A platinum-germanium based intermetallic ordered alloy catalyst, its preparation method and application

Abstract

This invention relates to the field of multi-metal alloy catalyst technology, specifically to a platinum-germanium-based intermetallic ordered alloy, its preparation method, and its application. The specific preparation method includes the following steps: mixing a platinum source, a germanium-containing metal source, a reducing agent, a surfactant, and a first organic solvent for a liquid-phase reaction to obtain a colloidal dispersion; mixing the colloidal dispersion with an alcohol solution and centrifuging to obtain a platinum-germanium-based alloy; and ultrasonically loading the platinum-germanium-based alloy and carbon black in a second organic solvent, followed by annealing to obtain a platinum-germanium-based intermetallic ordered alloy with a dendritic morphology. This invention, by introducing a germanium-containing metal source and synthesizing a platinum-germanium-based intermetallic ordered alloy through liquid-phase synthesis and low-temperature annealing, is beneficial for fuel cell electrocatalysis. It solves the problem that traditional high-temperature annealing methods, when preparing platinum-based ordered alloy catalysts, easily lead to catalyst particle agglomeration and size increase, reducing specific surface area and the number of active sites, thus affecting catalytic activity.

Description

Technical Field

[0001] This invention relates to the field of multi-metal alloy catalyst technology, specifically to a platinum-germanium based intermetallic ordered alloy catalyst, its preparation method, and its application. Background Technology

[0002] Fuel cells, as energy conversion devices with advantages such as high efficiency, environmental friendliness, and wide applicability, play a crucial role in promoting the green development of energy. However, in formic acid / alcohol fuel cells, the oxidation reaction at the anode currently faces two major challenges: a lack of highly active and durable anode catalysts. The performance of the anode catalyst directly affects the energy conversion efficiency and lifespan of the fuel cell, and these two problems severely restrict the commercialization and large-scale application of formic acid / alcohol fuel cells.

[0003] Although pure platinum catalysts are widely used in small molecule oxidation reactions, they exhibit insufficient activity, poor stability, and poor durability in the anodic oxidation reaction of formic acid / alcohol fuel cells, hindering their further utilization.

[0004] Research has revealed a synergistic effect between platinum and other non-precious metals. Based on this discovery, forming intermetallic compounds (Pt-M alloys) with platinum or one or more metals is an effective strategy to further advance fuel cell development. Compared to pure Pt catalysts, Pt-M alloy catalysts have achieved significant improvements in catalytic performance, substantially increasing mass activity. However, in the acidic environment typically found in fuel cells, the disordered atomic arrangement of Pt-M alloys leads to poor stability. Metal atoms are easily etched by the acidic medium, and as the reaction proceeds, metal atoms are continuously lost, further causing the collapse of the Pt-M alloy catalyst framework. This results in a rapid decline in the catalytic activity of the Pt-M alloy catalyst, severely impacting the long-term stable operation of the fuel cell.

[0005] To overcome the stability issues of Pt-M alloys with disordered atomic arrangements, platinum-based ordered alloy catalysts with ordered structures have been extensively studied. These catalysts, due to their unique atomic arrangement, exhibit excellent initial properties, oxidation resistance, and stability under acidic conditions, and are considered highly efficient catalysts beneficial for fuel cell development. High-temperature annealing is a commonly used method in the preparation of platinum-based ordered alloy catalysts. High-temperature annealing can promote the rearrangement of disordered Pt-M atoms; however, traditional high-temperature annealing methods often lead to particle agglomeration and coarse particle size in platinum-based alloy catalysts due to excessively high annealing temperatures, reducing specific surface area and the number of active sites, thus affecting the catalytic activity of the platinum-based alloy catalyst. Summary of the Invention

[0006] To address the problem that traditional high-temperature annealing methods for preparing platinum-based ordered alloy catalysts often lead to catalyst particle agglomeration and increased size, reducing specific surface area and the number of active sites, thus affecting catalytic activity, this invention provides a platinum-germanium-based intermetallic ordered alloy catalyst, its preparation method, and its application.

[0007] This invention introduces a germanium-containing metal source containing quasi-metallic germanium elements and synthesizes platinum-germanium-based intermetallic ordered alloys through liquid-phase synthesis and low-temperature annealing. This breaks the temperature limitation in the synthesis of platinum-based intermetallic compounds, which is beneficial for fuel cell electrocatalysis and improves catalytic activity.

[0008] To achieve the above objectives, the technical solution of the present invention is as follows.

