Platinum-palladium-ruthenium alloy nano-catalyst as well as preparation method and application thereof

Abstract

The invention discloses a platinum-palladium-ruthenium alloy nano-catalyst as well as a preparation method and application thereof, and relates to the technical field of methanol fuel cells. The preparation method of the platinum-palladium-ruthenium alloy nano-catalyst specifically comprises the following steps: firstly, carrying out acid pickling, refluxing and drying on conductive carbon black to obtain a carbon carrier, and carrying out ultrasonic dispersion on the carbon carrier through polyhydric alcohol to obtain carbon paste; dropwise adding the platinum-palladium-ruthenium precursor solution into the carbon paste, stirring and aging to obtain supported precursor carbon paste, and performing normal-pressure microwave reflux reaction to form carbon paste containing alloy particles; adding a cross-linking agent, performing suction filtration to obtain a solid, and sequentially performing oxidation liquid etching and multiple times of microwave reduction circulation treatment; and drying and grinding the obtained solid, carrying out segmented heat treatment in a mixed atmosphere, cooling to obtain a crude catalyst product, and finally washing and drying to obtain the platinum-palladium-ruthenium alloy nano-catalyst. The prepared platinum-palladium-ruthenium catalyst has the structural advantages of being uniform in size, ordered in alloy, firm in anchoring and resistant to dissolution, and low-platinum, high-activity, long-life and green production can be achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to a platinum-palladium-ruthenium alloy nanocatalyst and its preparation method and application, belonging to the technical field of methanol fuel cell. BACKGROUND

[0002] Carbon carriers have become the mainstream choice for methanol fuel cell catalysts due to their high specific surface area, excellent electrical conductivity, and low cost advantages. However, traditional preparation processes (such as chemical reduction-calcination, sol-gel method) face three key bottlenecks when loading platinum-palladium-ruthenium ternary alloy on the surface of carbon carriers. First, during the reduction process, local supersaturation of metal ions leads to imbalance between nucleation and growth, resulting in wide particle size distribution (5-15 nm) and severe agglomeration of alloy particles, which causes a decrease in electrochemical active surface area of more than 30%. Second, the limited oxygen-containing functional groups on the surface of carbon carriers can only form weak interactions with metal precursors, and after reduction, particles mainly rely on physical adsorption, leading to high particle shedding rate (>15%) under high potential or methanol oxidation intermediate attack, poor catalyst stability, and activity decay of up to 50% after 500h cycling. Finally, the high-temperature calcination process (>500℃) required to improve crystallinity easily causes the dissolution of ruthenium components in the form of volatile oxides, resulting in a 20-40% loss of surface ruthenium content, which destroys the platinum-ruthenium synergistic poison resistance mechanism and exacerbates the oxidation etching and pore structure collapse of the carbon carrier, damaging the conductive network. The above defects collectively result in high platinum metal usage, low peak power density, and insufficient durability of traditional PtPdRu / C catalysts, which cannot meet the U.S. Department of Energy's 2025 technical specifications (platinum loading ≤0.062mgPt / cm 2 , durability ≥5000h), and it is also difficult to achieve green production on a kilogram scale.

[0003] In view of the related technical bottlenecks, the present application aims to develop an innovative preparation strategy, with the core goal being to precisely regulate the structure and interface properties of platinum-palladium-ruthenium ternary nanoparticles on the surface of carbon carriers, so that they simultaneously possess uniform size, alloy order, strong anchoring, and component resistance to dissolution, and synergistically achieve low platinum usage, high catalytic activity, long-term stability, and scalable green production, thereby breaking through the comprehensive performance bottleneck of existing technologies that cannot simultaneously achieve high activity, high stability, high metal utilization, low cost, and low environmental emissions. SUMMARY

[0004] In view of the deficiencies of the related art, the present application provides a platinum-palladium-ruthenium alloy nanocatalyst and its preparation method and application. The platinum-palladium-ruthenium alloy nanocatalyst prepared has the structural properties of uniform size, alloy order, strong anchoring, and stable components, and simultaneously achieves the breakthroughs in comprehensive performance of low platinum high activity, long-term stability, and green scalability, solving the problems of agglomeration, poor stability, and low peak power density of platinum-palladium-ruthenium ternary alloy particles loaded on the surface of carbon carriers prepared by traditional preparation processes.

[0005] One of the purposes of the present application is to provide a preparation method of platinum-palladium-ruthenium alloy nanocatalyst, which specifically comprises the following steps: (1) Carbon carrier pre-dispersion: add conductive carbon black material (preferably Vulcan XC-72R as conductive carbon black material) into aqueous nitric acid solution, perform acid washing and heating reflux, then perform cleaning and drying to obtain a carbon carrier, and then place the carbon carrier in a polyol solution for ultrasonic dispersion to obtain a pre-dispersed carbon slurry.

[0006] (2) Low-temperature dropwise adsorption: prepare a precursor aqueous-alcoholic solution, and then drop the precursor aqueous-alcoholic solution into the pre-dispersed carbon slurry in a stirring state (preferably stirring at 250 rpm), continue stirring (preferably stirring at 250 rpm) after the dropwise addition is completed, and then age to obtain a supported precursor carbon slurry.

[0007] (3) Microwave heating reflux reduction: place the supported precursor carbon slurry in an atmospheric microwave reflux system for microwave heating reflux reaction, and then obtain a carbon slurry containing platinum-palladium-ruthenium alloy particles after the reaction is completed.

[0008] (4) Polyol protective layer fixation: add a crosslinking agent to the carbon slurry containing platinum-palladium-ruthenium alloy particles to obtain a solid-liquid mixture containing platinum-palladium-ruthenium alloy particles fixed by a polyol protective layer, and then perform suction filtration on the solid-liquid mixture to obtain a solid substance.

[0009] (5) Redox cycle pretreatment: place the solid substance in an oxidizing solution for surface etching, then perform suction filtration to obtain a filter cake, place the filter cake in an atmospheric microwave reflux system, add an organic solvent (preferably anhydrous ethanol) to the atmospheric microwave reflux system, and then perform multiple microwave heating reflux reduction cycle treatments to obtain a solid substance after reduction cycle treatment.

[0010] (6) Stepwise heat treatment: dry and grind the solid substance after reduction cycle treatment, then place it in a heating device (preferably a tube furnace) for stepwise heat treatment in a mixed gas atmosphere, and then cool to obtain a catalyst crude product.

[0011] (7) Post-treatment: wash and dry the catalyst crude product to obtain a platinum-palladium-ruthenium alloy nanocatalyst.

[0012] Preferably, the conductive carbon black material in step (1) is added in an amount of 0.02-0.05 g / mL in the aqueous nitric acid solution; the acid washing and heating reflux conditions are: using an aqueous nitric acid solution with a concentration of 1-2 mol / L, refluxing at 90°C for 2 h; the polyol solution is a mixed solution prepared according to a volume ratio of ethylene glycol to glycerol of (1-5):1; the carbon carrier is added in an amount of 0.02-0.05 g / mL in the polyol solution; the ultrasonic dispersion conditions are: ultrasonic dispersion at a frequency of 40 kHz for 30-60 min.

[0013] Preferably, the precursor aqueous-alcoholic solution in step (2) is prepared using H2PtCl6·6H2O (chloroplatinic acid, hexahydrate), Pd(NO3)2·2H2O (palladium(II) nitrate dihydrate), and RuCl3·xH2O (ruthenium trichloride hydrate), with a molar ratio of Pt:Pd:Ru of (1-5):1:1, and a total amount of Pt, Pd, and Ru in the precursor aqueous-alcoholic solution of 0.02-0.05 g / mL; the precursor aqueous-alcoholic solution is added to the pre-dispersed carbon slurry in a stirring state at a drop rate of 0.5 mL / min; the precursor aqueous-alcoholic solution is added to the pre-dispersed carbon slurry in a ratio of the total mass of Pt, Pd, and Ru in the precursor aqueous solution to the mass of the carbon carrier in step (1) of (0.4-2.4):1.

