Bimetal supported carbon-based catalyst as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of electrocatalyst energy, and particularly relates to a bimetallic supported carbon-based nano-catalyst as well as a preparation method and application thereof. Two metals in the catalyst are uniformly dispersed on a carbon carrier in the form of nano-particles and nano-sheets respectively, and are in close contact with each other; the metal nano-particles are used as catalytic active sites and have relatively strong adsorption and dissociation effects on sodium borohydride, and the metal nano-sheets effectively promote oxidation of reaction intermediates; as an anode catalyst of a direct sodium borohydride fuel cell, the composite material has relatively low charge transfer impedance, and has excellent catalytic activity and stability on sodium borohydride electrooxidation reaction. The preparation process is simple and effective, is good in repeatability, is easy for large-scale production, and has a wide application prospect.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrocatalyst energy, and particularly relates to a bimetal-loaded carbon-based catalyst, a preparation method thereof, and an application thereof. Background Art

[0002] Fuel cells have a relatively high theoretical energy density and can achieve a high energy output within a small volume. Therefore, they are expected to become the power source of a new generation of mobile electronic devices. At present, the relatively maturely developed proton exchange membrane fuel cells mainly use compressed hydrogen as fuel. However, the safety and cost problems brought by hydrogen storage and transportation still restrict the commercial development of proton exchange membrane fuel cells. In contrast, sodium borohydride, as a solid hydrogen storage material, not only has a high hydrogen content (10.6 wt%), but also has relatively stable chemical properties, showing significant advantages in terms of safety and portability. In addition, the theoretical energy density of sodium borohydride is as high as 9.3 kWh / kg, which makes the direct sodium borohydride fuel cell have broad development prospects in the field of power supply for mobile electronic devices.

[0003] In a direct sodium borohydride fuel cell, the anode is the electrooxidation reaction of sodium borohydride, and the cathode is the oxygen reduction reaction. Although it has been studied for many years, the actual output power density of the direct sodium borohydride fuel cell is still relatively low, and the anode catalyst therein plays an important role in improving the overall performance of the battery. Since the electrooxidation reaction mechanism of sodium borohydride is complex and involves a multi-electron transfer process, if the reaction intermediate cannot be oxidized in time, it will significantly reduce the energy density of the fuel cell and affect its continuous and stable energy output. Therefore, developing an efficient and stable anode catalyst to accelerate the oxidation process of the reaction intermediate is one of the effective ways to promote the industrial application of the direct sodium borohydride fuel cell. Summary of the Invention

[0004] The purpose of the present invention is to provide a bimetal-loaded carbon-based catalyst with high catalytic activity for the electrooxidation of sodium borohydride and a preparation method thereof.

[0005] The present invention also provides an application of the bimetal-loaded carbon-based catalyst, including providing an electrode that can be used as the anode of a direct sodium borohydride fuel cell. The bimetal-loaded carbon-based catalyst electrode has high electrooxidation activity for sodium borohydride, and reduces the charge transfer resistance and the interfacial impedance inside the battery.

[0006] The dual-metal supported carbon-based catalyst provided by the present invention comprises a carbon support, a first transition metal element and a second transition metal element; wherein, the first transition metal element is uniformly dispersed on the carbon support in the form of metal nanoparticles with an average particle size of 2-10 nm, and the second transition metal element is uniformly dispersed around the first transition metal element in the form of metal nanosheets; wherein, the mass percentage content of the carbon support is 30-90%, the mass percentage content of the first transition metal element is 5-50%, the mass percentage content of the second transition metal element is 5-50%, and the sum of the mass percentage contents of the materials is 100%; the first transition metal nanoparticles serve as catalytic active sites and have a strong adsorption and dissociation effect on sodium borohydride, and the second transition metal nanosheets promote the oxidation process of reaction intermediates on the metal nanoparticles.

[0007] Further:

[0008] The first transition metal element is selected from one of Ru, Ir, Pd, Pt, Au, Ag, and Mn.