[0009] The first aspect of this invention provides a method for preparing a platinum-germanium based intermetallic ordered alloy catalyst, comprising the following steps:

[0010] A precursor dispersion is obtained by mixing a platinum source, a germanium-containing metal source, a reducing agent, a surfactant, and a first organic solvent. A liquid-phase reaction is then carried out at 220℃±10℃ to obtain a colloidal dispersion. The germanium-containing metal source is a germanium source, or a mixture of a germanium source and an auxiliary metal source. The colloidal dispersion is mixed with an alcohol solution and centrifuged to obtain a platinum-germanium-based alloy. The platinum-germanium-based alloy and carbon black are subjected to ultrasonic carbon loading in a second organic solvent to obtain a carbon-loaded platinum-germanium-based alloy. The carbon-loaded platinum-germanium-based alloy is annealed at 400℃~500℃ to obtain a platinum-germanium-based intermetallic ordered alloy catalyst with a dendritic morphology.

[0011] Preferably, the platinum source is at least one of platinum acetylacetonate, chloroplatinic acid, and potassium chloroplatinate; the germanium source is germanium tetrachloride and / or germanium oxide; and the auxiliary metal source is at least one of copper, nickel, and iron.

[0012] Preferably, the copper source is copper acetylacetonate and / or copper chloride; the nickel source is nickel acetylacetonate and / or nickel chloride; and the iron source is iron acetylacetonate and / or ferric chloride.

[0013] Preferably, the reducing agent is at least one selected from glucose, citric acid, and ascorbic acid; the surfactant is a quaternary ammonium salt and / or a halide salt. For example, the quaternary ammonium salt is hexadecyltrimethylammonium chloride, and the halide salt is ammonium bromide.

[0014] Preferably, the first organic solvent is at least one of oleylamine, octadecene, ethylene glycol and benzyl alcohol; the alcohol solution is a cyclohexane-ethanol solution, and the volume ratio of cyclohexane to ethanol is 2:1; the second organic solvent is cyclohexane.

[0015] The present invention selects oleylamine, octadecene, ethylene glycol or benzyl alcohol as the first organic solvent, mainly for dissolving platinum source, germanium-containing metal source, reducing agent and surfactant to form a uniform colloidal precursor dispersion.

[0016] Preferably, when the germanium-containing metal source is a germanium source, the concentration of the platinum source in the precursor dispersion is 1 mg / mL to 2 mg / mL, the concentration of the germanium source is 0.4 μL / mL to 2 μL / mL, the concentration of the reducing agent is 5 mg / mL to 7 mg / mL, and the concentration of the surfactant is 5 mg / mL to 7 mg / mL.

[0017] Alternatively, when the germanium-containing metal source is a mixture of a germanium source and an auxiliary metal source, the concentration of the platinum source in the precursor dispersion is 1 mg / mL to 2 mg / mL, the concentration of the germanium source is 0.4 μL / mL to 2 μL / mL, the concentration of each auxiliary metal source is 0.5 mg / mL to 2 mg / mL, the concentration of the reducing agent is 5 mg / mL to 7 mg / mL, and the concentration of the surfactant is 5 mg / mL to 7 mg / mL.

[0018] Within the above concentration range, a uniform gel-like precursor dispersion can be formed. Through liquid-phase synthesis and low-temperature annealing, a platinum-germanium-based intermetallic ordered alloy catalyst with a dendritic morphology is synthesized.

[0019] Preferably, the volume ratio of the colloidal dispersion to the alcohol solution is 1:8 to 10; the mass ratio of the platinum-germanium alloy to the carbon black is 3:5; the annealing treatment is carried out under a hydrogen-argon mixture, with hydrogen accounting for 5% of the volume percentage of the hydrogen-argon mixture, and the annealing time is 1 to 4 hours.

[0020] In this invention, the time for introducing a 5% hydrogen-argon mixture is 15 min to 60 min.

[0021] In this invention, the cyclohexane-ethanol solution serves to separate the precipitated products. The centrifugation speed is preferably 8000 r / min to 9500 r / min, more preferably 9000 r / min, and the centrifugation time is preferably 3 min to 5 min.

[0022] Preferably, the centrifugation process also includes washing, and the washing solution is preferably a mixed solution of cyclohexane and ethanol, wherein the volume ratio of cyclohexane to ethanol in the mixed solution is preferably 1:1 to 3, more preferably 1:3; and the washing is preferably performed 2 to 3 times.

[0023] Preferably, the liquid phase reaction time for preparing the colloidal dispersion is 20 min to 120 min. In the reaction process for preparing the colloidal dispersion, the present invention involves chemical nucleation growth to obtain a colloidal dispersion containing dendritic intermetallic nanoproducts.

