Low-temperature direct ammonia fuel cell catalyst as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of fuel cell catalysts, and particularly relates to a low-temperature direct ammonia fuel cell catalyst and a preparation method and application thereof. Comprising the following steps: by taking hexadecyl trimethyl ammonium bromide as a template agent and a nitrogen source, resorcinol and formaldehyde resin as carbon sources and tetraethoxysilane as a silicon source, obtaining a nitrogen-doped mesoporous carbon sphere precursor in a system of a basic catalyst and a solvent; calcining the nitrogen-doped mesoporous carbon sphere precursor to obtain a nitrogen-doped mesoporous carbon sphere; and dissolving the nitrogen-doped mesoporous carbon spheres in an ethylene glycol solution to form a nitrogen-doped mesoporous carbon sphere solution, adding a soluble platinum salt and a soluble cobalt salt into the nitrogen-doped mesoporous carbon sphere solution, and carrying out a microwave reaction to obtain the low-temperature direct ammonia fuel cell catalyst. The platinum-cobalt bimetallic catalyst is prepared by taking the nitrogen-doped mesoporous carbon spheres as the carrier and loading the platinum-cobalt bimetallic, so that more platinum active sites can be exposed, and the AOR activity of the catalyst can be effectively improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of fuel cell catalysts, and particularly relates to a catalyst for a low-temperature direct ammonia fuel cell, a preparation method thereof, and an application thereof. Background Art

[0002] As a clean, efficient conversion and energy storage device, fuel cells are widely used due to their many advantages such as stable performance, pollution-free, and high safety. Currently, the most commonly used fuel cell is the hydrogen-oxygen fuel cell. However, hydrogen has a low energy density at normal temperature and pressure, and needs to be pressurized to store and transport it. Moreover, the dangerousness of hydrogen being flammable and explosive poses many technical challenges in aspects such as long-distance transportation and supply networks. To solve these problems, researchers have tried to store hydrogen in various materials by chemical means. Among them, ammonia, as a carbon-free hydrogen-rich energy carrier, has the characteristics of high energy density and high hydrogen content, and the transportation and storage infrastructure of ammonia is mature, making it a very promising option. Compared with the hydrogen-oxygen fuel cell, the anodic reaction of the low-temperature direct ammonia fuel cell is the oxidation of ammonia, which has the advantages of small volume, fast startup, and the ability to work at low temperature. However, the anodic reaction kinetics of the low-temperature direct ammonia fuel cell is slow, and a relatively high overpotential (>0.4V) is required to start, and strongly adsorbed reaction intermediates (such as *N and *NO) will cause the catalyst to quickly deactivate. To overcome these problems, it is urgent to find a suitable catalyst for the low-temperature direct ammonia fuel cell to improve the catalytic activity and promote the development of the low-temperature direct ammonia fuel cell.

[0003] There are mainly two catalysts with the most promising applications in low-temperature direct ammonia fuel cells, namely Pt-based noble metal catalysts and Ni-based non-noble metal catalysts. Among them, the Ni element in the Ni-based non-noble metal catalyst can be activated by potential cycling under alkaline conditions to form a protective layer of Ni(OH)2 on the surface and be converted into NiOOH in subsequent reactions, showing good application prospects. However, the Ni-based non-noble metal catalyst is very easy to corrode and is easily affected by nitrogen and oxygen species, resulting in a low overall efficiency. Currently, the most commonly used and most efficient catalyst for low-temperature direct ammonia fuel cells is still the Pt-based noble metal catalyst, but its stability is poor and the catalytic activity is limited. Summary of the Invention

[0004] To solve the above problems, the present invention provides a catalyst for a low-temperature direct ammonia fuel cell, a preparation method thereof, and an application thereof. A platinum-cobalt bimetallic catalyst is prepared by loading platinum and cobalt bimetals on a nitrogen-doped mesoporous carbon sphere as a carrier. It has a large specific surface area and good conductivity, and has good stability under the conditions of ammonia electrooxidation. The doping of cobalt element in the platinum-cobalt bimetallic catalyst can preferentially adsorb hydroxyl groups in the reaction process, which helps to expose more platinum active sites and can effectively improve the AOR activity of the catalyst.

[0005] The present invention solves the above technical problems through the following technical solutions.

