Preparation method of noble metal aerogel by two-step conversion and application of the noble metal aerogel in electrocatalytic oxygen evolution

Abstract

The application discloses a kind of noble metal aerogel two-step conversion preparation method and its electrocatalytic oxygen evolution application, preparation method includes the following steps: (1) heating noble metal salt aqueous solution obtains noble metal oxide hydrogel, and noble metal oxide aerogel is obtained after purification, drying;(2) noble metal oxide aerogel is obtained after annealing to obtain noble metal aerogel.The application can realize the controllable preparation and characteristic size regulation of a variety of single-component and multi-component noble metal oxide gel, noble metal aerogel by controlling noble metal salt type and dosage, reaction temperature, reaction atmosphere, annealing temperature, annealing time, annealing atmosphere.The noble metal aerogel obtained by the application exhibits excellent catalytic performance in electrocatalytic oxygen evolution application.

Description

Technical Field

[0001] This invention relates to the field of aerogels, specifically to a two-step conversion method for preparing noble metal aerogels and its electrocatalytic oxygen evolution application, belonging to the field of aerogels. Background Technology

[0002] Metal aerogels are porous materials entirely constructed from nanostructured metals. They combine the optical, electrical, and magnetic properties of metals with the large specific surface area and porous structure of aerogels, exhibiting superior performance in electrocatalysis. Recent studies have focused on a route of "metal salt → nanoparticles (NPs) → wet gel → aerogel," achieving continuous control of gel characteristic sizes within gold systems by manipulating reaction parameters. However, these methods require the introduction of additional chemical reagents such as initiators and reducing agents, increasing costs, exacerbating environmental pollution, and introducing more impurities into the aerogel. Furthermore, current methods cannot be applied to metals that are highly stable in NPs solutions (such as iridium (Ir)); and the ability to control the aerogel structure is limited by the wet chemical approach alone.

[0003] For example, some researchers reduced Ir with borohydride at 80°C. 3+ A foam composed of Ir particles with a size of 20–50 nm was obtained (DOI:10.1039 / c5cc03182f). However, this method requires expensive borohydride reducing agents, the product lacks the self-supporting structure of an aerogel, and the large size of the Ir particles prevents them from fully exhibiting the advantages of nanotechnology. Therefore, developing universal and novel aerogel preparation methods for noble metals, such as Ir, to achieve flexible control over their composition and characteristic size is of great significance for promoting the controllable preparation and practical application of noble metal aerogels. Summary of the Invention

[0004] The main objective of this invention is to provide a two-step conversion method for preparing noble metal aerogels and its electrocatalytic oxygen evolution application. The aim is to achieve the preparation and composition / structure control of various noble metal aerogels through a two-step wet-dry chemical reaction, providing a universal and novel synthesis method for certain metal aerogels that are difficult to prepare through the classic sol-gel process, and providing a universal method for controlling the structure and characteristic size of metal aerogels on a large scale.

[0005] This invention includes the following steps:

[0006] (1) Preparation of noble metal oxide hydrogels and aerogels

[0007] A noble metal oxide hydrogel is obtained by heating a noble metal salt solution; the noble metal oxide hydrogel is then purified and dried to obtain a noble metal oxide aerogel.

[0008] (2) Preparation of noble metal aerogels

[0009] Noble metal oxide aerogels are obtained by annealing them in a high-temperature inert / reducing atmosphere.

[0010] In step (1), the precious metal salt is one or more of the following: ammonium hexachloroiridate, potassium chloroplatinate, potassium tetrachloropalladium, ammonium chlororuthenium, ruthenium trichloride, and ammonium hexachloroosmium, and the reaction concentration is 0.2 mM to 30 mM.

[0011] In step (1), the reaction temperature of the heating process is 60-150℃, the heating rate is 0-10K / min, the reaction atmosphere is air, argon, nitrogen, oxygen or carbon dioxide, and the reaction time is 1-24h.

[0012] In step (1), the purification temperature is 15-35℃, and the hydrogel is washed 1-10 times with pure water within 12 hours. The purified noble metal oxide hydrogel is freeze-dried or supercritical dried. Before freeze-drying, it is washed 1-3 times with tert-butanol within 6 hours. After the solvent is finally tert-butanol, it is placed in liquid nitrogen for 1-10 minutes and finally freeze-dried at -80℃ to -20℃ for 1-10 hours.

