A bifunctional catalyst for oxide-supported ordered L10 phase Pt alloy particles, its preparation method, and its application.

Abstract

This invention provides a bifunctional catalyst supported on an oxide material with ordered L10-phase Pt alloy particles, its preparation method, and its application. The catalyst carrier consists of tungsten oxide and iridium alloy particles attached to it. The ordered L10-Pt alloy includes PtCoNi, PtCoCu, or PtCuNi. The catalyst of this invention uses dual-element doped tungsten oxide as the support for the Pt alloy particles. This support exhibits high oxygen vacancy concentration, excellent conductivity, and superior stability in acidic environments, making it a suitable ORR / HOR support with good activity and durability. Using an ordered Pt alloy as the catalytic active site provides greater controllability of its electronic structure and superior thermodynamic stability. Furthermore, by precisely controlling the strong metal-support interaction between tungsten oxide and Pt, the catalyst exhibits high ORR / HOR selectivity and activity. Fuel cells assembled using this bifunctional catalyst demonstrate excellent activity and stability.

Description

Technical Field

[0001] This invention belongs to the field of proton exchange membrane fuel cell cathode and anode catalyst technology, specifically relating to a bifunctional catalyst of oxide material supported on ordered L10 phase Pt alloy particles, its preparation method, and its application. Background Technology

[0002] Proton exchange membrane fuel cells (PEMFCs) represent a promising clean energy technology, but their large-scale commercialization is severely hampered by the high cost and limited durability of platinum (Pt)-based electrocatalysts. During the start-up / shutdown (SU / SD) operation of PEMFCs, reverse current causes the local cathode potential to rise to 1.5V, leading to severe oxidative corrosion of traditional carbon supports and Pt nanoparticles. This results in a 29% decrease in the electrochemical surface area (ECSA) of commercial Pt / C catalysts. To overcome these bottlenecks, the core research strategy focuses on the rational design of advanced catalyst supports to improve catalytic performance while reducing platinum loading. An ideal support material not only needs to efficiently disperse and stabilize platinum nanoparticles but also should modulate their electronic structure through interfacial interactions, thereby simultaneously improving catalyst activity and stability. Among various alternative supports, reducible corrosion-resistant metal oxides such as titanium dioxide (TiOx), zirconium dioxide (ZrOx), and tungsten oxide (WOx) have attracted significant attention due to their ability to form strong metal-support interactions (SMSI) with Pt-based nanoparticles. These interactions, relying on strong interfacial bonds, can effectively suppress the migration, aggregation, and dissolution of metal particles under harsh operating conditions such as potential fluctuations and frequent start-stop cycles. However, classical SMSI has a fundamental limitation: during heat treatment, some oxides migrate and form a physical coating layer driven by high surface energy, thereby encapsulating the active metal sites. This encapsulation effect severely hinders the contact between reactants and active sites, creating an inherent trade-off between catalyst durability and activity that is difficult to reconcile.

[0003] Therefore, there is an urgent need to develop a new Pt-based catalyst and a method for regulating SMSI to overcome the above problems, which provides a way of thinking for developing highly active and highly stable catalysts with related structures. Summary of the Invention

[0004] The purpose of this invention is to overcome the defects of the prior art and provide a bifunctional catalyst for oxide-supported ordered L10 phase Pt alloy particles, its preparation method and application, which solves the problem that it is difficult to balance durability and activity in the prior art due to SMSI of oxide-supported Pt alloy particles.

[0005] This invention provides the following technical solution: This invention provides a bifunctional catalyst supported on an oxide material with ordered L10-phase Pt alloy particles. The catalyst includes a support and Pt alloy particles attached to the support. The support is tungsten oxide, and the ordered L10-Pt alloy includes one of PtCoNi, PtCoCu, or PtCuNi.

[0006] Furthermore, the average diameter of the Pt alloy particles is 4 nm to 6 nm.

[0007] Furthermore, the loading of the Pt alloy particles accounts for 5% to 30% of the total weight of the catalyst.