[0006] One of the objectives of the present invention is to provide a preparation method for a catalyst of a low-temperature direct ammonia fuel cell, comprising the following steps: S1. Using cetyltrimethylammonium bromide as a template agent and nitrogen source, resorcinol and formaldehyde resin as carbon sources, and tetraethyl orthosilicate as a silicon source, in a system of an alkaline catalyst and a solvent, a nitrogen-doped mesoporous carbon sphere precursor is obtained by combining the soft template method and the hard template method.

[0007] S2. Under the atmosphere of a protective gas, the nitrogen-doped mesoporous carbon sphere precursor is calcined at 700-900 °C, and then the silicon dioxide is removed to obtain a nitrogen-doped mesoporous carbon sphere.

[0008] S3. Dissolving the nitrogen-doped mesoporous carbon sphere in an ethylene glycol solution to form a nitrogen-doped mesoporous carbon sphere solution, adding a platinum salt solution and a soluble cobalt salt to the nitrogen-doped mesoporous carbon sphere solution to form a reaction solution, and performing a microwave reaction to load platinum and cobalt on the nitrogen-doped mesoporous carbon sphere to obtain a catalyst for a low-temperature direct ammonia fuel cell.

[0009] Further, the molar ratio of cetyltrimethylammonium bromide, resorcinol, formaldehyde, and tetraethyl orthosilicate is 0.18-1.54:0.2-1.23:0.4-2.45:1.

[0010] Further, the concentration of the nitrogen-doped mesoporous carbon sphere solution is 0.07 wt% - 0.1 wt%.

[0011] Further, the platinum salt solution is a chloroplatinic acid solution, the concentration of the chloroplatinic acid solution is 18 mmol / L - 20 mmol / L, the soluble cobalt salt is cobalt chloride, the molar ratio of chloroplatinic acid and cobalt chloride is 2.5-3.5:1, the ethylene glycol solution is a mixed solution of ethylene glycol and isopropanol, and the volume ratio of ethylene glycol and isopropanol is 3-5:1.

[0012] Further, before the microwave reaction, the pH of the reaction solution is adjusted to 9-11, the power of the microwave reaction is 480 W - 800 W, and the microwave time is 90 s - 150 s.

[0013] Further, the heating rate of the calcination is 5 °C / min - 10 °C / min, and the heat preservation time is 1 h - 3 h.

[0014] Further, in the method of combining the soft template method and the hard template method, the reaction temperature is 60 °C - 80 °C, and the time is 20 h - 30 h.

[0015] Further, the volume ratio of the alkaline catalyst to the solvent is 0.5 - 4:700, the molar ratio of the alkaline catalyst to resorcinol is 1:0.8 - 4.1, the alkaline catalyst is ammonia water, the volume concentration of the ammonia water is 25% - 28%, and the solvent is a mixture of water and ethanol with a volume ratio of 500:100 - 400.

[0016] The second object of the present invention is to provide a catalyst for a low-temperature direct ammonia fuel cell, which is prepared by the above preparation method.

[0017] The third object of the present invention is to provide the application of the above-mentioned catalyst for a low-temperature direct ammonia fuel cell in a low-temperature direct ammonia fuel cell.

[0018] The present invention has the following beneficial effects compared with the prior art: The preparation method of the catalyst for a low-temperature direct ammonia fuel cell provided by the present invention synthesizes a nitrogen-doped mesoporous carbon sphere support by combining the soft template method and the hard template method. During the reaction process, cetyltrimethylammonium bromide (CTAB) is used as a soft template and fully dissolved in the solution to form micelles. Resorcinol and formaldehyde form phenolic resin through a polycondensation reaction, and the SiO2 generated by the hydrolysis of tetraethyl orthosilicate is wrapped and embedded in the CTAB micelles. Subsequently, during the calcination process, the phenolic resin is carbonized to form a carbon skeleton, and CTAB decomposes to form a mesoporous structure with a large specific surface area. Then, under microwave reaction, soluble platinum salt and soluble cobalt salt are reduced to form metal elements platinum and cobalt, which are loaded on the nitrogen-doped mesoporous carbon sphere support, realizing the stable loading of platinum-cobalt nanoparticles and having good stability under the conditions of ammonia electrooxidation. The doping of cobalt element in the platinum-cobalt bimetallic catalyst can preferentially adsorb hydroxyl groups during the reaction process, which helps to expose more platinum active sites and can effectively improve the AOR activity of the catalyst.