[0013] In step (2), the annealing temperature is 100–1000℃, the heating rate is 1–10 K / min, the holding time is 10–500 min, the gas flow rate is 50–500 sccm, and the annealing atmosphere is argon, nitrogen, or a mixture of 75% hydrogen and 25% argon. Changing the annealing temperature and time can control the composition and characteristic size of the noble metal aerogel. For example, a lower annealing temperature and shorter annealing time can obtain a noble metal aerogel containing some noble metal oxides. Higher annealing temperatures and holding times result in noble metal aerogels with larger characteristic sizes.

[0014] The present invention also provides a noble metal oxide hydrogel and a noble metal aerogel, which are prepared according to the above method.

[0015] This invention also provides the application of the above-mentioned noble metal aerogel in the electrocatalytic oxygen evolution reaction. Specifically, an appropriate amount of iridium-based or ruthenium-based noble metal aerogel is added to a mixed solution of isopropanol (or ethanol) and Nafion to make the aerogel concentration 1-10 mg / mL, preferably 2 mg / mL, and then ultrasonicated in an ice bath to obtain catalyst ink; an appropriate amount of ink is dropped onto the surface of the current collector and dried at room temperature to be used as the working electrode, with an aerogel loading of 0.08-0.5 mg / cm³. 2 0.1 mg / cm³ is preferred. 2The current collector is a glassy carbon electrode, a graphite electrode, carbon cloth, or carbon paper; in the three-electrode system, Pt sheet and Hg / HgO electrode are used as the counter electrode and reference electrode, respectively; electrochemical tests are carried out in an electrolyte saturated with an inert atmosphere, which is argon or nitrogen, and the electrolyte is 1M potassium hydroxide or 0.5M sulfuric acid.

[0016] The beneficial effects of this invention are reflected in:

[0017] (1) This invention utilizes a two-step conversion method (i.e., wet chemistry-dry chemistry coupling) to first prepare noble metal oxide aerogels and then anneal them at high temperatures to obtain noble metal aerogels. This method overcomes the limitation of traditional sol-gel synthesis, where some metal salt precursors are difficult to be directly reduced to elemental metals, and achieves a simple preparation from noble metal oxide aerogels to noble metal aerogels. This method is universally applicable to the synthesis of most metal aerogels.

[0018] (2) This invention does not require the use of reducing agents, initiators, or ligands. It prepares noble metal oxide gels by heating to promote the decomposition of metal salts, which reduces costs and environmental pollution, and avoids contamination of the aerogel by impurities.

[0019] (3) The present invention prepares noble metal oxide gel by heating metal salt solution and then controls the degree of annealing, which not only realizes the regulation of the composition of metal aerogel (such as controlling the ratio of oxide / metal), but also realizes the large-scale regulation of feature size (19-105nm).

[0020] (4) By simply controlling the type and quantity of metal salt precursors, the present invention can prepare single / multi-metal salt precursor solutions, and obtain single-component or multi-component noble metal oxide hydrogels and aerogels, which can be obtained by annealing treatment to obtain single-component or multi-component metal aerogels.

[0021] (5) Based on the abundant active sites, electron / mass transport channels and intrinsic high catalytic activity of ruthenium-based and iridium-based metal aerogels, and combined with the effective regulation of their composition and structure, this invention can be used as a highly efficient oxygen evolution reaction catalyst, promoting the application of metal aerogels in electrocatalytic water splitting. Attached Figure Description

[0022] Figure 1 Iroxide (IrO) x Aerogel, iridium oxide / iridium (IrO) x X-ray electron spectra of / Ir) aerogel, corresponding to Example 1.

[0023] Figure 2 Iroxide (IrO) x Scanning electron microscope images of iridium (Ir) aerogel under annealing conditions of 300℃ and 1000℃, corresponding to Example 2.

[0024] Figure 3 Osmium oxide (OsO) x X-ray diffraction patterns of aerogels and osmium (Os) aerogels, corresponding to Example 2.

[0025] Figure 4 Iridium (Ir) aerogel, ruthenium (Ru) aerogel, iridium palladium oxide (IrO) x -PdO x Macroscopic photographs of aerogels and iridium-palladium (Ir-Pd) aerogels, corresponding to Examples 2-4.

[0026] Figure 5 This is a schematic flowchart of the preparation method of iridium-palladium (Ir-Pd) metal aerogel, corresponding to Example 4.

[0027] Figure 6 Iridium-palladium (Ir-Pd) aerogel, metal oxide / metal (IrO) x / Ir-PdO x / Pd-OsO x Scanning electron microscope images of iridium-palladium-ruthenium-osmium (IrPdRuOs) aerogel and iridium-palladium-ruthenium-osmium (IrPdRuOs) aerogel, corresponding to Examples 4-6.