[0009] The second transition metal element is selected from one of Fe, Co, Ni, Cu, Zn, Mo, and Cr.

[0010] The carbon support is selected from one of conductive carbon black XC-72, conductive carbon black super P, conductive carbon black BP2000, and conductive carbon black acetylene black.

[0011] The present invention also provides a preparation method of the above dual-metal supported carbon-based catalyst, adopting the sol-gel method, and the specific steps are as follows:

[0012] (1) Prepare a mixed solution of dual-metal salts: Weigh 0.01-0.5 g of the first transition metal salt, 0.1-0.8 g of the second transition metal salt, and 0.05-0.5 g of the carbon support, add them to 10-100 mL of the dispersion liquid, ultrasonically disperse the mixed solution evenly, and then place the mixed solution in a refrigerator at -20-2 °C for 0.5-5 hours;

[0013] (2) Add epoxy compound: Slowly drop 1-20 mL of the epoxy compound and 5-50 mL of deionized water into the above mixed solution of metal salts simultaneously, with a dropping rate of 0.1-5 mL / min, and then make it evenly mixed by oscillation;

[0014] (3) Stand and precipitate: Let the above mixed solution stand for 12-72 hours, add an organic solvent and centrifuge to remove the unreacted metal precursor salts and the residual epoxy compound, and dry and grind the precipitate to obtain the dual-metal supported carbon-based catalyst.

[0015] Further:

[0016] The first transition metal salt described in step (1) is at least one of acetylacetonate, chloride, acetate, sulfate, and nitrate;

[0017] The second transition metal salt described in step (1) is at least one of acetylacetonate, chloride, acetate, sulfate, and nitrate;

[0018] The dispersion described in step (1) is at least one of water, ethanol, methanol, isopropanol, ethylene glycol, N,N-dimethylformamide, ethyl acetate, and dimethyl sulfoxide;

[0019] The epoxide described in step (2) is one or more of propylene oxide, butylene oxide, bromopropylene oxide, and epichlorohydrin;

[0020] The organic solvent described in step (3) is at least one of methanol, ethanol, ethylene glycol, n-propanol, isopropanol, acetone, ethyl acetate, and tetrahydrofuran;

[0021] The drying condition described in step (3) is one of vacuum drying, freeze drying, and supercritical fluid drying.

[0022] The present invention also provides a membrane electrode for the electrooxidation of sodium borohydride, and the specific steps are as follows:

[0023] Mix the bimetal-loaded carbon-based catalyst with an adhesive and a second organic solvent, ultrasonically disperse for 10 - 50 minutes to obtain a catalyst slurry, spray it on a proton exchange membrane to form a catalyst layer, which is used as the anode material of a direct sodium borohydride fuel cell. Spray a platinum-carbon catalyst with a platinum mass percentage of 5 - 80% on the other side of the proton exchange membrane in the same way as the cathode.

[0024] Furthermore, the adhesive is one of perfluorosulfonic acid resin solution, polytetrafluoroethylene solution, polyvinylidene fluoride solution, and Sustainion XA-9 alkaline ionomer solution; the second organic solvent is one or more of ethanol, methanol, ethylene glycol, isopropanol, and acetone; the proton exchange membrane is one of Nafion 117 membrane, Nafion 212 membrane, Nafion115 membrane, and Gore membrane, with a thickness of 5 - 100 μm, and the loading amount of the electrode catalyst layer is 0.5 mg / cm 2 -10 mg / cm 2 .

[0025] The present invention also provides a direct sodium borohydride fuel cell device. This device uses the above-mentioned membrane electrode as the anode and cathode of the fuel cell device, uses carbon cloth as the anode gas diffusion layer, uses carbon paper as the cathode gas diffusion layer, and is assembled by polytetrafluoroethylene gaskets, graphite plates engraved with serpentine flow channels, current collector plates, insulating plates and metal end plates. The fuel cell device is heated to 40 - 100 °C by a heating rod. The anode fuel is a mixed solution of sodium borohydride at 0.3 - 5 mol / L and sodium hydroxide at 0.2 - 3 mol / L, and the cathode is one of oxygen, air and hydrogen peroxide solution. A direct sodium borohydride fuel cell device is assembled.