[0024] Preferably, the mixing method is ultrasonic stirring, wherein the ultrasonic power of the ultrasonic stirring is preferably 50W to 100W, and can be 60W, 70W, 80W or 90W, and the time is preferably 20min to 60min, and can be 30min, 40min or 50min.

[0025] Preferably, the method for ultrasonically loading platinum-germanium-based alloys and carbon black in a second organic solvent is as follows:

[0026] The platinum-germanium alloy and carbon black were uniformly dispersed in a second organic solvent to obtain a platinum-germanium alloy-carbon black dispersion. An alcohol solution was added to the platinum-germanium alloy-carbon black dispersion, followed by centrifugation to obtain a carbon-loaded platinum-germanium alloy.

[0027] Preferably, in the platinum-germanium alloy-carbon black dispersion, the concentration of carbon black is 0.25 mg / mL to 1 mg / mL; and the concentration of platinum-germanium alloy is 1.8 mg / mL.

[0028] The second aspect of the present invention provides a platinum-germanium-based intermetallic ordered alloy catalyst, which is prepared by the method described in the first aspect of the present invention; the platinum-germanium-based intermetallic ordered alloy catalyst of the present invention has a dendritic morphology.

[0029] Preferably, the dendrite diameter of the platinum-germanium based intermetallic ordered alloy catalyst is 18 nm to 72 nm.

[0030] Preferably, when the germanium-containing metal source is a germanium source, the molar percentage of platinum in the platinum-germanium based intermetallic ordered alloy catalyst is 57.69%, the molar percentage of germanium is 42.31%, and the total is 100%.

[0031] Alternatively, when the germanium-containing metal source is a mixture of a germanium source and an auxiliary metal source, the molar percentage of platinum in the platinum-germanium based intermetallic ordered alloy catalyst is 82.81%, the molar percentage of germanium is 11.46%, and the remainder is auxiliary metal elements, totaling 100%.

[0032] The third aspect of this invention provides the application of a platinum-germanium-based intermetallic ordered alloy catalyst in the preparation of a fuel cell membrane electrode, wherein the platinum-germanium-based intermetallic ordered alloy catalyst is the platinum-germanium-based intermetallic ordered alloy catalyst described in the second aspect, and the fuel cell is a formic acid / alcohol fuel cell.

[0033] The platinum-germanium based intermetallic ordered alloy catalyst of the present invention exhibits excellent electrocatalytic performance when applied to fuel cells.

[0034] Preferably, the platinum-germanium-based intermetallic ordered alloy catalyst of the present invention can be used to catalyze the oxidation of formic acid or alcohols; wherein the alcohol is methanol and / or ethanol.

[0035] The beneficial effects of this invention are:

[0036] 1. This invention introduces a germanium-containing metal source containing quasi-metallic germanium elements, and synthesizes a platinum-germanium-based intermetallic ordered alloy catalyst through liquid-phase synthesis and low-temperature annealing. This breaks the temperature limitation in the synthesis of platinum-based intermetallic compounds, which is beneficial to the electrocatalysis of fuel cells and improves catalytic activity.

[0037] 2. The preparation conditions of the present invention are relatively mild and the operation is simple, which effectively avoids the problems of catalyst particle agglomeration and size increase caused by high-temperature calcination and transformation into an ordered phase, which reduces the specific surface area and the number of active sites and affects the catalytic activity.

[0038] 3. The platinum-germanium based intermetallic ordered alloy catalyst prepared by this invention not only has the structural characteristics of special high-activity sites, but also combines the unique electronic structure regulation advantages of intermetallic ordered structure, which makes it exhibit excellent electrocatalytic performance, including formic acid oxidation electrocatalytic performance and methanol or ethanol oxidation electrocatalytic performance. Attached Figure Description

[0039] Figure 1 Transmission electron microscopy (TEM) image of the dendritic binary platinum-germanium alloy prepared in Example 1.

[0040] Figure 2 Transmission electron microscopy (TEM) image of the platinum-germanium-based intermetallic ordered alloy catalyst prepared in Example 1.

[0041] Figure 3 The X-ray diffraction pattern of the platinum-germanium based intermetallic ordered alloy catalyst prepared in Example 1 is shown.