[0028] Figure 7 Iroxide (IrO) x Linear scanning voltammetry and overpotential comparison of iridium (Ir) aerogel, iridium-palladium (Ir-Pd) aerogel, and commercial ruthenium oxide (RuO2) for oxygen evolution reaction, corresponding to Example 9. Detailed Implementation

[0029] The present invention will be further described below with reference to embodiments:

[0030] Unless otherwise specified, all raw materials and equipment used in the following embodiments are commercially available products known in the art.

[0031] Example 1

[0032] Iridium oxide / iridium (IrO) x / Ir), platinum oxide / platinum (PtO) x / Pt), Palladium oxide / Palladium (PdO) x The preparation method of Pd aerogel includes the following steps:

[0033] (1) Preparation of metal oxide hydrogels

[0034] 50 μL each of 20 mM ammonium hexachloroiridate, potassium chloroplatinate, and potassium tetrachloropalladate were added to 4.95 mL of pure water and mixed thoroughly to obtain a concentration of 0.2 mM. The mixtures were then placed directly into an 80 °C oven under an air atmosphere and reacted for 4 h to obtain iridium oxide (IrO). x Platinum oxide (PtO) x ), Palladium oxide (PdO) x Hydrogel.

[0035] (2) Preparation of metal oxide aerogels

[0036] The metal oxide hydrogel was washed 10 times with pure water over 12 hours in a 35°C oven, followed by 3 washes with tert-butanol over 6 hours until tert-butanol was the final solvent. It was then held in liquid nitrogen at -196°C for 10 minutes and finally freeze-dried at -80°C for 5 hours to obtain IrO. x PtO x PdO x Aerogel. For example... Figure 1 IrO was demonstrated x X-ray electron spectroscopy of aerogels.

[0037] (3) Preparation of metal aerogels

[0038] Will IrO x PtO x PdO x Aerogels were annealed in a nitrogen atmosphere at a gas flow rate of 500 sccm, a heating rate of 10 K / min, an annealing temperature of 100 °C, and a holding time of 500 min, yielding iridium oxide / iridium (IrO) and iridium oxide / iridium (IrO) respectively. x / Ir), platinum oxide / platinum (PtO) x / Pt), Palladium oxide / Palladium (PdO) x / Pd) aerogel, such as Figure 1 For IrO x X-ray electron spectra of Ir aerogel.

[0039] Example 2

[0040] A method for preparing iridium (Ir) and osmium (Os) aerogels includes the following steps:

[0041] (1) Preparation of metal oxide hydrogels

[0042] 20 mM ammonium hexachloroiridate and 50 μL ammonium hexachloroosmium were added to 4.95 mL of pure water and mixed well, resulting in a concentration of 0.2 mM for each. The mixture was then placed in an 80 °C oven under an air atmosphere and reacted for 4 h to obtain iridium oxide (IrO). x ), Osmium oxide (OsO) x Hydrogel;

[0043] (2) Preparation of metal oxide aerogels

[0044] The metal oxide hydrogel was washed 10 times with pure water over 12 hours, and then washed once with tert-butanol over 6 hours until tert-butanol was the final solvent. It was then held in liquid nitrogen at -196°C for 10 minutes, and finally freeze-dried at -80°C for 10 hours to obtain IrO. x OsO x Aerogel. For example... Figure 2 IrO was demonstrated x The microstructure of aerogels, such as Figure 3 OsO was showcased x X-ray diffraction pattern of aerogel.

[0045] (3) Preparation of metal aerogels

[0046] Will IrO x The aerogel was annealed in a nitrogen atmosphere at a gas flow rate of 100 sccm, a heating rate of 10 K / min, an annealing temperature of 1000℃, and a holding time of 120 min to obtain Ir aerogels with large characteristic dimensions. Figure 2 The microstructure of Ir aerogel annealed at 1000℃ was demonstrated. IrO x OsO x Aerogels were annealed in a nitrogen atmosphere at a gas flow rate of 100 sccm, a heating rate of 10 K / min, an annealing temperature of 300℃, and a holding time of 120 min to obtain Ir and Os aerogels, respectively. Figure 2 The microstructure of Ir aerogel annealed at 300℃ was shown. Figure 3 The X-ray diffraction pattern of Os aerogel is shown, such as Figure 4 The macroscopic morphology of Ir aerogel annealed at 300℃ is shown.