[0026] Compared with the prior art, the technical solution of the present invention has the following advantages:

[0027] (1) The preparation method of the bimetal-loaded carbon-based catalyst in the present invention is simple, the preparation period is short, the active components of the obtained catalyst are evenly dispersed and the particle size is small, the repeatability is good, it is easy to be efficiently mass-produced, and it is beneficial to industrial development;

[0028] (2) Using the bimetal-loaded carbon-based catalyst as the electrocatalyst for sodium borohydride electrooxidation, the synergistic effect between the two transition elements improves the dispersion degree of the two components and reduces the interfacial resistance, thereby reducing the charge transfer resistance, promoting charge transfer, and improving the electrochemical characteristics of the electrode, showing high catalytic activity;

[0029] (3) Using the bimetal-loaded carbon-based catalyst provided by the present invention as the anode catalyst of a direct sodium borohydride fuel cell, the first transition metal element has a strong adsorption and dissociation effect on borohydride ions, which is beneficial to the formation of oxidation intermediates of borohydride. The second transition metal compound is in close contact with the first transition metal element and provides a large amount of reactants, which can react with the intermediate, promote the further oxidation and desorption of the intermediate on the active site of the first transition metal element, and thus release the active site. Therefore, the synergistic effect between the two transition metals accelerates the regeneration of the catalyst active site, making the catalyst show high power density and excellent stability. In addition, compared with oxygen and hydrogen peroxide solution commonly used in the cathode, using air in the cathode of the present invention can not only reduce costs, but also improve the practicability in mobile and portable devices, and has broad development prospects. Description of the Drawings

[0030] Figure 1 It is the X-ray diffraction pattern of the PdNi / C catalyst in the embodiment of the present invention.

[0031] Figure 2 It is the scanning electron microscope photograph of the PdNi / C catalyst in the embodiment of the present invention.

[0032] Figure 3It is the high-angle annular dark-field scanning transmission electron microscope photograph of the PdNi / C catalyst in the embodiment of the present invention.

[0033] Figure 4 It is the elemental distribution map of the PdNi / C catalyst in the embodiment of the present invention.

[0034] Figure 5 It is the X-ray photoelectron spectrum of the PdNi / C catalyst in the embodiment of the present invention. Among them, (a) is the 3d X-ray photoelectron spectrum of Pd in PdNi / C, and (b) is the 2p X-ray photoelectron spectrum of Ni in PdNi / C.

[0035] Figure 6 It is the cyclic voltammogram of the PdNi / C catalyst in the embodiment of the present invention and the activity comparison with Pd / C and Ni / C catalysts.

[0036] Figure 7 It is the electrochemical impedance spectrum of the PdNi / C catalyst in the embodiment of the present invention and the impedance comparison with Pd / C and Ni / C catalysts.

[0037] Figure 8 It is the performance of the direct borohydride fuel cell with the PdNi / C catalyst as the anode catalyst in the embodiment of the present invention and the performance comparison with Pd / C and Ni / C catalysts.

[0038] Figure 9 It is the stability test result of the direct borohydride fuel cell with the PdNi / C catalyst as the anode catalyst in the embodiment of the present invention.

[0039] Figure 10 It is the performance test result of the direct borohydride fuel cell with the PdCo / C catalyst as the anode catalyst in the embodiment of the present invention.

