Gallium monatomic porous carbon confinement osmium-based ultra-small cluster electrocatalyst as well as preparation method and application thereof

Abstract

The invention relates to the technical field of nano material electrocatalysis, and discloses a gallium monatomic porous carbon confinement osmium-based ultra-small cluster electrocatalyst and a preparation method and application thereof.The electrocatalyst comprises a porous carbon substrate, gallium monatomic and osmium nanoclusters, the gallium monatomic is anchored to the porous carbon substrate in a Ga-N bond bonding mode, and the osmium nanoclusters are anchored to the porous carbon substrate in a Ga-N bond bonding mode; the osmium nanoclusters are loaded on the surface and in pores of the porous carbon substrate. The problems of uneven distribution of active sites, component loss under current driving and the like are solved through the physical confinement effect of porous carbon, and the activity and stability are improved through coupled gallium monatomic double-site synergistic catalysis. Wherein the active component has the characteristics of small size, uniform particle size, uniform distribution and the like, the active component is anchored on the substrate by utilizing the confinement effect of microporous carbon, and the problems that the catalytic performance is reduced and the like due to the agglomeration behavior of the active component caused by thermal migration when the electrocatalyst is prepared through traditional high-temperature reduction are fully solved.

Description

Technical Field

[0001] This invention relates to the field of nanomaterial electrocatalysis technology, specifically to a gallium single-atom porous carbon-confined osmium-based ultrasmall cluster electrocatalyst, its preparation method, and its application. Background Technology

[0002] With the increasing severity of energy crises and environmental pollution, the global energy consumption structure is gradually shifting towards decarbonization. Hydrogen energy, possessing extremely high energy density and being a green product with zero carbon emissions, can be easily integrated into the existing energy structure as a green and efficient energy source. It can also be converted into electricity in a green and efficient manner through fuel cell technology. These characteristics give it the potential to become a mainstream energy source in the future and can effectively promote the decarbonization of the energy structure.

[0003] Electrolysis of water is currently an important method for producing clean hydrogen, and fuel cell technology is the main technology for converting hydrogen into electricity. However, the main barrier limiting the large-scale application of this technology lies in the high price, low activity, and low stability of its electrocatalysts. Currently, platinum-based materials are the mainstream choice for high-efficiency catalysts, but their high price and poor toxicity resistance in fuel cell systems severely hinder the widespread adoption of hydrogen electroconversion technology. To solve this problem, there is an urgent need to develop low-cost, high-activity, and high-stability electrocatalytic materials. Osmium (Os)-based catalysts are widely used in the catalysis field and have the lowest price among precious metals; using them in electrocatalysis would significantly reduce costs.

[0004] While osmium-based catalysts exhibit high catalytic activity for hydrogen evolution and hydroxide oxidation, their instability cannot be maintained over long periods, severely limiting their application in industrial production. In real-world reaction environments, electrocatalysts often face practical problems such as uneven distribution of active sites, limited number of active sites, loss of active components under current-driven conditions, and insufficient mass transfer and conductivity, seriously affecting their efficient utilization. Research indicates that nano-confinement effects can exert a unique enhancing effect on catalytic reactions, often manifesting as pore confinement, interlayer confinement, and atomic bond confinement. Nano-confinement helps to minimize the dissolution of active components, ensuring material stability. Furthermore, atomic bond effects not only enhance material stability but can also optimize the electronic structure of active components to some extent, regulating their catalytic activity. However, currently reported catalyst preparation methods do not effectively utilize nano-confinement effects, and the preparation processes are complex, costly, and difficult to achieve stable catalyst production.

