A method for preparing composite nanocatalyst

Abstract

This invention discloses a method for preparing a composite nanocatalyst, relating to the field of catalyst technology. The preparation method includes the following steps: S10, dissolving an iridium source, a ruthenium source, a platinum source, and an inorganic salt in deionized water and mixing to obtain a mixed solution; S20, dissolving a complexing agent in the mixed solution and mixing to obtain an intermediate solution; S30, evaporating and drying the intermediate solution to obtain a catalyst precursor; S40, heating the catalyst precursor in an oxygen-containing gas atmosphere at 200–350°C for 20–120 min, then raising the temperature to 400–650°C and heating for another 20–120 min, finally cooling and washing to obtain the composite nanocatalyst. The preparation method provided by this invention is simple, easy to implement, and highly reproducible, suitable for large-scale production, and the final Pt obtained is... x Ru y Ir 1‑x‑y O2 composite nanocatalysts have the advantages of low cost, high stability, and high catalytic activity, and have high application value in the electrocatalytic process of acidic oxygen evolution reaction.

Description

Technical Field

[0001] This invention relates to the field of catalyst technology, and in particular to a method for preparing a composite nanocatalyst. Background Technology

[0002] In the development of new energy sources, hydrogen energy has received widespread attention due to its advantages of being pollution-free and having high energy density. Hydrogen-related technologies have also developed rapidly in recent decades. Among them, water electrolysis for hydrogen production can directly convert electrical energy into hydrogen energy without generating any pollutants during the production process, making it a key technology for "green hydrogen" production. The hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) are the core reactions in the water electrolysis process. OER involves a four-electron transfer process, which is significantly slower in reaction kinetics than the two-electron process of HER, resulting in a higher overpotential. Therefore, designing more efficient OER catalysts to reduce the overpotential in the OER process and decrease energy loss in water electrolysis for hydrogen production is of paramount importance in water electrolysis research.

[0003] Based on the type of electrolyte, existing water electrolysis technologies can be divided into alkaline and acidic water electrolysis technologies. Alkaline water electrolysis technology has a longer research history and is more mature. In this technology, both the anode and cathode use non-precious metal nickel as electrode materials, thus reducing the production cost of the alkaline electrolyzer. However, alkaline electrolyzers have low operating current densities, and the produced hydrogen and oxygen are prone to cross-mixing. Furthermore, they require the use of highly corrosive alkaline electrolytes, resulting in large equipment investment and high maintenance costs. Acidic water electrolysis technology (also known as solid polymer electrolyte water electrolysis technology) uses proton exchange membranes as the electrolyte, avoiding gas mixing between the anode and cathode. It only requires the addition of pure water to the electrolyzer for electrolysis, offering advantages such as high hydrogen purity, high current density, and small equipment size. It is currently the focus of research in water electrolysis technology.

[0004] In a solid polymer electrolyte (SPE) electrolyzer, the area near the proton exchange membrane is affected by H... + It exhibits strong local acidity due to migration, and with H + With increasing concentration, the oxygen evolution reaction potential also increases significantly, exceeding the oxidation potential of most non-precious metal catalysts. This leads to a severe decrease in the stability of non-precious metal catalysts under these conditions, making them unsuitable for acidic OER catalysis. Currently, Ir (iridium)-based and Ru (ruthenium)-based oxides are considered two of the most efficient acidic OER catalysts. While RuO2 exhibits higher OER catalytic activity, IrO2 has a greater advantage in stability, and therefore, IrO2 has been used in commercial SPE electrolyzers. However, the catalytic performance of IrO2 is not ideal, and its high cost greatly limits its large-scale application. Therefore, there is an urgent need to develop a novel catalyst with low cost, high stability, and high catalytic activity. Summary of the Invention

[0005] The main objective of this invention is to propose a method for preparing composite nanocatalysts, aiming to provide a novel catalyst with low cost, high stability, and high catalytic activity.