[0040] Figure 11 It is the performance test result of the direct borohydride fuel cell with the PdCu / C catalyst as the anode catalyst in the embodiment of the present invention. Detailed implementation manners

[0041] Designing an efficient catalyst for the anodic borohydride electrooxidation reaction (BOR) is the key to improving the performance of direct borohydride fuel cells. At present, palladium-based catalysts exhibit high BOR catalytic activity due to their strong adsorption and dissociation ability for borohydride ions. However, palladium has an overly strong adsorption effect on the intermediate of BOR, dissociative hydrogen, resulting in the inability of dissociative hydrogen to be oxidized and desorbed in a timely manner, thus affecting the regeneration of the catalyst active sites and seriously hindering the improvement of the catalytic activity and stability of palladium-based catalysts.

[0042] The present invention provides a bimetallic supported carbon-based catalyst. A second transition metal is introduced into the palladium-based catalyst, and the two transition metal elements are uniformly dispersed on the carbon support. The synergistic effect between them is beneficial to the oxidative removal of the dissociative hydrogen, which is an intermediate in the BOR reaction, and promotes the regeneration of the active sites of the catalyst, thereby improving the catalytic activity and stability of the catalyst in the BOR process.

[0043] The present invention will be further introduced below through specific examples in conjunction with the accompanying drawings.

[0044] Example 1. A PdNi / C catalyst is prepared by a one-step method to uniformly disperse two metal elements, palladium and nickel, on the carbon support in ultra-small sizes.

[0045] (1) Preparation of the bimetallic supported carbon-based catalyst PdNi / C:

[0046] First, weigh 0.15 g of palladium chloride (PdCl 2 ), 0.44 g of nickel chloride hexahydrate (NiCl 2 ·6H 2 O) and disperse them in 30 mL of N,N-dimethylformamide. Then weigh 0.2 g of conductive carbon black XC-72 and add it to the above solution. Ultrasonic the mixture for 5 minutes to make it evenly mixed, and then place it in a refrigerator at -10 °C for 2 hours. Then, simultaneously dropwise add 20 mL of deionized water and 5 mL of propylene oxide to the mixed solution at the dropping rates of 1 mL / min and 0.25 mL / min respectively. After the dropping is completed, place the mixed solution on a vortex oscillator and oscillate it for 30 s to make it fully mixed. Then let the above solution stand at room temperature for 1 day, add acetone for centrifugal cleaning to remove the unreacted precursor salts and residual propylene oxide in it, and vacuum dry and grind the centrifuged precipitate to obtain the bimetallic supported carbon-based catalyst PdNi / C.

[0047] (Note: For comparison, the comparative samples Pd / C and Ni / C were prepared according to the same method and operating conditions.)

[0048] In this example, Figure 1 The X-ray diffraction pattern proves the successful loading of palladium and nickel. PdNi / C is mainly composed of metallic palladium and nickel hydroxide. From Figure 2 The scanning electron microscope photos of Figure 3 show the morphology of PdNi / C, which is mainly composed of particles and lamellae. It can be seen from the high-angle annular dark-field scanning transmission electron microscope photos ( Figure 4 ) that the catalyst particle size is small, less than 5 nm, and nickel hydroxide is distributed around metallic palladium, and the two are in close contact. The elemental distribution map ( Figure 5) The valence states of elements on the catalyst surface can be obtained. On the PdNi / C surface, the palladium element is mainly in the +2 valence state, with a small amount in the 0 valence state, and the nickel element is also mainly in the +2 valence state, with some in the +3 valence state.

[0049] (2) Preparation of the PdNi / C catalyst electrode:

[0050] Disperse 2.5 mg of the above PdNi / C catalyst in a 0.5 mL mixed solution of deionized water and ethanol with a volume ratio of 1:1. Then add 40 μL of a 5 wt% perfluorosulfonic acid resin solution. After ultrasonic treatment for 30 minutes, use a pipette to aspirate 3 μL of the mixed solution and drop-coat it onto a glassy carbon electrode with a diameter of 3 cm, and let it dry naturally at room temperature. Then use this glassy carbon electrode to test the electrochemical performance of the catalyst. From the cyclic voltammetry curve ( Figure 6 ) It can be obtained that, compared with Pd / C, PdNi / C has a higher current density, indicating that it has higher catalytic activity for BOR. The electrochemical impedance spectroscopy ( Figure 7 ) shows that PdNi / C exhibits a smaller radius of the AC impedance spectrum, indicating that the charge transfer resistance on it is lower, which is more conducive to the efficient progress of BOR.