[0005] In summary, inventing a novel high-performance electrocatalyst preparation method that is low-cost, highly active, highly stable, simple to prepare, and stable is of great significance and can greatly promote the development and popularization of hydrogen-to-electroconversion technology. Summary of the Invention

[0006] The main objective of this invention is to provide a low-cost, highly active, highly stable, and easily prepared single-atom porous carbon-confined osmium-based ultra-small cluster electrocatalyst and its preparation method. The osmium-based catalyst prepared by the method of this invention utilizes the physical confinement effect of microporous carbon to anchor the active components on the substrate, which can effectively prevent the loss of active components during the electrocatalytic process. In addition, gallium single atoms play a synergistic catalytic role as auxiliary catalytic sites, giving it high activity and high stability as a material for hydrogen evolution in water electrolysis and hydrogen hydroxide material in fuel cells.

[0007] To achieve the above objectives, in a first aspect, the present invention provides a method for preparing a gallium single-atom porous carbon-confined osmium-based ultrasmall cluster electrocatalyst, comprising the following steps: S1. Add biogelatin, nano silica, gallium nitrate hydrate, and 1,10-phenanthroline to deionized water in a mass ratio of 10~15:5~8:1:2~3, mix thoroughly and evenly, repeatedly freeze and thaw the mixture to produce a hydrogel complex, and freeze-dry it to form an aerogel. S2. The aerogel is heated to 700~900℃ under an inert atmosphere for pyrolysis treatment to form carbon-nitrogen materials. The obtained product is ground and then etched with an alkaline solution under water bath heating to remove nano-silica. After washing and drying, it is ground into powder to obtain a single-atom carbon precursor. S3. Add the single-atom carbon precursor and water-soluble osmium chloride metal salt to deionized water, mix thoroughly and evenly, then freeze with liquid nitrogen and freeze-dry. After thorough grinding, place it in a hydrogen / argon mixed atmosphere and heat to 300~500℃ for pyrolysis treatment to obtain gallium single-atom porous carbon confined osmium-based ultra-small cluster electrocatalyst. The osmium chloride metal salt accounts for 15-40% of the total mass of the osmium chloride metal salt and the single-atom carbon precursor, and more preferably 20-30%.

[0008] Water-soluble osmium chloride metal salts are selected from osmium trichloride (OsCl3) or osmium trichloride trihydrate (OsCl3·3H2O).

[0009] This invention relates to porous carbon prepared by an alkaline etching method, which is rich in micropores and has a high specific surface area. The alkaline solution used for alkaline etching is sodium hydroxide solution, potassium hydroxide solution, or ammonia water.

[0010] As a further preferred embodiment of the present invention, the gallium nitrate hydrate is gallium nitrate octahydrate or gallium nitrate nonahydrate.

[0011] As a further preferred embodiment of the present invention, the mass ratio of the biogelatin, nano-silica, gallium nitrate hydrate, and 1,10-phenanthroline is 2000~2500 : 1000~1500 : 170~190 : 400~500, and even more preferably 2400 : 1200 : 187 : 476.

[0012] As a further preferred technical solution of the present invention, the repeated freeze-thaw cycle is: freezing at -30~-10 ℃ for 6~24 hours, thawing at room temperature for 6~12 hours, and repeating the freeze-thaw cycle at least twice.

[0013] As a further preferred technical solution of the present invention, when the aerogel is heated to pyrolyze under an inert atmosphere, the heating rate is 3~5℃ / min and the pyrolysis time is 1~4 hours.

[0014] As a further preferred embodiment of the present invention, in the hydrogen / argon mixed atmosphere, the volume ratio of hydrogen is 5-20%, and more preferably the volume ratio of hydrogen to argon is 1:9.

[0015] In a second aspect, the present invention also provides a gallium single-atom porous carbon-confined osmium-based ultrasmall cluster electrocatalyst, which is prepared by the preparation method described above.

[0016] This invention addresses the problems of uneven distribution of active sites and component loss under current-driven conditions by utilizing the physical confinement effect of porous carbon, and enhances activity and stability through synergistic catalysis with gallium single atoms at two sites. In the electrocatalyst, gallium single atoms are anchored on the porous carbon substrate via Ga-N bonds, while osmium nanoclusters are loaded on the surface and within the pores of the porous carbon substrate.