[0006] To achieve the above objectives, this invention proposes a method for preparing a composite nanocatalyst, the method comprising the following steps:

[0007] S10. Dissolve the iridium source, ruthenium source, platinum source and inorganic salt in deionized water and mix well to obtain a mixed solution;

[0008] S20. Dissolve the complexing agent in the mixture and mix well to obtain an intermediate solution;

[0009] S30. The intermediate solution is evaporated and dried to obtain the catalyst precursor;

[0010] S40. The catalyst precursor is heated at 200-350°C for 20-120 min in an oxygen-containing gas atmosphere, then heated to 400-650°C for 20-120 min, and finally cooled and washed to obtain the composite nanocatalyst.

[0011] Optionally, the total concentration of iridium, ruthenium, and platinum in the mixture is 0.005–0.1 mol·L⁻¹. -1 The concentration of the inorganic salt is 1–10 mol·L⁻¹. -1 .

[0012] Optionally, the inorganic salt includes at least one of LiNO3, NaNO3, KNO3, and LiCl.

[0013] Optionally, the molar ratio of iridium, ruthenium, and platinum in the mixture is 1:0.1 to 2:0.1 to 2.

[0014] Optionally, the iridium source includes at least one selected from H2IrCl6 and its hydrate, IrCl3 and its hydrate, Ir(acac)3 and its hydrate, and Ir(CH3COO)3 and its hydrate; and / or,

[0015] The ruthenium source includes at least one of RuCl3 and its hydrate, Ru(acac)3 and its hydrate, and Ru(CH3COO)3 and its hydrate; and / or,

[0016] The platinum source includes at least one of H2PtCl6 and its hydrate, and PtCl4 and its hydrate.

[0017] Optionally, in step S20, the complexing agent includes at least one of citric acid, tartaric acid, ethylenediaminetetraacetic acid, hydroxyethylethylenediaminetriacetic acid, and their salts.

[0018] Optionally, in the intermediate solution, the amount of the complexing agent is a, and the sum of the amounts of iridium, ruthenium, and platinum is b, where a:b = 1:0.2 to 1.

[0019] Optionally, in step S30, the drying temperature is 50–90°C and the drying time is 6–12 hours.

[0020] Optionally, in step S40, the oxygen-containing gas includes either air or an oxygen-nitrogen mixture.

[0021] In the technical solution provided by this invention, Pt is prepared by heat-treating three metal compounds, Ru, Ir, and Pt (platinum). x Ru y Ir 1-x-y O2 composite nanocatalysts can reduce the Ir content, thereby reducing catalyst cost. Simultaneously, during catalysis, the oxygen atoms bonded to Pt can rapidly fill oxygen vacancies after Ir and Ru catalytic deoxygenation, reducing H+ ions under acidic conditions. + The corrosion effect on the catalyst increases its stability. By adding complexing agents and inorganic salts during the preparation process, the grain growth during the evaporation and crystallization process is effectively controlled, resulting in a composite nanocatalyst with small grain size and high grain boundary density, which provides denser catalytic active sites and thus high catalytic activity. In addition, the preparation method is simple, easy to implement, and highly reproducible, making it suitable for large-scale production. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 A schematic flowchart of an embodiment of the preparation method of the composite nanocatalyst provided by the present invention;

[0024] Figure 2 Pt prepared in Example 1 0.2 Ru 0.4 Ir 0.4 XRD pattern of O2 composite nanocatalyst;

[0025] Figure 3Pt prepared in Example 1 0.2 Ru 0.4 Ir 0.4 Scanning electron microscope image of O2 composite nanocatalyst loaded on the surface of membrane electrode;

[0026] Figure 4 Linear sweep voltammetry curves for Example 1, Comparative Examples 1-2, and a commercial IrO2 catalyst;

[0027] Figure 5 The catalysts prepared in Example 1 and Comparative Examples 1-2 were subjected to an ampere- ... -2 Stability test results under current density conditions;

[0028] Figure 6 Pt prepared in Example 1 0.2 Ru 0.4 Ir 0.4 Transmission electron microscopy images of the O2 composite nanocatalyst before and after the 100-hour stability test.