[0042] Figure 4 This is a comparison of the methanol oxidation activities of the platinum-germanium-based intermetallic ordered alloy catalysts prepared in Examples 1 and 2, the carbon-supported binary platinum-germanium alloy, and the commercial Pt / C catalyst under acidic conditions. In this comparison, 20% Pt / C represents the commercial Pt / C catalyst; the Pt-Ge binary alloy represents the carbon-supported binary platinum-germanium alloy; the annealed Pt-Ge alloy represents the platinum-germanium-based intermetallic ordered alloy catalyst of Example 1 after annealing at 400°C; the annealed Pt-Ge-Cu alloy represents the platinum-germanium-based intermetallic ordered alloy catalyst of Example 2 after annealing at 400°C; and the annealed Pt-Ge-Fe alloy represents the platinum-germanium-based intermetallic ordered alloy catalyst of Example 3 after annealing at 500°C.

[0043] Figure 5The figures show a comparison of the stability of the platinum-germanium-based intermetallic ordered alloy catalysts prepared in Examples 1 and 2, the carbon-supported binary platinum-germanium alloys, and the commercial Pt / C catalyst under acidic conditions for methanol oxidation. In the figures, 20% Pt / C represents the commercial Pt / C catalyst; Pt-Ge binary alloy represents the carbon-supported binary platinum-germanium alloy; annealed Pt-Ge alloy represents the platinum-germanium-based intermetallic ordered alloy catalyst of Example 1 after annealing at 400℃; annealed Pt-Ge-Cu alloy represents the platinum-germanium-based intermetallic ordered alloy catalyst of Example 2 after annealing at 400℃; and annealed Pt-Ge-Fe alloy represents the platinum-germanium-based intermetallic ordered alloy catalyst of Example 3 after annealing at 500℃.

[0044] Figure 6 The XRD patterns are of platinum-germanium alloys annealed at 400℃ and 600℃. Detailed Implementation

[0045] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0046] Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0047] In this invention, the platinum-germanium-based intermetallic ordered alloy catalyst possesses an intermetallic structure and a dendritic morphology, with the dendrite diameter ranging from 18 nm to 72 nm. The platinum-germanium-based intermetallic ordered alloy catalyst constructed in this invention is a multi-element intermetallic ordered nanosheet material with a nanosheet thickness at the nanoscale, exhibiting high activity and high stability.

[0048] Solid-state reaction is a method for synthesizing ordered nanoparticles using solid-state reactions at high temperatures. High temperatures enhance atomic mobility, facilitating the ordered arrangement of atoms within crystals. Generally, temperatures above 500℃ are required to achieve this ordered atomic arrangement. Due to the small size and high surface free energy of nanoparticles, temperatures above 500℃ promote Ostwald ripening and agglomeration, leading to increased nanoparticle size and uneven size distribution. However, for platinum-based alloy catalysts, particle agglomeration and coarse particle size reduce specific surface area and the number of active sites, thus affecting the catalytic activity of the platinum-based alloy catalyst. Figure 6 With Bragg's equation:

[0049] nλ =2dsinθ; where, n Represents the diffraction series; λd represents the X-ray wavelength; d represents the interplanar spacing; θ represents the Bragg angle.

[0050] Figure 6 These are XRD patterns of platinum-germanium alloys annealed at 400℃ and 600℃. The 600℃ annealed platinum-germanium alloy indicates the alloy annealed at 600℃; the 400℃ annealed platinum-germanium alloy indicates the alloy annealed at 400℃. Figure 6 As shown, the 2θ position of most diffraction peaks remains unchanged at both temperatures. According to Bragg's equation, if θ and λ remain constant, then d also remains constant, indicating that the main phase structure is unchanged. After heating to 600℃, some diffraction peaks, such as those near 40° and 45°, show significant enhancement. According to Bragg's equation, although d and θ remain unchanged, the increased peak intensity indicates that more grains satisfy the Bragg condition at higher temperatures, leading to increased material crystallinity and grain size. After heating to 600℃, some main peaks become sharper, and the full width at half maximum (FWHM) decreases, suggesting that the grain size may increase or the lattice distortion may decrease.

[0051] Based on this, the present invention introduces germanium, a metal quasi-metal, which exhibits metallic properties on the surface but displays both metallic and non-metallic properties in its chemical properties. By utilizing the duality of germanium, the reaction energy barrier is further reduced.

[0052] This invention also introduces abundant transition metal elements such as iron, nickel, and copper, which are not only inexpensive but can also reduce the energy required for the reaction in specific reaction steps. Combining these metal elements with the noble metal Pt forms a Pt-based multi-element alloy catalyst, which can exert a synergistic effect among multiple elements and improve catalytic performance.

[0053] The microstructure of the platinum-germanium intermetallic ordered alloy catalyst prepared by this invention is controllable, which is of great significance in the research of intermetallic ordered alloys. The preparation method provided by this invention is simple, feasible, and easy to scale up.