[0014] Preferably, the stirring time after the end of the drop in step (2) is 3 h; the aging time is 1 h.

[0015] Preferably, the microwave heating reflux reaction in step (3) is performed by increasing the temperature to 120-180°C at a power of 300 W, and then reducing the power to 200 W for refluxing for 20-90 min.

[0016] Preferably, the crosslinking agent in step (4) is a 0.1 mol / L, pH 4 citric acid-sodium citrate buffer solution; the carbon slurry containing the platinum-palladium-ruthenium alloy particles fixed by the polyol protective layer is added in an amount of 0.02-0.04 g / mL.

[0017] Preferably, the oxidizing solution in step (5) is a 10-30% H2O2 aqueous solution by mass percentage; the solid substance is added in the oxidizing solution in an amount of 0.02-0.04 g / mL; the surface etching is performed at 50°C for 1 h; the organic solvent is added to an atmospheric pressure microwave reflux system in a proportion of 1 g of solid substance to 50-100 mL of organic solvent; the microwave heating reflux reduction cycle treatment is performed at a power of 300 W to heat to 120-180°C, and then at a power of 200 W to reflux for 10-40 min; and the microwave heating reflux reduction cycle treatment is performed 4 times.

[0018] Preferably, in step (6), the mixed gas is a mixture of hydrogen and argon, wherein the content of hydrogen is 5% by volume percentage, and the balance is argon; and the conditions of the stepwise heat treatment are as follows: under the condition that the flow rate of the mixed gas is 100 mL / min, the temperature is raised to 450°C at a rate of 10°C / min and then maintained for 2 h.

[0019] The second object of the present application is to provide a platinum-palladium-ruthenium alloy nanocatalyst prepared by the preparation method.

[0020] The third object of the present application is to provide an application of the platinum-palladium-ruthenium alloy nanocatalyst prepared by the preparation method in catalyzing the electrochemical oxidation of methanol.

[0021] The mechanism of the present application is as follows: The present application realizes the uniformity of the size of the platinum-palladium-ruthenium alloy nanocatalyst particles and the alloying by optimizing the preparation process. The size distribution of the nanocatalyst particles is controlled to be uniform by the synergistic effect of the microwave heating reflux reduction and the redox cycle pretreatment, and the electrochemical active specific surface area (ECSA) is significantly increased. The reduction reaction of the metal precursor is highly synchronized by the synergistic effect of the preparation process, and the problems of particle agglomeration and uneven size distribution are avoided. The preparation process of the nanocatalyst particles of the present application is performed below 450°C, without high-temperature calcination or complex coating, and the energy consumption is low, and the metal utilization rate is high (>98%). The alloy ordering is realized, the volatilization loss of ruthenium is effectively inhibited, green production and low-cost preparation are realized, the bottleneck of the traditional process is broken, and an innovative technical path is provided for the efficient preparation of methanol fuel cell catalysts.

[0022] The present application has the following beneficial effects: (1) The preparation process of the platinum-palladium-ruthenium alloy nanocatalyst is performed below 450°C, without high-temperature calcination or complex coating, the energy consumption is reduced by ≥50%, the steps are continuous, and the separation can be performed by filtration, which is suitable for scale-up production.

[0023] (2) The platinum-palladium-ruthenium alloy nanocatalyst prepared in this invention has a particle size of 2~6nm and a narrow distribution (polydispersity index, i.e., PDI<0.15), a rich Pt-Ru surface layer and high defect density, and an electrochemically active specific surface area (ECSA) ≥85m². 2 / g.

[0024] (3) The platinum-palladium-ruthenium alloy nanocatalyst prepared in this invention has an initial potential (V vs. SCE) of 0.25, a peak potential (V vs. SCE) of 0.52, and a peak current of up to 13 mA.

[0025] (4) The preparation process of the present invention omits the inert atmosphere high-temperature calcination furnace and multiple water washing in the traditional process, the metal utilization rate is >98%, the single batch can be extended to the kilogram level, and the equipment investment is low. Attached Figure Description

[0026] Figure 1 The image shows a scanning transmission electron microscope (STEM) image and elemental mapping (20 nm) of the platinum-palladium-ruthenium alloy nanocatalyst prepared in Example 1 of this invention.

[0027] Figure 2 The image shows the cyclic voltammetry electrochemical test curve of the platinum-palladium-ruthenium nanocatalyst prepared in Example 1 of this invention.

[0028] Figure 3 The image shows the cyclic voltammetry electrochemical test curve of the platinum-palladium-ruthenium nanocatalyst prepared in Example 2 of this invention.

[0029] Figure 4 The image shows the cyclic voltammetry electrochemical test curve of the platinum-palladium-ruthenium nanocatalyst prepared in Example 3 of this invention.

[0030] Figure 5 The figure shows the cyclic voltammetry electrochemical test curve of the platinum-palladium-ruthenium nanocatalyst prepared in Comparative Example 1 of this invention. Detailed Implementation

[0031] To better illustrate the purpose, technical solution, and advantages of this invention, the invention will be further described below with reference to specific embodiments. In the embodiments and comparative examples of this invention, unless otherwise specified, all chemical reagents used were commercially available analytical grade reagents.

[0032] Example 1 A method for preparing a platinum-palladium-ruthenium alloy nanocatalyst specifically includes the following steps: (1) Carbon carrier pre-dispersion: Vulcan XC-72R is added to a concentrated nitric acid aqueous solution at 90°C for acid pickling reflux for 2h (wherein the addition amount of Vulcan XC-72R in the concentrated nitric acid aqueous solution is 0.02g / mL), then washed with deionized water to neutral, and dried at 80°C under vacuum to obtain a carbon carrier. The carbon carrier is dispersed in a polyol solution at 40kHz for 45min (wherein the addition amount of the carbon carrier in the polyol solution is 0.02g / mL) to obtain a uniformly pre-dispersed carbon slurry, wherein the polyol solution is prepared in a volume ratio of 2:1 of ethylene glycol to glycerol.

[0033] (2) Low-temperature dropwise adsorption: H2PtCl6·6H2O, Pd(NO3)2·2H2O, and RuCl3·xH2O are used to prepare a precursor hydroalcoholic solution (the molar ratio of Pt:Pd:Ru in the precursor solution is 3:1:1, and the total addition amount of Pt, Pd, and Ru in the precursor hydroalcoholic solution is 0.03g / mL). The precursor hydroalcoholic solution is added to the pre-dispersed carbon slurry stirred at 250rpm at 25°C at a dropwise addition rate of 0.5mL / min using a peristaltic pump. After the dropwise addition is completed, the stirring is continued at a speed of 250rpm for 3h, and then left to stand for 1h to obtain a supported precursor carbon slurry, wherein the precursor hydroalcoholic solution is added to the pre-dispersed carbon slurry in a ratio of 1:1 of the total mass of Pt, Pd, and Ru in the precursor aqueous solution to the mass of the carbon carrier in step (1).

[0034] (3) Microwave heating reflux reduction: The supported precursor carbon slurry is placed in an atmospheric microwave reflux system (the atmospheric microwave reflux system has a frequency of 2.45GHz and is equipped with a glass condenser tube). The microwave heating reflux reaction is carried out by first heating to 150°C at a power of 300W, and then refluxing at 200W for 60min. The polyol releases hydroxyl radicals in situ. The reaction is completed to obtain a carbon slurry containing 2-6nm platinum-palladium-ruthenium alloy particles.

[0035] (4) Polyol protective layer fixation: 0.1mol / L citric acid-sodium citrate buffer solution with a pH of 4 is added to the carbon slurry containing platinum-palladium-ruthenium alloy particles to obtain a solid-liquid mixture containing platinum-palladium-ruthenium alloy particles with a polyol protective layer (wherein the addition amount of the carbon slurry containing platinum-palladium-ruthenium alloy particles in the solid-liquid mixture containing platinum-palladium-ruthenium alloy particles with a polyol protective layer is 0.03g / mL), which prevents particle agglomeration. The solid-liquid mixture is subjected to suction filtration using a glass sand core filtration device to obtain a solid substance.

