Preparation method and application of graphene-coated non-noble metal supported noble metal monatomic catalyst

Abstract

This invention discloses a method for preparing a graphene-coated non-noble metal supported noble metal single-atom catalyst and its application in the electrocatalytic hydrogen oxidation / hydrogen evolution reaction. A few-layer (1-2 layers) graphene encapsulates a non-noble metal element / alloy using a hydrothermal coupled chemical deposition method, and noble metal single atoms are then supported on this graphene. The number of graphene layers prepared by this method is precisely controllable, and the types of metals selected for the inner and outer layers can cover most transition metals, exhibiting high versatility and adjustability. The graphene-coated non-noble metal support provided by this invention possesses good stability and corrosion resistance. The electron transfer effect from the inner metal layer to the outer single atoms effectively limits the aggregation of the supported noble metal single atoms, improving the catalytic activity and selectivity of the noble metal single atoms. This material demonstrates excellent activity and broad application prospects as an electrode material for the electrocatalytic hydrogen oxidation / hydrogen evolution reaction.

Description

Technical Field

[0001] This invention relates to a method for preparing a graphene-coated non-noble metal supported noble metal single-atom catalyst and its application in the electrocatalytic hydrogen oxidation / hydrogen evolution reaction. Background Technology

[0002] Hydrogen is a clean secondary energy carrier and an important chemical raw material. Compared to the current main method of methane reforming, the pathway of producing hydrogen by electrolyzing water using electricity generated from renewable energy sources has attracted much attention because it does not produce carbon dioxide. Similarly, hydrogen fuel cells have advantages such as high energy conversion efficiency, low noise, and zero carbon emissions. Currently, precious metal catalysts are difficult to replace due to their high stability and high activity in both the cathode of water electrolysis and the anode of hydrogen fuel cells. However, the high price and scarce natural reserves of precious metal materials limit the large-scale application of hydrogen production through water electrolysis. Precious metal single-atom catalysts, due to their 100% atom utilization rate and unique electronic structure characteristics, effectively reduce the loading of precious metals and have become an effective means of reducing the cost of precious metal-based catalysts. Currently, single-atom catalysts face challenges in long-term, harsh environment testing, such as the overall decrease in activity due to single-atom aggregation and insufficient support stability.

[0003] The rise of highly chemically inert graphene materials has provided a new opportunity to solve this problem. Encapsulating non-noble metal nanoparticles within graphene has proven to maintain good chemical stability of the inner metal layer even under harsh conditions (Angew. Chem. Int. Ed. 52, 371 (2013)). Using this type of material as a support to load noble metal single atoms, the non-noble metal nanoparticles rich in unpaired valence electrons can penetrate graphene and thus modulate the electronic state of the noble metal single atoms on the outside of graphene, providing a new pathway for controlling the selectivity and activity of single-atom catalysts through the support. Summary of the Invention

[0004] This invention utilizes a hydrothermal coupled chemical deposition method to prepare graphene-coated catalysts supporting noble metal single atoms on non-noble metals. The catalyst is synthesized at atmospheric pressure, precisely preparing 1-2 layers of graphene-encapsulated non-noble metal as a support for the noble metal single atoms. The types of metals in the core and outer layers can be easily tuned, allowing for single-component, two-component, or multi-element alloy compositions. The catalysts prepared by this method have simple and clear structures, maintaining good stability and catalytic activity even under harsh conditions. They have already demonstrated excellent catalytic performance in electrocatalytic water splitting and fuel cell systems. These materials hold promise for applications in optics, superconductivity, biomedicine, energy storage, and catalysis.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows:

[0006] The present invention provides a graphene-coated non-precious metal supported noble metal single-atom catalyst, wherein the non-precious metal element coated by the graphene is selected from at least one of manganese, iron, cobalt, nickel, copper, magnesium, titanium, and chromium; and the supported noble metal element is selected from at least one of ruthenium, rhodium, palladium, iridium, platinum, and gold.

[0007] In the above technical solution, the particle size of the graphene-coated non-noble metal carrier is 4-10 nm; the number of graphene layers is 1-2; and the loaded noble metal is a single-component or multi-component single-atom.

[0008] Another aspect of the present invention provides a method for preparing the catalyst according to claim 1, the method comprising the following steps:

[0009] (1) Using silica spheres as templates, the non-precious metal salt precursor and the weakly basic precursor are mixed and converted into layered non-precious metal oxides by hydrothermal method.

[0010] (2) Deoxidize the layered non-noble metal oxide at high temperature in a reducing atmosphere to obtain the corresponding metal monomer or alloy.

[0011] (3) A carbon source is introduced at the deoxidation temperature to form a graphene layer;

[0012] (4) The template agent was removed by acid washing, followed by washing to obtain a graphene-coated non-precious metal carrier.

[0013] (5) Noble metal single atoms are loaded onto a support to obtain a graphene-coated non-noble metal supported noble metal single atom catalyst.