[0029] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0030] To make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer are used. Where the manufacturer of the reagents or instruments is not specified, all are conventional products that can be purchased commercially.

[0031] Furthermore, the meaning of "and / or" throughout the text includes three parallel solutions. Taking "A and / or B" as an example, it includes solution A, solution B, or a solution that simultaneously satisfies A and B. In addition, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this invention.

[0032] Currently, Ir-based and Ru-based oxides are considered the two most efficient acidic OER catalysts. While RuO2 exhibits higher OER catalytic activity, IrO2 has a greater advantage in stability, and therefore, it has been used in commercial SPE electrolyzers. However, the catalytic performance of IrO2 is not ideal, and its high cost significantly limits its large-scale application.

[0033] Studies have shown that RuO2 and IrO2 have similar rutile lattices. The RuO2-IrO2 solid solution can effectively improve the stability of the catalyst and reduce the Ir content. However, during long-term use, the large number of oxygen vacancies formed in the RuO2 and IrO2 lattices during catalysis can still lead to the gradual corrosion and destruction of the catalyst structure, reducing its catalytic performance and stability.

[0034] Based on the above concept, this invention proposes a method for preparing composite nanocatalysts, which further dopes PtO2 onto Ru-based and Ir-based substrates to obtain PtO2. x Ru y Ir 1-x-y O2 composite nanocatalyst. Figure 1 The diagram shown is a schematic flow chart of an embodiment of the preparation method of the composite nanocatalyst provided by the present invention. Please refer to [link / reference needed]. Figure 1 As shown, in this embodiment, the preparation method of the composite nanocatalyst includes the following steps:

[0035] Step S10: Dissolve the iridium source, ruthenium source, platinum source and inorganic salt in deionized water and mix well to obtain a mixed solution.

[0036] The present invention does not limit the specific type of iridium source. Preferably, the iridium source includes at least one selected from H₂IrCl₆ and its hydrate, IrCl₃ and its hydrate, Ir(acac)₃ and its hydrate, and Ir(CH₃COO)₃ and its hydrate. These iridium sources are readily available, and excess components can be removed in gaseous form during subsequent heat treatment, thereby reducing impurities in the composite nanocatalyst. For the same reason, the ruthenium source preferably includes at least one selected from RuCl₃ and its hydrate, Ru(acac)₃ and its hydrate, and Ru(CH₃COO)₃ and its hydrate. In another embodiment, the platinum source includes at least one selected from H₂PtCl₆ and its hydrate, and PtCl₄ and its hydrate.

[0037] Furthermore, in the mixture, the molar ratio of iridium, ruthenium, and platinum is 1:0.1–2:0.1–2. Under this ratio, the prepared Pt... x Ru y Ir 1-x-y O2 composite nanocatalysts exhibit the best stability and are low in cost.

[0038] By adding inorganic salts, the growth of individual grains during crystallization can be suppressed. Preferably, the total concentration of iridium, ruthenium, and platinum in the mixture is 0.005–0.1 mol·L⁻¹. -1 The concentration of the inorganic salt is 1–10 mol·L⁻¹.-1 In this embodiment, by adding a large amount of inorganic salt, the agglomeration between grains during the subsequent heat treatment process was suppressed, thereby improving the catalytic activity.

[0039] In this embodiment, the inorganic salt includes at least one of LiNO3, NaNO3, KNO3, and LiCl, so that the inorganic salt is in a molten state at 400-650°C.

[0040] Step S20: Dissolve the complexing agent in the mixture and mix well to obtain an intermediate solution.

[0041] By adding a complexing agent, metal ions can be stabilized and their rapid precipitation can be prevented. This effectively controls the grain size during the evaporation and crystallization process, resulting in a composite nanocatalyst with small grain size and high grain boundary density. This provides dense catalytic active sites, thereby improving catalytic activity.