[0036] (5) Oxidation-reduction cycle pretreatment: the solid substance is placed in a 10% hydrogen peroxide aqueous solution by mass percentage (wherein the addition amount of the solid substance in the hydrogen peroxide aqueous solution is 0.02 g / mL), surface etching is performed at 50℃ for 1 h, then filtration is performed to obtain a filter cake, and then the filter cake is placed in an atmospheric pressure microwave reflux system, and anhydrous ethanol is added to the atmospheric pressure microwave reflux system (wherein the anhydrous ethanol is added to the atmospheric pressure microwave reflux system at a solid-liquid ratio of 1 g / 100 mL of the solid substance and the anhydrous ethanol), and the microwave heating reflux reduction cycle treatment is performed 4 times, first at a power of 300 W to heat to 150℃, and then at 200 W for 60 min, to construct a Pt-Ru-rich surface layer and reduce the CO adsorption energy, to obtain the solid substance after reduction cycle treatment.

[0037] (6) Stepwise heat treatment: the solid substance after reduction cycle treatment is vacuum dried at 60℃ for 12 h, then ground to a D50 particle size of ≤2 μm, then placed in a tube furnace, heated to 450℃ at a heating rate of 10℃ / min under a mixed atmosphere (the mixed atmosphere is composed of hydrogen and argon, wherein the content of hydrogen is 5% by volume, and the balance is argon), and held for 2 h, then naturally cooled to 350℃, and then cooled to room temperature by a high-speed fan, to obtain a catalyst crude product with uniform particle size and high defect density.

[0038] (7) Post-treatment: the catalyst crude product is washed with deionized water and anhydrous ethanol 3 times in turn, and then vacuum dried at 60℃ to a constant weight, to obtain a platinum-palladium-ruthenium alloy nanocatalyst (PtPdRu / C-1).

[0039] The PtPdRu / C-1 prepared in this example is subjected to scanning transmission electron microscopy and element distribution tests, and the test results are shown in Figure 1 The test results show that the platinum-palladium-ruthenium alloy nanocatalyst prepared in this example has a very uniform size and is uniformly distributed on the surface of the carbon carrier, without local aggregation or uneven distribution, which helps to improve the active surface area of the catalyst and thus improve the catalytic performance; the element distribution diagram shows that the Pt, Pd and Ru elements in the platinum-palladium-ruthenium alloy nanocatalyst prepared in this example are uniformly distributed to form a good alloy structure, rather than a simple physical mixture; such alloying structure helps to synergistically improve the performance of the catalyst.

[0040] The PtPdRu / C-1 prepared in this example is subjected to cyclic voltammetry electrochemical test, and the test results are shown in Figure 2As shown, the PtPdRu / C-1 tested has a starting potential (V vs. SCE) of 0.25, a peak potential (V vs. SCE) of 0.52, and a peak current of 13 mA. This is attributed to the uniformity of the catalyst size (2-6 nm and narrow distribution), the alloying effect, and the optimization of the surface structure. The synergy of the microwave heating reflux reduction and the redox cycle pretreatment in this embodiment enables the prepared platinum-palladium-ruthenium alloy nanocatalyst to have a small size and a high specific surface area, providing a large number of active sites for the catalytic reaction, reducing the reaction activation energy, thereby achieving a low starting potential and a high peak current; the synergy of the preparation process in this embodiment enables the prepared platinum-palladium-ruthenium alloy nanocatalyst to have excellent surface activity and CO poisoning resistance, and can achieve a high current density at a low potential, significantly improving the catalytic activity and stability of the catalyst. At the same time, the alloying of Pt, Pd, and Ru in the platinum-palladium-ruthenium alloy nanocatalyst prepared in this embodiment optimizes the electronic structure and improves the reaction kinetic performance.

[0041] Embodiment 2 A method for preparing a platinum-palladium-ruthenium alloy nanocatalyst, specifically comprising the following steps: (1) Carbon carrier pre-dispersion: Vulcan XC-72R is added to a 1.5 mol / L nitric acid aqueous solution for acid washing reflux at 90°C for 2 h (wherein the addition amount of Vulcan XC-72R in the nitric acid aqueous solution is 0.05 g / mL), then washed with deionized water to neutral, and vacuum dried at 80°C to obtain a carbon carrier. The carbon carrier is dispersed in a polyol solution by ultrasonic treatment at 40 kHz for 30 min (wherein the addition amount of the carbon carrier in the polyol solution is 0.05 g / mL) to obtain a uniformly dispersed carbon slurry, wherein the polyol solution is prepared by mixing ethylene glycol and glycerol in a volume ratio of 5:1.

[0042] (2) Low-temperature dropwise adsorption: H2PtCl6·6H2O, Pd(NO3)2·2H2O, and RuCl3·xH2O are used to prepare a precursor hydroalcoholic solution (the molar ratio of Pt:Pd:Ru in the precursor solution is 1:1:1, and the total addition amount of Pt, Pd, and Ru in the precursor hydroalcoholic solution is 0.05 g / mL). The precursor hydroalcoholic solution is added to the pre-dispersed carbon slurry stirred at 250 rpm at 25°C using a peristaltic pump at a dropwise addition rate of 0.5 mL / min. After the dropwise addition is completed, the stirring is continued at a speed of 250 rpm for 3 h, and then aged for 1 h. A supported precursor carbon slurry is obtained, wherein the precursor hydroalcoholic solution is added to the pre-dispersed carbon slurry in a ratio of 0.4:1 of the total mass of Pt, Pd, and Ru in the precursor aqueous solution to the mass of the carbon carrier in step (1).

[0043] (3) Microwave heating reflux reduction: the supported precursor carbon slurry is placed in a normal pressure microwave reflux system (the normal pressure microwave reflux system has a frequency of 2.45 GHz and is provided with a glass condenser), first heated to 120°C under a power of 300 W, then kept at 200 W for 20 min for microwave heating reflux reaction, and the hydroxyl radicals are released in situ by the polyhydric alcohol, and the carbon slurry containing 2-6 nm platinum-palladium-ruthenium alloy particles is obtained.

[0044] (4) Polyhydric alcohol protective layer fixation: 0.1 mol / L citric acid-sodium citrate buffer solution with a pH of 4 is added to the carbon slurry containing platinum-palladium-ruthenium alloy particles to obtain a solid-liquid mixture containing platinum-palladium-ruthenium alloy particles fixed by a polyhydric alcohol protective layer (the addition amount of the carbon slurry containing platinum-palladium-ruthenium alloy particles in the solid-liquid mixture containing platinum-palladium-ruthenium alloy particles fixed by a polyhydric alcohol protective layer is 0.02 g / mL), which prevents particle agglomeration, and the solid-liquid mixture is filtered by a glass sand core filtering device to obtain a solid substance.

[0045] (5) Redox cycle pretreatment: the solid substance is placed in a 20% hydrogen peroxide aqueous solution (the addition amount of the solid substance in the hydrogen peroxide aqueous solution is 0.04 g / mL), surface etching is performed at 50°C for 1 h, then the solid substance is filtered to obtain a filter cake, the filter cake is then placed in a normal pressure microwave reflux system, and anhydrous ethanol is added to the normal pressure microwave reflux system (the anhydrous ethanol is added to the normal pressure microwave reflux system at a solid-liquid ratio of 1 g / 50 mL), and the microwave heating reflux reduction cycle treatment is performed four times, first heated to 120°C under a power of 300 W, then kept at 200 W for 20 min, to construct a Pt-Ru-rich surface layer and reduce the CO adsorption energy, and obtain a solid substance after reduction cycle treatment.

[0046] (6) Stepwise heat treatment: the solid substance after reduction cycle treatment is vacuum dried at 60°C for 12 h, then ground to a particle size of D50≤2 μm, then placed in a tube furnace, heated to 450°C at a heating rate of 10°C / min under a mixed gas atmosphere (the mixed gas atmosphere is composed of hydrogen and argon, and the content of hydrogen is 5% by volume, and the balance is argon), and kept at 450°C for 2 h, then naturally cooled to 350°C, and then cooled to room temperature by a high-speed fan, to obtain a catalyst crude product with uniform particle size and high defect density.