[0008] This invention also provides a method for preparing the above-mentioned oxide material supported on ordered L10 phase Pt alloy particles bifunctional catalyst, comprising the following steps: S1. Disperse tungsten salt and transition metal salt in deionized water. After uniform dispersion, heat and stir, then centrifuge and dry to obtain tungsten oxide precursor. S2. The tungsten oxide precursor is dispersed to form a uniform dispersion, a platinum source is added to the dispersion, and ultrasonication is performed to form a uniform clear liquid. The mixture is then dried by impregnation and heat treatment to obtain a powder. S3. The above powder is subjected to ultrasonic treatment in an alkaline solution, and the catalyst is obtained after centrifugation.

[0009] Further, in step S1, the transition metal salt is a combination of two of cobalt salt, copper salt and nickel salt, and the molar ratio of the tungsten salt and the two transition metal salts is 2:(1~2):(1~2).

[0010] Further, the tungsten salt is one or more of tungsten trichloride, sodium tungstate, and ammonium tungstate; the cobalt salt is one or more of cobalt nitrate hexahydrate, cobalt chloride, and cobalt acetylacetonate; the copper salt is one or more of copper nitrate, copper chloride, and copper sulfate; and the nickel source is one or more of nickel nitrate hexahydrate, nickel chloride, and nickel acetylacetonate.

[0011] Furthermore, in step S1, the heating temperature is 40~60℃ and the stirring time is 4~8h.

[0012] Furthermore, in step S2, the heat treatment conditions are: heating temperature of 600℃~700℃, and heating time of 1h~3h.

[0013] Further, in step S3, the alkaline solution is one or more of potassium hydroxide and sodium hydroxide, with a concentration of 0.1~1M, and the ultrasonic treatment time is 0~12h.

[0014] The present invention also provides the application of the above-mentioned oxide material supported on ordered L10 phase Pt alloy particles as a bifunctional catalyst in proton exchange membrane fuel cells as a cathode and anode bifunctional catalyst.

[0015] The present invention has the following beneficial effects: 1. The oxide material-supported ordered L10 phase Pt alloy particle catalyst provided by this invention uses bimetallic doped tungsten oxide as the support for Pt alloy particles, generating more oxygen vacancies and exhibiting better conductivity and activity. Simultaneously, according to the pH-potential diagram, tungsten oxide is stable under strongly acidic and high-voltage conditions, giving it good stability as a HOR / ORR support. Using ordered L10 phase Pt alloy particles as catalytic active sites provides greater controllability of the electronic structure compared to traditional pure Pt particles, and its more moderate adsorption strength for oxygen intermediates results in better HOR / ORR activity. Furthermore, its more negative binding energy provides higher thermodynamic stability. Both factors jointly improve the activity and stability of the bifunctional catalysts for fuel cells' anode and cathode. The synthesis process is simple, energy-saving and emission-reducing, easy for mass production, and extends the service life of fuel cells. 2. The L10 phase Pt alloy particles in the catalyst of this invention include one of PtCoNi, PtCoCu or PtCuNi alloy. Alloying can reduce the amount of Pt used to reduce costs. 3. In this invention, the cathode L10 phase Pt alloy particles are preferably PtCoCu alloy, and the anode L10 phase Pt alloy particles are preferably PtCoNi alloy. Furthermore, the SMSI effect exists between tungsten oxide and the Pt alloy, which simultaneously reduces the degradation of the support and Ir particles, resulting in high stability. 4. The present invention preferably uses Pt alloy particles with an average diameter of 4 nm to 6 nm, which are smaller than the Pt particles prepared by existing technologies, have more reactive sites and reaction surface area, and thus significantly improve catalytic activity. 5. In this invention, by controlling the degree of SMSI through alkaline washing, the occurrence of anode-side side reactions, such as ORR, can be effectively suppressed, the selectivity of HOR can be improved, the occurrence of reverse current can be suppressed, and thus the corrosion resistance of the catalyst can be enhanced.