[0051] (Note: For comparison, the reference samples of Pd / C and Ni / C catalyst electrodes were prepared according to the same method and operating conditions.)

[0052] (3) The present invention provides a method for preparing a membrane electrode of a direct sodium borohydride fuel cell:

[0053] For the anode side, weigh 25 mg of the above PdNi / C catalyst and disperse it in 2 mL of isopropanol. At the same time, add 180 μL of a 5 wt% perfluorosulfonic acid resin solution. After ultrasonic treatment for 30 minutes, take 0.2 mL of the mixed solution and spray it on a Gore proton exchange membrane with a thickness of 12 μm and dry it. The effective area is 1 cm 2 ; for the cathode side, weigh 25 mg of a Pt / C catalyst with a platinum mass percentage of 40% and disperse it in 2 mL of isopropanol. At the same time, add 180 μL of a 5 wt% perfluorosulfonic acid resin solution. After ultrasonic treatment for 30 minutes, take 0.2 mL of the mixed solution and spray it on the other side of the above Gore proton exchange membrane and dry it. The effective area is 1 cm 2 .

[0054] (Note: For comparison, the reference samples of Pd / C and Ni / C catalyst membrane electrodes were prepared according to the same method and operating conditions.)

[0055] (4) An assembly and testing method for a direct sodium borohydride fuel cell:

[0056] The fuel cell device uses the above-mentioned membrane electrode as the anode and cathode of the battery, uses carbon cloth as the anode gas diffusion layer, uses carbon paper as the cathode gas diffusion layer, and is assembled by a polytetrafluoroethylene gasket, a graphite plate engraved with a serpentine flow channel, a current collector plate, an insulating plate, and a metal end plate. The anode uses a mixed solution of 2M NaBH 4 and 1M NaOH as the anode fuel, and is circulated by a peristaltic pump at a flow rate of 100 mL / min; air is introduced into the cathode side, and the gas flow rate is controlled at 300 mL / min by a gas flow meter. To ensure sufficient reaction of air on the cathode side, a back pressure of 100 kPa is applied at the cathode outlet. The above device is heated to 80 °C by a heating rod. Tested under the above conditions, the performance results are as Figure 8 shown. The open circuit voltage of PdNi / C is 1.02 V, slightly higher than that of Pd / C (0.98 V), and the output power density of PdNi / C is 625 mW / cm 2 , which is 2.3 times the power density of Pd / C (268 mW / cm 2 ). In addition, as Figure 9 shown, the PdNi / C catalyst exhibits excellent stability and can operate stably at a current density of 200 mA / cm 2 for more than 120 hours.

[0057] Example 2, a PdCo / C catalyst, in which two metal elements, palladium and cobalt, are uniformly dispersed on a carbon support in ultra-small sizes by a one-step method.

[0058] (1) Preparation of the bimetallic-loaded carbon-based catalyst PdCo / C:

[0059] First, weigh 0.15 g of palladium chloride (PdCl 2 ), 0.48 g of cobalt chloride hexahydrate (CoCl 2 ·6H 2 O) and disperse them in 30 mL of N,N-dimethylformamide. Then weigh 0.2 g of conductive carbon black XC-72 and add it to the above solution. After ultrasonic mixing of the mixture for 5 minutes to make it uniformly mixed, place it in a -10 °C refrigerator for 2 hours. Then, 20 mL of deionized water and 5 mL of propylene oxide are simultaneously added dropwise to the mixed solution at dropping rates of 1 mL / min and 0.25 mL / min respectively. After the dropping is completed, place the mixed solution on a vortex oscillator and oscillate it for 30 s to make it fully mixed. Then, leave the above solution standing at room temperature for 1 day, add acetone for centrifugal cleaning to remove the unreacted precursor salts and residual propylene oxide, and vacuum-dry and grind the centrifuged precipitate to obtain the bimetallic-loaded carbon-based catalyst PdCo / C.