[0047] (7) Post-treatment: the catalyst crude product is washed with deionized water and anhydrous ethanol three times in turn, and then vacuum dried at 60°C until the weight is constant, to obtain a platinum-palladium-ruthenium alloy nanocatalyst (PtPdRu / C-2).

[0048] Scanning transmission electron microscopy (STEM) and elemental distribution analysis were performed on the PtPdRu / C-2 prepared in this embodiment. The results showed that the platinum-palladium-ruthenium alloy nanocatalyst prepared in this embodiment has a very uniform size and is evenly distributed on the surface of the carbon support, without local aggregation or uneven distribution. This uniform size distribution helps to increase the active surface area of ​​the catalyst, thereby improving its catalytic performance. The elemental distribution diagram shows that in the platinum-palladium-ruthenium alloy nanocatalyst prepared in this embodiment, Pt, Pd, and Ru are evenly distributed to form a good alloy structure, rather than a simple physical mixture. This alloy structure helps to synergistically improve the performance of the catalyst.

[0049] The PtPdRu / C-2 prepared in this embodiment was subjected to cyclic voltammetry electrochemical testing, and the test results are as follows: Figure 3 As shown, the PtPdRu / C-2 catalyst exhibited an onset potential (V vs. SCE) of 0.25, a peak potential (V vs. SCE) of 0.52, and a peak current of 7 mA. In this embodiment, the synergistic effect of microwave heating reflux reduction and redox cycle pretreatment resulted in a platinum-palladium-ruthenium alloy nanocatalyst with small size and high specific surface area, providing numerous active sites for the catalytic reaction and lowering the activation energy, thus achieving a low onset potential and high peak current. Furthermore, the synergistic effect of the preparation process resulted in a platinum-palladium-ruthenium alloy nanocatalyst with excellent surface activity and resistance to CO poisoning, achieving high current density at low potentials, significantly improving the catalyst's catalytic activity and stability. Simultaneously, the alloying of Pt, Pd, and Ru in the platinum-palladium-ruthenium alloy nanocatalyst prepared in this embodiment optimized the electronic structure and improved reaction kinetics.

[0050] Example 3 A method for preparing a platinum-palladium-ruthenium alloy nanocatalyst specifically includes the following steps: (1) Pre-dispersion of carbon support: VulcanXC-72R was added to a 2 mol / L nitric acid aqueous solution and refluxed at 90°C for 2 h (the amount of VulcanXC-72R added to the nitric acid aqueous solution was 0.03 g / mL). After that, it was washed with deionized water until neutral and dried under vacuum at 80°C to obtain carbon support. The carbon support was placed in a polyol solution and ultrasonically dispersed at 40 kHz for 60 min (the amount of carbon support added to the polyol solution was 0.03 g / mL) to obtain a pre-dispersed uniform carbon slurry. The polyol solution was prepared in a volume ratio of ethylene glycol to glycerol of 1:1.

[0051] (2) Low-temperature dropwise adsorption: A precursor hydroalcoholic solution (the molar ratio of Pt:Pd:Ru in the precursor solution is 5:1:1, and the total addition amount of Pt, Pd and Ru in the precursor hydroalcoholic solution is 0.05 g / mL) is prepared by using H2PtCl6·6H2O, Pd(NO3)2·2H2O and RuCl3·xH2O. The precursor hydroalcoholic solution is dropwise added to the pre-dispersed carbon slurry stirred at 250 rpm at 25°C by using a peristaltic pump at a dropwise adding rate of 0.5 mL / min. After the dropwise adding is completed, the stirring is continued at a rotation speed of 250 rpm for 3 h, and then the standing and aging is performed for 1 h. Thus, a supported precursor carbon slurry is obtained. The precursor hydroalcoholic solution is dropwise added to the pre-dispersed carbon slurry according to the ratio of the total mass of Pt, Pd and Ru in the precursor aqueous solution to the mass of the carbon carrier in step (1) being 2.4:1.

[0052] (3) Microwave heating reflux reduction: The supported precursor carbon slurry is placed in an atmospheric microwave reflux system (the frequency of the atmospheric microwave reflux system is 2.45 GHz, and the atmospheric microwave reflux system is provided with a glass condenser). The microwave heating reflux reaction is performed by first heating to 180°C at a power of 300 W, and then refluxing at 200 W for 90 min. The hydroxyl radicals are released in situ by using polyhydric alcohols. Thus, a carbon slurry containing 2-6 nm platinum-palladium-ruthenium alloy particles is obtained.

[0053] (4) Polyhydric alcohol protective layer fixation: A 0.1 mol / L citric acid-sodium citrate buffer solution with a pH of 4 is added to the carbon slurry containing the platinum-palladium-ruthenium alloy particles. Thus, a solid-liquid mixture containing the platinum-palladium-ruthenium alloy particles with a polyhydric alcohol protective layer (the addition amount of the carbon slurry containing the platinum-palladium-ruthenium alloy particles with a polyhydric alcohol protective layer in the solid-liquid mixture is 0.04 g / mL) is obtained. The particle agglomeration is prevented, and the glass sand core filtering device is used to perform suction filtration on the solid-liquid mixture. Thus, a solid substance is obtained.

[0054] (5) Redox cycle pretreatment: The solid substance is placed in a 30% hydrogen peroxide aqueous solution (the addition amount of the solid substance in the hydrogen peroxide aqueous solution is 0.03 g / mL). The surface etching is performed at 50°C for 1 h. Then, the suction filtration is performed. Thus, a filter cake is obtained. Subsequently, the filter cake is placed in an atmospheric microwave reflux system, and anhydrous ethanol is added to the atmospheric microwave reflux system (the anhydrous ethanol is added to the atmospheric microwave reflux system according to the solid-liquid ratio of the solid substance and the anhydrous ethanol being 1 g / 80 mL). The microwave heating reflux reduction cycle treatment is performed four times by first heating to 180°C at a power of 300 W, and then refluxing at 200 W for 90 min. Thus, a Pt-Ru-rich surface layer is constructed, the CO adsorption energy is reduced, and a solid substance after reduction cycle treatment is obtained.

[0055] (6) Segmented heat treatment: The solid material after reduction cycle treatment is vacuum dried at 60℃ for 12h, then ground to D50 particle size ≤2μm, and then placed in a tube furnace and heated to 450℃ at a heating rate of 10℃ / min under a mixed atmosphere (the mixed atmosphere consists of hydrogen and argon, where the hydrogen content is 5% by volume and the remainder is argon) and held for 2h. Then it is naturally cooled to 350℃, and then cooled to room temperature by a high-speed fan to obtain a crude catalyst product with uniform particle size and high defect density.

[0056] (7) Post-treatment: The crude catalyst product was washed three times with deionized water and anhydrous ethanol, and then dried under vacuum at 60°C to constant weight to obtain platinum-palladium-ruthenium alloy nanocatalyst (PtPdRu / C-3).

[0057] The PtPdRu / C-3 prepared in this embodiment was subjected to cyclic voltammetry electrochemical testing, and the test results are as follows: Figure 4 As shown, the PtPdRu / C-3 catalyst exhibited an initial potential (V vs. SCE) of 0.28, a peak potential (V vs. SCE) of 0.51, and a peak current of 9.9 mA. In this embodiment, the synergistic effect of microwave heating reflux reduction and redox cycle pretreatment resulted in a platinum-palladium-ruthenium alloy nanocatalyst with small size and high specific surface area, providing numerous active sites for the catalytic reaction and lowering the activation energy, thus achieving a low initial potential and high peak current. Furthermore, the synergistic effect of the preparation process resulted in a platinum-palladium-ruthenium alloy nanocatalyst with excellent surface activity and resistance to CO poisoning, achieving high current density at low potentials, significantly improving the catalyst's catalytic activity and stability. Simultaneously, the alloying of Pt, Pd, and Ru in the platinum-palladium-ruthenium alloy nanocatalyst prepared in this embodiment optimized the electronic structure and improved reaction kinetics.