[0017] As a further preferred embodiment of the present invention, in the electrocatalyst, the loading of gallium single atoms is 1.6~2.3wt%, the loading of osmium nanoclusters is 4.0~24.0wt%, and the average particle size of the osmium nanoclusters is 0.5~1.5nm. More preferably, the loading of osmium nanoclusters is 5.0~20.0wt%, for example, 5.0wt%, 6.0wt%, 7.0wt%, 10.0wt%, 15.0wt%, etc., which are not limited values.

[0018] In a third aspect, the present invention also provides a gallium single-atom porous carbon-confined osmium-based ultra-small cluster electrocatalyst for use in the hydrogen evolution reaction at the cathode of water electrolysis and the hydrogen oxidation reaction at the anode of a fuel cell.

[0019] Compared with the prior art, the present invention has the following advantages: (1) The preparation method of the present invention is simple, does not require too many complex processes, the synthesized product is controllable, and it is easy to achieve batch preparation.

[0020] (2) The synthesis process of this invention does not require the introduction of too many materials and does not rely on expensive reagents such as traditional organic solvents, thus significantly reducing the preparation cost.

[0021] (3) The porous carbon prepared by this invention has excellent electrical conductivity and is rich in micropores, resulting in excellent mass transfer effect. Its advantageous high specific area significantly increases the full contact between the active components of the catalyst and the electrolyte, thereby improving the catalytic effect.

[0022] (4) The gallium single-atom porous carbon confined osmium-based ultra-small cluster electrocatalyst prepared by the present invention has the characteristics of small size, uniform particle size and uniform distribution of active components. The method utilizes the confinement effect of microporous carbon to anchor the active components on the substrate, which fully solves the problem of the agglomeration behavior of active components caused by thermal migration during the preparation of electrocatalysts at traditional high temperature reduction, which leads to a decrease in catalytic performance. Attached Figure Description

[0023] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0024] Figure 1 The nitrogen adsorption-desorption curves are those of the gallium single-atom porous carbon substrate prepared in Example 1.

[0025] Figure 2 The nitrogen adsorption-desorption curves are those of the gallium single-atom porous carbon confined osmium-based ultra-small cluster electrocatalyst prepared in Example 1.

[0026] Figure 3 This is a transmission electron microscope (TEM) image of the gallium single-atom porous carbon-confined osmium-based ultra-small cluster electrocatalyst prepared in Example 1.

[0027] Figure 4 The image shows the polarization curves of the hydrogen evolution reaction in water electrolysis of the gallium single-atom porous carbon-confined osmium-based ultra-small cluster electrocatalyst prepared in Example 1, and their comparison with those of a commercial 20% Pt / C catalyst. In the image, a is the linear sweep voltammetry curve, and b is the voltammetry curve at 100 mA·cm⁻¹. -2 Overpotential at current density.

[0028] Figure 5 This is a constant current stability test diagram of the hydrogen evolution reaction in water electrolysis of the gallium single-atom porous carbon confined osmium-based ultra-small cluster electrocatalyst prepared in Example 1.

[0029] Figure 6 This is a transmission electron microscope (TEM) image of the gallium single-atom porous carbon-confined osmium-based ultra-small cluster electrocatalyst prepared in Example 1 after a 100-hour constant current stability test.

[0030] Figure 7The image shows the polarization curves of the hydrogenation reaction in a fuel cell using the gallium single-atom porous carbon-confined osmium-based ultra-small cluster electrocatalyst prepared in Example 4, and its comparison with that of a commercial 20% Pt / C catalyst.

[0031] Figure 8 The kinetic current density of the hydrogenation reaction in a fuel cell prepared by the gallium single-atom porous carbon confined osmium-based ultra-small cluster electrocatalyst in Example 4 is compared with that of a commercial 20% Pt / C catalyst.