[0060] (2) Preparation of the PdCo / C catalyst electrode:

[0061] Disperse 2.5 mg of the above PdCo / C catalyst in a 0.5 mL mixed solution of deionized water and isopropanol with a volume ratio of 1:1. Then add 40 μL of 5 wt% Sustainion XA-9 solution. After ultrasonic treatment for 30 minutes, use a pipette to aspirate 3 μL of the mixed solution and drop-coat it onto a glassy carbon electrode with a diameter of 3 cm, and let it dry naturally at room temperature.

[0062] (3) The present invention provides a method for preparing a membrane electrode of a direct sodium borohydride fuel cell:

[0063] For the anode side, weigh 25 mg of the above PdCo / C catalyst and disperse it in 2 mL of ethanol. At the same time, add 180 μL of 5 wt% Sustainion XA-9 solution. After ultrasonic treatment for 30 minutes, take 0.2 mL of the mixed solution and spray it on a Nafion 212 membrane with a thickness of 50 μm and dry it. The effective area is 1 cm 2 ; for the cathode side, weigh 25 mg of a Pt / C catalyst with a platinum mass percentage of 40% and disperse it in 2 mL of ethanol. At the same time, add 180 μL of 5 wt% Sustainion XA-9 solution. After ultrasonic treatment for 30 minutes, take 0.2 mL of the mixed solution and spray it on the other side of the above Nafion 212 membrane and dry it. The effective area is 1 cm 2 .

[0064] (4) The present invention provides an assembly and testing method for a direct sodium borohydride fuel cell: The fuel cell device uses the above membrane electrode as the anode and cathode of the battery, uses carbon cloth as the anode gas diffusion layer, uses carbon paper as the cathode gas diffusion layer, and is assembled by a polytetrafluoroethylene gasket, a graphite plate with a serpentine flow channel, a current collector plate, an insulating plate, and a metal end plate. The anode uses a mixed solution of 2M NaBH 4 and 1M NaOH as the anode fuel, and uses a peristaltic pump for circulation with a flow rate of 100 mL / min; air is introduced into the cathode side, and the gas flow rate is controlled to be 300 mL / min through a gas flow meter. To ensure sufficient reaction of air on the cathode side, a back pressure of 100 kPa is applied at the cathode outlet. The above device is heated to 80 °C by a heating rod. Test according to the above conditions, and the obtained performance results, such as Figure 10 shown, the open circuit voltage of PdCo / C is 1.0 V, and the output power density is 400 mW / cm 2 .

[0065] Example 3, a PdCu / C catalyst, in which two metal elements, palladium and copper, are uniformly dispersed on a carbon support in ultra-small sizes by a one-step method.

[0066] (1) Preparation of the bimetal-loaded carbon-based catalyst PdCu / C:

[0067] First, weigh 0.15 g of palladium chloride (PdCl 2 ), 0.32 g of copper chloride dihydrate (CuCl 2 ·2H 2 O) and disperse them in 30 mL of N,N-dimethylformamide. Then weigh 0.2 g of conductive carbon black XC-72 and add it to the above solution. After ultrasonically mixing the mixture for 5 minutes to make it homogeneous, place it in a -10 °C refrigerator for 2 hours. Then, simultaneously dropwise add 20 mL of deionized water and 5 mL of propylene oxide to the mixed solution at dropping rates of 1 mL / min and 0.25 mL / min respectively. After the dropping is completed, place the mixed solution on a vortex oscillator and oscillate it for 30 s to make it fully mixed. Then leave the above solution to stand at room temperature for 1 day, add acetone for centrifugal cleaning to remove the unreacted precursor salts and residual propylene oxide in it, and vacuum dry and grind the centrifuged precipitate to obtain the bimetal-loaded carbon-based catalyst PdCu / C.