[0019] The present invention realizes the stable loading of platinum-cobalt nanoparticles by means of microwave reaction. During this process, ethylene glycol decomposes to produce acetaldehyde, and the acetaldehyde reduces the metal elements, and finally the metal elements are loaded onto the substrate. Compared with the traditional catalyst synthesis method, microwave radiation is a fast, uniform and effective heating method. During the heating process, ethylene glycol not only acts as a reducing agent but also acts as a protective agent and a dispersant, so that the prepared catalyst is uniformly dispersed and has good catalytic performance. Description of the Drawings

[0020] Figure 1 It is the SEM morphology structure diagram of the nitrogen-doped mesoporous carbon sphere of the present invention. Figure 1 In it, a is the morphology structure diagram of the nitrogen-doped mesoporous carbon sphere at a size of 1 μm, and b is the morphology structure diagram of the nitrogen-doped mesoporous carbon sphere at a size of 200 nm.

[0021] Figure 2X-ray diffraction and X-ray photoelectron spectroscopy spectra of the PtCo / NMCS catalyst prepared in Example 1 of the present invention Figure 2 In (a) of Figure 2 , it is the X-ray diffraction spectrum, (b) is the full X-ray photoelectron spectroscopy spectrum, (c) is the X-ray photoelectron spectroscopy spectrum of Pt, (d) is the X-ray photoelectron spectroscopy spectrum of C, and (e) is the X-ray photoelectron spectroscopy spectrum of Co.

[0022] Figure 3 CV comparison chart of the catalysts prepared in Examples 1 to 9 of the present invention.

[0023] Figure 4 CV comparison chart of the catalysts prepared in Example 1 of the present invention and Comparative Examples 1 to 5.

[0024] Figure 5 i-t curve comparison chart of the catalysts prepared in Example 1 of the present invention and Comparative Examples 1 to 5. Detailed implementation manners

[0025] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0026] It should be noted that the professional terms used in the present invention are only for the purpose of describing specific embodiments and are not intended to limit the protection scope of the present invention. Unless otherwise specifically stated, various raw materials, reagents, instruments, and equipment used in the following embodiments of the present invention can be obtained through market purchases or prepared by existing methods.

[0027] There are mainly two types of catalysts with the most promising applications in low-temperature direct ammonia fuel cells, namely Pt-based noble metal catalysts and Ni-based non-noble metal catalysts. Among them, the Ni element in the Ni-based non-noble metal catalyst can be activated by potential cycling under alkaline conditions to form a protective layer of Ni(OH)2 on the surface and be converted into NiOOH in subsequent reactions, showing good application prospects. However, Ni-based non-noble metal catalysts are very prone to corrosion and are easily affected by nitrogen and oxygen species, resulting in low overall efficiency. Currently, the most commonly used and most efficient low-temperature direct ammonia fuel cell catalyst is still the Pt-based noble metal catalyst. Alloying Pt with transition metal elements can change the electronic structure properties of the catalyst surface and produce a synergistic effect with Pt while reducing the usage amount of noble metals and costs in the catalyst, thereby enhancing the activity and stability of the catalyst, which is a research direction with great application prospects.

[0028] Based on this, the present invention provides a preparation method of a catalyst for a low-temperature direct ammonia fuel cell, comprising the following steps: S1. Using cetyltrimethylammonium bromide as a template agent and nitrogen source, resorcinol and formaldehyde resin as carbon sources, and tetraethyl orthosilicate as a silicon source, in a system of an alkaline catalyst and a solvent, a nitrogen-doped mesoporous carbon sphere precursor is obtained by combining the soft template method and the hard template method.

[0029] S2. Under a protective gas atmosphere, the nitrogen-doped mesoporous carbon sphere precursor is calcined at 700 - 900 °C, and then the silicon dioxide is removed to obtain a nitrogen-doped mesoporous carbon sphere.

[0030] S3. Dissolving the nitrogen-doped mesoporous carbon sphere in an ethylene glycol solution to form a nitrogen-doped mesoporous carbon sphere solution, adding a platinum salt solution and a soluble cobalt salt to the nitrogen-doped mesoporous carbon sphere solution to form a reaction solution, and performing a microwave reaction to load platinum and cobalt on the nitrogen-doped mesoporous carbon sphere, thereby obtaining a catalyst for a low-temperature direct ammonia fuel cell.