[0054] In the following embodiments, the carbon-loaded binary platinum-germanium alloy is annealed after drying. The drying temperature is preferably 15°C to 30°C, more preferably 20°C; the drying time is preferably 12h to 36h, more preferably 24h.

[0055] The technical solution of the present invention will be further described below through specific embodiments.

[0056] In the following embodiments, unless otherwise specified, the methods described are conventional methods; and unless otherwise specified, the reagents and materials described are commercially available.

[0057] Example 1

[0058] A method for preparing a platinum-germanium based intermetallic ordered alloy catalyst includes the following steps:

[0059] Step 1: Platinum acetylacetonate, germanium chloride, glucose, and hexadecyltrimethylammonium chloride were dissolved in oleylamine solvent at concentrations of 2 mg / mL, 0.6 μL / mL, 6 mg / mL, and 6 mg / mL, respectively. The solutions were sonicated for 50 min at a power of 100 W to obtain a pale yellow, uniform, gel-like precursor dispersion. The precursor dispersion was transferred to an oil bath and heated to 220°C. The reaction was then carried out at 220°C ± 10°C for 30 min, followed by a 30 min holding period, after which heating was stopped. After cooling to room temperature, a black gel-like dispersion was formed.

[0060] Step 2: Add 40 mL of cyclohexane-ethanol mixed solution to 5 mL of black colloidal dispersion, where the volume ratio of cyclohexane to ethanol is 2:1. Then centrifuge at 9000 r / min for 5 min, and then wash twice with cyclohexane-ethanol mixed solution, where the volume ratio of cyclohexane to ethanol is 1:3, to obtain a dendritic binary platinum-germanium alloy with an average diameter of 46 nm, where the molar ratio of Pt to Ge is 58:42.

[0061] Step 3: Disperse 5 mg of carbon black XC-72R in 10 mL of cyclohexane and sonicate for 10 min at a power of 100 W until uniformly dispersed to obtain a carbon black solution. Disperse 3 mg of the binary platinum-germanium alloy from Step 2 in 6 mL of cyclohexane and sonicate for 1 min at a power of 100 W until uniformly dispersed to obtain a binary platinum-germanium alloy dispersion. Add the binary platinum-germanium alloy dispersion to the carbon black solution and continue sonicating for 60 min at a power of 100 W to obtain a black cyclohexane dispersion.

[0062] Add 30 mL of cyclohexane-ethanol mixed solution to the black cyclohexane dispersion, wherein the volume ratio of cyclohexane to ethanol is 2:1. Then centrifuge at 9000 r / min for 4 min and dry to obtain carbon-loaded binary platinum-germanium alloy.

[0063] Step 4: The carbon-loaded binary platinum-germanium alloy is placed in a square ceramic boat with dimensions of 20mm × 20mm × 17mm. After passing a 5% hydrogen-argon mixture for 30 minutes, heating begins at a rate of 5℃ / min to 400℃. After holding at this temperature for 2 hours, the mixture is allowed to cool naturally to obtain a platinum-germanium based intermetallic ordered alloy catalyst.

[0064] Example 2

[0065] A method for preparing a platinum-germanium based intermetallic ordered alloy catalyst includes the following steps:

[0066] Step 1: Platinum acetylacetonate, copper acetylacetonate, germanium chloride, glucose, and hexadecyltrimethylammonium chloride were dissolved in oleylamine solvent at concentrations of 2 mg / mL, 0.6 mg / mL, 0.6 μL / mL, 6 mg / mL, and 6 mg / mL, respectively. The solutions were sonicated for 50 min at a power of 100 W to obtain a uniform yellow gel-like precursor dispersion. The precursor dispersion was transferred to an oil bath and heated to 220°C. The reaction was carried out at 220°C for 30 min, followed by a 30 min holding period. Heating was then stopped, and the mixture was allowed to cool to room temperature to form a black gel-like dispersion.

[0067] Step 2: Add 40 mL of cyclohexane-ethanol mixed solution to 5 mL of black colloidal dispersion, where the volume ratio of cyclohexane to ethanol is 2:1. Then centrifuge at 9000 r / min for 5 min, and then wash twice with cyclohexane-ethanol mixed solution, where the volume ratio of cyclohexane to ethanol is 1:3, to obtain a dendritic ternary platinum-germanium-copper alloy with an average diameter of 37.95 nm, where the molar ratio of Pt, Ge, and Cu is 83:11:6.