[0047] Example 3

[0048] The preparation method of ruthenium (Ru) aerogel includes the following steps:

[0049] (1) Preparation of metal oxide hydrogels

[0050] 100 μL of 10 mM ammonium ruthenium chloride or ruthenium trichloride was added to 4.90 mL of pure water and mixed well, resulting in a concentration of 0.2 mM. The reaction atmosphere was air, the heating rate was 10 K / min, the reaction temperature was 150 °C, and the reaction was carried out for 4 h to obtain ruthenium oxide (RuO). x Hydrogel;

[0051] (2) Preparation of metal oxide aerogels

[0052] Wash RuO with pure water within 12 hours. xThe hydrogel was subjected to eight washes, followed by two washes with tert-butanol over six hours until tert-butanol was the final solvent. The gel was then held at -196°C in liquid nitrogen for 10 minutes, and finally freeze-dried at -80°C for 4 hours to obtain RuO. x Aerogel.

[0053] (3) Preparation of metal aerogels

[0054] RuO x The aerogel was annealed in an argon atmosphere at a gas flow rate of 50 sccm, a heating rate of 10 K / min, an annealing temperature of 300℃, and a holding time of 120 min to obtain Ru aerogel, as shown below. Figure 4 The macroscopic morphology of Ru aerogel is shown.

[0055] Example 4

[0056] A method for preparing iridium-palladium (Ir-Pd) aerogel includes the following steps:

[0057] (1) Preparation of metal oxide hydrogels

[0058] 83.4 μL of 20 mM ammonium hexachloroiridate and 41.6 μL of 20 mM potassium tetrachloropalladate were added to 4.875 mL of pure water at 30 °C and mixed well, resulting in a metal salt concentration of 0.5 mM. The solution was bubbled with oxygen for 1 min, sealed, and placed in a 60 °C oven for 24 h to obtain iridium oxide (IrO). x )-Palladium oxide (PdO) x Hydrogel.

[0059] (2) Preparation of metal oxide aerogels

[0060] Wash IrO with pure water within 12 hours. x -PdO x The hydrogel was subjected to six washes, followed by three washes with tert-butanol over five hours until tert-butanol was the final solvent. The gel was then held at -196°C in liquid nitrogen for 10 minutes, and finally freeze-dried at -80°C for five hours to obtain IrO. x -PdO x Aerogel. For example... Figure 4 As shown, IrO x -PdO x Macroscopic image of aerogel.

[0061] (3) Preparation of metal aerogels

[0062] Will IrO x -PdO x The aerogel was annealed in an atmosphere of 75% hydrogen and 25% argon at a gas flow rate of 200 sccm, a heating rate of 1 K / min, an annealing temperature of 300℃, and a holding time of 10 min to obtain Ir-Pd aerogel. Figure 4 The macroscopic morphology of Ir-Pd aerogels was shown, such as... Figure 5 A schematic diagram of the process for preparing Ir-Pd aerogel is shown. Figure 6 The microstructure of Ir-Pd aerogel was shown.

[0063] Example 5

[0064] IrO x / Ir-PdO x / Pd-OsO x The preparation method of / Os metal aerogel includes the following steps:

[0065] (1) Preparation of metal oxide hydrogels

[0066] 17.9 μL of 20 mM ammonium hexachloroiridate, 17.9 μL of 20 mM potassium tetrachloropalladiumate, and 89.3 μL of 20 mM ammonium hexachloroosmium were added to 4.875 mL of pure water and mixed well, resulting in a metal salt concentration of 0.5 mM. The reaction atmosphere was argon, the reaction temperature was 90 °C, and the reaction was carried out for 3 h to obtain iridium oxide (IrO). x )-Palladium oxide (PdO) x )-Osmium oxide (OsO) x Hydrogel.

[0067] (2) Preparation of metal oxide aerogels

[0068] Wash IrO with pure water within 12 hours. x -PdO x -OsO x The hydrogel was washed 10 times, then washed 3 times with tert-butanol over 6 hours until tert-butanol was the final solvent. The mixture was then held at -196°C in liquid nitrogen for 10 minutes, and finally freeze-dried at -80°C for 5 hours to obtain IrO. x -PdO x -OsO x Aerogel.

