Platinum-germanium-based intermetallic ordered alloy catalyst as well as preparation method and application thereof

Abstract

The invention relates to the technical field of multi-metal alloy catalysts, in particular to a platinum-germanium-based intermetallic ordered alloy and a preparation method and application thereof. The specific preparation method comprises the following steps: mixing a platinum source, a germanium-containing metal source, a reducing agent, a surfactant and a first organic solvent, and carrying out a liquid phase reaction to obtain a colloidal dispersion liquid; the colloidal dispersion liquid and an alcoholic solution are mixed and then centrifuged, and platinum-germanium-based alloy is obtained; and the platinum-germanium-based alloy and carbon black are subjected to ultrasonic carbon loading in a second organic solvent, annealing treatment is carried out, and the platinum-germanium-based intermetallic ordered alloy with the dendritic morphology is obtained. The platinum-germanium-based intermetallic ordered alloy is synthesized by introducing a germanium-containing metal source, liquid-phase synthesis and low-temperature annealing, so that electro-catalysis of a fuel cell is facilitated, and the problems that when a platinum-based ordered alloy catalyst is prepared by a traditional high-temperature annealing method, catalyst particles are easy to agglomerate, the size is increased, the specific surface area and the number of active sites are reduced, and the preparation cost is reduced are solved. The catalytic activity is influenced.

Description

Technical Field

[0001] The present invention relates to the technical field of multi-metal alloy catalysts, and in particular to a platinum-germanium-based ordered intermetallic alloy catalyst, a preparation method thereof, and applications thereof. Background Art

[0002] Fuel cells, as energy conversion devices with advantages such as high efficiency, environmental friendliness, and versatility, play a key role in promoting the green development of energy. However, the anode oxidation reaction in formic acid / alcohol fuel cells currently faces two major challenges: the lack of highly active and durable anode catalysts. The performance of the anode catalyst directly affects the energy conversion efficiency and service life of the fuel cell. These two issues have seriously hindered 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 durability in the anodic oxidation reaction of formic acid / alcohol fuel cells, hindering their further use.

[0004] Studies have found that there is a synergistic effect between metallic platinum and other non-precious metal elements. Based on this discovery, forming an intermetallic compound between platinum and one or more metals, namely Pt-M alloy, is an effective strategy to promote the further development of fuel cells. Compared with pure Pt catalysts, Pt-M alloy catalysts have achieved significant improvements in catalytic performance and have improved mass activity to a considerable extent. However, in the acidic environment where fuel cells are usually located, the stability of Pt-M alloys with disordered atomic arrangements is poor. Metal atoms are easily etched by acidic media. As the reaction proceeds, metal atoms are continuously lost, further leading to the collapse of the skeleton structure of the Pt-M alloy catalyst, causing the catalytic activity of the Pt-M alloy catalyst to drop rapidly, seriously affecting the long-term stable operation of the fuel cell.

[0005] In order to overcome the stability problem of Pt-M alloys with disordered atomic arrangement, some platinum-based ordered alloy catalysts with ordered structures have been widely studied. Due to their unique atomic arrangement structure, these catalysts exhibit good initial performance, oxidation resistance and stability under acidic conditions, and are considered to be efficient catalysts that are beneficial to the development of fuel cells. In the process of preparing platinum-based ordered alloy catalysts, high-temperature annealing is a commonly used method. High-temperature annealing can promote the rearrangement of disordered Pt-M atoms. However, traditional high-temperature annealing methods often lead to agglomeration of platinum-based alloy catalyst particles and coarse particle size due to excessively high annealing temperatures, reducing the specific surface area and the number of active sites, thereby affecting the catalytic activity of the platinum-based alloy catalyst. Summary of the Invention

[0006] In order to solve the problem that the traditional high-temperature annealing method can easily lead to catalyst particle agglomeration and size increase when preparing platinum-based ordered alloy catalysts, reduce the specific surface area and the number of active sites, and affect the catalytic activity, the present invention provides a platinum-germanium-based intermetallic ordered alloy catalyst and its preparation method and application.

[0007] The present invention introduces a germanium-containing metal source containing a metalloid germanium element, synthesizes a platinum-germanium-based metal ordered alloy through liquid phase synthesis and low-temperature annealing, breaks the temperature limit in the synthesis of platinum-based metal compounds, is beneficial to fuel cell electrocatalysis, and improves catalytic activity.

