased, reaching a minimum of 3.33 eV (bimetallic@vacancy-type ZIF-8 composite material). This indicates a strong charge redistribution at the interface between the noble metal and the vacancy-type ZIF-8, and a significant electronic coupling between the noble metal and the carbon substrate.

[0077] Furthermore, different electrodeposition sequences (Ru first then Pt, Pt first then Ru, or Ru+Pt co-deposition) lead to differences in the intensity and mode of interaction between Ru and Pt, as well as between noble metals and vacancy-type ZIF-8, which in turn cause differences in the degree of Fermi level shift and the efficiency of interfacial charge transfer.

[0078] The stepwise reduction of the Fermi level indicates that this invention achieves precise layer-by-layer control of the electronic structure of the vacancy-type ZIF-8 carbon substrate through a three-step combined strategy of "pyrolysis to create defects—electrochemical etching to create vacancies—electrodeposition to anchor noble metals." The reduction of the Fermi level is beneficial for increasing the surface electron density of the bimetallic@vacancy-type ZIF-8 composite material, accelerating the interfacial electron transfer rate in the alkaline HER process. Simultaneously, the construction of Ru-Pt bimetallic synergistic sites optimizes the kinetic energy barriers of water molecule dissociation and hydrogen intermediate adsorption / desorption, thereby significantly improving the catalytic performance of the hydrogen evolution reaction.

[0079] Depend on Figure 16The results show that, under the same current density, the overpotential of the electrolyzers using Ru-Pt@vacancy-type ZIF-8, RuPt@vacancy-type ZIF-8, Pt-Ru@vacancy-type ZIF-8, Pt@vacancy-type ZIF-8, Ru@vacancy-type ZIF-8, and vacancy-type ZIF-8 as catalysts increases from small to large. This indicates that, in terms of the overall performance of water electrolysis for hydrogen production, the bimetallic@vacancy-type ZIF-8 composite material is superior to the monometallic@vacancy-type ZIF-8 composite material, and significantly superior to vacancy-type ZIF-8. Furthermore, the performance difference caused by the order of deposition demonstrates that the synergistic effect of Ru and Pt does exist and significantly affects the kinetics of the water electrolysis for hydrogen production.

[0080] Figure 17 The Tafel polarization curves are for vacant ZIF-8, the bimetallic@vacant ZIF-8 composites of Examples 1-3, and the monometallic@vacant ZIF-8 composites of Comparative Examples 1-2. A smaller slope indicates faster reaction kinetics and easier interfacial charge transfer in the water electrolysis hydrogen production reaction. Common rate-limiting steps and overpotential ranges in alkaline electrolyte water electrolysis hydrogen production reactions are: Volmer (hydrolysis) ~120 mV / dec, Heyrovsky (electrochemical desorption) ~40 mV / dec, and Tafel (chemical recombination) ~40 mV / dec. The figures show that hydrolysis is difficult and interfacial charge transfer is slow in vacant ZIF-8 and Ru@vacant ZIF-8 catalysts. The overpotentials are significantly reduced in RuPt@vacant ZIF-8, Pt-Ru@vacant ZIF-8, and Pt@vacant ZIF-8 catalysts, but still fall within the Volmer–Heyrovsky synergistic region. The overpotential of Ru-Pt@vacancy-type ZIF-8 is close to the Tafel region, and the reaction is close to rapid recombination and desorption control. This indicates that the pre-deposited Ru promotes hydrolysis, and the subsequently introduced Pt optimizes the binding of H* and the desorption of H2, thereby simultaneously lowering the reaction energy barrier and minimizing the Tafel slope.

[0081] Depend on Figure 18 The results show that the electrode plate using Ru@vacancy-type ZIF-8 as the catalyst exhibits better stability and lower potential compared to the electrode plate using Pt@vacancy-type ZIF-8 as the catalyst, while bimetallic deposition compensates for the limited stability of Pt atoms under alkaline conditions; among them, Ru-Pt@vacancy-type ZIF-8 exhibits the best hydrolysis stability. In summary, the bimetallic synergistic effect not only enhances the activity of hydrogen production through water electrolysis but also significantly improves the structural stability under alkaline conditions.

