A bifunctional catalyst and its preparation method and application

Abstract

The present invention discloses a bifunctional catalyst and a preparation method and application thereof, belonging to the technical field of fuel cell catalysts. The preparation method of the bifunctional catalyst comprises the following steps: S01: a first intermediate product of a metal nanoparticle of an OER catalyst precursor is reduced and deposited on the surface of a metal oxide carrier; S02: the first intermediate product obtained in step S01 is subjected to a high-temperature calcination oxidation treatment to obtain a second intermediate product; S03: a second reduction deposition of metal nanoparticles of a HOR catalyst on the second intermediate product obtained in step S02 to obtain a bifunctional catalyst. The bifunctional catalyst prepared by the present invention can catalyze the oxygen evolution reaction OER at the anode of water electrolysis and the hydrogen oxidation reaction HOR at the anode of a fuel cell, and can be used in an integrated renewable fuel cell stack, and the preparation method is simple, which can be extended to the product fields of backup power supply, hydrogen energy storage, etc.

Description

Technical Field

[0001] The invention belongs to the technical field of fuel cell catalysts, and in particular relates to a bifunctional catalyst and a preparation method and application thereof. Background Art

[0002] Proton exchange membrane fuel cell (PEMFC) is a device that converts chemical energy stored in hydrogen into electrical energy. It is mainly composed of membrane electrode, bipolar plate, current collector, end plate, etc. The membrane electrode includes a perfluorosulfonic acid proton exchange membrane in the middle, an anode catalyst layer, a cathode catalyst layer, an anode diffusion layer and a cathode diffusion layer, and is sealed by a frame. Unitized regenerative fuel cell (URFC) is a high-efficiency energy storage device derived from PEMFC technology. It can operate in two modes: fuel cell power generation and water electrolysis to produce hydrogen. It is usually mainly used in hybrid energy storage recommendation systems for solar aircraft and spacecraft. In recent years, URFC has attracted much attention. It can be used in the fields of long-term energy storage backup power supply and hydrogen energy storage. It uses wind power, photovoltaic and other volatile renewable energy sources to electrolyze water to produce hydrogen. Hydrogen is stored in high-pressure hydrogen bottles or solid hydrogen storage devices. In the fuel cell mode, hydrogen enters the URFC device to generate electricity. It is a new type of backup power supply equipment that does not require hydrogen replenishment. At the same time, it can be used for grid peak load power supply or portable energy system. Compared with the split PEM electrolyzer and PEM fuel cell stack combination system, the URFC energy storage system has a more compact structure and higher integration. The system can be more miniaturized and easier to maintain.

[0003] For URFC devices, the research focus is on the preparation of bifunctional catalysts and catalytic layers. Figure 1As shown, in the water electrolysis mode, oxygen evolution reaction (OER) occurs at the anode and hydrogen evolution reaction (HER) occurs at the cathode. In the fuel cell mode, hydrogen oxidation reaction (HOR) occurs at the anode and oxygen reduction reaction (ORR) occurs at the cathode. There are currently two main combination modes: (1) OER and ORR are on the same side of the catalyst layer, and HER and HOR are on the same side of the catalyst layer; (2) OER and HOR are on the same side of the catalyst layer, and HER and ORR are on the same side of the catalyst layer. For the OER reaction, the anode potential is usually higher than 1.5V, so when the anode catalyst is used to produce hydrogen by electrolysis of water, a carbon support cannot be used. For the Pt / C catalyst, it has high catalytic activity for ORR, HOR, and HER.

[0004] For the first mode, mechanical mixing of Pt-based and Ir-based catalysts or PtIr-based alloy catalysts is mainly used. Energy Environ. Sci., 2020, 13, 4872 reported that Pt black and Ir black were mixed in a solvent, and then the catalytic layer was prepared by spraying to achieve bifunctional OER and ORR catalysis. However, the Ir black and Pt black particles of this process are large, the catalyst utilization rate is low, and the catalytic layer is prepared only by mechanical mixing, and the overall catalytic performance is poor.