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

[0009] The first aspect of the present invention provides a method for preparing a platinum-germanium-based ordered intermetallic alloy catalyst, comprising 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; a liquid phase reaction is then carried out at 220°C±10°C 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 then centrifuged to obtain a platinum-germanium-based alloy; the platinum-germanium-based alloy and carbon black are ultrasonically carbon-loaded 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°C-500°C to obtain a platinum-germanium-based intermetallic ordered alloy catalyst with a dendritic morphology.

[0010] 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 a copper source, a nickel source and an iron source.

[0011] 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 ferric acetylacetonate and / or ferric chloride.

[0012] Preferably, the reducing agent is at least one of glucose, citric acid, and ascorbic acid; and 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.

[0013] 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; and the second organic solvent is cyclohexane.

[0014] The present invention selects oleylamine, octadecene, ethylene glycol or benzyl alcohol as the first organic solvent, which is mainly used to dissolve the platinum source, the germanium-containing metal source, the reducing agent and the surfactant to form a uniform colloidal precursor dispersion.

[0015] Preferably, when the germanium-containing metal source is a germanium source, in the precursor dispersion, the concentration of the platinum source 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.

[0016] Alternatively, when the germanium-containing metal source is a mixture of a germanium source and an auxiliary metal source, in the precursor dispersion, the concentration of the platinum source 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.

[0017] In the above concentration range, a uniform colloidal precursor dispersion can be formed, and a platinum-germanium-based metal ordered alloy catalyst with a dendritic morphology can be synthesized through liquid phase synthesis and low-temperature annealing.

[0018] Preferably, the volume ratio of the colloidal dispersion to the alcohol solution is 1:8-10; the mass ratio of the platinum-germanium-based alloy to the carbon black is 3:5; the annealing treatment is carried out under a hydrogen-argon mixture, and the volume percentage of hydrogen in the hydrogen-argon mixture is 5%, and the annealing treatment time is 1h-4h.

[0019] In the present invention, the time for introducing 5% hydrogen-argon mixed gas is 15 minutes to 60 minutes.

[0020] In the present invention, the cyclohexane-ethanol solution is used to separate the precipitated product. In the present invention, the centrifugal speed is preferably 8000 r / min to 9500 r / min, more preferably 9000 r / min, and the centrifugal time is preferably 3 min to 5 min.

[0021] Preferably, the centrifugation process also includes washing, and the washing liquid used for washing is preferably a mixed solution of cyclohexane and ethanol, and the volume ratio of cyclohexane to ethanol in the mixed solution of cyclohexane and ethanol is preferably 1:1 to 3, more preferably 1:3; the number of times of washing is preferably 2 to 3 times.

[0022] Preferably, the liquid phase reaction time for preparing the colloidal dispersion is 20 minutes to 120 minutes. In the reaction process for preparing the colloidal dispersion, chemical nucleation growth is performed to obtain a colloidal dispersion containing dendritic intermetallic nanoproducts.

[0023] Preferably, the mixing method is ultrasonic stirring, and 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.

[0024] Preferably, the method of ultrasonically carbon-loading the platinum-germanium based alloy and carbon black in the second organic solvent is: The platinum-germanium based alloy and carbon black are uniformly dispersed in a second organic solvent to obtain a platinum-germanium based alloy-carbon black dispersion; an alcohol solution is added to the platinum-germanium based alloy-carbon black dispersion, followed by centrifugation to obtain a carbon-loaded platinum-germanium based alloy.

[0025] Preferably, in the platinum-germanium based alloy-carbon black dispersion, the concentration of carbon black is 0.25 mg / mL to 1 mg / mL; the concentration of the platinum-germanium based alloy is 1.8 mg / mL.

[0026] The second aspect of the present invention provides a platinum-germanium-based ordered metal alloy catalyst, which is prepared by the preparation method of the platinum-germanium-based ordered metal alloy catalyst described in the first aspect; the platinum-germanium-based ordered metal alloy catalyst of the present invention has a dendritic morphology.

[0027] Preferably, the dendritic diameter of the platinum-germanium based ordered intermetallic alloy catalyst is 18 nm to 72 nm.

[0028] Preferably, when the germanium-containing metal source is a germanium source, the molar percentage of platinum element in the platinum-germanium-based intermetallic ordered alloy catalyst is 57.69%, and the molar percentage of germanium element is 42.31%, which is 100% in total.