[0016] 6. In this invention, the cathode L10 phase Pt alloy particles are preferably PtCoCu alloy, and the anode L10 phase Pt alloy particles are preferably PtCoNi alloy. Moreover, there is an SMSI effect between tungsten oxide and Pt alloy, which reduces the degradation of the support and Ir particles and has high stability. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a high-resolution transmission electron microscope image of the catalyst prepared in Example 1 of the present invention. Figure 1 Both (a) and (b) in the image are transmission electron microscope images at a 50 nm scale. Figure 2 This is the X-ray diffraction pattern of the catalyst prepared according to Example 1 of the present invention; Figure 3 These are electrochemical performance graphs of the catalysts prepared according to Examples 1, 1, and 2 of this invention. Figure 4 This is a stability test diagram of the catalyst prepared according to Example 1 of the present invention; Figure 5 This is a performance diagram of the cathode fuel cell constructed using the catalyst prepared in Example 1 of this invention. Figure 6 This is a performance diagram of the anode fuel cell with the catalyst prepared according to Example 1 of the present invention. Figure 7 This is a high-potential cycling performance diagram of the fuel cell with the catalyst prepared according to Example 1 of the present invention; Figure 8 This is a graph showing the ECSA degradation performance after the start-stop test of the catalyst constructed in Example 1 of this invention; Figure 9 This is a graph showing the HOR electrochemical performance of the catalyst prepared in Example 2 of this invention and commercial Pt-C. Detailed Implementation The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. 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.

[0019] This invention provides a bifunctional catalyst supported on an oxide material with ordered L10-phase Pt alloy particles. The catalyst includes a support and Pt alloy particles attached to the support. The support is tungsten oxide, and the ordered L10-Pt alloy includes one of PtCoNi, PtCoCu, or PtCuNi.

[0020] This catalyst uses bimetallic doped tungsten oxide as a support for Pt alloy particles, generating more oxygen vacancies and exhibiting better conductivity and activity. The L10 phase Pt alloy particles include one of PtCoNi, PtCoCu, or PtCuNi alloys. Alloying can reduce the amount of Pt used, thereby reducing costs. Moreover, this invention preferably uses Pt alloy particles with an average diameter of 4 nm to 6 nm, which are smaller than the Pt particles prepared by existing technologies, possessing more reactive sites and a larger specific surface area, thus significantly improving catalytic activity.

[0021] The catalyst was prepared by the following steps: S1. Disperse tungsten salt and transition metal salt in deionized water. After uniform dispersion, heat and stir, then centrifuge and dry to obtain tungsten oxide precursor. S2. The tungsten oxide precursor is dispersed to form a uniform dispersion, a platinum source is added to the dispersion, and ultrasonication is performed to form a uniform clear liquid. The mixture is then dried by impregnation and heat treatment to obtain a powder. S3. The above powder is subjected to ultrasonic treatment in an alkaline solution, and the catalyst is obtained after centrifugation.

[0022] In this invention, there is a strong metal-support interaction between the synthesized tungsten oxide and Pt alloy nanoparticles. By adding different precursor salts, ordered L10 phase Pt alloy particle catalysts supported on oxide materials with different elemental compositions are obtained, thereby improving the stability and activity of the catalyst.

[0023] In this invention, the synthesized tungsten oxide exhibits a strong metal-carrier interaction with the Pt alloy nanoparticles. By controlling different alkaline washing and ultrasonication times, the degree of tungsten oxide coating on the Pt can be controlled, thereby controlling the degree of SMSI between Pt and tungsten oxide. Furthermore, the adsorption of hydrogen and oxygen intermediates is optimized. Simultaneously, hydrogen and oxygen intermediates can form overflows between Pt and tungsten oxide with different degrees of SMSI, accelerating reaction kinetics and efficiency, thus giving it better HOR and ORR activities.

[0024] Starting from the conductivity of materials, this invention selects a dual-element doped tungsten oxide material that remains stable at >1.5V and has good conductivity as a carrier. This greatly improves the stability of the catalyst under the operating conditions of proton exchange membrane fuel cells, especially under start-up and shutdown conditions, where it has a stability far exceeding that of currently commercial catalysts. This is very important for promoting the large-scale application of fuel cells.