[0005] In addition, another technical route is to prepare an Ir-based alloy catalyst with dual-functional catalytic capabilities of OER and ORR. For example, ACS Appl. Energy Mater. 2020, 3, 1423-1428 reported a three-dimensional interconnected nanoporous PtIr film (np-PtIr) for URFC. Compared with Pt and Ir alone, the URFC performance of np-PtIr is 21% and 485% higher, respectively. The specific synthesis steps are as follows: first, a Pt substrate is prepared, and then a Pt, Ir and Os element precursor solution film is prepared on the surface of the Pt substrate. After drying, it is calcined at 1100°C in an Ar / H2 atmosphere, and finally the Os element is dissolved by an electrochemical method. The preparation process steps are too cumbersome and the cost is high, which is not conducive to batch preparation. At the same time, the layered PtIr film is difficult to evenly combine with the proton-conducting ionomer, resulting in too low proton conduction efficiency of the catalytic layer, which ultimately affects the URFC performance.

[0006] For the second mode, the OER and HOR reactions are placed on the same catalyst layer, and there are relatively few reports on this mode. Compared with the first mode, Pt / C can meet the rapid HER and ORR catalytic reactions, and the commercialization of Pt / C catalysts is relatively high. With the development of PEM fuel cells, the Pt loading required for ORR on the cathode side is getting smaller and smaller, so this mode has great potential for future development.

[0007] In summary, the prior art of bifunctional catalysts has the following limitations and disadvantages:

[0008] 1. URFC usually uses an oxygen electrode with OER and ORR on the same side, which is mainly a mechanical mixture of Ir and Pt-based catalysts or an alloy catalyst containing Ir and Pt, with poor catalytic performance and low catalyst utilization.

[0009] 2. Traditional bifunctional OER / HOR catalysts are mainly prepared by physically mixing OER and HOR catalysts into a catalytic layer, which leads to structural separation and difficulty in ensuring uniformity. When conducting the electrolytic water oxygen evolution reaction and the fuel cell hydrogen oxidation reaction respectively, the physical mixing of the two catalysts will lead to the obstruction of the mass transfer of gases, protons, electrons, water and other substances in the catalytic layer, and the catalytic reaction zone cannot be continuous, while accelerating the attenuation of catalytic activity.

[0010] 3. Previously reported literature and patents mostly use unsupported OER and HOR catalyst particles, the catalyst particle size is too large, the catalyst utilization rate is too low, the mass activity is low, and it is easy to agglomerate.

[0011] 4. In the water electrolysis mode, OER is at a high potential (≥1.5V). If a carrier-loaded precious metal catalyst is prepared, a conductive metal oxide carrier that is resistant to high potential and acid corrosion is required. Summary of the invention

[0012] In order to solve the defects and shortcomings of the existing related technologies, the present invention provides a bifunctional catalyst and a preparation method and application thereof. The bifunctional catalyst is a bifunctional catalyst that can catalyze the oxygen evolution reaction (OER) at the anode of water electrolysis and the hydrogen oxidation reaction (HOR) at the anode of a fuel cell. The bifunctional catalyst layer prepared by the catalyst provided by the present invention can be applied to an integrated renewable fuel cell stack and promoted to the fields of backup power supplies, hydrogen energy storage and other products.

[0013] The technical solution of the present invention is as follows:

[0014] A method for preparing a bifunctional catalyst comprises the following steps:

[0015] S01: On metal oxide support (M1O x ) surface by one-step reduction deposition of OER catalyst precursor metal (M2) nanoparticles (M1Ox @M2);

[0016] S02: The first product (M1O x @M2) is subjected to high temperature calcination and oxidation treatment to obtain the second intermediate product (M1O x @M2O y );

[0017] S03: The second product (M10) obtained in step S02 x @M2O y ) to obtain a bifunctional catalyst (M1O x @M2O y @M3);

[0018] The molar ratio of the OER catalyst precursor metal (M2) to the HOR catalyst metal (M3) is 0.1-10.