[0031] First, a nitrogen-doped mesoporous carbon sphere support is synthesized by combining the soft template method and the hard template method. During the reaction process, CTAB is fully dissolved in the solution as a soft template to form micelles. Resorcinol and formaldehyde undergo a polycondensation reaction to form phenolic resin, which wraps the SiO2 generated by the hydrolysis of TEOS (tetraethyl orthosilicate) and embeds it into the CTAB micelles. Subsequently, during the calcination process, the phenolic resin is carbonized to form a carbon skeleton, CTAB decomposes, and a mesoporous structure is formed. Finally, SiO2 is removed by NaOH to form the final NMCS support, realizing the stable loading of platinum-cobalt nanoparticles. Then, a soluble platinum salt and a soluble cobalt salt are jointly added to the nitrogen-doped mesoporous carbon sphere solution for microwave heating. During this process, ethylene glycol decomposes to produce acetaldehyde, and the acetaldehyde reduces the metal elements, and finally the metal elements are loaded onto the substrate. Compared with the traditional catalyst synthesis method, microwave radiation is a fast, uniform, and effective heating method. And during the heating process, ethylene glycol not only acts as a reducing agent but also serves as a protective agent and a dispersant, so that the prepared catalyst is uniformly dispersed and has good stability under the conditions of ammonia electrooxidation. The doping of cobalt elements in the platinum-cobalt bimetallic catalyst can preferentially adsorb hydroxyl groups during the reaction process, which helps to expose more platinum active sites, can effectively improve the AOR activity of the catalyst, and has good catalytic performance.

[0032] In a specific embodiment, the molar ratio of cetyltrimethylammonium bromide, resorcinol, formaldehyde and tetraethyl orthosilicate is 0.18 - 1.54:0.2 - 1.23:0.4 - 2.45:1. It should be noted that in the present invention, CTAB is used as a soft template and is fully dissolved in the solution to form micelles. Resorcinol and formaldehyde form phenolic resin through a polycondensation reaction, and the SiO2 generated by the hydrolysis of TEOS is wrapped and embedded in the CTAB micelles. If the ratio of CTAB to resorcinol is too small, the template coverage will be incomplete; if it is too large, the surfactant residue will block the pores. If the ratio of CTAB to TEOS is inappropriate, the hierarchical pore structure of the carbon spheres will fail. If the ratio of resorcinol to formaldehyde is too low, the rate of the polycondensation reaction will be too fast, resulting in local agglomeration; if it is too high, the crosslinking degree of the phenolic resin will be low, and the carbon spheres are prone to collapse. If the ratio of TEOS to phenolic resin is too high, the carbon spheres are easy to break; if it is too low, the hierarchical pore effect of the carbon spheres will be weakened.

[0033] In a specific embodiment, the concentration of the nitrogen-doped mesoporous carbon sphere solution is 0.07 wt% - 0.1 wt%. It should be noted that in the present invention, the nitrogen-doped mesoporous carbon spheres are used as carriers to load cobalt and platinum. An appropriate concentration of the nitrogen-doped mesoporous carbon spheres can form a catalyst with uniform dispersion and good catalytic performance. However, when the concentration of the mesoporous carbon spheres is too high, agglomeration may occur, reducing the performance of the catalyst; if the concentration is too low, the yield of the catalyst will be low, and the content of cobalt and platinum loaded will be low.

[0034] In the present invention, the platinum salt solution is chloroplatinic acid solution, the concentration of the chloroplatinic acid solution is 18 mmol / L - 20 mmol / L, the soluble cobalt salt is cobalt chloride, the molar ratio of chloroplatinic acid to cobalt chloride is 2.5 - 3.5:1, and the ethylene glycol solution is a mixed solution of ethylene glycol and isopropanol, and the volume ratio of ethylene glycol to isopropanol is 3 - 5:1. It should be noted that the chloroplatinic acid solution is an ethylene glycol solution of chloroplatinic acid. In a preferred embodiment, the concentration of the chloroplatinic acid solution is 19.2 mmol / L, and the molar ratio of chloroplatinic acid to cobalt chloride is 3:1. The chloroplatinic acid and cobalt chloride are added in a proportion of 20 wt% of the metal elements in the catalyst. By using transition metal cobalt, the amount of platinum can be reduced, and the electronic structure properties of the catalyst surface can be changed, producing a synergistic effect with platinum, thereby enhancing the activity and stability of the catalyst.