[0068] Step 3: Disperse 5 mg of carbon black XC-72R in 10 mL of cyclohexane and sonicate for 10 min at a power of 100 W until uniformly dispersed to obtain a carbon black solution. Disperse 3 mg of the ternary platinum-germanium-copper alloy from Step 2 in 6 mL of cyclohexane and sonicate for 1 min at a power of 100 W until uniformly dispersed to obtain a ternary platinum-germanium alloy dispersion. Add the ternary platinum-germanium alloy dispersion to the carbon black solution and continue sonicating for 60 min at a power of 100 W to obtain a black cyclohexane dispersion.

[0069] Add 30 mL of cyclohexane-ethanol mixed solution to the black cyclohexane dispersion, wherein the volume ratio of cyclohexane to ethanol is 2:1. Then centrifuge at 9000 r / min for 4 min and dry to obtain carbon-loaded ternary platinum-germanium alloy.

[0070] Step 4: Place the carbon-loaded ternary platinum-germanium alloy into a square ceramic boat with dimensions of 20mm × 20mm × 17mm. After passing a 5% hydrogen-argon mixture for 30 minutes, heating begins at a rate of 5℃ / min to 400℃. After holding at this temperature for 2 hours, the mixture is allowed to cool naturally to obtain a platinum-germanium based intermetallic ordered alloy catalyst.

[0071] Example 3

[0072] A method for preparing a platinum-germanium-iron intermetallic ordered alloy catalyst includes the following steps:

[0073] Step 1: Platinum acetylacetone, iron acetylacetone, germanium chloride, glucose, and ammonium bromide were dissolved in oleylamine solvent at concentrations of 2 mg / mL, 0.6 mg / mL, 0.6 μL / mL, 6 mg / mL, and 6 mg / mL, respectively. The solutions were sonicated for 50 min at a power of 100 W to obtain a uniform yellow gel-like precursor dispersion. The precursor dispersion was then transferred to an oil bath and heated to 220°C. The reaction was carried out at 220°C for 30 min, followed by a 30 min holding period. Heating was then stopped, and the mixture was allowed to cool to room temperature to form a black gel-like dispersion.

[0074] Step 2: Add 40 mL of cyclohexane-ethanol mixed solution to 5 mL of black colloidal dispersion, where the volume ratio of cyclohexane to ethanol is 2:1. Then centrifuge at 9000 r / min for 5 min, and then wash twice with cyclohexane-ethanol mixed solution, where the volume ratio of cyclohexane to ethanol is 1:3, to obtain a dendritic ternary platinum-germanium-iron alloy with an average diameter of 37.95 nm, wherein the molar ratio of Pt, Ge, and Fe is 83:11:6.

[0075] Step 3: Disperse 5 mg of carbon black XC-72R in 10 mL of cyclohexane and sonicate for 10 min at a power of 100 W until uniformly dispersed to obtain a carbon black solution. Disperse 3 mg of the ternary platinum-germanium-iron alloy from Step 2 in 6 mL of cyclohexane and sonicate for 1 min at a power of 100 W until uniformly dispersed to obtain a ternary platinum-germanium alloy dispersion. Add the ternary platinum-germanium alloy dispersion to the carbon black solution and continue sonicating for 60 min at a power of 100 W to obtain a black cyclohexane dispersion.

[0076] Add 30 mL of cyclohexane-ethanol mixed solution to the black cyclohexane dispersion, wherein the volume ratio of cyclohexane to ethanol is 2:1. Then centrifuge at 9000 r / min for 4 min and dry to obtain carbon-loaded ternary platinum-germanium alloy.

[0077] Step 4: Place the carbon-loaded ternary platinum-germanium alloy into a square ceramic boat with dimensions of 20mm × 20mm × 17mm. After passing a 5% hydrogen-argon mixture for 30 minutes, heating begins at a rate of 5℃ / min to 500℃. After holding at this temperature for 2 hours, the mixture is allowed to cool naturally to obtain a platinum-germanium based intermetallic ordered alloy catalyst.

[0078] Test 1: Transmission electron microscopy analysis, high-resolution transmission electron microscopy analysis, and X-ray diffraction analysis.

[0079] The platinum-germanium based intermetallic ordered alloy catalyst prepared in Example 1 was analyzed by transmission electron microscopy, high-resolution transmission electron microscopy, and X-ray diffraction, respectively. The results are as follows: Figures 1-3 As shown.

[0080] Depend on Figure 1 and Figure 2 It can be seen that the dendritic diameter of the platinum-germanium based intermetallic ordered alloy catalyst prepared in Example 1 is 18 nm to 72 nm.

[0081] Depend on Figure 3 It can be seen that the platinum-germanium based intermetallic ordered alloy catalyst prepared in Example 1 exhibits an ordered structure.