[0019] In step S01,

[0020] The specific steps of the primary reduction deposition are: x ) is mixed evenly with a salt containing an OER catalyst precursor metal (M2), a stabilizer, a reducing agent, and a solvent, and heated to 100-200°C by microwave in an inert atmosphere and maintained for 5min-6h to reduce the loaded OER catalyst precursor metal (M2) particles, and then washed after aging for 1h-48h, and dried and collected.

[0021] The metal oxide support (M1O x ) is at least one of a metal vacancy, an oxygen vacancy or a high potential corrosion resistant metal oxide carrier having no vacancy structure. Further preferably, the metal oxide carrier (M1O x ) is at least one of niobium oxide Nb2O5, titanium oxide Ti4O7, tantalum oxide (Ta2O5), and antimony tin oxide (ATO). Preferably, the metal oxide carrier (M1O x ) concentration ≤10mg / ml.

[0022] The salt containing the OER catalyst precursor metal (M2) is at least one of an Ir salt or a Ru salt; the Ir salt is preferably iridium chloride IrCl3, IrCl3·nH2O, iridium acetylacetonate C 15 H 21At least one of IrO6, chloroiridic acid H2IrCl6, H2IrCl6·nH2O, ammonium chloroiridate H8Cl6IrN2, potassium chloroiridate K2IrCl6, sodium chloroiridate Na3IrCl6·nH2O, and Na2IrCl6·6H2O, wherein n is the water content coefficient in the salt; the Ru salt is preferably ruthenium chloride RuCl3, RuCl3·nH2O, ruthenium acetylacetonate C 15 H 21 At least one of O6Ru, ammonium hexachlororuthenate (NH4)2RuCl6, hexaammineruthenium chloride Ru(NH3)6Cl3, and potassium hexachlororuthenate K3RuCl6, wherein n is the water content coefficient in the salt.

[0023] The solvent is preferably at least one of ethylene glycol or oleylamine.

[0024] The stabilizer is preferably at least one of citric acid, sodium citrate, polyvinyl pyrrolidone, cyclopentane, oleic acid, sodium hydroxide, ethylene glycol or oleylamine. The stabilizer accounts for at least 2 wt% of the solvent.

[0025] The reducing agent is preferably at least one of NaHB4, ascorbic acid, sodium hypophosphite, ethylene glycol or oleylamine.

[0026] More preferably, the reducing agent and the solvent are both ethylene glycol, and the stabilizer is sodium hydroxide and ethylene glycol. Sodium hydroxide is added to ethylene glycol to adjust the alkalinity and play a stabilizing role.

[0027] Further preferably, the metal oxide carrier (M1O x ): The usage ratio of salt containing OER catalyst precursor metal (M2): sodium hydroxide: ethylene glycol is 80-120 mg: 130-150 mg: 220-260 mg: 55-80 mL.

[0028] The cleaning is performed at least once, more preferably 1 to 8 times.

[0029] In step S2,

[0030] The specific steps of the high temperature calcination oxidation treatment are: heating the first intermediate product (M1O x @M2) is subjected to high temperature calcination oxidation, the high temperature calcination temperature is 300-800°C, the high temperature calcination time is 0.5-10h, and the second intermediate product (M1O x @M2O x ).

[0031] The heating device is a tubular furnace, a muffle furnace or other heating devices.

[0032] The thermal oxidation is performed in an air atmosphere or other oxygen-containing atmosphere.

[0033] In step S3,

[0034] The specific steps of the secondary reduction deposition are: x @M2O x ) is mixed evenly with a salt containing a HOR catalyst metal (M3), a stabilizer, a reducing agent, and a solvent, and heated to 100-200° C. by microwave in an inert atmosphere, and maintained for 5 min-6 h to reduce the loaded HOR catalyst metal (M3) particles, and washed after aging for 1 h-48 h, and dried and collected to obtain a bifunctional catalyst (M1O x @M2O y @M3).