[0025] This invention discloses an ordered L10 phase Pt alloy particle catalyst supported on an oxide material, which avoids material shedding and degradation during high-potential operation, significantly improving catalyst stability. Using tungsten oxide as the catalyst support greatly enhances the support's conductivity, overcoming the low conductivity of oxides, and the presence of the oxide also ensures the stability of the support itself. Simultaneously, the presence of the Pt alloy interface significantly accelerates electron transport within the support, increasing the activity of the oxygen evolution reaction. Finally, not only does the electronic effect of the ordered Pt alloy modulate the adsorption strength of the active sites, but the presence of SMSI between the oxide and Pt also limits the degradation of the iridium alloy particles, greatly improving catalyst stability. Furthermore, by controlling the degree of SMSI, the overflow of intermediates between the support and the Pt alloy is achieved, further accelerating reaction efficiency and preventing excessive oxygen accumulation, thus enhancing activity and stability.

[0026] The present invention will be further illustrated below through specific embodiments.

[0027] In the following embodiments, all instruments and other equipment used, unless otherwise specified, are conventional products that can be purchased through legitimate channels. Unless otherwise specified, all methods described are conventional methods, and all raw materials are available from publicly available commercial sources.

[0028] Example 1: A tungsten oxide-supported ordered L10 phase PtCoCu alloy particle catalyst, wherein the loading of Pt alloy particles accounts for 10-20% of the total catalyst weight, is prepared as follows: S1: 660 mg of sodium tungstate, 291 mg of cobalt nitrate hexahydrate and 187 mg of copper nitrate (molar ratio 2:1:1) were weighed and dispersed in 20 mL of deionized water. The mixture was ultrasonically dispersed in an ultrasonic machine for 15 min, then mixed and stirred at 40 °C for 4 h before centrifugation and drying to obtain tungsten oxide precursor.

[0029] S2: 50 mg of tungsten oxide precursor was dispersed in 20 mL of ethanol solution and ultrasonically dispersed for 15 min. Then, 10 mg of chloroplatinic acid aqueous solution was added, and the mixture was impregnated at 60 °C to obtain a dry powder.

[0030] S3: The above-mentioned dried powder was heat-treated in a 5% Ar / H2 mixed gas at a temperature of 600℃ and a time of 3h.

[0031] S4: The above catalyst was dispersed in 20 mL of 0.1 M potassium hydroxide and ultrasonically washed for 3 h to partially remove the WOx coating layer on the surface. Subsequently, the resulting solution was centrifuged at 9000 rpm for 10 min. The centrifuged product was washed three times with a mixture of deionized water and ethanol at a volume ratio of 4:1, and then freeze-dried to obtain a black powder.

[0032] Example 2: The catalyst is prepared by tungsten oxide-supported ordered L10 phase PtCoNi alloy particles, wherein the loading of Pt alloy particles accounts for 10-20% of the total weight of the catalyst. The specific preparation steps are as follows: S1: 660 mg of sodium tungstate, 291 mg of cobalt nitrate hexahydrate and 291 mg of nickel nitrate hexahydrate (molar ratio 2:1:1) were weighed and dispersed in 20 mL of deionized water. The mixture was ultrasonically dispersed for 15 min in an ultrasonic machine, then mixed and stirred at 40 °C for 4 h before centrifugation and drying to obtain tungsten oxide precursor.

[0033] S2: 50 mg of tungsten oxide precursor was dispersed in 20 mL of ethanol solution and ultrasonically dispersed for 15 min. Then, 10 mg of chloroplatinic acid aqueous solution was added, and the mixture was impregnated at 60 °C to obtain a dry powder.

[0034] S3: The above-mentioned dried powder was heat-treated in a 5% Ar / H2 mixed gas at a temperature of 600℃ and a time of 3h.