[0042] Therefore, during the evaporation and crystallization process, the complexing agent and inorganic salt work synergistically to better control the size of the crystals, resulting in a catalyst with higher grain boundary density and denser catalytic active sites, thus exhibiting high catalytic activity.

[0043] The complexing agent includes at least one of citric acid, tartaric acid, ethylenediaminetetraacetic acid, hydroxyethylethylenediaminetriacetic acid and their salts. All of the above substances can complex with Ir, Ru and Pt, and are low in cost.

[0044] In order to better control grain growth and thus achieve higher catalytic activity, preferably, in the intermediate solution, the amount of the complexing agent is a, and the sum of the amounts of iridium, ruthenium and platinum is b, where a:b = 1:0.2 to 1, that is, it can be 1:0.2, 1:0.24, 1:0.3, 1:0.4, 1:0.5, 1:0.7, 1:0.85, 1:1, etc.

[0045] Step S30: Evaporate and dry the intermediate solution to obtain the catalyst precursor.

[0046] The present invention does not limit the specific parameters of the drying process, as long as the mixture is completely evaporated. In this embodiment, the drying temperature is 50-90°C and the drying time is 6-12 hours.

[0047] Step S40: The catalyst precursor is heated at 200-350°C for 20-120 min in an oxygen-containing gas atmosphere, then heated to 400-650°C for 20-120 min, and finally cooled and washed to obtain the composite nanocatalyst.

[0048] When the catalyst precursor is calcined at 200–350 °C, the platinum, iridium, and ruthenium sources are converted into their corresponding oxides. Then, the temperature is raised to 400–650 °C to melt the inorganic salts. The large amount of inorganic salts in the molten state separates the catalyst nanocrystals, thereby preventing the agglomeration of the oxide nanocrystals (i.e., preventing the small nanocrystals that have already been formed from regrowing into a single mass during heating).

[0049] Furthermore, by adding a large amount of inorganic salt and using programmed temperature rise during heat treatment, it is helpful to form a two-dimensional nanosheet structure by bonding between nanocrystals. When the prepared composite nanocatalyst is applied to the acidic oxygen evolution reaction, the catalyst needs to be loaded onto the surface of the membrane electrode. The nanosheet structure in the catalyst can form a porous secondary structure on the surface of the membrane electrode, which increases the exposure area of ​​the active sites in the catalyst, thereby improving the catalytic performance.

[0050] The oxygen-containing gas includes either air or an oxygen-nitrogen mixture. For ease of acquisition and low cost, the oxygen-containing gas is preferably air.

[0051] Currently, there are also methods to modify RuO2-IrO2 composite catalysts by doping with Pt. However, in this method, elemental Pt is used as the dopant, and the Pt black powder is mechanically doped into the RuO2 and IrO2 grains in the form of nanoparticles. This only plays a role in improving the conductivity and does not have a substantial effect on improving the stability of the catalyst under long-term use.

[0052] In the technical solution provided by this invention, Pt is prepared by calcining three metal compounds, Ru, Ir, and Pt, in an oxygen-containing gas atmosphere. x Ru y Ir 1-x-y O2 composite nanocatalysts can reduce the Ir content, thereby reducing catalyst cost. Simultaneously, during catalysis, the oxygen atoms bonded to Pt can rapidly fill oxygen vacancies after Ir and Ru catalytic deoxygenation, reducing H+ ions under acidic conditions. + The corrosion effect on the catalyst increases its stability; by adding complexing agents and inorganic salts during the preparation process, the grain growth during the evaporation and crystallization process is effectively controlled, resulting in a composite nanocatalyst with small grain size and high grain boundary density, thus providing denser catalytic active sites and thus high catalytic activity; moreover, the preparation method is simple, easy to implement, and highly reproducible, making it suitable for large-scale production.