[0058] Scanning transmission electron microscopy (STEM) and elemental distribution analysis were performed on the PtPdRu / C-3 prepared in this embodiment. The results showed that the platinum-palladium-ruthenium alloy nanocatalyst prepared in this embodiment has a very uniform size and is evenly distributed on the surface of the carbon support, without local aggregation or uneven distribution. This uniform size distribution helps to increase the active surface area of ​​the catalyst, thereby improving its catalytic performance. The elemental distribution diagram shows that in the platinum-palladium-ruthenium alloy nanocatalyst prepared in this embodiment, Pt, Pd, and Ru are evenly distributed to form a good alloy structure, rather than a simple physical mixture. This alloy structure helps to synergistically improve the performance of the catalyst.

[0059] Comparative Example 1 A method for preparing a platinum-palladium-ruthenium alloy nanocatalyst specifically includes the following steps: (1) Carbon carrier pre-dispersion: Vulcan XC-72R is added to a concentrated nitric acid aqueous solution at 90°C for acid pickling reflux for 2h (wherein the addition amount of Vulcan XC-72R in the concentrated nitric acid aqueous solution is 0.02g / mL), then washed with deionized water to neutral, and dried at 80°C under vacuum to obtain a carbon carrier. The carbon carrier is dispersed in a polyol solution by ultrasonic treatment at 40kHz for 45min (wherein the addition amount of the carbon carrier in the polyol solution is 0.02g / mL), to obtain a uniformly dispersed carbon slurry. The polyol solution is prepared by mixing ethylene glycol and glycerol in a volume ratio of 2:1.

[0060] (2) Low-temperature dropwise adsorption: H2PtCl6·6H2O, Pd(NO3)2·2H2O and RuCl3·xH2O are used to prepare a precursor aqueous-alcoholic solution (the molar ratio of Pt:Pd:Ru in the precursor solution is 3:1:1, and the total addition amount of Pt, Pd and Ru in the precursor aqueous-alcoholic solution is 0.03g / mL). The precursor aqueous-alcoholic solution is added dropwise into the pre-dispersed carbon slurry stirred at 250rpm at 25°C by using a peristaltic pump at a dropwise addition rate of 0.5mL / min. After the dropwise addition is completed, the stirring is continued at a rotation speed of 250rpm for 3h, and then the mixture is left to stand for 1h to obtain a supported precursor carbon slurry. The precursor aqueous-alcoholic solution is added dropwise into the pre-dispersed carbon slurry in a ratio of 1:1 based on the total mass of Pt, Pd and Ru in the precursor aqueous solution and the mass of the carbon carrier in step (1).

[0061] (3) Microwave heating reflux reduction: The supported precursor carbon slurry is placed in an atmospheric microwave reflux system (the frequency of the atmospheric microwave reflux system is 2.45GHz, and a glass condenser tube is provided). The microwave heating reflux reaction is carried out by first heating to 150°C at a power of 300W, and then refluxing at 200W for 10min. The polyol releases hydroxyl radicals in situ. The reaction is completed to obtain a carbon slurry containing 2-6nm platinum-palladium-ruthenium alloy particles.

[0062] (4) Polyol protective layer fixation: 0.1mol / L citric acid-sodium citrate buffer solution with a pH of 4 is added to the carbon slurry containing the platinum-palladium-ruthenium alloy particles to obtain a solid-liquid mixture containing the platinum-palladium-ruthenium alloy particles with a polyol protective layer (wherein the addition amount of the carbon slurry containing the platinum-palladium-ruthenium alloy particles in the solid-liquid mixture containing the platinum-palladium-ruthenium alloy particles with a polyol protective layer is 0.03g / mL), to prevent particle agglomeration. The solid-liquid mixture is filtered by using a glass sand core filter device to obtain a solid substance.

[0063] (5) Redox cycle pretreatment: the solid substance is placed in a 10% hydrogen peroxide aqueous solution (wherein the addition amount of the solid substance in the hydrogen peroxide aqueous solution is 0.02 g / mL), surface etching is carried out at 50℃ for 1 h, then filtration is performed to obtain a filter cake, and then the filter cake is placed in an atmospheric pressure microwave reflux system, and anhydrous ethanol is added to the atmospheric pressure microwave reflux system (wherein the anhydrous ethanol is added to the atmospheric pressure microwave reflux system at a solid-liquid ratio of 1 g / 100 mL of the solid substance and the anhydrous ethanol), and the microwave heating reflux reduction cycle treatment is carried out 4 times, first at a power of 300 W to heat to 150℃, and then at a power of 200 W to heat to 150℃ for 60 min, to construct a Pt-Ru-rich surface layer and reduce the CO adsorption energy, thereby obtaining the solid substance after reduction cycle treatment.

[0064] (6) Stepwise heat treatment: the solid substance after reduction cycle treatment is vacuum dried at 60℃ for 12 h, then ground to a D50 particle size of ≤2 μm, and then placed in a tube furnace and heated to 450℃ at a heating rate of 10℃ / min under a mixed atmosphere (the mixed atmosphere is composed of hydrogen and argon, wherein the content of hydrogen is 5% by volume, and the balance is argon), and then held for 2 h, then naturally cooled to 350℃, and then cooled to room temperature by a high-speed fan, thereby obtaining a catalyst crude product.

[0065] (7) Post-treatment: the catalyst crude product is washed with deionized water and anhydrous ethanol 3 times in sequence, and then vacuum dried at 60℃ until the weight is constant, thereby obtaining a platinum-palladium-ruthenium alloy nanocatalyst (PtPdRu / C-4).

[0066] The PtPdRu / C-4 prepared in the present comparative example is subjected to electrochemical testing by cyclic voltammetry, and the test results show that the starting potential (V vs. SCE) of the PtPdRu / C-4 catalyst is 0.3, the peak potential (V vs. SCE) is 0.58, and the peak current is 6 mA. This is because, during the preparation process, the microwave heating reflux time is short (10 min), which leads to incomplete reduction of the metal precursor. Transmission electron microscopy (TEM) test results show that the size distribution of the platinum-palladium-ruthenium alloy nanocatalyst prepared in the present comparative example is not uniform, and the number of active sites is reduced. In addition, the short reduction time fails to form an optimized surface structure, which limits the activity and reaction kinetics of the catalyst in the methanol oxidation reaction. Therefore, although the composition of the catalyst is similar to that of the examples, the electrochemical performance of the catalyst is significantly reduced due to the difference in the preparation process, and the high-efficiency catalytic effect in the examples cannot be achieved.

[0067] Comparative Example 2 A method for preparing a platinum-palladium-ruthenium alloy nanocatalyst, specifically comprising the following steps: (1) Carbon carrier pre-dispersion: Vulcan XC-72R is added to a concentrated nitric acid aqueous solution at 90°C for acid pickling reflux for 2h (wherein the addition amount of Vulcan XC-72R in the concentrated nitric acid aqueous solution is 0.02g / mL), then washed with deionized water to neutral, and dried at 80°C under vacuum to obtain a carbon carrier. The carbon carrier is dispersed in a polyol solution at 40kHz for 45min (wherein the addition amount of the carbon carrier in the polyol solution is 0.02g / mL) to obtain a uniformly pre-dispersed carbon slurry, wherein the polyol solution is prepared in a volume ratio of 2:1 of ethylene glycol to glycerol.

[0068] (2) Low-temperature dropwise adsorption: H2PtCl6·6H2O, Pd(NO3)2·2H2O, and RuCl3·xH2O are used to prepare a precursor hydroalcoholic solution (the molar ratio of Pt:Pd:Ru in the precursor solution is 3:1:1, and the total addition amount of Pt, Pd, and Ru in the precursor hydroalcoholic solution is 0.03g / mL). The precursor hydroalcoholic solution is added to the pre-dispersed carbon slurry stirred at 250rpm at 25°C at a dropwise addition rate of 0.5mL / min using a peristaltic pump. After the dropwise addition is completed, the stirring is continued at a speed of 250rpm for 3h, and then left to stand for 1h to obtain a supported precursor carbon slurry, wherein the precursor hydroalcoholic solution is added to the pre-dispersed carbon slurry in a ratio of 1:1 of the total mass of Pt, Pd, and Ru in the precursor aqueous solution to the mass of the carbon carrier in step (1).