[0082] Test 2: Electrocatalytic performance test of methanol oxidation.

[0083] The electrocatalytic performance of methanol oxidation was tested on the platinum-germanium based intermetallic ordered alloy catalysts prepared in Examples 1 to 3.

[0084] The specific testing methods and conditions are as follows:

[0085] All electrochemical test data were collected by the Shanghai Chenhua workstation. A three-electrode system was used to test the electrocatalytic performance of methanol oxidation: the working electrode was a Pine disk electrode, loaded using a drop-coating method. First, the powder sample of the platinum-germanium based intermetallic ordered alloy catalyst was dissolved in 5% Nafion solution and isopropanol, sonicated in cold water for 20 min, and uniformly dispersed to obtain a 6 mg / mL slurry. This slurry was then drop-coated twice, totaling 20 μL, onto the surface of a glassy carbon electrode, and subsequently dried with an infrared lamp to obtain the catalyst-loaded working electrode. Nafion solution is a perfluorosulfonic acid polymer solution. The reference electrode was a saturated calomel electrode. The counter electrode was a carbon rod. The methanol oxidation electrolyte was a methanol-perchloric acid solution, with a methanol concentration of 0.5 M and a perchloric acid concentration of 0.1 M. The potential window for methanol oxidation was 0.1 V vs. RHE to 1.2 V vs. RHE, with a scan rate of 50 mV·s. -1 .

[0086] Stability testing: Tested at 0.35V for 6000s; using a commercial Pt / C catalyst as a control. Test results are as follows... Figure 4 and Figure 5 As shown.

[0087] Test sample:

[0088] The platinum-germanium-based intermetallic ordered alloy catalyst prepared in Example 1 is denoted as the annealed Pt-Ge alloy. The carbon-supported binary platinum-germanium alloy in Example 1 is denoted as the Pt-Ge binary alloy. The platinum-germanium-based intermetallic ordered alloy catalyst prepared in Example 2 is denoted as the annealed Pt-Ge-Cu alloy. The platinum-germanium-based intermetallic ordered alloy catalyst prepared in Example 3 is denoted as the annealed Pt-Ge-Fe alloy. The commercial Pt / C catalyst is denoted as 20% Pt / C.

[0089] Table 1. Test results of electrocatalytic performance of methanol oxidation

[0090]

[0091] Note: "-" indicates none. The 6000s stability test result represents the ratio of the current density at the end to the current density at the beginning.

[0092] Depend on Figure 4 As can be seen from the results in Table 1, the platinum-germanium based intermetallic ordered alloy catalyst of Example 1 after annealing at 400℃ exhibits superior methanol oxidation performance and can be used as a catalyst for methanol oxidation.

[0093] Among the catalysts tested, the platinum-germanium-based intermetallic ordered alloy catalyst of Example 1, annealed at 400°C, exhibited the best methanol oxidation performance compared to commercial Pt / C catalysts and carbon-supported binary platinum-germanium alloys. The reaction pathway involved methanol dehydrogenation and oxidation. At 0.35V, the methanol oxidation current density of the platinum-germanium-based intermetallic ordered alloy catalyst of Example 1, annealed at 400°C, was 26 mA·cm⁻¹. -2 This represents approximately 5.3 times higher current density for methanol oxidation than that of commercial Pt / C catalysts. The current densities in Examples 2 and 3 were 16.6 mA·cm⁻¹, respectively. -2 and 20.0 mA·cm -2 Although lower than in Example 1, it is still significantly higher than the 4.9 mA·cm⁻¹ of commercial Pt / C catalysts. -2 .

[0094] Depend on Figure 5 The 6000s stability test results showed that the platinum-germanium based intermetallic ordered alloy catalyst of Example 1, after annealing at 400℃, had better stability than the commercial Pt / C catalyst. The stability of Examples 2 and 3 was 13.0% and 16.4%, respectively, slightly lower than that of Example 1, but they still showed excellent methanol oxidation performance at the methanol oxidation current density and could be used as catalysts for methanol oxidation.

[0095] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a platinum-germanium based intermetallic ordered alloy catalyst, characterized in that, Includes the following steps: A platinum source, a germanium-containing metal source, a reducing agent, a surfactant, and a first organic solvent are mixed to obtain a precursor dispersion; then a liquid-phase reaction is carried out at 220℃±10℃ to obtain a colloidal dispersion; the germanium-containing metal source is a germanium source, or a mixture of a germanium source and an auxiliary metal source; during the reaction process to prepare the colloidal dispersion, chemical nucleation growth is carried out to obtain a colloidal dispersion containing dendritic intermetallic nanoproducts. The colloidal dispersion was mixed with an alcohol solution and then centrifuged to obtain a platinum-germanium based alloy. Platinum-germanium based alloy and carbon black were subjected to ultrasonic carbon loading in a second organic solvent to obtain a carbon-loaded platinum-germanium based alloy; the carbon-loaded platinum-germanium based alloy was then annealed at 400℃~500℃ to obtain a platinum-germanium based intermetallic ordered alloy catalyst with a dendritic morphology.