[0053] In addition, the preparation method proposed in this invention avoids grain agglomeration by adding a large amount of inorganic salt and using programmed temperature rise during heat treatment. At the same time, the prepared composite nanocatalyst has a two-dimensional sheet structure. When the composite nanocatalyst is used for acidic oxygen evolution reaction, the nanosheet structure can form a porous secondary structure on the surface of the membrane electrode, increasing the exposure area of ​​active sites in the catalyst, thereby improving the catalytic performance of the membrane electrode.

[0054] In summary, the preparation method provided by this invention is simple, easy to implement, and highly reproducible, making it suitable for large-scale production. The resulting composite nanocatalyst has the advantages of low cost, high stability, and high catalytic activity, and has high application value in the electrocatalytic process of acidic oxygen evolution reaction.

[0055] The technical solution of the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings. It should be understood that the following embodiments are only used to explain the present invention and are not intended to limit the present invention.

[0056] Example 1

[0057] (1) Dissolve 258 mg of H₂IrCl₆·6H₂O, 131 mg of RuCl₃·xH₂O (of which the Ru content is 38 wt%), 129 mg of H₂PtCl₆·6H₂O, and 12.8 g of NaNO₃ in 50 mL of deionized water and mix thoroughly to obtain a mixture, namely: in the mixture, the molar ratio of Ir, Ru, and Pt is 1:1:0.5, and the total concentration of Ir, Ru, and Pt is 0.025 mol·L⁻¹. -1 The concentration of NaNO3 is 3 mol·L⁻¹ -1 ;

[0058] (2) Dissolve 1.29g of sodium citrate in the above mixture and mix well to obtain an intermediate solution, i.e., a (amount of sodium citrate): b (sum of the amounts of Ir, Ru and Pt) = 1:0.25;

[0059] (3) The above intermediate solution was evaporated and dried at 60°C for 8 hours to obtain the catalyst precursor;

[0060] (4) The above catalyst precursor was heated at 250°C for 40 min in air, and then heated to 450°C for 40 min. After heating, it was naturally cooled and removed, washed three times with deionized water, and then dried to obtain Pt. 0.2 Ru 0.4 Ir 0.4 O2 composite nanocatalyst.

[0061] The Pt obtained in this embodiment 0.2 Ru 0.4 Ir0.4 X-ray diffraction (XRD) was performed on the O2 composite nanocatalyst, and the results are as follows: Figure 2 As shown. By Figure 2 As can be seen, due to the extremely small crystal size of the composite nanocatalyst, its XRD diffraction peaks are weak, but the presence of corresponding diffraction peaks for IrO2, RuO2, and PtO2 in the diffraction pattern can still be confirmed. That is, the present invention has successfully prepared PtO2. 0.2 Ru 0.4 Ir 0.4 O2 composite nanocatalyst.

[0062] The obtained Pt 0.2 Ru 0.4 Ir 0.4 O2 composite nanocatalysts were loaded onto the surface of the membrane electrode and then characterized using scanning electron microscopy. The results are as follows: Figure 3 As shown. By Figure 3 As can be seen, the composite nanocatalyst nanosheets stacked on the surface of the membrane electrode form a variety of pore structures with different pore sizes, which is beneficial to the contact between the active sites of the catalyst and the liquid phase during electrolysis, thereby improving the catalytic performance.

[0063] Example 2

[0064] (1) Dissolve 52.9 mg of IrCl3·3H2O, 78.2 mg of RuCl3·xH2O (of which the Ru content is 38 wt%), 15.3 mg of PtCl4, and 6.90 g of LiNO3 in 50 mL of deionized water and mix thoroughly to obtain a mixture, namely: the molar ratio of Ir, Ru, and Pt in the mixture is 1:2:0.33, and the total concentration of Ir, Ru, and Pt is 0.01 mol·L⁻¹. -1 The concentration of LiNO3 is 2 mol·L⁻¹ -1 ;

[0065] (2) Dissolve 168 mg of disodium ethylenediaminetetraacetate in the above mixture and mix well to obtain an intermediate solution, i.e., a (amount of 168 mg of disodium ethylenediaminetetraacetate): b (sum of the amounts of Ir, Ru and Pt) = 1:1;

[0066] (3) The above intermediate solution was evaporated and dried at 75°C for 9 hours to obtain the catalyst precursor;

[0067] (4) The above catalyst precursor was heated at 200°C for 30 min in air, and then heated to 400°C for 30 min. After heating, it was naturally cooled and removed, washed three times with deionized water, and then dried to obtain Pt. 0.1 Ru 0.6 Ir 0.3O2 composite nanocatalyst.