[0032] Figure 9 This is a stability test diagram of the hydrogenation reaction in a fuel cell using the gallium single-atom porous carbon-confined osmium-based ultra-small cluster electrocatalyst prepared in Example 4, under an overpotential of 100 mV.

[0033] The objectives, features, and advantages of this invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0034] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0035] Unless otherwise defined, the technical terms used in the following embodiments have the same meanings as commonly understood by those skilled in the art to which this invention pertains. Unless otherwise specified, the experimental reagents used in the following embodiments are conventional biochemical reagents; and the experimental methods described are conventional methods.

[0036] Example 1 (1) Weigh 240mg of biological gelatin and 120mg of nano silica (particle size 1~10nm) and mix them thoroughly in 10ml of deionized water under magnetic stirring. Then place them in a 60℃ water bath and stir magnetically for 20~30 minutes to form a uniform dispersion (a). (2) Weigh 18.7 mg of gallium nitrate hydrate (Ga(NO3)3·9H2O) and 47.6 mg of 1,10-phenanthroline and dissolve them in 1 ml of deionized water to form solution (b); (3) Add solution (b) to dispersion (a) dropwise using a syringe. When adding, turn on magnetic stirring at 400-600 rpm and change the water bath temperature to 40°C. Stir for 2 hours to ensure thorough mixing. (4) Repeatedly freeze and thaw the mixture prepared in step (3) to produce a hydrogel complex. The specific details are: freeze at -20℃ for 18 hours, thaw at room temperature for 8 hours, and repeat the freeze and thaw process three times. (5) The hydrogel complex prepared in step (4) is subjected to vacuum freeze-drying for 24 hours to prepare aerogel. (6) The aerogel prepared in step (5) is subjected to high-temperature pyrolysis under an argon atmosphere, specifically: the heating rate is 3℃ / min, the pyrolysis temperature is 900℃, and the pyrolysis time is 2 hours. (7) The pyrolysis product in step (6) is ground and then etched with 0.5 M sodium hydroxide solution at 70°C for 90 minutes to remove nano-silica. The etched product is vacuum filtered and cleaned, vacuum dried at 60°C, and then fully ground and collected. The product is gallium single atom supported porous nano carbon, named Ga1@pCA (porous carbonaerogels). (8) Add 5.33 mg of osmium chloride hydrate (OsCl3·3H2O) to 30 ml of deionized water, sonicate for 1 hour, and then stir magnetically to prepare solution (c); (9) Add 20 mg of porous carbon nanomaterial Ga1@pCA to solution (c), sonicate for 1 hour, and then magnetically stir at 600 rpm to fully disperse and mix it to prepare a dispersion (d); (10) The dispersion (d) was frozen in liquid nitrogen and then placed in a freeze dryer for vacuum freeze drying for 24 hours; (11) After collecting the freeze-dried product, grind it, place it in a crucible, put it in a tube furnace, and carry out high-temperature pyrolysis treatment in a mixed atmosphere of hydrogen / argon (volume ratio of 1:9), wherein the heating rate is 5℃ / min, the pyrolysis temperature is 400℃, and the pyrolysis time is 3 hours. (12) The pyrolysis product was taken out, ground, and collected. This product is a gallium single-atom porous carbon-confined osmium-based ultra-small cluster electrocatalyst, named Os AC. 0.08 / Ga1@pCA.

[0037] Figure 1 The nitrogen adsorption-desorption curves of the gallium single-atom porous carbon substrate prepared in Example 1 demonstrate that the prepared carbon substrate has a high specific surface area, abundant micro-mesoporous structure, and excellent mass transfer function.

[0038] like Figure 2 As shown, the nitrogen adsorption-desorption curves of the prepared gallium single-atom porous carbon-confined osmium-based ultra-small cluster electrocatalyst demonstrate that the prepared catalyst has a large specific surface area and rich pore structure. The differences in pore size and specific surface area between the catalyst and the carbon substrate prove that the osmium group clusters grow in the pores and play a role in porous confinement.