[0029] Alternatively, when the germanium-containing metal source is a mixture of a germanium source and an auxiliary metal source, the molar percentage of platinum element in the platinum-germanium-based metal ordered alloy catalyst is 82.81%, the molar percentage of germanium element is 11.46%, and the remainder is the auxiliary metal element, totaling 100%.

[0030] The third aspect of the present invention provides an application of a platinum-germanium-based metal ordered alloy catalyst in the preparation of a fuel cell membrane electrode, wherein the platinum-germanium-based metal ordered alloy catalyst is the platinum-germanium-based metal ordered alloy catalyst described in the second aspect, and the fuel cell is a formic acid / alcohol fuel cell.

[0031] The platinum-germanium-based ordered intermetallic alloy catalyst of the present invention is applied to fuel cells and has excellent electrocatalytic performance.

[0032] Preferably, the platinum-germanium-based ordered intermetallic alloy catalyst of the present invention can be used to catalyze the oxidation of formic acid or alcohol; the alcohol is methanol and / or ethanol.

[0033] Beneficial effects of the present invention: 1. The present invention introduces a germanium-containing metal source containing the metalloid germanium element, synthesizes a platinum-germanium-based metal ordered alloy catalyst through liquid phase synthesis and low-temperature annealing, breaks the temperature limit in the synthesis of platinum-based metal compounds, is beneficial to fuel cell electrocatalysis, and improves catalytic activity.

[0034] 2. The preparation conditions of the present invention are relatively mild and the operation is simple, which effectively avoids the problem of catalyst particle agglomeration and size increase caused by high-temperature calcination to transform into an ordered phase, reducing the specific surface area and the number of active sites, and affecting the catalytic activity.

[0035] 3. The platinum-germanium-based intermetallic ordered alloy catalyst prepared by the present invention not only has the structural characteristics of a special structure with high active sites, but also combines the unique electronic structure regulation advantages of the intermetallic ordered structure, so that it exhibits excellent electrocatalytic performance, including formic acid oxidation electrocatalytic performance and methanol or ethanol oxidation electrocatalytic performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a transmission electron microscope image of the dendritic binary platinum-germanium alloy prepared in Example 1.

[0037] Figure 2 This is a transmission electron microscope image of the platinum-germanium based intermetallic ordered alloy catalyst prepared in Example 1.

[0038] Figure 3 This is the X-ray diffraction pattern of the platinum-germanium based ordered intermetallic alloy catalyst prepared in Example 1.

[0039] Figure 4 This chart compares the methanol oxidation activities of the platinum-germanium-based ordered intermetallic alloy catalysts prepared in Examples 1 and 2, as well as the carbon-loaded binary platinum-germanium alloy and a commercial Pt / C catalyst under acidic conditions. 20% Pt / C represents the commercial Pt / C catalyst; Pt-Ge binary alloy represents the carbon-loaded binary platinum-germanium alloy; annealed Pt-Ge alloy represents the 400°C annealed platinum-germanium-based ordered intermetallic alloy catalyst prepared in Example 1; annealed Pt-Ge-Cu alloy represents the 400°C annealed platinum-germanium-based ordered intermetallic alloy catalyst prepared in Example 2; and annealed Pt-Ge-Fe alloy represents the 500°C annealed platinum-germanium-based ordered intermetallic alloy catalyst prepared in Example 3.

[0040] Figure 5This chart compares the methanol oxidation stability performance of the Pt / Ge-based intermetallic ordered alloy catalysts prepared in Examples 1 and 2, as well as the carbon-loaded binary Pt / Ge alloys and commercial Pt / C catalysts under acidic conditions. 20% Pt / C represents the commercial Pt / C catalyst; Pt-Ge binary alloy represents the carbon-loaded binary Pt / Ge alloy; annealed Pt-Ge alloy represents the Pt / Ge-based intermetallic ordered alloy catalyst annealed at 400°C in Example 1; annealed Pt-Ge-Cu alloy represents the Pt / Ge-based intermetallic ordered alloy catalyst annealed at 400°C in Example 2; and annealed Pt-Ge-Fe alloy represents the Pt / Ge-based intermetallic ordered alloy catalyst annealed at 500°C in Example 3.