[0068] Example 3

[0069] (1) Dissolve 516 mg of H2IrCl6·6H2O, 195 mg of Ru(acac)3, 259 mg of H2PtCl6·6H2O, and 25.3 g of KNO3 in 50 mL of deionized water and mix thoroughly to obtain a mixture. The molar ratio of Ir, Ru, and Pt in the mixture is 1:0.5:1, and the total concentration of Ir, Ru, and Pt is 0.05 mol·L⁻¹. -1 The concentration of inorganic salts is 5 mol·L⁻¹ -1 ;

[0070] (2) Dissolve 1.88g of tartaric acid in the above mixture and mix well to obtain an intermediate solution, i.e., a (amount of tartaric acid): b (sum of the amounts of Ir, Ru and Pt) = 1:0.2;

[0071] (3) The above intermediate solution was slowly evaporated and dried at 60°C to obtain the catalyst precursor;

[0072] (4) The above catalyst precursor was heated at 300°C for 30 min in an air atmosphere, and then heated to 480°C for 60 min. After heating, it was naturally cooled and removed, washed three times with deionized water, and then dried to obtain the composite nanocatalyst.

[0073] Example 4

[0074] (1) Dissolve 35.2 mg of Ir(CH3COO)3·H2O, 54.4 mg of Ru(CH3COO)3, 52.3 mg of H2PtCl6·6H2O, and 10.6 g of LiCl in 50 mL of deionized water and mix thoroughly to obtain a mixture. The molar ratio of Ir, Ru, and Pt in the mixture is 1:2:2, and the total concentration of Ir, Ru, and Pt is 0.01 mol·L⁻¹. -1 The concentration of inorganic salts is 1–10 mol·L⁻¹ -1 ;

[0075] (2) Dissolve hydroxyethyl ethylenediamine triacetic acid in the above mixture and mix well to obtain an intermediate solution, i.e., a (amount of hydroxyethyl ethylenediamine triacetic acid): b (sum of the amounts of Ir, Ru and Pt) = 1:0.5;

[0076] (3) The above intermediate solution was evaporated and dried at 90°C for 6 hours to obtain the catalyst precursor;

[0077] (4) The above catalyst precursor was heated at 280°C for 40 min in air, then heated to 620°C for 90 min. After heating, it was naturally cooled and removed, washed three times with deionized water, and then dried to obtain Pt. 0.4 Ru 0.4 Ir 0.2 O2 composite nanocatalyst.

[0078] Example 5

[0079] (1) Dissolve 515 mg H2IrCl6·6H2O, 26.2 mg RuCl3·xH2O (of which the Ru content is 38 wt%), 77.7 mg H2PtCl6·6H2O, and 4.27 g NaNO3 in 50 mL of deionized water and mix thoroughly to obtain a mixture, namely: in the mixture, the molar ratio of Ir, Ru, and Pt is 1:0.1:0.15, and the total concentration of Ir, Ru, and Pt is 0.025 mol·L⁻¹. -1 The concentration of NaNO3 is 1 mol·L⁻¹ -1 ;

[0080] (2) Dissolve 1.29g of sodium citrate in the above mixture and mix well to obtain an intermediate solution, i.e., a (amount of sodium citrate): b (sum of the amounts of Ir, Ru and Pt) = 1:0.25;

[0081] (3) The above intermediate solution was slowly evaporated and dried at 50°C for 12 hours to obtain the catalyst precursor;

[0082] (4) The above catalyst precursor was heated at 200°C for 120 min in air, then heated to 650°C for 20 min. After heating, it was naturally cooled and removed, washed three times with deionized water, and then dried to obtain Pt. 0.12 Ru 0.08 Ir 0.8 O2 composite nanocatalyst.