[0014] In the above technical solution, further, in step (1), the non-precious metal salt precursor is selected from at least one of the non-precious metal cations nitrate, acetate, chlorate or sulfate;

[0015] The weakly basic precursor is used to adjust the pH of the solution and is selected from at least one of urea, ammonia, ammonium fluoride, sodium hydroxide, sodium carbonate, and cyclohexamethylenetetramine.

[0016] The particle size of the silica sphere template agent is 40–400 nm;

[0017] The mass ratio of the non-precious metal salt precursor to silica spheres is 1 to 5:1;

[0018] The molar ratio of any two non-noble metal cation salts in the multi-component non-noble metal salt precursor is 1:10 to 10:1.

[0019] In the above technical solution, further, in step (2), the reducing atmosphere is hydrogen and an inert gas in a volume ratio of 1:1 to 10; the inert gas is argon or nitrogen; and the deoxygenation temperature is 600 to 1000°C.

[0020] In the above technical solution, further, in step (3), the carbon source is at least one of methane, methanol, acetonitrile, ethane, ethylene, acetylene, ethanol, propylene, pyridine, and pyrrole; the carbon source is introduced for 2 to 10 minutes and the flow rate is 40 to 300 mL / min.

[0021] In the above technical solution, the acid used in step (4) is a hydrofluoric acid solution with a mass concentration of 5-20%, and the pickling time is 4-10 hours.

[0022] In the above technical solution, further, in step (5), the method of loading non-precious metal single atoms onto the carrier is: loading precious metals onto the carrier by electrostatic adsorption, atomic vapor deposition or magnetron sputtering.

[0023] In the above technical solutions, further, in the electrostatic adsorption method and the atomic vapor deposition method, the noble metal salt precursor is at least one of chloroplatinic acid, ammonium chlororhodium chloroacetonate, chloroiridium chloroacetonate, sodium chloroiridium chloroacetonate, chloroauric acid, ruthenium trichloride, potassium hexachloropalladium acetonate, trimethyl(methylcyclopentadienyl)platinum, palladium hexafluoroacetylacetonate, dimethyl ruthenium dicerocene, dichloro(pentamethylcyclopentadienyl)rhodium, ruthenium target, rhodium target, palladium target, iridium target, platinum target, and gold target.

[0024] In another aspect, the present invention provides the application of the above-described catalyst in an electrocatalytic hydrogen oxidation / hydrogen evolution reaction.

[0025] The beneficial effects of this invention are as follows:

[0026] 1. The carrier material prepared using this invention has the advantages of uniform particle size and precise control over the number of graphene layers to 1-2 layers. The 1-2 layers of graphene maximize the protection against the influence of the inner metal particles on the outer noble metal layer. Raman spectroscopy results demonstrate that the surface carbon layer is highly graphitized, improving its overall corrosion and oxidation resistance.

[0027] 2. The types of metal components inside the support material prepared using this invention are easily adjustable, and can be designed as single-component, dual-component, or multi-component alloy components according to the needs of noble metal catalysts.

[0028] 3. The composition of the supported noble metal material prepared using this invention is easily adjustable and can be adjusted according to specific chemical reactions, making it easy to operate and producing large quantities.

[0029] 4. Electron microscopy and infrared spectroscopy analysis showed that the noble metal prepared by this method was dispersed in the form of single atoms on the outer surface of graphene; long-term stability tests proved that the support effectively suppressed the aggregation of noble metal single atoms.

[0030] 5. The catalyst prepared using this invention can adapt to various complex environments and exhibits excellent catalytic performance in electrocatalytic hydrogen evolution / hydrogenation systems in acidic environments. Attached Figure Description

[0031] Figure 1 The image shows a high-angle annular image of a graphene-coated nickel-cobalt nanoalloy loaded with Pt single atoms, corrected for spherical aberration, in Example 3, where a is the dark field and b is the bright field.

[0032] Figure 2 The results of the non-in-situ surface-enhanced attenuated total internal reflection infrared CO adsorption experiment of graphene-coated cobalt-nickel alloy supported single-atom platinum material in Example 3 are as follows:

[0033] Figure 3 The graphs are from the 30,000-cycle cyclic voltammetry test of the sample in Example 9, where a is the polarization curve before and after the test, and b is the constant potential stability test graph after 250 hours.

[0034] Figure 4 The graph shows the performance of Application Example 1 in the electrocatalytic hydrogen evolution reaction. Detailed Implementation

[0035] The following examples illustrate the preparation method and reaction performance of a graphene-coated non-noble metal supported noble metal single-atom catalyst provided by the present invention. However, the scope of the claims of the present invention is not limited to these examples. Furthermore, the examples only provide some conditions for achieving this objective, and do not imply that these conditions must be met to achieve this objective.

[0036] Examples 1-5 describe the modulation of the metal types in the inner layer of graphene; Examples 3, 6-8 describe the modulation of the types of noble metals loaded on the outer layer of graphene; Examples 9-10 describe the methods for modulating the loading of noble metals.