[0041] Figure 6 The XRD patterns of platinum-germanium alloy after annealing at 400℃ and 600℃. DETAILED DESCRIPTION

[0042] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0043] Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative work shall fall within the scope of protection of the present invention.

[0044] In the present invention, the platinum-germanium-based ordered intermetallic alloy catalyst has an intermetallic structure and a dendritic morphology, with the dendritic diameter of the platinum-germanium-based ordered intermetallic alloy catalyst ranging from 18 nm to 72 nm. The platinum-germanium-based ordered intermetallic alloy catalyst constructed in the present invention is a multi-component ordered intermetallic nanosheet material with a nanometer-scale thickness, exhibiting high activity and stability.

[0045] The solid-phase reaction method is a method of synthesizing ordered phase nanoparticles by using solid-phase reaction under high temperature conditions. High temperature can enhance atomic mobility and facilitate the orderly arrangement of atoms within the crystal. Generally speaking, the temperature required to obtain an ordered atomic arrangement is usually higher than 500°C. Due to the small size of nanoparticles and high surface free energy, high temperatures above 500°C will promote Ostwald ripening and agglomeration, resulting in an increase in the size of nanoparticles and uneven size distribution. However, for platinum-based alloy catalysts, particle agglomeration and coarse particle size will reduce the specific surface area and the number of active sites, thereby affecting the catalytic activity of platinum-based alloy catalysts. Combined Figure 6 With the Bragg equation:

[0046] nλ =2dsinθ; where n represents the diffraction order; λrepresents the X-ray wavelength; d represents the interplanar spacing; θ represents the Bragg angle.

[0047] Figure 6 The XRD patterns of platinum-germanium alloys annealed at 400°C and 600°C are shown below. 600°C annealed platinum-germanium alloys refer to platinum-germanium alloys annealed at 600°C; 400°C annealed platinum-germanium alloys refer to platinum-germanium alloys annealed at 400°C. Figure 6 As shown, the 2θ positions of most diffraction peaks remain unchanged at both temperatures. According to the Bragg equation, if θ remains constant and λ is fixed, then d also remains unchanged, indicating that the primary phase structure remains unchanged. After heating at 600°C, some diffraction peaks, such as those near 40° and 45°, become significantly stronger. According to the Bragg equation, although d and θ remain unchanged, the increased peak intensity indicates that due to the high temperature, more grains meet the Bragg condition, resulting in increased crystallinity and larger grains. After heating at 600°C, some of the main peaks become sharper and the full width at half maximum decreases, suggesting that the grain size may have increased or the lattice distortion has decreased.

[0048] On this basis, the present invention introduces germanium among the metalloid elements, which exhibits metallic properties on the surface but exhibits both metallic and non-metallic properties in chemical properties. The duality of germanium is utilized to further reduce the reaction energy barrier.

[0049] The present 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. These metal elements are combined with the precious metal Pt to form a Pt-based multi-element alloy catalyst, which can exert a synergistic effect between multiple elements and improve catalytic performance.

[0050] The microstructure of the platinum-germanium intermetallic ordered alloy catalyst prepared by the present invention is controllable, which is of great significance in the research of intermetallic ordered alloys. The preparation method provided by the present invention is simple and feasible and can be easily prepared on a large scale.

[0051] In the following embodiments, the carbon-loaded binary platinum-germanium alloy is annealed after drying, and 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.

[0052] The technical solution of the present invention is further described below through specific embodiments.

[0053] In the following examples, the methods described are conventional methods unless otherwise specified; the reagents and materials described are commercially available unless otherwise specified.

[0054] Example 1 A method for preparing a platinum-germanium-based ordered intermetallic alloy catalyst comprises the following steps: Step 1: Dissolve platinum acetylacetonate, germanium chloride, glucose, and cetyltrimethylammonium chloride in oleylamine at concentrations of 2 mg / mL, 0.6 μL / mL, 6 mg / mL, and 6 mg / mL, respectively. Ultrasonicate for 50 minutes at 100 W to obtain a pale yellow, uniform, colloidal precursor dispersion. Transfer the precursor dispersion to an oil bath and heat it to 220°C. Incubate at 220°C ± 10°C for 30 minutes, maintain the temperature for another 30 minutes, and then stop heating. After cooling to room temperature, a black, colloidal dispersion is obtained.