[0039] like Figure 3 As shown, the transmission electron microscope (TEM) image of the prepared gallium single-atom porous carbon-confined osmium-based ultra-small cluster electrocatalyst shows that the osmium cluster particles are approximately 0.8~1.2 nm in size, with uniform particle size and distribution.

[0040] The synthesized materials were characterized by surface area (BET) measurement and transmission electron microscopy (TEM), demonstrating that the synthesized catalyst is rich in microporous structure and that osmium is in the form of ultrasmall nanoclusters. Example 1 presents the synthesized gallium single-atom porous carbon-confined osmium-based ultrasmall cluster electrocatalyst Os AC. 0.08 / Ga1@pCA, as measured by inductively coupled plasma optical emission spectrometry (ICP-OES), has a Ga content of 1.97% and an Os content of 8.53%.

[0041] Electrochemical testing: The electrochemical linear sweep voltammetry performance was obtained under a three-electrode testing system, by testing the prepared Os AC in 1M KOH electrolyte. 0.08 / Ga1@pCA samples were tested. 2 mg of the sample was dispersed in a mixed solution of water / isopropanol (volume ratio 1:1) and Nafion solution (concentration 20 μL / mL). The dispersion was ultrasonically performed to obtain a homogeneous catalyst slurry. The slurry was dropped onto carbon paper and dried to serve as the working electrode. The catalyst loading was 1 mg·cm⁻¹. -2 With a carbon rod as the counter electrode and Hg / HgO as the reference electrode, the measured potentials were all converted into reversible hydrogen electrode potentials.

[0042] Figure 4 For the obtained Os AC 0.08 Linear sweep voltammetry curves of / Ga1@pCA sample and commercial Pt / C (20%) in the hydrogen evolution reaction of water electrolysis, at 100 mA·cm⁻¹. -2 At this current density, its overpotential is as low as 62mV, while the overpotential of commercial 20% Pt / C at this current density is 115mV, indicating that this Os AC... 0.08 The / Ga1@pCA catalyst exhibits high catalytic activity.

[0043] Figure 5 For the obtained Os AC 0.08 The figure shows the constant current stability test results of the hydrogen evolution reaction of the / Ga1@pCA sample during water electrolysis at 10 mA·cm⁻¹. -2 The catalyst can operate stably for 100 hours under constant current density, which proves that the prepared electrocatalyst has excellent stability in the hydrogen evolution reaction.

[0044] Figure 6 For the obtained Os AC 0.08 Transmission electron microscopy (TEM) images of the / Ga1@pCA sample after a 100-hour constant current stability test demonstrate that porous carbon can effectively prevent the loss of active components during the reaction process.

[0045] Example 2 The synthesis method in this embodiment is basically the same as that in Example 1, except that only the amount of osmium chloride hydrate (OsCl3·3H2O) added is changed, that is, 3.56 mg of osmium chloride hydrate is used as the metal precursor, and other synthesis conditions remain unchanged.

[0046] The electrocatalytic material synthesized in Example 2 was named Os AC. 0.04 The / Ga1@pCA sample contained 2.21% Ga and 4.24% Os. Its morphology was observed to be consistent with that of Example 1. The synthesized sample showed small, uniformly sized, and evenly distributed osmium clusters, with well-exposed active sites. The testing conditions remained unchanged from Example 1, and the obtained sample was tested at 100 mA·cm⁻¹. -2 At a current density of , its overpotential is 226mV.

[0047] Example 3 The synthesis method in this embodiment is basically the same as that in Example 1, except that only the amount of osmium chloride hydrate (OsCl3·3H2O) added is changed, and 7.11 mg of osmium chloride hydrate is used as the metal precursor. Other synthesis conditions remain unchanged.