[0037] Example 1

[0038] (1) Dissolve 6.0g of tetraethoxysilane dispersed in 30% ethylene glycol in 100mL of deionized water, stir, add 7.2mmol of cobalt nitrate hexahydrate and stir until the solution is clear and transparent, add 1.8g of urea and ultrasonically disperse evenly.

[0039] (2) After refluxing the dispersion obtained in step (1) at 100°C for 10 hours, let it stand and cool to room temperature. After washing with deionized water, centrifuge and dry the product in a vacuum oven at 120°C for 12 hours to remove moisture.

[0040] (3) Grind the dried sample from step (2) into powder and place it in a tube furnace to reduce carbon deposits. Under an atmosphere of Ar:H2 = 3:1, raise the temperature to 900°C at a rate of 10°C / min. At this temperature, introduce methane at a gas rate of 100 ml / min and maintain for 5 min before naturally cooling to room temperature.

[0041] (4) The sample obtained in step (3) was stirred in a 10% hydrofluoric acid aqueous solution and treated at room temperature for 8 hours. Then it was washed with deionized water and filtered until the pH of the filtrate was 7.

[0042] (5) Dry the sample obtained in step (4) in a vacuum oven at 60°C for 12 hours;

[0043] (6) Weigh 50 mg of the sample obtained in step (5) and add it to 10 mL of aqueous solution to disperse and stir. Dilute the concentrated chloroplatinic acid solution to 5 mL and put it into a syringe. Inject it into the carrier dispersion at 41 uL / min using a micro-injection pump and stir for 2 h.

[0044] (7) After the solution obtained in step (6) is allowed to stand for 1 hour to settle, it is centrifuged to remove the upper layer of liquid and then dried in a vacuum oven at 70°C for 12 hours to obtain a carbon-encapsulated cobalt-supported single-atom platinum catalyst, denoted as Cat1.

[0045] The results of aberration-resolved transmission electron microscopy (TEM) dark-field phase and infrared CO adsorption experiments both indicate that the Pt on the outer side of the carbon layer is dispersed in the form of single atoms; aberration-resolved TEM bright-field phase indicates that the thickness of the carbon layer is 1 to 2 layers; only diffraction peaks of metallic cobalt appear in the X-ray diffraction spectrum, and synchrotron radiation near-edge absorption spectrum data prove that cobalt in this material is in the metallic state.

[0046] Example 2

[0047] (1) Dissolve 6.0g of tetraethoxysilane dispersed in 30% ethylene glycol in 100mL of deionized water, stir, add 7.2mmol of nickel acetate tetrahydrate and stir until the solution is clear and transparent, then add 1.8g of urea and ultrasonically disperse it evenly.

[0048] (2) After refluxing the dispersion obtained in step (1) at 100°C for 10 hours, let it stand and cool to room temperature. After washing with deionized water, centrifuge and dry the product in a vacuum oven at 120°C for 12 hours to remove moisture.

[0049] (3) Grind the dried sample from step (2) into powder and place it in a tube furnace to reduce carbon deposits. Under an atmosphere of Ar:H2 = 3:1, raise the temperature to 900°C at a rate of 10°C / min. At this temperature, introduce methane at a gas rate of 100 ml / min and maintain for 5 min before naturally cooling to room temperature.

[0050] (4) The sample obtained in step (3) was stirred in a 10% hydrofluoric acid aqueous solution and treated at room temperature for 8 hours. Then it was washed with deionized water and filtered until the pH of the filtrate was 7.

[0051] (5) Dry the sample obtained in step (4) in a vacuum oven at 60°C for 12 hours;

[0052] (6) Weigh 50 mg of the sample obtained in step (5) and add it to 10 mL of aqueous solution to disperse and stir. Dilute the concentrated chloroplatinic acid solution to 5 mL and put it into a syringe. Inject it into the carrier dispersion at 41 uL / min using a micro-injection pump and stir for 2 h.

[0053] (7) After the solution obtained in step (6) is allowed to stand for 1 hour to settle, it is centrifuged to remove the upper layer of liquid and then dried in a vacuum oven at 70°C for 12 hours to obtain a carbon-encapsulated nickel-supported single-atom platinum catalyst, denoted as Cat2.

[0054] The results of aberration-resolved transmission electron microscopy (TEM) dark-field phase and infrared CO adsorption experiments both indicate that the Pt on the outer side of the carbon layer is dispersed in the form of single atoms. Aberration-resolved TEM bright-field phase shows that the thickness of the carbon layer is 1 to 2 layers, but unlike Cat1, this material contains a very small amount of carbon nanotubes. Only metallic nickel diffraction peaks appear in the X-ray diffraction spectrum, and synchrotron radiation near-edge absorption spectrum data proves that nickel in this material is in a metallic state.

[0055] Example 3

[0056] (1) Dissolve 6.0g of tetraethoxysilane dispersed in 30% ethylene glycol in 100mL of deionized water, stir, add 3.6mmol nickel acetate tetrahydrate and 3.6mmol cobalt nitrate hexahydrate and stir until the solution is clear and transparent, add 1.8g urea and ultrasonically disperse evenly.