[0069] (3) Preparation of metal aerogels

[0070] Will IrO x -PdO x -OsO x The aerogel was annealed in an argon atmosphere at a gas flow rate of 200 sccm, a heating rate of 10 K / min, an annealing temperature of 300 °C, and a holding time of 30 min to obtain IrO. x / Ir-PdO x / Pd-OsO x / Os aerogel, such as Figure 6 IrO was demonstrated x / Ir-PdO x / Pd-OsOx Microstructure of / Os aerogel.

[0071] Example 6

[0072] The preparation method of iridium palladium osmium ruthenium (IrPdRuOs) aerogel includes the following steps:

[0073] (1) Preparation of metal oxide hydrogels

[0074] Mix 1.25 mL each of 30 mM ammonium hexachloroiridate, potassium tetrachloropalladate, ruthenium trichloride, and ammonium hexachloroosmium, resulting in a metal salt concentration of 30 mM. React under a carbon dioxide atmosphere at 90 °C for 3 hours to obtain iridium oxide (IrO). x )-Palladium oxide (PdO) x )-Ruthenium oxide (RuO) x )-Osmium oxide (OsO) x Hydrogel.

[0075] (2) Preparation of metal oxide aerogels

[0076] Wash IrO with pure water within 12 hours. x -PdO x -RuO x -OsO x The hydrogel was washed 10 times, then washed 3 times with tert-butanol over 6 hours until the solvent was finally tert-butanol. The mixture was then held at -196°C in liquid nitrogen for 5 minutes, and finally freeze-dried at -80°C for 5 hours to obtain IrO. x -PdO x -RuO x -OsO x Aerogel.

[0077] (3) Preparation of metal aerogels

[0078] Will IrO x -PdO x -RuO x -OsO x The aerogel was annealed in an argon atmosphere at a gas flow rate of 500 sccm, a heating rate of 5 K / min, an annealing temperature of 300℃, and a holding time of 180 min to obtain IrPdRuOs aerogel. Figure 6 As shown, the microstructure of IrPdRuOs aerogel is illustrated.

[0079] Example 7

[0080] IrO x / Ir-PdO x / Pd-OsO x / Os-PtO x / Pt-RuOx The preparation method of / Ru aerogel includes the following steps:

[0081] (1) Preparation of metal oxide hydrogels

[0082] 20.8 μL each of 30 mM ammonium hexachloroiridate, potassium tetrachloropalladiumate, ammonium hexachloroosmium, potassium chloroplatinate, and ammonium chlororuthenate were added to 4.917 mL of pure water and mixed well, resulting in a metal salt concentration of 0.5 mM. The reaction atmosphere was nitrogen, the reaction temperature was 100 °C, and the reaction was carried out for 3 h to obtain iridium oxide (IrO). x )-Palladium oxide (PdO) x )-Osmium oxide (OsO) x )-Platinum oxide (PtO) x )-Ruthenium oxide (RuO) x Hydrogel.

[0083] (2) Preparation of metal oxide aerogels

[0084] Wash IrO with pure water within 12 hours. x -PdO x -OsO x -PtO x -RuO x The hydrogel was washed 10 times, then washed 3 times with tert-butanol over 6 hours until tert-butanol was the final solvent. The mixture was then held at -196°C in liquid nitrogen for 10 minutes, and finally freeze-dried at -80°C for 5 hours to obtain IrO. x -PdO x -OsO x -PtO x -RuO x Aerogel.

[0085] (3) Preparation of metal aerogels

[0086] Will IrO x -PdO x -OsO x -PtO x -RuO x The aerogel was annealed in an argon atmosphere at a gas flow rate of 50 sccm, a heating rate of 10 K / min, an annealing temperature of 150 °C, and a holding time of 120 min to obtain IrO. x / Ir-PdO x / Pd-OsO x / Os-PtO x / Pt-RuO x / Ru aerogel.

[0087] Example 8

[0088] The preparation method of iridium-palladium-osmium-platinum-ruthenium (IrPdOsPtRu) aerogel includes the following steps:

[0089] (1) Preparation of metal oxide hydrogels

[0090] 83.3 μL each of 30 mM ammonium hexachloroiridate, potassium tetrachloropalladiumate, ammonium hexachloroosmium, potassium chloroplatinate, and ammonium chlororuthenate were added to 4.667 mL of pure water and mixed well, resulting in a metal salt concentration of 2 mM. The reaction atmosphere was air, the reaction temperature was 120 °C, and the reaction was carried out for 3 h to obtain iridium oxide (IrO). x )-Palladium oxide (PdO) x )-Osmium oxide (OsO) x )-Platinum oxide (PtO) x )-Ruthenium oxide (RuO) x Hydrogel.