[0083] Example 6

[0084] (1) Dissolve 515 mg of H₂IrCl₆·6H₂O, 39.3 mg of RuCl₃·xH₂O (of which the Ru content is 38 wt%), 51.8 mg of H₂PtCl₆·6H₂O, and 42.7 g of NaNO₃ in 50 mL of deionized water and mix thoroughly to obtain a mixture, namely: in the mixture, the molar ratio of Ir, Ru, and Pt is 1:0.15:0.1, and the total concentration of Ir, Ru, and Pt is 0.025 mol·L⁻¹. -1 The concentration of NaNO3 is 10 mol·L⁻¹-1 ;

[0085] (2) Dissolve 1.29g of sodium citrate in the above mixture and mix well to obtain an intermediate solution, i.e., a (amount of sodium citrate): b (sum of the amounts of Ir, Ru and Pt) = 1:0.25;

[0086] (3) The above intermediate solution was evaporated and dried at 70°C for 8 hours to obtain the catalyst precursor;

[0087] (4) The above catalyst precursor was heated at 350°C for 20 min in air, then heated to 450°C for 120 min. After heating, it was allowed to cool naturally and removed, washed three times with deionized water, and then dried to obtain Pt. 0.08 Ru 0.12 Ir 0.8 O2 composite nanocatalyst.

[0088] Comparative Example 1

[0089] Except for step (2), i.e. without adding a complexing agent, the remaining steps are the same as in Example 1, and the composite nanocatalyst is finally obtained, which is named Pt. 0.2 Ru 0.4 Ir 0.4 O2-N.

[0090] Comparative Example 2

[0091] Except for the absence of a platinum source, the remaining steps are the same as in Example 1, ultimately yielding Ru. 0.5 Ir 0.5 O2 composite nanocatalyst;

[0092] That is, step (1) is:

[0093] H₂IrCl₆·6H₂O, RuCl₃·xH₂O, and NaNO₃ were dissolved in 50 mL of deionized water and mixed thoroughly to obtain a mixture in which the molar ratio of Ir to Ru was 1:1 and the total concentration of Ir and Ru was 0.025 mol·L⁻¹. -1 The concentration of NaNO3 is 3 mol·L⁻¹ -1 .

[0094] The catalysts prepared in the above embodiments and comparative examples were tested as follows.

[0095] (I) Catalytic performance testing

[0096] The composite nanocatalysts prepared in Examples 1 and 1-2, as well as the 99.9% commercial IrO2 catalyst from Innochem, were used to test the catalytic performance of the acidic oxygen evolution reaction. A three-electrode system was used in the tests, with a platinum wire as the counter electrode and a silver / silver chloride electrode as the reference electrode. 5 mg of the catalyst to be tested was dispersed in 2 mL of a 1:1 mixture of water and ethanol, and 40 μL of 5% Nafion solution was added as a binder to obtain a catalyst dispersion. This catalyst dispersion was then uniformly coated onto the surface of a glassy carbon electrode, resulting in a final catalyst loading of 0.25 mg / cm³. 2 The test system used 0.5M H2SO4 as the electrolyte, and the linear sweep voltammetry curve was obtained. The test results are as follows: Figure 4 As shown.

[0097] Depend on Figure 4 It can be seen that the Pt prepared in Example 1 0.2 Ru 0.4 Ir 0.4 O2 catalyst at 10 mA·cm -2 The overpotential at the specified current density was only 285 mV, which is 70 mV lower than that of a commercial IrO2 catalyst under the same conditions. Meanwhile, the catalytic performance of each comparative example was significantly lower than that of the example, indicating that the addition of the platinum source and the complexing agent both played crucial roles in improving the catalytic performance of this catalyst.