[0082] Depend on Figure 19It is obtained that Ru / RuO2 (112 mA, 55 mV / dec), RuO2 (110 mA, 120.5 mV / dec, Information source: Zhu Y, Klingenhof M, Gao C, et al. Facilitating alkaline hydrogen evolution reaction on the hetero-interfaced Ru / RuO2 through Pt single atoms doping[J]. Nat Commun, 2024, 15(1): 1447.), NiRu-LDH (165 mA, 107 mV / dec), NiRu-OH (191 mA, 106 mV / dec, Information source: Li D, Chen X, Lv Y, et al. An effective hybrid electrocatalyst for the alkaline HER: Highly dispersed Pt sites immobilized by a functionalized NiRu-hydroxide[J]. Applied Catalysis B: Environmental, 2020, 269: 118824.), Pt / CNTs (56 mA, 90.5 mV / dec, Information source: Zhao K, Zhang J, Li H, et al. Boosting HER performance by using plasma prepared N-doped CNTs to support Pt nanoparticles[J]. International Journal of Hydrogen Energy, 2024, 90: 1271-1278.), Pt-Mo6S8 (124 mA, 88 mV / dec, Information source: Liu M, Lv G, Liu H, et al. Pt / Mo chalcogenide composite deriving from Pt-Mo6S8 by high temperature shock for enhanced HER performance[J]. Chinese Chemical Letters, 2024, 35(3): 108459.), Pt M@CN (59mA, 77.7mV / dec, Source: Liu X, Song X, Jiang G, et al. PtSingle-Atom collaborate with Pt Atom-Clusters by an In-Situ confined strategy for accelerating electrocatalytic hydrogen evolution[J]. Chemical Engineering Journal, 2024, 481: 148430.). Compared with existing technologies, this invention improves the construction method of defective ZIF-8 substrates by combining electrochemical etching with atomic-level noble metal deposition, achieving precise control over the density of ZIF-8 defect sites and the interface structure.

[0083] Unlike traditional methods that introduce defects through chemical etching or high-temperature treatment, this invention employs an electrochemical method to controllably etch ZIF-8 under mild conditions. This effectively exposes and stabilizes abundant metal coordination unsaturated sites, providing a stable support for the anchoring of noble metal atoms. Based on this, Ru, Pt single-metal, and bimetallic atoms are anchored in a highly dispersed manner on the vacancy-type ZIF-8 carbon substrate, significantly modulating the catalyst's interfacial electronic structure and enhancing the synergistic effects between the metal-support and metal-metal interactions, thereby optimizing the adsorption and desorption behavior of the hydrogen intermediate (H*). Electrochemical test results show that the noble metal-deposited vacancy-type ZIF-8 catalyst prepared in this invention exhibits a lower hydrogen evolution overpotential and a smaller Tafel slope in alkaline electrolyte, significantly improving the reaction kinetics and energy conversion efficiency of the hydrogen evolution reaction in water electrolysis.

[0084] Meanwhile, this method has a simple process flow, good repeatability, and is applicable to the atomic-level construction of different precious metals and their bimetallic systems. It has good scalability and industrial application prospects, and can be widely used in the field of efficient water electrolysis for hydrogen production.

[0085] It should be noted that when numerical ranges are involved in this invention, it should be understood that both endpoints of each numerical range, as well as any value between the two endpoints, can be selected. Since the S-method used is the same as in the embodiments, preferred embodiments are described here to avoid redundancy. Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this invention.