[0057] (2) After refluxing the dispersion obtained in step (1) at 100°C for 10 hours, let it stand and cool to room temperature. After washing with deionized water, centrifuge and dry the product in a vacuum oven at 120°C for 12 hours to remove moisture.

[0058] (3) Grind the dried sample from step (2) into powder and place it in a tube furnace to reduce carbon deposits. Under an atmosphere of Ar:H2 = 3:1, raise the temperature to 900°C at a rate of 10°C / min. At this temperature, introduce methane at a gas rate of 100 ml / min and maintain for 5 min before naturally cooling to room temperature.

[0059] (4) The sample obtained in step (3) was stirred in a 10% hydrofluoric acid aqueous solution and treated at room temperature for 8 hours. Then it was washed with deionized water and filtered until the pH of the filtrate was 7.

[0060] (5) Dry the sample obtained in step (4) in a vacuum oven at 60°C for 12 hours;

[0061] (6) Weigh 50 mg of the sample obtained in step (5) and add it to 10 mL of aqueous solution to disperse and stir. Dilute the concentrated chloroplatinic acid solution to 5 mL and put it into a syringe. Inject it into the carrier dispersion at 41 uL / min using a micro-injection pump and stir for 2 h.

[0062] (7) After the solution obtained in step (6) is allowed to stand for 1 hour to settle, it is centrifuged to remove the upper layer of liquid and then dried in a vacuum oven at 70°C for 12 hours to obtain a carbon-encapsulated nickel-cobalt supported single-atom platinum catalyst, denoted as Cat3.

[0063] Figure 1 The image shows a high-angle annular image of a graphene-coated nickel-cobalt nanoalloy loaded with Pt single atoms, corrected for spherical aberration, in Example 3, where a is the dark field and b is the bright field. Figure 2 The results of the non-in-situ surface-enhanced attenuated total internal reflection infrared CO adsorption experiment of graphene-coated cobalt-nickel alloy-supported single-atom platinum material in Example 3 show that there is no adsorption peak after 1800 wavenumbers, which proves that there are no platinum clusters or nanoparticles, and that the platinum atoms are all isolated and dispersed on the outer surface of graphene.

[0064] The results of aberration-resolved transmission electron microscopy (TEM) dark-field phase and infrared CO adsorption experiments both indicate that the Pt on the outer side of the carbon layer is dispersed in the form of single atoms. The aberration-resolved TEM bright-field phase shows that the thickness of the carbon layer is 1 to 2 layers, and no carbon nanotubes are generated. Only nickel-cobalt alloy diffraction peaks appear in the X-ray diffraction spectrum, and the synchrotron radiation near-edge absorption spectrum data proves that nickel and cobalt are in the metallic state in this material.

[0065] Example 4

[0066] (1) Dissolve 6.0g of tetraethoxysilane dispersed in 30% ethylene glycol in 100mL of deionized water, stir, add 3.6mmol nickel acetate tetrahydrate and 3.6mmol ferric nitrate nonahydrate and stir until the solution is clear and transparent, then add 1.8g urea and ultrasonically disperse it evenly.

[0067] (2) After refluxing the dispersion obtained in step (1) at 100°C for 10 hours, let it stand and cool to room temperature. After washing with deionized water, centrifuge and dry the product in a vacuum oven at 120°C for 12 hours to remove moisture.

[0068] (3) Grind the dried sample from step (2) into powder and place it in a tube furnace to reduce carbon deposits. Under an atmosphere of Ar:H2 = 3:1, raise the temperature to 900°C at a rate of 10°C / min. At this temperature, introduce methane at a gas rate of 100 ml / min and maintain for 5 min before naturally cooling to room temperature.

[0069] (4) The sample obtained in step (3) was stirred in a 10% hydrofluoric acid aqueous solution and treated at room temperature for 8 hours. Then it was washed with deionized water and filtered until the pH of the filtrate was 7.

[0070] (5) Dry the sample obtained in step (4) in a vacuum oven at 60°C for 12 hours;

[0071] (6) Weigh 50 mg of the sample obtained in step (5) and add it to 10 mL of aqueous solution to disperse and stir. Dilute the concentrated chloroplatinic acid solution to 5 mL and put it into a syringe. Inject it into the carrier dispersion at 41 uL / min using a micro-injection pump and stir for 2 h.

[0072] (7) After the solution obtained in step (6) is allowed to stand and settle for 1 hour, it is centrifuged to remove the upper layer of liquid and then dried in a vacuum oven at 70°C for 12 hours to obtain a carbon-encapsulated nickel-iron supported single-atom platinum catalyst, denoted as Cat4.