[0055] In step 2, 40 mL of a cyclohexane-ethanol mixture (volume ratio of cyclohexane to ethanol: 2:1) was added to 5 mL of the black colloidal dispersion. The dispersion was then centrifuged at 9,000 rpm for 5 minutes and then washed twice with a cyclohexane-ethanol mixture (volume ratio of cyclohexane to ethanol: 1:3). This yielded a dendritic binary platinum-germanium alloy with an average diameter of 46 nm and a molar ratio of Pt to Ge of 58:42.

[0056] Step 3: Disperse 5 mg of carbon black XC-72R in 10 mL of cyclohexane and ultrasonicate for 10 min at a power of 100 W. After uniform dispersion, a carbon black solution is obtained. Disperse 3 mg of the binary platinum-germanium alloy in step 2 in 6 mL of cyclohexane and ultrasonicate for 1 min at a power of 100 W. After uniform dispersion, a binary platinum-germanium alloy dispersion is obtained. Add the binary platinum-germanium alloy dispersion to the carbon black solution and continue ultrasonicating for 60 min at a power of 100 W to obtain a black cyclohexane dispersion.

[0057] 30 mL of a cyclohexane-ethanol mixed solution was added to the black cyclohexane dispersion, wherein the volume ratio of cyclohexane to ethanol was 2:1, followed by centrifugation at 9000 r / min for 4 min and drying to obtain a carbon-loaded binary platinum-germanium alloy.

[0058] In step 4, the carbon-loaded binary platinum-germanium alloy was placed in a square porcelain boat measuring 20 mm x 20 mm x 17 mm. A 5% hydrogen-argon mixture was introduced for 30 minutes, followed by heating at a rate of 5°C / min to 400°C. The mixture was held at this temperature for 2 hours and then cooled naturally to obtain a platinum-germanium-based ordered intermetallic alloy catalyst.

[0059] Example 2 A method for preparing a platinum-germanium-based ordered intermetallic alloy catalyst comprises the following steps: Step 1: Platinum acetylacetonate, copper acetylacetonate, germanium chloride, glucose, and cetyltrimethylammonium chloride are dissolved in oleylamine solvent at concentrations of 2 mg / mL, 0.6 mg / mL, 0.6 uL / mL, 6 mg / mL, and 6 mg / mL, respectively. The mixture is ultrasonically treated for 50 minutes at a power of 100 W to obtain a yellow, uniform, colloidal precursor dispersion. The precursor dispersion is transferred to an oil bath and heated to 220°C. The mixture is reacted at 220°C for 30 minutes, kept warm for another 30 minutes, and then the mixture is stopped and cooled to room temperature to produce a black, colloidal dispersion.

[0060] Step 2: To 5 mL of the black colloidal dispersion, 40 mL of a cyclohexane-ethanol mixture solution (volume ratio of cyclohexane to ethanol: 2:1) was added. The dispersion was then centrifuged at 9000 rpm for 5 minutes and then washed twice with a cyclohexane-ethanol mixture solution (volume ratio of cyclohexane to ethanol: 1:3). This yielded a dendritic ternary platinum-germanium-copper alloy with an average diameter of 37.95 nm and a molar ratio of Pt, Ge, and Cu of 83:11:6.

[0061] Step 3: Disperse 5 mg of carbon black XC-72R in 10 mL of cyclohexane and ultrasonicate for 10 min at a power of 100 W. After uniform dispersion, a carbon black solution is obtained. Disperse 3 mg of the ternary platinum-germanium-copper alloy in step 2 in 6 mL of cyclohexane and ultrasonicate for 1 min at a power of 100 W. After uniform dispersion, a ternary platinum-germanium alloy dispersion is obtained. Add the ternary platinum-germanium alloy dispersion to the carbon black solution and continue ultrasonicating for 60 min at a power of 100 W to obtain a black cyclohexane dispersion.

[0062] 30 mL of a cyclohexane-ethanol mixed solution was added to the black cyclohexane dispersion, wherein the volume ratio of cyclohexane to ethanol was 2:1, followed by centrifugation at 9000 r / min for 4 min. After drying, a carbon-loaded ternary platinum-germanium alloy was obtained.

[0063] In step 4, the carbon-loaded ternary platinum-germanium alloy was placed in a square porcelain boat measuring 20 mm x 20 mm x 17 mm. A 5% hydrogen-argon mixture was introduced for 30 minutes, followed by heating at a rate of 5°C / min to 400°C. The mixture was held at this temperature for 2 hours and then cooled naturally to obtain a platinum-germanium-based ordered intermetallic alloy catalyst.