[0069] (3) Microwave heating reflux reduction: The supported precursor carbon slurry is placed in an atmospheric microwave reflux system (the atmospheric microwave reflux system has a frequency of 2.45GHz and is equipped with a glass condenser tube). The microwave heating reflux reaction is carried out by first heating to 150°C at a power of 300W, and then refluxing at 200W for 100min. The polyol releases hydroxyl radicals in situ. The reaction is completed to obtain a carbon slurry containing 2-6nm platinum-palladium-ruthenium alloy particles.

[0070] (4) Polyol protective layer fixation: 0.1mol / L citric acid-sodium citrate buffer solution with a pH of 4 is added to the carbon slurry containing platinum-palladium-ruthenium alloy particles to obtain a solid-liquid mixture containing platinum-palladium-ruthenium alloy particles with a polyol protective layer (wherein the addition amount of the carbon slurry containing platinum-palladium-ruthenium alloy particles in the solid-liquid mixture containing platinum-palladium-ruthenium alloy particles with a polyol protective layer is 0.03g / mL), which prevents particle agglomeration. The solid-liquid mixture is subjected to suction filtration using a glass sand core filter device to obtain a solid substance.

[0071] (5) Redox cycle pretreatment: the solid substance was placed in a 10% hydrogen peroxide aqueous solution (wherein the addition amount of the solid substance in the hydrogen peroxide aqueous solution was 0.02 g / mL), surface etching was performed at 50°C for 1 h, then filtration was performed to obtain a filter cake, and then the filter cake was placed in an atmospheric pressure microwave reflux system, and anhydrous ethanol was added to the atmospheric pressure microwave reflux system (wherein the anhydrous ethanol was added to the atmospheric pressure microwave reflux system at a solid-liquid ratio of 1 g / 100 mL), and then 4 cycles of microwave heating reflux reduction treatment were performed, wherein the temperature was first increased to 150°C at a power of 300 W, and then the temperature was maintained at 200 W for 60 min, to construct a Pt-Ru-rich surface layer and reduce the CO adsorption energy, thereby obtaining a solid substance after reduction cycle treatment.

[0072] (6) Stepwise heat treatment: the solid substance after reduction cycle treatment was vacuum dried at 60°C for 12 h, then ground to a D50 particle size of ≤2 μm, and then placed in a tube furnace, and then heated to 450°C at a heating rate of 10°C / min under a hydrogen and argon mixed atmosphere (the content of hydrogen in the hydrogen and argon mixed atmosphere was 5% by volume, and the balance was argon), and then maintained at 450°C for 2 h, then naturally cooled to 350°C, and then cooled to room temperature by a high-speed fan, thereby obtaining a catalyst crude product with uniform particle size and high defect density.

[0073] (7) Post-treatment: the catalyst crude product was washed with deionized water and anhydrous ethanol 3 times in sequence, and then vacuum dried at 60°C until the weight was constant, thereby obtaining a platinum-palladium-ruthenium alloy nanocatalyst (PtPdRu / C-5).

[0074] The PtPdRu / C-5 prepared in the present comparative example was subjected to electrochemical testing by cyclic voltammetry, and the test results showed that the starting potential (V vs. SCE) of the PtPdRu / C-5 catalyst was 0.32, the peak potential (V vs. SCE) was 0.6, and the peak current was 6.5 mA. This was because the microwave heating reflux time in the present comparative example was too long (100 min), which led to excessive growth and agglomeration of the nanocatalyst particles. Transmission scanning electron microscopy testing showed that the platinum-palladium-ruthenium alloy nanocatalyst prepared in the present comparative example still had uniform size distribution. However, the electrochemical testing by cyclic voltammetry showed that the exposure efficiency of the active sites was reduced. In addition, the long reduction time destroyed the optimized structure of the catalyst surface, which led to poor reaction kinetics, thereby causing the starting potential and peak potential to increase. This shows that unreasonable setting of the microwave heating time can significantly affect the performance of the catalyst, and even if the number of active sites is increased, it cannot make up for the deficiency in reaction kinetics.

[0075] Comparative Example 3 A method for preparing a platinum-palladium-ruthenium alloy nanocatalyst, specifically comprising the following steps: (1) Carbon support pre-dispersion: Vulcan XC-72R was added to a 2 mol / L nitric acid aqueous solution and acid-washed at 90°C for 2 h (wherein the addition amount of Vulcan XC-72R in the nitric acid aqueous solution was 0.03 g / mL), then washed with deionized water to neutral, and dried at 80°C under vacuum to obtain a carbon support. The carbon support was dispersed in a polyol solution by ultrasonic treatment at 40 kHz for 60 min (wherein the addition amount of the carbon support in the polyol solution was 0.03 g / mL) to obtain a uniformly dispersed carbon slurry, wherein the polyol solution was prepared by mixing ethylene glycol and glycerol at a volume ratio of 1:1.

[0076] (2) Low-temperature dropwise adsorption: A precursor aqueous-alcoholic solution was prepared by mixing H2PtCl6·6H2O, Pd(NO3)2·2H2O and RuCl3·xH2O (the molar ratio of Pt:Pd:Ru in the precursor solution was 5:1:1, and the total addition amount of Pt, Pd and Ru in the precursor aqueous-alcoholic solution was 0.05 g / mL). The precursor aqueous-alcoholic solution was added dropwise into the pre-dispersed carbon slurry stirred at 250 rpm at a rate of 0.5 mL / min at 25°C using a peristaltic pump. After the dropwise addition was completed, the stirring was continued at a speed of 250 rpm for 3 h, and then the mixture was allowed to stand for 1 h to obtain a supported precursor carbon slurry. The precursor aqueous-alcoholic solution was added dropwise into the pre-dispersed carbon slurry at a ratio of 2.4:1 based on the total mass of Pt, Pd and Ru in the precursor aqueous solution and the mass of the carbon support in step (1).

[0077] (3) Oil bath heating reflux reduction: The supported precursor carbon slurry was heated and refluxed at 150°C for 60 min under oil bath heating and condensation to obtain a carbon slurry containing platinum-palladium-ruthenium alloy particles with a size of 2-6 nm.

[0078] (4) Polyol protective layer fixation: A 0.1 mol / L citric acid-sodium citrate buffer solution with a pH of 4 was added to the carbon slurry containing the platinum-palladium-ruthenium alloy particles to obtain a solid-liquid mixture containing the platinum-palladium-ruthenium alloy particles with a polyol protective layer (wherein the addition amount of the carbon slurry containing the platinum-palladium-ruthenium alloy particles with a polyol protective layer in the solid-liquid mixture was 0.04 g / mL), which prevented particle agglomeration. The solid-liquid mixture was filtered by a glass sand core filter device to obtain a solid substance.

[0079] (5) Redox cycle pretreatment: the solid substance was placed in a 30% hydrogen peroxide aqueous solution (wherein the addition amount of the solid substance in the hydrogen peroxide aqueous solution was 0.03 g / mL), surface etching was carried out at 50°C for 1 h, then filtration was carried out to obtain a filter cake, then the filter cake was placed in an atmospheric oil bath system, and anhydrous ethanol was added to the atmospheric oil bath system at 1 g / 100 ml (wherein the anhydrous ethanol was added to the atmospheric oil bath system at a solid-liquid ratio of 1 g / 80 mL of solid substance and anhydrous ethanol), heating reflux reduction cycle treatment was carried out at 120°C for 4 times of 40 min, and the solid substance after reduction cycle treatment was obtained.

[0080] (6) Stepwise heat treatment: the solid substance after reduction cycle treatment was vacuum dried at 60°C for 12 h, then ground to a D50 particle size of ≤2 μm, then placed in a tube furnace, heated to 450°C at a heating rate of 10°C / min under a mixed gas atmosphere (the mixed gas atmosphere was composed of hydrogen and argon, wherein the content of hydrogen was 5% by volume, and the balance was argon), and kept for 2 h, then naturally cooled to 350°C, then cooled to room temperature by high-speed fan, and a catalyst crude product with uniform particle size and high defect density was obtained.