[0098] (II) Stability Testing

[0099] The composite nanocatalysts prepared in Example 1 and Comparative Examples 1-2 were subjected to an atmosphere of 50 mA·cm⁻¹. -2 Stability tests were conducted under a constant current density, and the test results are as follows: Figure 5 and Figure 6 As shown.

[0100] Depend on Figure 5 It can be seen that, in the 100-hour stability test, the composite nanocatalyst prepared in Example 1 exhibits better stability than Comparative Examples 1 and 2. Furthermore, after 100 hours, the catalyst voltage in Example 1 only increased by 7 mV, indicating that the composite nanocatalyst prepared in this invention possesses excellent stability during the OER process.

[0101] Figure 6 These are transmission electron microscopy (TEM) images of the composite nanocatalyst prepared in Example 1 before and after a 100-hour stability test. Figure 6 It can be seen that the morphology of the composite nanocatalyst did not change significantly during the 100-hour test.

[0102] The composite nanocatalysts prepared in Examples 2-6 were subjected to the same detection and analysis as in Example 1 above, and the obtained catalysts were determined to be Pt. xRu y Ir 1-x-y O2, and the catalyst is low in cost, has high catalytic activity and high stability.

[0103] The above are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the patent protection scope of the present invention.

Claims

1. A method for preparing a composite nanocatalyst, characterized in that, Includes the following steps: S10. Dissolve the iridium source, ruthenium source, platinum source and inorganic salt in deionized water and mix well to obtain a mixed solution; in the mixed solution, the molar ratio of iridium, ruthenium and platinum is 1:0.1~2:0.1~2. S20. Dissolve the complexing agent in the mixture and mix well to obtain an intermediate solution; S30. The intermediate solution is evaporated and dried to obtain the catalyst precursor; S40. The catalyst precursor is heated at 200-350°C for 20-120 min in an oxygen-containing gas atmosphere, then heated to 400-650°C for 20-120 min, and finally cooled and washed to obtain the composite nanocatalyst.

2. The method for preparing the composite nanocatalyst as described in claim 1, characterized in that, The total concentration of iridium, ruthenium, and platinum in the mixture is 0.005–0.1 mol·L⁻¹. -1 The concentration of the inorganic salt is 1–10 mol·L⁻¹. -1 .

3. The method for preparing the composite nanocatalyst as described in claim 2, characterized in that, The inorganic salt includes at least one of LiNO3, NaNO3, KNO3, and LiCl.

4. The method for preparing the composite nanocatalyst as described in claim 1, characterized in that, The iridium source includes at least one of H2IrCl6 and its hydrate, IrCl3 and its hydrate, Ir(acac)3 and its hydrate, and Ir(CH3COO)3 and its hydrate; and / or, The ruthenium source includes at least one of RuCl3 and its hydrate, Ru(acac)3 and its hydrate, and Ru(CH3COO)3 and its hydrate; and / or, The platinum source includes at least one of H2PtCl6 and its hydrate, and PtCl4 and its hydrate.

5. The method for preparing the composite nanocatalyst as described in claim 1, characterized in that, In step S20, the complexing agent includes at least one of citric acid, tartaric acid, ethylenediaminetetraacetic acid, hydroxyethylethylenediaminetriacetic acid, and their salts.

6. The method for preparing the composite nanocatalyst as described in claim 1, characterized in that, In the intermediate solution, the amount of the complexing agent is a, and the sum of the amounts of iridium, ruthenium, and platinum is b, where a:b = 1:0.2~1.

7. The method for preparing the composite nanocatalyst as described in claim 1, characterized in that, In step S30, the drying temperature is 50-90°C and the drying time is 6-12 hours.

8. The method for preparing the composite nanocatalyst as described in claim 1, characterized in that, In step S40, the oxygen-containing gas includes either air or an oxygen-nitrogen mixture.

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