Claims

1. A bimetallic@vacancy type ZIF-8 composite material, characterized in that, The vacancy-type ZIF-8 consists of Ru and Pt atomic-level active sites anchored on the surface of the vacancy-type ZIF-8. The Ru and Pt are dispersed on the surface of the vacancy-type ZIF-8 in a single-atom or diatomic near-neighbor form and do not form a metallic crystalline phase.

2. A method for preparing the bimetallic@vacancy-type ZIF-8 composite material according to claim 1, characterized in that, Includes the following steps: Soluble zinc salt and 2-methylimidazole were coordinated in the liquid phase to generate three-dimensional porous ZIF-8. After being pyrolyzed at 350°C in air, some of the 2-methylimidazole ligands underwent dehydrogenation, cleavage and carbonization, resulting in the reconstruction of the Zn-N coordination environment and the formation of organic framework defects that retain the main framework of ZIF-8, thus obtaining defective ZIF-8. Defect-type ZIF-8 is loaded onto a conductive substrate to obtain an electrode sheet loaded with defect-type ZIF-8; A standard three-electrode system was used, with a carbon rod as the counter electrode, an Hg / HgO electrode as the reference electrode, and an electrode sheet loaded with defective ZIF-8 as the working electrode. Electrochemical etching was performed in an alkaline electrolyte to selectively extract Zn species from the defective ZIF-8 framework. At the same time, the organic framework underwent local collapse and reconstruction, resulting in a nitrogen-containing carbon substrate rich in defects, and metal vacancies were formed in situ to form vacancy-type ZIF-8, thus obtaining a vacancy-type ZIF-8 carrier electrode. Using a vacancy-type ZIF-8 carrier electrode as the working electrode, electrodeposition was performed in an electrolyte containing noble metal ions, so that the noble metal was anchored in an atomically dispersed state at the metal vacancy sites in the vacancy-type ZIF-8, resulting in a bimetallic@vacancy-type ZIF-8 composite material; wherein the noble metal ions are Ru ions and Pt ions.

3. The preparation method according to claim 2, characterized in that, The molar ratio of soluble zinc salt to 2-methylimidazole is 1:10~80.

4. The preparation method according to claim 2, characterized in that, In the electrode sheet with defective ZIF-8 loading, the loading of defective ZIF-8 is 0.5 mg / cm³. 2 ~2.0mg / cm 2 .

5. The preparation method according to claim 2, characterized in that, Electrochemical etching is performed using pulsed potential activation, which is achieved by alternating short cathode pulses and short anode pulses. The cathode potential is -2.0V to -0.8V, the anode potential is +0.8V to +2.0V, the duration of each pulse is 0.1s to 5s, the number of pulses is 50 to 1000 times per cycle, and the activation cycle is 1 to 10 times.

6. The preparation method according to claim 2, characterized in that, The electrodeposition is a sequential bimetallic deposition: Ru is deposited first and then Pt is deposited to obtain Ru-Pt@vacancy type ZIF-8, or Pt is deposited first and then Ru is deposited to obtain Pt-Ru@vacancy type ZIF-8.

7. The preparation method according to claim 6, characterized in that, The sequential bimetallic deposition was performed using either chronoamperometry or chronopotentialometry, with a deposition potential of -2.0V to -0.5V, a single deposition time of 10s to 10000s, and a total deposition time of 100s to 50000s.

8. The preparation method according to claim 2, characterized in that, The electrodeposition is a bimetallic co-deposition: co-deposition is carried out in an electrolyte containing both Ru and Pt ions to obtain RuPt@vacancy type ZIF-8.

9. The preparation method according to claim 8, characterized in that, The bimetallic co-deposition was performed using a chronoamperometry method, with a deposition potential of -2.0V to -0.5V and a deposition time of 10s / cycle to 10000s / cycle, repeated for 1 to 10 cycles.

10. The application of the bimetallic@vacancy-type ZIF-8 composite material according to claim 1 in the preparation of a hydrogen evolution reaction electrode for water electrolysis under alkaline conditions.

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