[0081] (7) Post-treatment: the catalyst crude product was washed with deionized water and anhydrous ethanol for 3 times, respectively, and then vacuum dried at 60°C to a constant weight to obtain a platinum-palladium-ruthenium alloy nanocatalyst (PtPdRu / C-6).

[0082] The PtPdRu / C-6 prepared in the present comparative example was subjected to electrochemical test by cyclic voltammetry, and the test results were as follows: Figure 5As shown, the PtPdRu / C-6 catalyst tested had a starting potential (V vs. SCE) of 0.28, a peak potential (V vs. SCE) of 0.50, and a peak current of 4.5 mA, due to the use of oil bath heating instead of microwave heating for the reflux reduction in the preparation process. Oil bath heating relies on heat conduction, resulting in uneven temperature distribution in the reaction system, and failing to achieve the rapid and uniform reduction effect of microwave heating. This uneven heating method makes the reduction reaction of metal precursors unsynchronized in space-time, resulting in a wider size distribution of nano-catalyst particles and more severe agglomeration, thereby reducing the number of effective active sites. The platinum-palladium-ruthenium alloy nano-catalyst prepared in the present comparative example was tested by scanning transmission electron microscopy and element distribution, and it was found that the platinum-palladium-ruthenium alloy nano-catalyst prepared in the present comparative example had a wide size distribution and obvious local aggregation and agglomeration. The particle morphology was irregular and the sphericity was poor; the element distribution map showed that the signal area of Pt, Pd and Ru had low overlap, and the distribution was uneven and there was obvious element segregation, which indicated that the platinum-palladium-ruthenium alloy nano-catalyst of the present comparative example failed to form a uniform ternary alloy structure, and was closer to a physical mixture or a composite with an unclear core-shell structure. In addition, the low efficiency and temperature fluctuations (±5~10℃) of oil bath heating made the precise control of redox cycles ineffective, and failed to effectively build surface active sites, further reducing the intrinsic activity and anti-poisoning ability of the catalyst. Therefore, although the starting potential and peak potential of the catalyst were low, the insufficient number of active sites and insufficient optimization of surface structure led to a significant reduction in peak current, and a substantial decline in overall catalytic performance.

[0083] Specifically, oil bath heating relies on indirect heat conduction of the reactor wall, whose heat transfer efficiency is limited by the low thermal conductivity and high viscosity characteristics of the carbon slurry system, resulting in an inevitable significant temperature gradient in the reaction liquid: the near-wall area is overheated while the center area is underheated. This non-uniform temperature field makes the reduction reaction of metal precursors asynchronous in space-time: the high-temperature area nucleates too early and too fast, triggering explosive nucleation and Ostwald ripening, while the low-temperature area nucleates late and growth is limited, ultimately causing the alloy particle size distribution to widen, the morphology to be uncontrollable, and the tendency of particle agglomeration driven by surface energy differences between particles to increase. More critically, the core of the redox cycle lies in precisely tailoring the surface atomic structure by adjusting the activation energy barrier difference between the oxidation and reduction steps: H2O2 etching requires moderate oxidation of the surface Pd and Ru atoms without damaging the Pt framework, and the subsequent ethanol reduction requires selective redeposition of Pt and Ru to enrich the surface active sites; however, the slow response characteristics and temperature fluctuations (±5-10°C) of oil bath heating make it difficult to accurately match the reaction kinetics, resulting in a loss of control over etching depth and reduction selectivity, which leads to the failure of surface element reconstruction and the inability to form a Pt-Ru-rich structure resistant to CO poisoning. In contrast, microwave-assisted bulk homogeneous heating not only creates a zero-gradient reaction field through instantaneous penetrating energy transfer, making the nucleation-growth kinetics highly synchronized at the millisecond scale, but also ensures a narrow particle distribution. Therefore, the microwave field is not only a tool to improve heat transfer efficiency, but also a core technology to achieve nanoscale kinetic regulation and selective synthesis of surface chemistry, which plays an irreplaceable decisive role in suppressing particle agglomeration, optimizing alloy structure, and improving intrinsic activity and resistance to poisoning.

[0084] Comparative Example 4 A method for preparing a platinum-palladium-ruthenium alloy nanocatalyst, specifically comprising the following steps: (1) Carbon carrier pre-dispersion: Vulcan XC-72R is added to a 1 mol / L nitric acid aqueous solution at 90°C for acid washing reflux for 2 h (wherein the addition amount of Vulcan XC-72R in the nitric acid aqueous solution is 0.02 g / mL), then washed with deionized water to neutral, and vacuum dried at 80°C to obtain a carbon carrier. The carbon carrier is dispersed in a polyol solution by ultrasonic treatment at 40 kHz for 45 min (wherein the addition amount of the carbon carrier in the polyol solution is 0.02 g / mL) to obtain a pre-dispersed uniform carbon slurry, wherein the polyol solution is prepared by mixing ethylene glycol and glycerol in a volume ratio of 2:1.

[0085] (2) Low-temperature dropwise adsorption: A precursor hydroalcoholic solution (the molar ratio of Pt:Pd:Ru in the precursor solution is 3:1:1, and the total addition amount of Pt, Pd and Ru in the precursor hydroalcoholic solution is 0.03 g / mL) is prepared by using H2PtCl6·6H2O, Pd(NO3)2·2H2O and RuCl3·xH2O. The precursor hydroalcoholic solution is dropwise added to the pre-dispersed carbon slurry stirred at 250 rpm at 25°C by using a peristaltic pump at a dropwise adding rate of 0.5 mL / min. After the dropwise adding is completed, the stirring is continued at a rotation speed of 250 rpm for 3 h, and then the standing and aging is performed for 1 h. Thus, a supported precursor carbon slurry is obtained. The precursor hydroalcoholic solution is dropwise added to the pre-dispersed carbon slurry according to the ratio of 1:1 between the total mass of Pt, Pd and Ru in the precursor aqueous solution and the mass of the carbon carrier in step (1).

[0086] (3) Microwave heating reflux reduction: The supported precursor carbon slurry is placed in an atmospheric microwave reflux system (the frequency of the atmospheric microwave reflux system is 2.45 GHz, and the system is provided with a glass condenser). The microwave heating reflux reaction is performed by first heating to 150°C at a power of 300 W, and then refluxing at 200 W for 60 min. The hydroxyl radicals are released in situ by using polyhydric alcohols. Thus, a carbon slurry containing 2-6 nm platinum-palladium-ruthenium alloy particles is obtained.

[0087] (4) Polyhydric alcohol protective layer fixation: A 0.1 mol / L citric acid-sodium citrate buffer solution with a pH of 4 is added to the carbon slurry containing the platinum-palladium-ruthenium alloy particles. Thus, a solid-liquid mixture containing the platinum-palladium-ruthenium alloy particles with a polyhydric alcohol protective layer (the addition amount of the carbon slurry containing the platinum-palladium-ruthenium alloy particles with a polyhydric alcohol protective layer in the solid-liquid mixture is 0.03 g / mL) is obtained. The particle agglomeration is prevented, and the glass sand core filtering device is used to perform suction filtration on the solid-liquid mixture. Thus, a solid substance is obtained.

[0088] (5) Stepwise heat treatment: The solid substance is vacuum dried at 60°C for 12 h, and then ground to a D50 particle size of ≤2 μm. Subsequently, the solid substance is placed in a tube furnace, heated to 450°C at a heating rate of 10°C / min under a mixed atmosphere (the mixed atmosphere is composed of hydrogen and argon, and the content of hydrogen is 5% by volume, and the balance is argon), and then kept at 450°C for 2 h. Subsequently, the natural cooling is performed to 350°C, and then the high-speed fan air cooling is performed to room temperature. Thus, a catalyst crude product is obtained.