[0091] (2) Preparation of metal oxide aerogels

[0092] Wash IrO with pure water within 12 hours. x -PdO x -OsO x -PtO x -RuO x The hydrogel was washed 10 times, then washed 3 times with tert-butanol over 6 hours until tert-butanol was the final solvent. The mixture was then held at -196°C in liquid nitrogen for 10 minutes, and finally freeze-dried at -80°C for 5 hours to obtain IrO. x -PdO x -OsO x -PtO x -RuO x Aerogel.

[0093] (3) Preparation of metal aerogels

[0094] Will IrO x -PdO x -OsO x -PtO x -RuO x The aerogel was annealed in an argon atmosphere with a gas flow rate of 50 sccm, a heating rate of 10 K / min, an annealing temperature of 300℃, and a holding time of 120 min to obtain IrPdOsPtRu aerogel.

[0095] Example 9

[0096] Iridium oxide (IrO) x When aerogels, iridium (Ir) aerogels, iridium-palladium (Ir-Pd) aerogels, and commercial RuO2 are used as catalysts for the electrocatalytic oxygen evolution reaction, the following steps are included:

[0097] 1.0 mg IrO x Aerogel, Ir aerogel, Ir-Pd aerogel, and commercial RuO2 were dispersed in a mixed solution of 425 μL ethanol and 75 μL Nafion (1 wt.%), respectively, and sonicated in an ice bath for 30 min to obtain four dispersions with a concentration of 2 mg / mL. 10 μL of each dispersion was then dropped onto the surface of a clean, dry glassy carbon electrode with an area of ​​0.1963 cm². 2 That is, the aerogel loading is 0.1 mg / cm³. 2 After the solvent evaporates at room temperature, Pt sheet and Hg / HgO electrode are used as the working electrode and reference electrode, respectively. Linear scan voltammetry is performed in a nitrogen-saturated electrolyte (1M potassium hydroxide) with a voltage range of 0.18–0.80 V and a scan rate of 10 mV / s. Figure 7 For IrO x Electrocatalytic oxygen evolution reaction performance of aerogels, Ir aerogels, Ir-Pd aerogels, and RuO2. At 10 mA cm⁻¹ -2 At the given current density, the overpotential of commercial RuO2 is 330 mV, while that of IrO2 is... x The overpotentials of aerogel, Ir aerogel, and Ir-Pd aerogel are 255 mV, 310 mV, and 292 mV, respectively.

[0098] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. 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 two-step conversion method for preparing noble metal aerogels, characterized in that, Includes the following steps: (1) Preparation of noble metal oxide hydrogels and aerogels Heating an aqueous solution of a noble metal salt yields a noble metal oxide hydrogel, which is then purified and dried to obtain a noble metal oxide aerogel. In step (1), the precious metal salt is one or more of the following: ammonium hexachloroiridate, potassium chloroplatinate, potassium tetrachloropalladium, ammonium chlororuthenate, ruthenium trichloride, and ammonium hexachloroosmium, and the reaction concentration is 0.2 mM to 30 mM; In step (1), the reaction temperature of the heating process is 60-150 °C, the heating rate is 0.1-10 K / min, the reaction atmosphere is air, argon, nitrogen, oxygen or carbon dioxide, and the reaction time is 1-24 h. (2) Preparation of noble metal aerogels Noble metal oxide aerogels are obtained by annealing them in an inert or reducing atmosphere.

2. The two-step conversion method for preparing noble metal aerogels as described in claim 1, characterized in that, In step (1), the purification temperature is 15-35 °C, and the purification method is to wash the hydrogel in pure water 1-10 times within 12 h; the purified noble metal oxide hydrogel is freeze-dried or supercritical dried: before freeze-drying, it is washed with tert-butanol 1-3 times within 6 h until the solvent is finally tert-butanol, then placed in liquid nitrogen for 1-30 min, and finally freeze-dried at -80 °C to -20 °C for 1-10 h.

3. The two-step conversion method for preparing noble metal aerogels as described in claim 1, characterized in that, In step (2), the annealing temperature is 100-1000 ℃, the heating rate is 1-10 K / min, the holding time is 10-500 min, the gas flow rate is 50-500 sccm, and the annealing atmosphere is argon, nitrogen, or a mixture of 75% hydrogen and 25% argon.

4. A noble metal aerogel, characterized in that, Prepared according to the method of any one of claims 1 to 3.

5. The application of the noble metal aerogel as described in claim 4 in the electrocatalytic oxygen evolution reaction.

Images