[0064] Example 3 A method for preparing a platinum-germanium-iron intermetallic ordered alloy catalyst comprises the following steps: Step 1: Platinum acetylacetonate, ferric acetylacetonate, germanium chloride, glucose, and ammonium bromide are dissolved in oleylamine solvent at concentrations of 2 mg / mL, 0.6 mg / mL, 0.6 uL / mL, 6 mg / mL, and 6 mg / mL, respectively. The mixture is ultrasonically treated for 50 minutes at a power of 100 W to obtain a yellow, uniform, colloidal precursor dispersion. The precursor dispersion is transferred to an oil bath and heated to 220°C. The mixture is reacted at 220°C for 30 minutes, kept warm for another 30 minutes, and then the mixture is stopped and cooled to room temperature to produce a black, colloidal dispersion.

[0065] Step 2: To 5 mL of the black colloidal dispersion, 40 mL of a cyclohexane-ethanol mixture solution (volume ratio of cyclohexane to ethanol: 2:1) was added. The dispersion was then centrifuged at 9000 rpm for 5 minutes and then washed twice with a cyclohexane-ethanol mixture solution (volume ratio of cyclohexane to ethanol: 1:3). This yielded a dendritic ternary platinum-germanium-iron alloy with an average diameter of 37.95 nm. The molar ratio of Pt, Ge, and Fe was 83:11:6.

[0066] Step 3: Disperse 5 mg of carbon black XC-72R in 10 mL of cyclohexane and ultrasonicate for 10 min at a power of 100 W. After uniform dispersion, a carbon black solution is obtained. Disperse 3 mg of the ternary platinum-germanium-iron alloy in step 2 in 6 mL of cyclohexane and ultrasonicate for 1 min at a power of 100 W. After uniform dispersion, a ternary platinum-germanium alloy dispersion is obtained. Add the ternary platinum-germanium alloy dispersion to the carbon black solution and continue ultrasonicating for 60 min at a power of 100 W to obtain a black cyclohexane dispersion.

[0067] 30 mL of a cyclohexane-ethanol mixed solution was added to the black cyclohexane dispersion, wherein the volume ratio of cyclohexane to ethanol was 2:1, followed by centrifugation at 9000 r / min for 4 min. After drying, a carbon-loaded ternary platinum-germanium alloy was obtained.

[0068] In step 4, the carbon-loaded ternary platinum-germanium alloy was placed in a square porcelain boat measuring 20 mm x 20 mm x 17 mm. A 5% hydrogen-argon mixture was introduced for 30 minutes, followed by heating at a rate of 5°C / min to 500°C. The mixture was held at this temperature for 2 hours and then cooled naturally to obtain a platinum-germanium-based ordered intermetallic alloy catalyst.

[0069] Test 1: Transmission electron microscopy analysis, high-resolution transmission electron microscopy analysis, and X-ray diffraction analysis.

[0070] The platinum-germanium-based ordered metal alloy catalyst prepared in Example 1 was subjected to transmission electron microscopy analysis, high-resolution transmission electron microscopy analysis and X-ray diffraction analysis, and the results are as follows: Figures 1 to 3 shown.

[0071] Depend on Figure 1 and Figure 2 It can be seen that the dendritic diameter of the platinum-germanium-based ordered intermetallic alloy catalyst prepared in Example 1 is 18 nm to 72 nm.

[0072] Depend on Figure 3 It can be seen that the platinum-germanium based intermetallic ordered alloy catalyst prepared in Example 1 shows an ordered structure.

[0073] Test 2: Methanol oxidation electrocatalytic performance test.

[0074] The electrocatalytic performance of methanol oxidation was tested on the platinum-germanium based intermetallic ordered alloy catalysts prepared in Examples 1 to 3.

[0075] The specific test methods and conditions are as follows: 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 by drop coating: first, the powder sample of the platinum-germanium-based metal ordered alloy catalyst was dissolved in 5% nafion solution and isopropanol, and then sonicated in cold water for 20 minutes. After uniform dispersion, a 6 mg / mL slurry was obtained. A total of 20 μL was drop-coated on the surface of the glassy carbon electrode in two times, and then dried with an infrared lamp to obtain a catalyst-loaded working electrode. The 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, in which the concentration of methanol was 0.5 M and the concentration of perchloric acid was 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 .