2. The method for preparing the platinum-germanium based intermetallic ordered alloy catalyst according to claim 1, characterized in that, The platinum source is at least one of platinum acetylacetonate, chloroplatinic acid, and potassium chloroplatinate; the germanium source is germanium tetrachloride and / or germanium oxide; and the auxiliary metal source is at least one of copper, nickel, and iron.

3. The method for preparing the platinum-germanium based intermetallic ordered alloy catalyst according to claim 2, characterized in that, The copper source is copper acetylacetone and / or copper chloride; the nickel source is nickel acetylacetone and / or nickel chloride; and the iron source is iron acetylacetone and / or ferric chloride.

4. The method for preparing the platinum-germanium based intermetallic ordered alloy catalyst according to claim 1, characterized in that, The reducing agent is at least one of glucose, citric acid, and ascorbic acid; the surfactant is a quaternary ammonium salt and / or a halide salt.

5. The method for preparing the platinum-germanium based intermetallic ordered alloy catalyst according to claim 1, characterized in that, The first organic solvent is at least one of oleylamine, octadecene, ethylene glycol and benzyl alcohol; the alcohol solution is a cyclohexane-ethanol solution, and the volume ratio of cyclohexane to ethanol is 2:1; the second organic solvent is cyclohexane.

6. The method for preparing the platinum-germanium based intermetallic ordered alloy catalyst according to claim 1, characterized in that, When the germanium-containing metal source is a germanium source, the concentration of the platinum source in the precursor dispersion is 1 mg / mL to 2 mg / mL, the concentration of the germanium source is 0.4 μL / mL to 2 μL / mL, the concentration of the reducing agent is 5 mg / mL to 7 mg / mL, and the concentration of the surfactant is 5 mg / mL to 7 mg / mL. Alternatively, when the germanium-containing metal source is a mixture of a germanium source and an auxiliary metal source, the concentration of the platinum source in the precursor dispersion is 1 mg / mL to 2 mg / mL, the concentration of the germanium source is 0.4 μL / mL to 2 μL / mL, the concentration of each auxiliary metal source is 0.5 mg / mL to 2 mg / mL, the concentration of the reducing agent is 5 mg / mL to 7 mg / mL, and the concentration of the surfactant is 5 mg / mL to 7 mg / mL.

7. The method for preparing the platinum-germanium based intermetallic ordered alloy catalyst according to claim 1, characterized in that, The volume ratio of the colloidal dispersion to the alcohol solution is 1:8 to 10; the mass ratio of the platinum-germanium alloy to the carbon black is 3:5; the annealing treatment is carried out under a hydrogen-argon mixture, with hydrogen accounting for 5% of the volume of the hydrogen-argon mixture, and the annealing time is 1 to 4 hours.

8. A platinum-germanium based intermetallic ordered alloy catalyst, characterized in that, The catalyst is prepared by the method described in any one of claims 1 to 7; the platinum-germanium-based intermetallic ordered alloy catalyst has a dendritic morphology.

9. The platinum-germanium based intermetallic ordered alloy catalyst according to claim 8, characterized in that, The dendrite diameter of the platinum-germanium based intermetallic ordered alloy catalyst is 18 nm to 72 nm. When the germanium-containing metal source is a germanium source, the molar percentage of platinum in the platinum-germanium based intermetallic ordered alloy catalyst is 57.69%, the molar percentage of germanium is 42.31%, and the total is 100%. Alternatively, when the germanium-containing metal source is a mixture of a germanium source and an auxiliary metal source, the molar percentage of platinum in the platinum-germanium based intermetallic ordered alloy catalyst is 82.81%, the molar percentage of germanium is 11.46%, and the remainder is auxiliary metal elements, totaling 100%.

10. The application of a platinum-germanium based intermetallic ordered alloy catalyst in the preparation of fuel cell membrane electrode assembly, characterized in that, The platinum-germanium based intermetallic ordered alloy catalyst is the platinum-germanium based intermetallic ordered alloy catalyst according to claim 8, and the fuel cell is a formic acid / alcohol fuel cell.

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