[0035] The salt containing the HOR catalyst metal (M3) is at least one of salts containing Pt, Ru, Pd, and Rh metal elements. Further preferably, the salt containing the HOR catalyst metal (M3) is chloroplatinic acid H2PtCl6·6H2O.

[0036] The solvent is preferably at least one of ethylene glycol or oleylamine.

[0037] The stabilizer is preferably at least one of citric acid, sodium citrate, polyvinyl pyrrolidone, cyclopentane, oleic acid, sodium hydroxide, ethylene glycol or oleylamine. The stabilizer accounts for at least 2 wt% in the solvent.

[0038] The reducing agent is preferably at least one of NaHB4, ascorbic acid, sodium hypophosphite, ethylene glycol or oleylamine.

[0039] More preferably, the reducing agent and the solvent are both ethylene glycol, and the stabilizer is sodium hydroxide and ethylene glycol. Sodium hydroxide is added to ethylene glycol to adjust the alkalinity and play a stabilizing role.

[0040] More preferably, the usage ratio of the salt containing the HOR catalyst metal (M3): sodium hydroxide: ethylene glycol is 130-150 mg: 220-260 mg: 55-80 mL.

[0041] The cleaning is performed at least once, more preferably 1 to 8 times.

[0042] A bifunctional catalyst is prepared by the method.

[0043] The bifunctional catalyst (M1O x @M2O y @M3), the composition includes a metal oxide carrier (M1Ox ), precious metal catalysts with OER performance (M2O y ) nanoparticles and precious metal catalyst nanoparticles with HOR performance (M3).

[0044] The metal oxide support (M1O x ) is a metal vacancy or an oxygen vacancy or has at least one structure without a vacancy structure; further, the metal oxide carrier (M1O x ) is at least one of niobium oxide Nb2O5, titanium suboxide Ti4O7, tantalum oxide (Ta2O5), and antimony tin oxide (ATO);

[0045] The noble metal catalyst (M2O y ) is at least one of iridium dioxide IrO2, ruthenium dioxide RuO2, or iridium dioxide, ruthenium dioxide, and Ir alloy doped with other elements;

[0046] The noble metal catalyst (M3) having HOR performance is at least one of Pt, Ru, Pd, Rh or alloy catalysts based on these elements.

[0047] In the process of preparing the bifunctional catalyst, the present invention prepares the noble metal catalyst (M2O y ) process, the salt containing the OER catalyst precursor metal (M2) needs to be reduced first, then calcined at high temperature in an oxygen or air atmosphere to form an oxide, and then the HOR catalyst metal (M3) nanoparticles are reduced and deposited. If the OER catalyst and the HOR catalyst precursor are loaded at the same time, the subsequent high-temperature calcination will cause the oxidation problem of Pt black and Pd black.

[0048] The above-mentioned bifunctional catalyst is a bifunctional catalyst that can catalyze the oxygen evolution reaction OER at the anode of water electrolysis and the hydrogen oxidation reaction HOR at the anode of the fuel cell, and is used in an integrated renewable fuel cell stack; and then applied to product fields such as backup power supply and hydrogen energy storage.

[0049] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0050] 1. The present invention breaks through the conventional inertial thinking of physically mixing two OER and HOR catalysts, and starts from the structural regulation mechanism and catalytic mechanism of the catalyst to in-situ load OER (RuO2, IrO2, RuIrO x The two catalysts (such as Pt, Ru, Pd nanoparticles) and HOR catalysts (Pt, Ru, Pd nanoparticles) are combined to synergistically enhance the bifunctional catalytic effect.

[0051] 2. In order to meet the dual-functional catalytic requirements of OER and HOR and to avoid the disadvantages of mechanical mixing of the two traditional catalysts, the present invention loads the OER and HOR catalyst particles on the surface of the same highly conductive metal oxide support, which can effectively control the particle size, avoid agglomeration, and improve the catalyst utilization rate.

[0052] 3. The metal oxide carrier used in the present invention can withstand the high potential of the anode of electrolyzed water, while ensuring high conductivity and accelerating the electron transmission capacity of the catalytic layer.