[0076] Stability test: Tested at 0.35V for 6000s; commercial Pt / C catalyst was used as control. Figure 4 and Figure 5 shown.

[0077] Test sample: The platinum-germanium-based ordered intermetallic alloy catalyst prepared in Example 1 is denoted as annealed Pt-Ge alloy. The binary platinum-germanium alloy after carbon loading in Example 1 is denoted as Pt-Ge binary alloy. The platinum-germanium-based ordered intermetallic alloy catalyst prepared in Example 2 is denoted as annealed Pt-Ge-Cu alloy. The platinum-germanium-based ordered intermetallic alloy catalyst prepared in Example 3 is denoted as annealed Pt-Ge-Fe alloy. The commercial Pt / C catalyst is denoted as 20% Pt / C.

[0078] Table 1 Methanol oxidation electrocatalytic performance test results

[0079] Note: “-” indicates no current. The 6000s stability test result represents the ratio of the current density at the end to the current density at the beginning.

[0080] Depend on Figure 4 From the results in Table 1, it can be seen that the platinum-germanium-based intermetallic ordered alloy catalyst prepared in Example 1 after annealing at 400° C. exhibits excellent methanol oxidation performance and can be used as a catalyst in methanol oxidation.

[0081] Compared with commercial Pt / C catalysts and carbon-loaded binary platinum-germanium alloys, the platinum-germanium-based ordered intermetallic alloy catalyst from Example 1, annealed at 400°C, exhibited the best methanol oxidation performance, with a reaction pathway consisting of methanol dehydrogenation and oxidation. At a voltage of 0.35 V, the methanol oxidation current density of the platinum-germanium-based ordered intermetallic alloy catalyst from Example 1, annealed at 400°C, was 26 mA cm -2 , which is about 5.3 times higher than the methanol oxidation current density of commercial Pt / C catalyst. The current density of Example 2 and Example 3 is 16.6 mA·cm -2 and 20.0 mA·cm -2 , although lower than that of Example 1, it is still significantly higher than the 4.9 mA·cm of the commercial Pt / C catalyst. -2 .

[0082] Depend on Figure 5 The 6000-second stability test results show that the stability of the Pt / Ge-based ordered intermetallic alloy catalyst of Example 1 after annealing at 400°C is superior to that of the commercial Pt / C catalyst. The stabilities of Examples 2 and 3 were 13.0% and 16.4%, respectively, slightly lower than that of Example 1. However, these catalysts still exhibited excellent methanol oxidation performance at a methanol oxidation current density, demonstrating their applicability as catalysts for methanol oxidation.

[0083] The above are only 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 in the scope of protection of the present invention.

Claims

1. A method for preparing a platinum-germanium-based ordered intermetallic alloy catalyst, characterized in that: The following steps are involved: 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; and a liquid phase reaction is then carried out at 220°C ± 10°C 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 the alcohol solution and then centrifuged to obtain a platinum-germanium based alloy; The platinum-germanium-based alloy and carbon black are ultrasonically carbon-loaded 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° C. to 500° C. to obtain a platinum-germanium-based intermetallic ordered alloy catalyst with a dendritic morphology.

2. The method for preparing the platinum-germanium based ordered intermetallic 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 a copper source, a nickel source and an iron source.

3. The method for preparing the platinum-germanium based ordered intermetallic alloy catalyst according to claim 2, characterized in that: 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 ferric acetylacetonate and / or ferric chloride.

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

5. The method for preparing the platinum-germanium based ordered intermetallic 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 ordered intermetallic alloy catalyst according to claim 1, characterized in that: When the germanium-containing metal source is a germanium source, in the precursor dispersion, the concentration of the platinum source 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, in the precursor dispersion, the concentration of the platinum source 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 ordered intermetallic alloy catalyst according to claim 1, characterized in that: The volume ratio of the colloidal dispersion to the alcohol solution is 1:8-10; the mass ratio of the platinum-germanium based alloy to the carbon black is 3:5; the annealing treatment is carried out under a hydrogen-argon mixed gas, and the volume percentage of hydrogen in the hydrogen-argon mixed gas is 5%, and the annealing treatment time is 1h-4h.

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

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

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

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