[0035] In a specific embodiment, before the microwave reaction, the pH of the reaction solution is adjusted to 9 - 11, the power of the microwave reaction is 480W - 800W, and the microwave time is 90s - 150s. It should be noted that in the present invention, platinum and cobalt are loaded on nitrogen-doped mesoporous carbon spheres by means of microwave reaction to obtain a catalyst for low-temperature direct ammonia fuel cells. Compared with other catalyst synthesis methods, microwave radiation is a fast, uniform, and effective heating method. During the heating process, ethylene glycol not only acts as a reducing agent but also serves as a protective agent and a dispersant, so that the prepared catalyst is uniformly dispersed and has good catalytic performance.

[0036] In the present invention, before the microwave reaction, the pH of the reaction solution is adjusted with a KOH / ethylene glycol solution, and the mass fraction of KOH in the KOH / ethylene glycol solution is 5wt.%. After the microwave reaction is completed, the pH of the reaction solution is adjusted to 4 with nitric acid, then stirred, filtered, washed, and dried to obtain a catalyst for low-temperature direct ammonia fuel cells.

[0037] In a specific embodiment, the heating rate of calcination is 5℃ / min - 10℃ / min, and the heat preservation time is 1h - 3h.

[0038] In the present invention, to remove silicon dioxide, the calcined product is added to an NaOH solution for etching to remove silicon dioxide, and the concentration of the NaOH solution is 1.5mol / L - 2.5mol / L.

[0039] In a specific embodiment, in the method combining the soft template method and the hard template method, the reaction temperature is 60℃ - 80℃, and the time is 20h - 30h.

[0040] In a specific embodiment, the volume ratio of the alkaline catalyst to the solvent is 0.5 - 4:700, the molar ratio of the alkaline catalyst to resorcinol is 1:0.8 - 4.1, the alkaline catalyst is ammonia water, the volume concentration of ammonia water is 25% - 28%, and the solvent is a mixture of water and ethanol with a volume ratio of 500:100 - 400.

[0041] The following is further illustrated by specific examples.

[0042] Example 1 A preparation method of a catalyst for low-temperature direct ammonia fuel cells includes the following steps: S1. Mix 100 mL of water, 40 mL of ethanol, and 0.2 mL of ammonia water, stir evenly in an oil bath at 70 °C, then add 2 g of cetyltrimethylammonium bromide. After stirring evenly, add 0.55 g of resorcinol and 0.74 mL of formaldehyde in sequence. After stirring evenly, quickly add 3 mL of tetraethyl orthosilicate, and continuously stir and react for 24 h. After the reaction is completed, centrifuge the stirred solution, wash it five times with ethanol, and dry it in a vacuum oven at 80 °C for 24 h to obtain brown nitrogen-doped mesoporous carbon sphere precursor powder.

[0043] S2. Grind the nitrogen-doped mesoporous carbon sphere precursor powder, then heat it to 800 °C at a rate of 5 °C / min in a nitrogen atmosphere and calcine it for 3 h, and then cool it with the furnace to obtain spherical porous carbon / silica composite. React the spherical porous carbon / silica composite in 2 mol / L NaOH solution for 24 h to remove silica in the sample. Filter the reacted solution by suction, wash it 5 times with deionized water, and dry it in a vacuum oven at 80 °C for 24 h to obtain nitrogen-doped mesoporous carbon spheres.

[0044] S3. Weigh 40 mg of NMCS, add it to a mixed solvent of 40 mL of ethylene glycol and 10 mL of isopropanol, and ultrasonically oscillate it evenly; weigh 2.409 mL of ethylene glycol solution of chloroplatinic acid (the concentration of chloroplatinic acid in the ethylene glycol solution is 19.2 mmol / L) and 3.8 mg of cobalt chloride and add them to the mixed solution, ultrasonically stir and mix evenly, adjust the pH value of the mixed solution to 10 with KOH / ethylene glycol solution (the mass fraction of KOH in the KOH / ethylene glycol solution is 5 wt.%), and carry out microwave reaction at a power of 800 W for 90 s; take out the reaction solution and let it cool naturally; after the solution cools, adjust the pH value of the solution to 4 with nitric acid solution, and stir overnight; filter by suction, wash it three times with ethanol and deionized water respectively, and dry it in a vacuum oven at 60 °C for 24 h to obtain a low-temperature direct ammonia fuel cell catalyst.