[0053] 4. The preparation method of the bifunctional catalyst of the present invention is simple and easy, does not require expensive equipment, has low cost, and can achieve scaled-up production by continuous delivery of the subsequent solution. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 This is a schematic diagram of the working principle of URFC;

[0055] Figure 2 Schematic diagram of the preparation process of OER and HOR bifunctional catalysts;

[0056] Figure 3 This is the XRD result diagram of the bifunctional catalyst;

[0057] Figure 4 : is the catalytic performance polarization curve of the bifunctional catalyst HOR; wherein A is the catalyst of Example 1 (IrO2 / Pt molar ratio is 1), B is the catalyst of Example 2 (IrO2 / Pt molar ratio is 2), and C is the catalyst of Example 3 (IrO2 / Pt molar ratio is 5);

[0058] Figure 5 Polarization curve of OER catalytic performance of bifunctional catalyst. DETAILED DESCRIPTION

[0059] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0060] In addition, if there are descriptions involving "first", "second", "once", "secondary", etc. in the embodiments of the present invention, the descriptions of "first", "second", "once", "secondary", etc. are only used for descriptive purposes and cannot be understood as indicating or suggesting their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first", "second", "once", "secondary" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in the field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0061] At present, the traditional bifunctional OER / HOR catalyst is mainly prepared by physically mixing the OER and HOR catalysts into a catalytic layer, which leads to structural separation and difficulty in ensuring uniformity. When the electrolysis of water oxygen evolution reaction and the fuel cell hydrogen oxidation reaction are carried out separately, the physical mixing of the two catalysts will lead to the obstruction of the mass transfer of gases, protons, electrons, water and other substances in the catalytic layer, the catalytic reaction zone cannot be continuous, and the catalytic activity decay is accelerated. In order to solve the above technical problems, the present invention proposes a bifunctional catalyst and its preparation method and application.

[0062] Example 1: IrO2 / Pt molar ratio of 1 in bifunctional catalyst

[0063] A method for preparing a bifunctional catalyst (IrO2 / Pt molar ratio is 1), comprising the following steps (preparation process as Figure 2 shown):

[0064] S01: 100 mg Nb2O5 carrier, 140.8 mg chloroiridic acid H2IrCl6·6H2O, and 0.24 g sodium hydroxide were dissolved in 60 mL ethylene glycol, dispersed evenly by ultrasonication, and stirred at room temperature for 30 min; then the mixture was heated to 160°C by microwave under an inert atmosphere and kept for 10 min to reduce the iridium-loaded Ir particles, aged for 2 h, washed 4 times, and dried and collected to obtain the product Nb2O5 / Ir;

[0065] S02: The dried product Nb2O5 / Ir is placed in a muffle furnace and oxidized in an air atmosphere at a thermal oxidation temperature of 500°C and a holding time of 2 hours to obtain the product Nb2O5 / IrO2;

[0066] S03: The S02 product Nb2O5 / IrO2 was dissolved in 60mL of ethylene glycol with 136.7mg of chloroplatinic acid H2PtCl6·6H2O and 0.24g of sodium hydroxide, dispersed evenly by ultrasonication, and stirred at room temperature for 30min; the mixed solution was heated to 160°C by microwave under a nitrogen atmosphere and maintained for 10min to reduce the loaded platinum Pt particles. After aging for 2h, it was washed 6 times and dried and collected to obtain the Nb2O5 / IrO2 / Pt bifunctional catalyst.