[0068] (2) Preparation of the PdCu / C catalyst electrode:

[0069] Disperse 2.5 mg of the above PdCu / C catalyst in a mixed solution of 0.5 mL of deionized water and ethylene glycol with a volume ratio of 1:1. Then add 40 μL of a 5 wt% perfluorosulfonic acid resin solution to it. After ultrasonically mixing for 30 minutes, use a pipette to aspirate 3 μL of the mixed solution and drop-coat it onto a glassy carbon electrode with a diameter of 3 cm, and let it air-dry at room temperature.

[0070] (3) The present invention provides a method for preparing a membrane electrode of a direct sodium borohydride fuel cell:

[0071] For the anode side, weigh 25 mg of the above PdCu / C catalyst and disperse it in 2 mL of ethylene glycol. At the same time, add 180 μL of a 5 wt% perfluorosulfonic acid resin solution. After ultrasonically mixing for 30 minutes, take 0.2 mL of the mixed solution and spray it on a Nafion 115 membrane with a thickness of 120 μm and dry it. The effective area is 1 cm 2 ; for the cathode side, weigh 25 mg of a Pt / C catalyst with a platinum mass percentage of 40% and disperse it in 2 mL of ethylene glycol. At the same time, add 180 μL of a 5 wt% perfluorosulfonic acid resin solution. After ultrasonically mixing for 30 minutes, take 0.2 mL of the mixed solution and spray it on the other side of the above Nafion 115 membrane and dry it. The effective area is 1 cm 2 .

[0072] (4) The present invention provides an assembly and testing method for a direct sodium borohydride fuel cell: The fuel cell device uses the above membrane electrode as the anode and cathode of the battery, uses carbon cloth as the anode gas diffusion layer, uses carbon paper as the cathode gas diffusion layer, and is assembled by a polytetrafluoroethylene gasket, a graphite plate with a serpentine flow channel, a current collector plate, an insulating plate, and a metal end plate. The anode uses 2M NaBH4 A mixed solution of [substance] and 1M NaOH is used as the anode fuel, circulated by a peristaltic pump at a flow rate of 100 mL / min; air is introduced on the cathode side, and the gas flow rate is controlled by a gas flow meter at 300 mL / min. To ensure sufficient reaction of air on the cathode side, a back pressure of 100 kPa is applied at the cathode outlet. The above device is heated to 80 °C by a heating rod. Testing is carried out according to the above conditions, and the performance results obtained are as Figure 11 shown. The open-circuit voltage of PdCu / C is 1.1 V, and the output power density is 309 mW / cm 2 .

Claims

1. A bimetallic supported carbon-based catalyst, characterized in that: It includes a carbon carrier, a first transition metal element and a second transition metal element; wherein the first transition metal element is uniformly dispersed on the carbon carrier in the form of metal nanoparticles with an average particle size of 2-10nm, and the second transition metal element is uniformly dispersed around the first transition metal element in the form of metal nanosheets; wherein the mass percentage of the carbon carrier is 30-90%, the mass percentage of the first transition metal element is 5-50%, the mass percentage of the second transition metal element is 5-50%, and the sum of the mass percentages of the materials is 100%; the first transition metal nanoparticles serve as catalytic active sites and have a strong adsorption and dissociation effect on sodium borohydride, and the second transition metal nanosheets promote the oxidation process of the reaction intermediates on the metal nanoparticles.

2. The bimetallic supported carbon-based catalyst according to claim 1, characterized in that: The first transition metal element is one of Ru, Ir, Pd, Pt, Au, Ag, and Mn; the second transition metal element is one of Fe, Co, Ni, Cu, Zn, Mo, and Cr; the carbon carrier is one of conductive carbon black XC-72, conductive carbon black super P, conductive carbon black BP2000, and conductive carbon black acetylene black.