[0048] The synthesized electrocatalytic material was named Os AC. 0.12 The / Ga1@pCA sample contained 1.89% Ga and 12.53% Os. Its morphology was observed to be consistent with that of Example 1. The synthesized sample showed small, uniformly sized, and evenly distributed osmium clusters, with well-exposed active sites. The testing conditions remained unchanged from Example 1, and the obtained sample was tested at 100 mA·cm⁻¹. -2 At current densities, its overpotential is as low as 80mV.

[0049] Example 4 The synthesis method in this embodiment is basically the same as that in Example 1, except that only the amount of osmium chloride hydrate (OsCl3·3H2O) added is changed, and 8.89 mg of osmium chloride hydrate is used as the metal precursor. Other synthesis conditions remain unchanged.

[0050] The synthesized electrocatalytic material was named Os AC. 0.16 The / Ga1@pCA sample contained 1.80% Ga and 16.05% Os, with the same morphology and composition as in Example 1. The synthesized sample exhibited small, uniformly sized, and evenly distributed osmium clusters, with well-exposed active sites. Under unchanged testing conditions, the obtained sample was tested at 100 mA·cm⁻¹. -2 At current densities of , its overpotential is as low as 91mV.

[0051] The Os AC prepared in Example 40.16 The hydrogen oxidation performance of the fuel cell was tested using / Ga1@pCA. Electrochemical linear sweep voltammetry was obtained using a three-electrode system with a 0.1M KOH solution as the electrolyte. 4 mg of sample was dispersed in a mixed solution of water / isopropanol (volume ratio 3:7) and Nafion solution (concentration 30 μL / mL), and ultrasonically dispersed to obtain a homogeneous catalyst slurry. 10 μL of this slurry was dropped onto a glassy carbon electrode and dried to serve as the working electrode, with a platinum sheet as the counter electrode and Ag / AgCl as the reference electrode. All measured potentials were converted to reversible hydrogen electrode potentials. After activation, the polarization curve was tested under H2 saturation conditions.

[0052] Figure 7 For the obtained Os AC 0.16 Linear sweep voltammetry curves of / Ga1@pCA samples with commercial Pt / C (20%) indicate that this Os AC 0.16 The / Ga1@pCA catalyst exhibits a high limiting current density.

[0053] Figure 8 For the obtained Os AC 0.16 The kinetic current density of the hydrogenation reaction in the fuel cell of the / Ga1@pCA sample and its comparison with that of commercial 20% Pt / C demonstrate the excellent kinetics of this electrocatalyst material.

[0054] Figure 9 For the obtained Os AC 0.16 The stability test diagram of the hydrogenation reaction of the fuel cell of the / Ga1@pCA sample at an overpotential of 100mV demonstrates that the prepared electrocatalyst has excellent stability in the hydrogenation reaction.

[0055] Example 5 The synthesis method in this embodiment is basically the same as that in Example 1, except that only the amount of osmium chloride hydrate (OsCl3·3H2O) added is changed, and 12.44 mg of osmium chloride hydrate is used as the metal precursor. Other synthesis conditions remain unchanged.

[0056] The synthesized electrocatalytic material was named Os AC. 0.23 The / Ga1@pCA sample contained 1.62% Ga and 23.32% Os, with the same morphology and composition as in Example 1. The synthesized sample had smaller osmium clusters, but localized agglomeration was observed, indicating that the active components were not fully utilized. Under unchanged testing conditions, the obtained sample was tested at 100 mA·cm⁻¹. -2 At a current density of 60 mV, its overpotential is as low as 60 mV, and its high activity is mainly due to the excessive loading of active components.

[0057] In summary, using 5.33 mg OsCl3·3H2O (i.e., an Os loading of 8 wt%) maximizes the utilization of the active component and provides the optimal catalytic activity for the alkaline HER reaction; using 8.89 mg OsCl3·3H2O (i.e., an Os loading of 16 wt%) provides the optimal catalytic activity for the alkaline HOR reaction. However, when the amount of OsCl3·3H2O used exceeds 12.44 mg (i.e., an Os loading of 23 wt%), the osmium component will aggregate, its morphology will change, and the active component will not fully exert its effect.