[0045] Example 2 A preparation method of a low-temperature direct ammonia fuel cell catalyst, comprising the following steps: S1. Mix 100 mL of water, 40 mL of ethanol, and 0.1 mL of ammonia water, stir evenly in an oil bath at 70 °C, then add 2 g of cetyltrimethylammonium bromide. After stirring evenly, add 0.55 g of resorcinol and 0.74 mL of formaldehyde in sequence. After stirring evenly, quickly add 3 mL of tetraethyl orthosilicate, and continuously stir and react for 24 h. After the reaction is completed, centrifuge the stirred solution, wash it five times with ethanol, and dry it in a vacuum oven at 80 °C for 24 h to obtain brown nitrogen-doped mesoporous carbon sphere precursor powder.

[0046] S2. Grind the nitrogen-doped mesoporous carbon sphere precursor powder, then heat it to 800 °C at a rate of 5 °C / min in a nitrogen atmosphere for calcination, hold the temperature for 3 h, and then cool it with the furnace to obtain a spherical porous carbon / silica composite. React the spherical porous carbon / silica composite in a 2 mol / L NaOH solution for 24 h to remove the silica in the sample. Filter the reacted solution by suction, wash it 5 times with deionized water, and dry it in a vacuum oven at 80 °C for 24 h to obtain nitrogen-doped mesoporous carbon spheres.

[0047] S3. Weigh 40 mg of NMCS and add it to a mixed solvent of 40 mL of ethylene glycol and 10 mL of isopropanol, and ultrasonically oscillate to make it uniform. Weigh 2.409 mL of chloroplatinic acid and 3.8 mg of cobalt chloride and add them to the mixed solution, ultrasonically stir to make it uniform, and adjust the pH value of the mixed solution to 10 with a KOH / ethylene glycol solution (the mass fraction of KOH in the KOH / ethylene glycol solution is 5 wt.%). Carry out a microwave reaction at a power of 800 W for 90 s; take out the reaction solution and let it cool naturally; after the solution cools, adjust the pH value of the solution to 4 with a nitric acid solution and stir overnight; filter by suction, wash it three times with ethanol and deionized water respectively, and dry it in a vacuum oven at 60 °C for 24 h to obtain a low-temperature direct ammonia fuel cell catalyst.

[0048] Example 3 A preparation method of a low-temperature direct ammonia fuel cell catalyst, comprising the following steps: S1. Mix 100 mL of water, 40 mL of ethanol and 0.4 mL of ammonia water, stir evenly in an oil bath at 70 °C, then add 2 g of cetyltrimethylammonium bromide, stir evenly and then add 0.55 g of resorcinol and 0.74 mL of formaldehyde in sequence, stir evenly and then quickly add 3 mL of tetraethyl orthosilicate, continuously stir and react for 24 h. After the reaction ends, centrifuge the stirred solution, wash it five times with ethanol, and dry it in a vacuum oven at 80 °C for 24 h to obtain a brown nitrogen-doped mesoporous carbon sphere precursor powder.

[0049] S2. Grind the nitrogen-doped mesoporous carbon sphere precursor powder, then heat it to 800 °C at a rate of 5 °C / min in a nitrogen atmosphere for calcination, hold the temperature for 3 h, and then cool it with the furnace to obtain a spherical porous carbon / silica composite. React the spherical porous carbon / silica composite in a 2 mol / L NaOH solution for 24 h to remove the silica in the sample. Filter the reacted solution by suction, wash it 5 times with deionized water, and dry it in a vacuum oven at 80 °C for 24 h to obtain nitrogen-doped mesoporous carbon spheres.

[0050] S3. Weigh 40 mg of NMCS and add it to a mixed solvent of 40 mL of ethylene glycol and 10 mL of isopropanol, and ultrasonically oscillate to make it uniform; weigh 2.409 mL of chloroplatinic acid and 3.8 mg of cobalt chloride and add them to the mixed solution, ultrasonically mix and stir evenly, use a KOH / ethylene glycol solution (the mass fraction of KOH in the KOH / ethylene glycol solution is 5 wt.%) to adjust the pH value of the mixed solution to 10, and carry out microwave reaction at a power of 800 W for 90 s; take out the reaction solution and let it cool naturally; after the solution cools, use nitric acid solution to adjust the pH value of the solution to 4 and stir overnight; carry out suction filtration separation, wash it three times with ethanol and deionized water respectively, and dry it in a vacuum oven at 60 °C for 24 h to obtain a catalyst for low-temperature direct ammonia fuel cells.