[0035] Comparative Example 1: A tungsten oxide-supported ordered L10 phase PtCoCu alloy particle catalyst, wherein the loading of Pt alloy particles accounts for 10-30% of the total catalyst weight, is prepared by the following steps: S1: 660 mg of sodium tungstate, 291 mg of cobalt nitrate hexahydrate and 187 mg of copper nitrate (molar ratio 2:1:1) were weighed and dispersed in 20 mL of deionized water. The mixture was ultrasonically dispersed in an ultrasonic machine for 15 min, then mixed and stirred at 40 °C for 4 h before centrifugation and drying to obtain tungsten oxide precursor.

[0036] S2: 50 mg of tungsten oxide precursor was dispersed in 20 mL of ethanol solution and ultrasonically dispersed for 15 min. Then, 10 mg of chloroplatinic acid aqueous solution was added, and the mixture was impregnated at 60 °C to obtain a dry powder.

[0037] S3: The above-mentioned dried powder was heat-treated in a 5% Ar / H2 mixed gas at a temperature of 600℃ and a time of 3h.

[0038] S4: The above catalyst was dispersed in 20 mL of 0.1 M potassium hydroxide and ultrasonically washed for 12 h to partially remove the WOx coating layer on the surface. Subsequently, the resulting solution was centrifuged at 9000 rpm for 10 min. The centrifuged product was washed three times with a mixture of deionized water and ethanol at a volume ratio of 4:1, and then freeze-dried to obtain a black powder.

[0039] Comparative Example 2: A tungsten oxide-supported ordered L10 phase PtCoCu alloy particle catalyst, wherein the loading of Pt alloy particles accounts for 10-20% of the total catalyst weight, is prepared as follows: S1: 660 mg of sodium tungstate, 291 mg of cobalt nitrate hexahydrate and 187 mg of copper nitrate (molar ratio 2:1:1) were weighed and dispersed in 20 mL of deionized water. The mixture was ultrasonically dispersed in an ultrasonic machine for 15 min, then mixed and stirred at 40 °C for 4 h before centrifugation and drying to obtain tungsten oxide precursor.

[0040] S2: 50 mg of tungsten oxide precursor was dispersed in 20 mL of ethanol solution and ultrasonically dispersed for 15 min. Then, 10 mg of chloroplatinic acid aqueous solution was added, and the mixture was impregnated at 60 °C to obtain a dry powder.

[0041] S3: The above-mentioned dried powder was heat-treated in a 5% Ar / H2 mixed gas at a temperature of 600℃ and a time of 3h.

[0042] Figure 1 This is a high-resolution transmission electron microscope image of the catalyst prepared in Example 1. Figure 2 The X-ray diffraction pattern of the catalyst prepared in Example 1 is shown below. Figure 2 As can be seen from the XRD curve, no characteristic peaks of crystalline tungsten oxide were observed, and no lattice fringes were observed, indicating that tungsten oxide exists in an amorphous, non-crystalline form. This also indicates that Pt exists in the form of Cu-doped L10-PtCo ordered alloy.

[0043] Figure 3 The graph shows a comparison of the electrochemical performance of the catalyst in Example 1 with that of Comparative Examples 1 and 2. The MA at 0.9 V vs. RHE is 1.95 A mgPt-1. Figure 4 The graph shows the performance of the catalyst of Example 1 under 0.6-1.0 V vs. RHE conditions. After 600,000 cycles, the MA only decreased by 18.5%, indicating that the catalyst prepared in Example 1 has excellent stability. Figure 5 and Figure 6 This is a performance diagram of the cathode and anode of the catalyst in Example 1 during fuel cell testing. Figure 7 This is a high-potential cycling performance diagram of the fuel cell in Example 1. Figure 8This is a graph showing the ECSA attenuation performance after the start-stop test in Example 1. Figure 9 The graphs show the HOR electrochemical performance of Example 2 and commercial Pt-C.