[0073] The results of aberration-resolved transmission electron microscopy (TEM) dark-field phase and infrared CO adsorption experiments both indicate that the Pt on the outer side of the carbon layer is dispersed in the form of single atoms. Aberration-resolved TEM bright-field phase shows that the thickness of the carbon layer is 1 to 2 layers, with a very small amount of carbon nanotubes generated. Only nickel-iron alloy diffraction peaks appear in the X-ray diffraction spectrum, and synchrotron radiation near-edge absorption spectrum data prove that nickel and iron in this material are in a metallic state.

[0074] Example 5

[0075] (1) Dissolve 6.0g of tetraethoxysilane dispersed in 30% ethylene glycol in 100mL of deionized water, stir, add 3.6mmol of cobalt nitrate tetrahydrate and 3.6mmol of ferric nitrate nonahydrate and stir until the solution is clear and transparent, then add 1.8g of urea and ultrasonically disperse it evenly.

[0076] (2) After refluxing the dispersion obtained in step (1) at 100°C for 10 hours, let it stand and cool to room temperature. After washing with deionized water, centrifuge and dry the product in a vacuum oven at 120°C for 12 hours to remove moisture.

[0077] (3) Grind the dried sample from step (2) into powder and place it in a tube furnace to reduce carbon deposits. Under an atmosphere of Ar:H2 = 3:1, raise the temperature to 900°C at a rate of 10°C / min. At this temperature, introduce methane at a gas rate of 100 ml / min and maintain for 5 min before naturally cooling to room temperature.

[0078] (4) The sample obtained in step (3) was stirred in a 10% hydrofluoric acid aqueous solution and treated at room temperature for 8 hours. Then it was washed with deionized water and filtered until the pH of the filtrate was 7.

[0079] (5) Dry the sample obtained in step (4) in a vacuum oven at 60°C for 12 hours;

[0080] (6) Weigh 50 mg of the sample obtained in step (5) and add it to 10 mL of aqueous solution to disperse and stir. Dilute the concentrated chloroplatinic acid solution to 5 mL and put it into a syringe. Inject it into the carrier dispersion at 41 uL / min using a micro-injection pump and stir for 2 h.

[0081] (7) After the solution obtained in step (6) is allowed to stand for 1 hour to settle, it is centrifuged to remove the upper layer of liquid and then dried in a vacuum oven at 70°C for 12 hours to obtain a carbon-encapsulated cobalt-iron supported single-atom platinum catalyst, denoted as Cat5.

[0082] The results of aberration-resolved transmission electron microscopy (TEM) dark-field phase and infrared CO adsorption experiments both indicate that the Pt on the outer side of the carbon layer is dispersed in the form of single atoms. Aberration-resolved TEM bright-field phase shows that the thickness of the carbon layer is 1 to 2 layers, and no carbon nanotubes are generated. Only cobalt-iron alloy diffraction peaks appear in the X-ray diffraction spectrum, and synchrotron radiation near-edge absorption spectrum data prove that cobalt and iron in this material are in a metallic state.

[0083] Example 6

[0084] (1) Dissolve 6.0g of tetraethoxysilane dispersed in 30% ethylene glycol in 100mL of deionized water, stir, add 3.6mmol of cobalt nitrate hexahydrate and 3.6mmol of tetrahydrate and nickel acetate, stir until the solution is clear and transparent, add 1.8g of urea and ultrasonically disperse evenly.

[0085] (2) After refluxing the dispersion obtained in step (1) at 100°C for 10 hours, let it stand and cool to room temperature. Wash it with deionized water and centrifuge it. Dry the product in a vacuum oven at 120°C for 12 hours to remove moisture.

[0086] (3) Grind the dried sample from step (2) into powder and place it in a tube furnace to reduce carbon deposits. Under an atmosphere of Ar:H2 = 3:1, raise the temperature to 900°C at a rate of 10°C / min. At this temperature, introduce methane at a gas rate of 100 ml / min and maintain for 5 min before naturally cooling to room temperature.

[0087] (4) The sample obtained in step (3) was stirred in a 10% hydrofluoric acid aqueous solution and treated at room temperature for 8 hours. Then it was washed with deionized water and filtered until the pH of the filtrate was 7.

[0088] (5) Dry the sample obtained in step (4) in a vacuum oven at 60°C for 12 hours;

[0089] (6) Weigh 50 mg of the sample obtained in step (5) and add it to 10 mL of aqueous solution to disperse and stir. Dilute the concentrated ammonia chlororhodium solution to 5 mL and put it into a syringe. Inject it into the carrier dispersion at 41 uL / min using a micro-injection pump and stir for 2 h.

[0090] (7) After the solution obtained in step (6) is allowed to stand for 1 hour to settle, it is centrifuged to remove the upper layer of liquid and then dried in a vacuum oven at 70°C for 12 hours to obtain a carbon-encapsulated cobalt-nickel supported single-atom rhodium catalyst, denoted as Cat6.

[0091] The results of aberration-resolved transmission electron microscopy (TEM) dark-field phase and infrared CO adsorption experiments both indicate that the Rh on the outer side of the carbon layer is dispersed in the form of single atoms. Aberration-resolved TEM bright-field phase shows that the thickness of the carbon layer is 1 to 2 layers, and no carbon nanotubes are generated. Only cobalt-iron alloy diffraction peaks appear in the X-ray diffraction spectrum, and synchrotron radiation near-edge absorption spectrum data prove that cobalt and nickel in this material are in a metallic state.