3. A method for preparing a bimetallic supported carbon-based catalyst as claimed in claims 1-2, characterized in that: The sol-gel method is used, and the specific steps are as follows: (1) preparing a bimetallic salt mixed solution: weighing 0.01-0.5 g of a first transition metal salt, 0.1-0.8 g of a second transition metal salt, and 0.05-0.5 g of a carbon support, adding them to 10-100 mL of a dispersion solution, ultrasonically dispersing the mixed solution to make it uniform, and then placing the mixed solution in a -20-2°C refrigerator for 0.5-5 hours; (2) adding the epoxy compound: slowly dropwise adding 1-20 mL of the epoxy compound and 5-50 mL of deionized water into the above-mentioned bimetallic salt mixed solution at a dropping speed of 0.1-5 mL / min, and then oscillating to mix them evenly; (3) Standing and precipitation: The mixed solution is allowed to stand for 12-72 hours, an organic solvent is added and centrifuged to remove the metal precursor salt that has not participated in the reaction and the residual epoxy compound, and the precipitate is dried and ground to obtain a bimetallic supported carbon-based catalyst.

4. The preparation method according to claim 3, characterized in that: In step (1), the first transition metal salt is at least one of acetylacetonate, chloride, acetate, sulfate, and nitrate; In step (1), the second transition metal salt is at least one of acetylacetonate, chloride, acetate, sulfate, and nitrate; The dispersion liquid in step (1) is at least one of water, ethanol, methanol, isopropanol, ethylene glycol, N,N-dimethylformamide, ethyl acetate, and dimethyl sulfoxide; The epoxy compound in step (2) is one or more of propylene oxide, butylene oxide, epibromopropane and epichlorohydrin; The organic solvent in step (3) is at least one of methanol, ethanol, ethylene glycol, n-propanol, isopropanol, acetone, ethyl acetate and tetrahydrofuran; The drying condition in step (3) is one of vacuum drying, freeze drying and supercritical fluid drying.

5. A membrane electrode for sodium borohydride electrooxidation, comprising the following steps: The bimetallic supported carbon-based catalyst is mixed with a binder and a second organic solvent, and ultrasonically dispersed for 10-50 minutes to obtain a catalyst slurry, which is sprayed on a proton exchange membrane to form a catalyst layer as the anode of a direct sodium borohydride fuel cell; and a platinum-carbon catalyst with a platinum mass percentage of 5-80% is sprayed on the other side of the proton exchange membrane as a cathode in the same manner.

6. The use according to claim 5, characterized in that: The binder is one of perfluorosulfonic acid resin solution, polytetrafluoroethylene solution, polyvinylidene fluoride solution, and Sustainion XA-9 alkaline ionomer solution; the second organic solvent is one or more of ethanol, methanol, ethylene glycol, isopropanol, and acetone; the proton exchange membrane is one of Nafion 117 membrane, Nafion 212 membrane, Nafion 115 membrane, and Gore membrane, with a thickness of 5-100 μm, and the loading amount of the electrode catalyst layer is 0.5 mg / cm 2 -10 mg / cm 2 .

7. A direct sodium borohydride fuel cell device, using the membrane electrode as the cathode and anode of the battery device, carbon cloth as the anode gas diffusion layer, carbon paper as the cathode gas diffusion layer, and assembled by a polytetrafluoroethylene gasket, a graphite plate engraved with a serpentine flow channel, a collector plate, an insulating plate and a metal end plate; the battery device is heated to 40-100°C by a heating rod; the anode fuel is a mixed solution of 0.3-5 mol / L sodium borohydride and 0.2-3 mol / L sodium hydroxide, and the cathode is one of oxygen, air and hydrogen peroxide solution, and a direct sodium borohydride fuel cell device is assembled.

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