[0067] Example 2: IrO2 / Pt molar ratio in bifunctional catalyst is 2

[0068] A method for preparing a bifunctional catalyst (IrO2 / Pt molar ratio is 2), comprising the following steps:

[0069] S01: 100 mg Nb2O5 carrier, 140.8 mg chloroiridic acid H2IrCl6·6H2O, and 0.24 g sodium hydroxide were dissolved in 60 mL ethylene glycol, dispersed evenly by ultrasonication, and stirred at room temperature for 30 min; then the mixture was heated to 160°C by microwave under an inert atmosphere and kept for 10 min to reduce the iridium-loaded Ir particles, aged for 2 h, washed 4 times, and dried and collected;

[0070] S02: The dried product Nb2O5 / Ir is placed in a muffle furnace and oxidized in an air atmosphere at a thermal oxidation temperature of 500°C and a holding time of 2 hours to obtain the product Nb2O5 / IrO2;

[0071] S03: The S02 product was dissolved in 60 mL of ethylene glycol with 68.35 mg of chloroplatinic acid H2PtCl6·6H2O and 0.24 g of sodium hydroxide, dispersed evenly by ultrasonication, and stirred at room temperature for 30 min; the mixed solution was heated to 160°C by microwave under a nitrogen atmosphere and maintained for 10 min to reduce the loaded platinum Pt particles. After aging for 2 h, it was washed 6 times and dried and collected to obtain the Nb2O5 / IrO2 / Pt bifunctional catalyst.

[0072] Example 3: IrO2 / Pt molar ratio of bifunctional catalyst is 5

[0073] A method for preparing a bifunctional catalyst (IrO2 / Pt molar ratio is 5) comprises the following steps:

[0074] S01: 100 mg Nb2O5 carrier, 140.8 mg chloroiridic acid H2IrCl6·6H2O, and 0.24 g sodium hydroxide were dissolved in 60 mL ethylene glycol, dispersed evenly by ultrasonication, and stirred at room temperature for 30 min; then the mixture was heated to 160°C by microwave under an inert atmosphere and kept for 10 min to reduce the iridium-loaded Ir particles, aged for 2 h, washed 4 times, and dried and collected;

[0075] S02: The dried product Nb2O5 / Ir is placed in a muffle furnace and oxidized in an air atmosphere at a thermal oxidation temperature of 500°C and a holding time of 2 hours to obtain the product Nb2O5 / IrO2;

[0076] S03: The S02 product was dissolved in 60 mL of ethylene glycol with 27.34 mg of chloroplatinic acid H2PtCl6·6H2O and 0.24 g of sodium hydroxide, dispersed evenly by ultrasonication, and stirred at room temperature for 30 min; the mixed solution was heated to 160°C by microwave under a nitrogen atmosphere and maintained for 10 min to reduce the loaded platinum Pt particles. After aging for 2 h, it was washed 6 times and dried and collected to obtain the Nb2O5 / IrO2 / Pt bifunctional catalyst.

[0077] The XRD results of the Nb2O5 / IrO2 / Pt bifunctional catalysts prepared in Examples 1 to 3 are shown in FIG. Figure 3 The HOR catalytic performance polarization curves of the Nb2O5 / IrO2 / Pt bifunctional catalysts prepared in Examples 1 to 3 (as shown in FIG. Figure 4 ) and OER catalytic performance polarization curves (as shown Figure 5 The results show that the prepared bifunctional catalyst has excellent HOR catalytic performance and OER catalytic performance.

[0078] The above-mentioned bifunctional catalyst is a bifunctional catalyst that can catalyze the oxygen evolution reaction OER at the anode of water electrolysis and the hydrogen oxidation reaction HOR at the anode of the fuel cell, and is used in an integrated renewable fuel cell stack; and then applied to product fields such as backup power supply and hydrogen energy storage.

[0079] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0080] 1. The present invention breaks through the conventional inertial thinking of physically mixing two OER and HOR catalysts, and starts from the structural regulation mechanism and catalytic mechanism of the catalyst to in-situ load OER (RuO2, IrO2, RuIrO x The two catalysts (such as Pt, Ru, Pd nanoparticles) and HOR catalysts (Pt, Ru, Pd nanoparticles) are combined to synergistically enhance the bifunctional catalytic effect.

[0081] 2. The present invention loads OER and HOR catalyst particles on the surface of the same highly conductive metal oxide support, which can effectively control the particle size, avoid agglomeration, and improve catalyst utilization.