[0092] Example 7

[0093] (1) Dissolve 6.0g of tetraethoxysilane dispersed in 30% ethylene glycol in 100mL of deionized water, stir, add 3.6mmol of cobalt nitrate hexahydrate and 3.6mmol of tetrahydrate and nickel acetate, stir until the solution is clear and transparent, add 1.8g of urea and ultrasonically disperse evenly.

[0094] (2) After refluxing the dispersion obtained in step (1) at 100°C for 10 hours, let it stand and cool to room temperature. After washing with deionized water, centrifuge and dry the product in a vacuum oven at 120°C for 12 hours to remove moisture.

[0095] (3) Grind the dried sample from step (2) into powder and place it in a tube furnace to reduce carbon deposits. Under an atmosphere of Ar:H2 = 3:1, raise the temperature to 900°C at a rate of 10°C / min. At this temperature, introduce methane at a gas rate of 100 ml / min and maintain for 5 min before naturally cooling to room temperature.

[0096] (4) The sample obtained in step (3) was stirred in a 10% hydrofluoric acid aqueous solution and treated at room temperature for 8 hours. Then it was washed with deionized water and filtered until the pH of the filtrate was 7.

[0097] (5) Dry the sample obtained in step (4) in a vacuum oven at 60°C for 12 hours;

[0098] (6) Weigh 50 mg of the sample obtained in step (5) and add it to 10 mL of aqueous solution to disperse and stir. Dilute the concentrated chloroiridium acid solution to 5 mL and put it into a syringe. Inject it into the carrier dispersion at 41 uL / min using a micro-injection pump and stir for 2 h.

[0099] (7) After the solution obtained in step (6) is allowed to stand for 1 hour to settle, it is centrifuged to remove the upper layer of liquid and then dried in a vacuum oven at 70°C for 12 hours to obtain a carbon-encapsulated cobalt-nickel supported single-atom iridium catalyst, denoted as Cat7.

[0100] The results of aberration-resolved transmission electron microscopy (TEM) dark-field phase and infrared CO adsorption experiments both indicate that the Ir on the outer side of the carbon layer is dispersed in the form of single atoms; aberration-resolved TEM bright-field phase shows that the thickness of the carbon layer is 1 to 2 layers, and no carbon nanotubes are generated; only cobalt-iron alloy diffraction peaks appear in the X-ray diffraction spectrum, and synchrotron radiation near-edge absorption spectrum data prove that cobalt and nickel in this material are in a metallic state.

[0101] Example 8

[0102] (1) Dissolve 6.0g of tetraethoxysilane dispersed in 30% ethylene glycol in 100mL of deionized water, stir, add 3.6mmol of cobalt nitrate hexahydrate and 3.6mmol of tetrahydrate and nickel acetate, stir until the solution is clear and transparent, add 1.8g of urea and ultrasonically disperse evenly.

[0103] (2) After refluxing the dispersion obtained in (1) at 100°C for 10 hours, let it stand and cool to room temperature. After washing with deionized water, centrifuge and dry the product in a vacuum oven at 120°C for 12 hours to remove moisture.

[0104] (3) Grind the dried sample from (2) into powder and place it in a tube furnace to reduce carbon deposits. Under an atmosphere of Ar:H2 = 3:1, raise the temperature to 900°C at a rate of 10°C / min. At this temperature, introduce methane at a gas rate of 100 ml / min and maintain for 5 min before naturally cooling to room temperature.

[0105] (4) The sample obtained in (3) was stirred in a 10% hydrofluoric acid aqueous solution and treated at room temperature for 8 hours. Then it was washed with deionized water and filtered until the pH of the filtrate was 7.

[0106] (5) Dry the sample obtained in (4) in a vacuum oven at 60℃ for 12 hours;

[0107] (6) Weigh 50 mg of the sample obtained in (5) and add it to 10 mL of aqueous solution to disperse and stir. Dilute the ruthenium trichloride concentrated solution to 5 mL and put it into a syringe. Inject it into the carrier dispersion at 41 uL / min using a micro-injection pump and stir for 2 h.

[0108] (7) After the solution obtained in step (6) is allowed to stand and settle for 1 hour, it is centrifuged to remove the upper layer of liquid and then dried in a vacuum oven at 70°C for 12 hours to obtain a carbon-encapsulated cobalt-nickel supported single-atom ruthenium catalyst, denoted as Cat8.

[0109] The results of aberration-resolved transmission electron microscopy (TEM) dark-field phase and infrared CO adsorption experiments both indicate that Ru on the outer side of the carbon layer is dispersed in the form of single atoms; aberration-resolved TEM bright-field phase shows that the thickness of the carbon layer is 1 to 2 layers, and no carbon nanotubes are generated; only cobalt-iron alloy diffraction peaks appear in the X-ray diffraction spectrum, and synchrotron radiation near-edge absorption spectrum data prove that cobalt and nickel in this material are in a metallic state.