[0044] Compared to commercial Pt-C catalysts, the oxide-supported ordered L10 phase Pt alloy particle catalyst, after alkali washing with 0.1 MKOH for 3 h, showed a mass activity (MA) of 1.95 A mgPt⁻¹ in ORR tests, with a 18.5% decrease after 600,000 cycles at 0.6–1.0 V. Without alkali washing, the oxide-supported ordered L10 phase Pt alloy particle catalyst, after 2000 s of constant potential operation at 10,000 ppm CO / H₂, showed a current density decay rate of only 19.2%. Simultaneously, the membrane electrode assembly of the oxide-supported ordered L10 phase Pt alloy particle bifunctional catalyst achieved a mass activity of 0.78 A mgPt⁻¹ at 0.9 V in a PEMFC, with a MA decay rate of only 17.4% after 10,000 cycles at a high potential of 1.0–1.5 V, and an ECSA decay of only 3% after 800 start-stop tests.

[0045] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An oxide material-supported ordered LlO-phase Pt alloy particle bifunctional catalyst characterized in that, The catalyst includes a support and Pt alloy particles attached to the support, wherein the support is tungsten oxide and the Pt alloy includes one of PtCoNi, PtCoCu, or PtCuNi.

2. The oxide material supported ordered LlO phase Pt alloy particle bifunctional catalyst of claim 1, wherein: The average diameter of the Pt alloy particles is 4 nm to 6 nm.

3. The oxide material supported ordered LlO phase Pt alloy particle bifunctional catalyst of claim 1, wherein: The loading of the Pt alloy particles accounts for 5% to 30% of the total weight of the catalyst.

4. Process for the preparation of a bifunctional catalyst of oxide material supported ordered LlO phase Pt alloy particles according to any one of claims 1 to 3, characterized in that: Includes the following steps: S1. Disperse tungsten salt and transition metal salt in deionized water. After uniform dispersion, heat and stir, then centrifuge and dry to obtain tungsten oxide precursor. S2. The tungsten oxide precursor is dispersed to form a uniform dispersion, a platinum source is added to the dispersion, and ultrasonication is performed to form a uniform clear liquid. The mixture is then dried by impregnation and heat treatment to obtain a powder. S3. The above powder is subjected to ultrasonic treatment in an alkaline solution, and the catalyst is obtained after centrifugation.

5. The method for preparing a bifunctional catalyst of oxide material supported ordered LlO phase Pt alloy particles according to claim 4, characterized in that: In step S1, the transition metal salt is a combination of two of cobalt salt, copper salt and nickel salt, and the molar ratio of tungsten salt to the two transition metal salts is 2:(1~2):(1~2).

6. The method for preparing a bifunctional catalyst of oxide material supported ordered LlO phase Pt alloy particles according to claim 5, characterized in that: The tungsten salt is one or more of tungsten trichloride, sodium tungstate, and ammonium tungstate; the cobalt salt is one or more of cobalt nitrate hexahydrate, cobalt chloride, and cobalt acetylacetonate; the copper salt is one or more of copper nitrate, copper chloride, and copper sulfate; and the nickel source is one or more of nickel nitrate hexahydrate, nickel chloride, and nickel acetylacetonate.

7. The method for preparing the bifunctional catalyst of oxide material supported on ordered L10 phase Pt alloy particles as described in claim 4, characterized in that: In step S1, the heating temperature is 40~60℃ and the stirring time is 4~8h.

8. The method for preparing the bifunctional catalyst of oxide material supported on ordered L10 phase Pt alloy particles as described in claim 4, characterized in that: In step S2, the heat treatment conditions are: heating temperature of 600℃~700℃ and heating time of 1h~3h.

9. The method for preparing the bifunctional catalyst of oxide material supported on ordered L10 phase Pt alloy particles as described in claim 4, characterized in that: In step S3, the alkaline solution is one or more of potassium hydroxide and sodium hydroxide, with a concentration of 0.1~1M, and the ultrasonic treatment time is 0~12h.

10. The application of the oxide material-supported ordered L10 phase Pt alloy particle catalyst according to any one of claims 1-3 as a bifunctional catalyst for the anode and cathode in a proton exchange membrane fuel cell.

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