[0082] 3. The metal oxide carrier used in the present invention can withstand the high potential of the anode of electrolyzed water, while ensuring high conductivity and accelerating the electron transmission capacity of the catalytic layer.

[0083] 4. The preparation method of the bifunctional catalyst of the present invention is simple and easy, does not require expensive equipment, has low cost, and can achieve scaled-up production by continuous delivery of the subsequent solution.

[0084] 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 and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a bifunctional catalyst, characterized in that: The following steps are involved: S01: a first intermediate product of reducing and depositing the OER catalyst precursor metal nanoparticles on the surface of the metal oxide support; S02: subjecting the first intermediate product obtained in step S01 to high-temperature calcination and oxidation treatment to obtain a second intermediate product; S03: secondary reduction deposition of HOR catalyst metal nanoparticles on the second product obtained in step S02 to obtain a bifunctional catalyst; The molar ratio of the OER catalyst precursor metal to the HOR catalyst metal is 0.1-10; In step S01, the specific steps of the primary reduction deposition are: uniformly mixing the metal oxide support with the salt containing the OER catalyst precursor metal, the stabilizer, the reducing agent, and the solvent, heating the mixture to 100-200° C. by microwave in an inert atmosphere, and maintaining the temperature for 5 min-6 h to reduce the loaded OER catalyst precursor metal particles, aging the mixture for 1 h-48 h, washing the mixture, and drying and collecting the mixture; The reducing agent and the solvent are both ethylene glycol; the stabilizer is sodium hydroxide and ethylene glycol; The metal oxide support: the salt containing the OER catalyst precursor metal: sodium hydroxide: ethylene glycol is used in a ratio of 80-120 mg: 130-150 mg: 220-260 mg: 55-80 mL; In step S3, the specific steps of the secondary reduction deposition are: uniformly mixing the second product obtained in step S02 with a salt containing a HOR catalyst metal, a stabilizer, a reducing agent, and a solvent, heating the mixture to 100-200° C. by microwave heating under an inert atmosphere, and maintaining the mixture for 5 min-6 h to reduce and load the HOR catalyst metal particles, aging the mixture for 1 h-48 h, washing the mixture, and drying and collecting the mixture to obtain a bifunctional catalyst; The reducing agent and the solvent are both ethylene glycol; the stabilizer is sodium hydroxide and ethylene glycol; The usage ratio of the salt containing the HOR catalyst metal: sodium hydroxide: ethylene glycol is 130-150 mg: 220-260 mg: 55-80 mL.

2. The method for preparing a bifunctional catalyst according to claim 1, characterized in that: In step S01, the metal oxide carrier is at least one of niobium oxide, titanium oxide, tantalum oxide, and antimony tin oxide; The salt containing the OER catalyst precursor metal is at least one of an Ir salt or a Ru salt; the Ir salt is IrCl3, IrCl3·nH2O, C 15 H 21 At least one of IrO6, H2IrCl6, H2IrCl6·nH2O, H8Cl6IrN2, K2IrCl6, Na3IrCl6·nH2O, Na2IrCl6·6H2O, the Ru salt is RuCl3, RuCl3·nH2O, C 15 H 21 At least one of O6Ru, (NH4)2RuCl6, Ru(NH3)6Cl3, K3RuCl6, wherein n is the water content coefficient in the salt.

3. The method for preparing a bifunctional catalyst according to claim 1, characterized in that: In step S2, the specific steps of the high-temperature calcination and oxidation treatment are: the first intermediate product obtained in step S01 is subjected to high-temperature calcination and oxidation in a heating device, the high-temperature calcination temperature is 300-800°C, and the high-temperature calcination time is 0.5-10h to obtain a second intermediate product.

4. The method for preparing a bifunctional catalyst according to claim 1, characterized in that: In step S3, the salt containing the HOR catalyst metal is at least one of salts containing Pt, Ru, Pd, and Rh metal elements.

5. A bifunctional catalyst obtained by the preparation method according to any one of claims 1 to 4.

6. The bifunctional catalyst according to claim 5 is used in an integrated renewable fuel cell stack.

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