[0110] Example 9

[0111] (1) Dissolve 6.0g of tetraethoxysilane dispersed in 30% ethylene glycol in 100mL of deionized water, stir, add 3.6mmol of cobalt nitrate hexahydrate and 3.6mmol of tetrahydrate and nickel acetate, stir until the solution is clear and transparent, add 1.8g of urea and ultrasonically disperse evenly.

[0112] (2) After refluxing the dispersion obtained in step (1) at 100°C for 10 hours, let it stand and cool to room temperature. Wash it with deionized water and centrifuge it. Dry the product in a vacuum oven at 120°C for 12 hours to remove moisture.

[0113] (3) Grind the dried sample from step (2) into powder and place it in a tube furnace to reduce carbon deposits. Under an atmosphere of Ar:H2 = 3:1, raise the temperature to 900°C at a rate of 10°C / min. At this temperature, introduce methane at a gas rate of 100 ml / min and maintain for 5 min before naturally cooling to room temperature.

[0114] (4) The sample obtained in step (3) was stirred in a 10% hydrofluoric acid aqueous solution and treated at room temperature for 8 hours. Then it was washed with deionized water and filtered until the pH of the filtrate was 7.

[0115] (5) The sample obtained in step (4) was dried in a vacuum oven at 60°C for 12 hours to obtain the carrier;

[0116] (6) Weigh 100 mg of the sample obtained in step (5) and place it into the atomic vapor deposition chamber. Using nitrogen as the carrier gas, heat the sample to 180°C and then introduce trimethyl (methylcyclopentadienyl) platinum using nitrogen as the carrier gas. Maintain for 10 minutes, then switch back to nitrogen to purge the sample surface for 30 minutes. Replace nitrogen with oxygen to remove the organic ligands from the platinum source at 180°C.

[0117] (7) The O2 adsorbed on the surface of the sample obtained in (6) was purged with nitrogen at 180℃ to obtain the catalyst, which was denoted as Cat9.

[0118] The results of aberration-resolved transmission electron microscopy (TEM) dark-field phase and infrared CO adsorption experiments both indicate that the Pt on the outer side of the carbon layer is dispersed in the form of single atoms; aberration-resolved TEM bright-field phase shows that the thickness of the carbon layer is 1 to 2 layers, and no carbon nanotubes are generated; only cobalt-iron alloy diffraction peaks appear in the X-ray diffraction spectrum, and synchrotron radiation near-edge absorption spectrum data prove that cobalt and nickel in this material are in the metallic state.

[0119] Example 10

[0120] (1) Dissolve 6.0g of tetraethoxysilane dispersed in 30% ethylene glycol in 100mL of deionized water, stir, add 3.6mmol of cobalt nitrate hexahydrate and 3.6mmol of tetrahydrate and nickel acetate, stir until the solution is clear and transparent, add 1.8g of urea and ultrasonically disperse evenly.

[0121] (2) After refluxing the dispersion 100 obtained in step (1) for 10 hours, let it stand and cool to room temperature, wash it with deionized water and centrifuge it. Dry the product in a vacuum oven at 120°C for 12 hours to remove moisture.

[0122] (3) Grind the dried sample from step (2) into powder and place it in a tube furnace to reduce carbon deposits. Under an atmosphere of Ar:H2 = 3:1, raise the temperature to 900°C at a rate of 10°C / min. At this temperature, introduce methane at a gas rate of 100 ml / min and maintain for 5 min before naturally cooling to room temperature.

[0123] (4) The sample obtained in step (3) was stirred in a 10% hydrofluoric acid aqueous solution and treated at room temperature for 8 hours. Then it was washed with deionized water and filtered until the pH of the filtrate was 7.

[0124] (5) The sample obtained in step (4) was dried in a vacuum oven at 60°C for 12 hours to obtain the carrier;

[0125] (6) Weigh 200mg of the sample obtained in step (5) and put it into the magnetron sputtering cavity, using argon as the carrier gas with a flow rate of 50sccm;

[0126] (7) A platinum target was selected and DC sputtering was used. The sputtering power was 50W, the sputtering pressure was 3Pa, and the sputtering time was 1min to obtain the catalyst, which was denoted as Cat10.

[0127] The results of aberration-resolved transmission electron microscopy (TEM) dark-field phase and infrared CO adsorption experiments both indicate that the Pt on the outer side of the carbon layer is dispersed in the form of single atoms; aberration-resolved TEM bright-field phase shows that the thickness of the carbon layer is 1 to 2 layers, and no carbon nanotubes are generated; only cobalt-iron alloy diffraction peaks appear in the X-ray diffraction spectrum, and synchrotron radiation near-edge absorption spectrum data prove that cobalt and nickel in this material are in the metallic state.