[0089] (6) Post-treatment: The catalyst crude product is sequentially washed with deionized water and anhydrous ethanol for 3 times, and then vacuum dried at 60°C to a constant weight. Thus, a platinum-palladium-ruthenium alloy nanocatalyst (PtPdRu / C-7) is obtained.

[0090] The PtPdRu / C-7 prepared in the present comparative example was subjected to electrochemical test by cyclic voltammetry, and the test results showed that the starting potential (V vs. SCE) of the PtPdRu / C-7 catalyst was 0.29, the peak potential (V vs. SCE) was 0.55, and the peak current was 5.5 mA. These electrochemical data directly reflect the performance of the catalyst in the methanol oxidation reaction. Higher starting potential and peak potential indicate that the catalyst needs a higher potential to start the reaction and reach the maximum current density, which is mainly due to the omission of the redox cycle pretreatment step, resulting in the failure to form an optimized Pt-Ru-rich active layer on the surface of the catalyst, insufficient number of active sites and uneven distribution, which increases the activation energy of the reaction. Lower peak current further indicates that the catalyst has lower catalytic efficiency in the methanol oxidation process, and the utilization efficiency of the active sites is not high, indicating that the surface structure and reaction kinetics of the catalyst have not been fully optimized. Transmission scanning electron microscopy and element distribution test were performed on the platinum-palladium-ruthenium alloy nanocatalyst prepared in the present comparative example. The transmission scanning electron microscopy test showed that the surface of the platinum-palladium-ruthenium alloy nanocatalyst prepared in the present comparative example was smooth and lacked high-density defect structures. The element distribution test results showed that although the Pt, Pd and Ru elements overlapped in the particle interior, the signal intensity of the Ru element in the surface layer region was significantly weaker than that of Pt and Pd, which indicated that the platinum-palladium-ruthenium alloy nanocatalyst prepared in the present comparative example failed to achieve preferential reconstruction of elements on the surface, and the Ru element failed to effectively enrich on the surface to play its key role in resisting CO poisoning.

[0091] The above has described various embodiments of the present application, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes are obvious to those skilled in the art without departing from the scope and spirit of the described embodiments. The selection of terms used herein is intended to best explain the principles, practical applications, or improvements to the technology in the market of the embodiments, or to enable other ordinary skilled persons in the art to understand the embodiments disclosed herein.

Claims

1. A method for preparing a platinum-palladium-ruthenium alloy nanocatalyst, characterized in that, Specifically, the following steps are included: (1) Carbon support pre-dispersion: The conductive carbon black material is added to the nitric acid aqueous solution, acid washed and heated under reflux, then washed and dried to obtain the carbon support. The carbon support is placed in a polyol solution and ultrasonically dispersed to obtain the pre-dispersion carbon slurry. (2) Low-temperature dropwise adsorption: Prepare a precursor aqueous alcohol solution, add the precursor aqueous alcohol solution dropwise to a pre-dispersed carbon slurry under stirring, and continue stirring and aging after the dropwise addition is completed to obtain a supported precursor carbon slurry; (3) Microwave heating reflux reduction: The supported precursor carbon paste is placed in an atmospheric pressure microwave reflux system for microwave heating reflux reaction. After the reaction is completed, carbon paste containing platinum palladium ruthenium alloy particles is obtained. (4) Polyol protective layer fixation: A crosslinking agent is added to the carbon slurry containing platinum-palladium-ruthenium alloy particles to obtain a solid-liquid mixture of platinum-palladium-ruthenium alloy particles with a polyol protective layer fixation. The solid-liquid mixture is then filtered to obtain a solid substance. (5) Redox cycle pretreatment: The solid material is placed in an oxidizing liquid for surface etching, then filtered to obtain a filter cake. The filter cake is placed in an atmospheric pressure microwave reflux system, and an organic solvent is added to the atmospheric pressure microwave reflux system. Multiple microwave heating reflux reduction cycle treatments are performed to obtain the solid material after reduction cycle treatment. (6) Segmented heat treatment: The solid material after reduction cycle treatment is dried and ground, and then placed in a heating device for segmented heat treatment under a mixed atmosphere. After cooling, the crude catalyst product is obtained. (7) Post-processing: The crude catalyst product is washed and dried to obtain platinum-palladium-ruthenium alloy nanocatalyst.

2. The preparation method of the platinum-palladium-ruthenium alloy nanocatalyst according to claim 1, characterized in that, In step (1), the amount of conductive carbon black material added to the nitric acid aqueous solution is 0.02~0.05 g / mL; the conditions for acid washing and reflux are: using a nitric acid aqueous solution with a concentration of 1~2 mol / L, refluxing at 90℃ for 2 h; the polyol solution is a mixed solution prepared with a volume ratio of ethylene glycol and glycerol of (1~5):1; the amount of carbon support added to the polyol solution is 0.02~0.05 g / mL; the conditions for ultrasonic dispersion are: ultrasonic dispersion at a frequency of 40 kHz for 30~60 min.

3. The preparation method of the platinum-palladium-ruthenium alloy nanocatalyst according to claim 1, characterized in that, In step (2), the precursor aqueous alcohol solution is prepared using H2PtCl6·6H2O, Pd(NO3)2·2H2O, and RuCl3·xH2O, wherein the molar ratio of Pt:Pd:Ru is (1~5):1:1, and the total amount of Pt, Pd, and Ru added to the precursor aqueous alcohol solution is 0.02~0.05 g / mL; the dropping rate of the precursor aqueous alcohol solution added to the pre-dispersed carbon slurry under stirring is 0.5 mL / min; the precursor aqueous alcohol solution is added to the pre-dispersed carbon slurry according to the ratio of the total mass of Pt, Pd, and Ru in the precursor aqueous solution to the mass ratio of the carbon carrier in step (1) is (0.4~2.4):

1.

4. The preparation method of the platinum-palladium-ruthenium alloy nanocatalyst according to claim 1, characterized in that, The stirring time after the addition in step (2) is 3 hours; the aging time is 1 hour.

5. The preparation method of the platinum-palladium-ruthenium alloy nanocatalyst according to claim 1, characterized in that, The conditions for microwave heating reflux reaction in step (3) are as follows: heat to 120~180℃ with a power of 300W, and then reduce the power to 200W and keep reflux for 20~90min.

6. The method for preparing the platinum-palladium-ruthenium alloy nanocatalyst according to claim 1, characterized in that, In step (4), the crosslinking agent is a 0.1 mol / L citrate-sodium citrate buffer solution with a pH of 4; the amount of carbon paste containing platinum-palladium-ruthenium alloy particles added to the solid-liquid mixture of platinum-palladium-ruthenium alloy particles containing a polyol protective layer is 0.02~0.04 g / mL.

7. The method for preparing the platinum-palladium-ruthenium alloy nanocatalyst according to claim 1, characterized in that, In step (5), the oxidizing solution is an aqueous H2O2 solution with a mass percentage concentration of 10-30%; the amount of solid material added to the oxidizing solution is 0.02-0.04 g / mL; the surface etching conditions are: surface etching at 50℃ for 1 h; the organic solvent is added to the atmospheric pressure microwave reflux system at a solid-liquid ratio of 1 g / (50-100) mL; the microwave heating reflux reduction cycle treatment conditions are: heating to 120-180℃ at 300W power, and then holding at 200W power for 10-40 min; the microwave heating reflux reduction cycle treatment is performed 4 times.

8. The method for preparing the platinum-palladium-ruthenium alloy nanocatalyst according to claim 1, characterized in that, In step (6), the mixed atmosphere is a mixture of hydrogen and argon, wherein the hydrogen content is 5% by volume and the remainder is argon; the conditions for the segmented heat treatment are: under the condition that the flow rate of the mixed atmosphere is 100 mL / min, the temperature is raised to 450℃ at a heating rate of 10℃ / min and held for 2 hours.

9. The platinum-palladium-ruthenium alloy nanocatalyst prepared by the method according to any one of claims 1 to 8.

10. The application of the platinum-palladium-ruthenium alloy nanocatalyst according to claim 9 in the catalytic electrochemical oxidation reaction of methanol.

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