[0058] While specific embodiments of the present invention have been described above, those skilled in the art should understand that these are merely illustrative examples, and various changes or modifications can be made to these embodiments without departing from the principles and essence of the present invention. The scope of protection of the present invention is defined only by the appended claims.

Claims

1. A method for preparing a gallium single-atom porous carbon-confined osmium-based ultrasmall cluster electrocatalyst, characterized in that, Includes the following steps: S1. Add biogelatin, nano silica, gallium nitrate hydrate, and 1,10-phenanthroline to deionized water in a mass ratio of 10~15:5~8:1:2~3, mix thoroughly and evenly, repeatedly freeze and thaw the mixture to produce a hydrogel complex, and freeze-dry it to form an aerogel. S2. The aerogel is heated to 700~900℃ under an inert atmosphere for pyrolysis treatment. The obtained product is ground and then etched with an alkaline solution under water bath heating to remove nano-silica. After washing and drying, it is ground into powder to obtain a single-atom carbon precursor. S3. Add the single-atom carbon precursor and water-soluble osmium chloride metal salt to deionized water, mix thoroughly and evenly, then freeze with liquid nitrogen and freeze-dry. After thorough grinding, place it in a hydrogen / argon mixed atmosphere and heat to 300~500℃ for pyrolysis treatment to obtain gallium single-atom porous carbon confined osmium-based ultra-small cluster electrocatalyst. The osmium chloride metal salt accounts for 15-40% of the total mass of the osmium chloride metal salt and the single-atom carbon precursor.

2. The method for preparing gallium single-atom porous carbon-confined osmium-based ultrasmall cluster electrocatalyst according to claim 1, characterized in that, The mass ratio of the biogelatin, nano-silica, gallium nitrate hydrate, and 1,10-phenanthroline is 2000~2500 : 1000~1500 : 170~190 : 400~500.

3. The method for preparing gallium single-atom porous carbon-confined osmium-based ultrasmall cluster electrocatalyst according to claim 1, characterized in that, Repeated freeze-thaw cycles are as follows: freeze at -30 to -10 ℃ for 6 to 24 hours, thaw at room temperature for 6 to 12 hours, and repeat the freeze-thaw cycle at least twice.

4. The method for preparing gallium single-atom porous carbon-confined osmium-based ultrasmall cluster electrocatalyst according to claim 1, characterized in that, When the aerogel is pyrolyzed under an inert atmosphere, the heating rate is 3~5℃ / min and the pyrolysis time is 1~4 hours.

5. The method for preparing gallium single-atom porous carbon-confined osmium-based ultrasmall cluster electrocatalyst according to claim 1, characterized in that, In the hydrogen / argon mixed atmosphere, the volume percentage of hydrogen is 5-20%.

6. A gallium single-atom porous carbon-confined osmium-based ultrasmall cluster electrocatalyst, characterized in that, The electrocatalyst is prepared by any one of claims 1-5, and comprises a porous carbon substrate, gallium single atoms and osmium nanoclusters. The gallium single atoms are anchored on the porous carbon substrate by Ga-N bonding, and the osmium nanoclusters are loaded on the surface and inside the pores of the porous carbon substrate.

7. The gallium single-atom porous carbon-confined osmium-based ultrasmall cluster electrocatalyst according to claim 6, characterized in that, In the electrocatalyst, the loading of gallium single atoms is 1.6~2.3wt%, the loading of osmium nanoclusters is 4.0~24.0wt%, and the average particle size of osmium nanoclusters is 0.5~1.5nm.

8. The application of the gallium single-atom porous carbon-confined osmium-based ultrasmall cluster electrocatalyst according to claim 6 in water electrolysis and fuel cell reactions.

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