[0128] Application Example 1

[0129] The graphene-coated cobalt-nickel alloy materials obtained in Examples 3, 6-8 were used as catalysts for electrocatalytic HER, and the effects of different noble metal single atoms on the catalytic performance were investigated.

[0130] 1. Test System Setup: The test setup is a three-electrode system. The reference electrode is Ag / AgCl, the counter electrode is a graphite carbon rod, and the working electrode is a 5mm diameter glassy carbon electrode. The electrolyte is a 0.5M H₂SO₄ solution. During the test, a gas bubbling device is used to saturate the electrolyte with Ar. The working electrode undergoes a series of cleaning processes before testing, including Al₂O₃ polishing, rinsing with anhydrous ethanol and deionized water, etc.

[0131] 2. Preparation of the working electrode: 5 mg of catalyst sample was added to 2 mL of anhydrous ethanol and ultrasonically dispersed for 5 min. Then, 50 μL of 5% Nafion / isopropanol solution was added and ultrasonically dispersed for 20 min to obtain a catalyst slurry. 39 μL of the slurry was dropwise added to a glassy carbon electrode and allowed to air dry before testing. The catalyst loading was 0.5 mg / cm³. 2 .

[0132] 3. Catalytic performance evaluation method: The electrolytic cell temperature was maintained at 25℃ using circulating water. The activity of the HER catalyst was tested by polarization curves, and the potential required for different catalysts to reach a certain reduction current density was compared (see...). Figure 2 Compared to other precious metal single-atom particles, Pt exhibits better activity.

[0133] The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A graphene-coated non-noble metal supported noble metal single-atom catalyst, characterized in that: The graphene-coated non-noble metal element is selected from at least one of manganese, iron, cobalt, nickel, copper, magnesium, titanium and chromium; and the loaded noble metal element is selected from at least one of ruthenium, rhodium, palladium, iridium, platinum and gold. The particle size of the graphene-coated non-noble metal carrier is 4-10 nm; the number of graphene layers is 1-2; and the loaded noble metal is a single component or a multi-component single atom.

2. A method for preparing the catalyst of claim 1, characterized in that the method comprises the following steps: (1) mixing a non-noble metal salt precursor and a weak alkaline precursor uniformly by using silica spheres as a template agent, and converting them into layered non-noble metal oxides by a hydrothermal method; (2) performing high-temperature deoxidation of the layered non-noble metal oxides in a reducing atmosphere to obtain corresponding metal monomers or alloys; (3) introducing a carbon source to form a graphene layer at the deoxidation temperature; (4) removing the template agent by acid washing, followed by washing to obtain a graphene-coated non-noble metal carrier; (5) loading noble metal single atoms onto the carrier to obtain a graphene-coated non-noble metal loaded noble metal single atom catalyst. In step (1), the non-noble metal salt precursor is selected from at least one of nitrate, acetate, chlorate or sulfate of a non-noble metal cation; 3. The method of claim 2, wherein: The weak alkaline precursor is used to adjust the pH of the solution and is selected from at least one of urea, ammonia, ammonium fluoride, sodium hydroxide, sodium carbonate and cyclen. The particle size of the silica sphere template agent is 40-400 nm. The mass ratio of the non-noble metal salt precursor to the silica sphere is 1-5:

1. The molar ratio of any two non-noble metal cation salts in the multi-component non-noble metal salt precursor is 1:10-10:

1. In step (2), the reducing atmosphere is hydrogen and an inert gas, and the volume ratio of hydrogen to the inert gas is 1:1-10; the inert gas is one of argon and nitrogen; and the deoxidation temperature is 600-1000°C.

4. The method of claim 2, wherein: In step (3), the carbon source is at least one of methane, methanol, acetonitrile, ethane, ethylene, acetylene, ethanol, propylene, pyridine and pyrrole; the introduction time of the carbon source is 2-10 min; and the flow rate is 40-300 mL / min.

5. The method of claim 2, wherein: In step (4), the acid solution used for acid washing is a hydrofluoric acid solution with a mass concentration of 5-20%, and the acid washing time is 4-10 h.

6. The method of claim 2, wherein: In step (5), the method for loading the non-noble metal single atom onto the carrier is that the noble metal is loaded onto the carrier by an electrostatic adsorption method, atomic vapor deposition or magnetron sputtering.

7. The method of claim 2, wherein: In the electrostatic adsorption method and the atomic vapor deposition method, the noble metal salt precursor is at least one of chloroplatinic acid, chloro rhodium acid ammonia, chloro iridic acid, sodium chloro iridic acid, chloro auric acid, ruthenium trichloride, potassium hexachloropalladate, trimethyl(methylcyclopentadienyl) platinum, palladium hexafluoroacetyl acetonate, dimethyl rutheniumocene, dichloro(pentamethylcyclopentadienyl) rhodium, a ruthenium target, a rhodium target, a palladium target, an iridium target, a platinum target and a gold target.

8. The method of claim 7, wherein:

9. Application of the catalyst of claim 1 in electrocatalytic hydrogen oxidation / hydrogen evolution reactions. ​

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