[0051] Example 4 A preparation method of a catalyst for low-temperature direct ammonia fuel cells, comprising the following steps: S1. Mix 100 mL of water, 40 mL of ethanol and 0.2 mL of ammonia water, stir evenly in an oil bath at 70 °C, then add 2 g of cetyltrimethylammonium bromide, after stirring evenly, add 0.55 g of resorcinol and 0.74 mL of formaldehyde in sequence, after stirring evenly, quickly add 3 mL of tetraethyl orthosilicate, continuously stir and react for 24 h, after the reaction ends, centrifuge the stirred solution, wash it five times with ethanol, and dry it in a vacuum oven at 80 °C for 24 h to obtain brown nitrogen-doped mesoporous carbon sphere precursor powder.

[0052] S2. Grind the nitrogen-doped mesoporous carbon sphere precursor powder, then heat it to 700 °C at a rate of 5 °C / min in a nitrogen atmosphere and calcine it for 3 h, and then cool it with the furnace to obtain a spherical porous carbon / silica composite. React the spherical porous carbon / silica composite in a 2 mol / L NaOH solution for 24 h to remove the silica in the sample. Carry out suction filtration separation on the reacted solution, wash it 5 times with deionized water, and dry it in a vacuum oven at 80 °C for 24 h to obtain nitrogen-doped mesoporous carbon spheres.

[0053] S3. Weigh 40 mg of NMCS and add it to a mixed solvent of 40 mL of ethylene glycol and 10 mL of isopropanol, and ultrasonically oscillate to make it uniform; weigh 2.409 mL of chloroplatinic acid and 3.8 mg of cobalt chloride and add them to the mixed solution, ultrasonically mix and stir evenly, use a KOH / ethylene glycol solution (the mass fraction of KOH in the KOH / ethylene glycol solution is 5 wt.%) to adjust the pH value of the mixed solution to 10, and carry out microwave reaction at a power of 800 W for 90 s; take out the reaction solution and let it cool naturally; after the solution cools, use nitric acid solution to adjust the pH value of the solution to 4 and stir overnight; carry out suction filtration separation, wash it three times with ethanol and deionized water respectively, and dry it in a vacuum oven at 60 °C for 24 h to obtain a catalyst for low-temperature direct ammonia fuel cells.

[0054] Example 5 A preparation method of a catalyst for a low-temperature direct ammonia fuel cell, comprising the following steps: S1. Mix 100 mL of water, 40 mL of ethanol, and 0.2 mL of ammonia water, stir evenly in an oil bath at 70 °C, then add 2 g of cetyltrimethylammonium bromide, stir evenly, and then sequentially add 0.55 g of resorcinol and 0.74 mL of formaldehyde. After stirring evenly, quickly add 3 mL of tetraethyl orthosilicate, continuously stir and react for 24 h. After the reaction is completed, centrifuge the stirred solution, wash it five times with ethanol, and dry it in a vacuum oven at 80 °C for 24 h to obtain brown nitrogen-doped mesoporous carbon sphere precursor powder.

[0055] S2. Grind the nitrogen-doped mesoporous carbon sphere precursor powder, then heat it to 900 °C at a rate of 5 °C / min in a nitrogen atmosphere and calcine it for 3 h, and then cool it with the furnace to obtain spherical porous carbon / silica composite. React the spherical porous carbon / silica composite in 2 mol / L NaOH solution for 24 h to remove silica in the sample. Filter the reacted solution by suction, wash it 5 times with deionized water, and dry it in a vacuum oven at 80 °C for 24 h to obtain nitrogen-doped mesoporous carbon spheres.

[0056] S3. Weigh 40 mg of NMCS, add it to a mixed solvent of 40 mL of ethylene glycol and 10 mL of isopropanol, and ultrasonically oscillate it evenly; weigh 2.409 mL of chloroplatinic acid and 3.8 mg of cobalt chloride and add them to the mixed solution, ultrasonically stir and mix evenly, adjust the pH value of the mixed solution to 10 with KOH / ethylene glycol solution (the mass fraction of KOH in the KOH / ethylene glycol solution is 5 wt.%), and carry out microwave reaction for 90 s at a power of 800 W; take out the reaction solution and let it cool naturally; after the solution cools, adjust the pH value of the solution to 4 with nitric acid solution, and stir overnight; filter by suction, wash it three times with ethanol and deionized water respectively, and dry it in a vacuum oven at 60 °C for 24 h to obtain a catalyst for a low-temperature direct ammonia fuel cell.

[0057] Example 6 A preparation method of a catalyst for a low-temperature direct ammonia fuel cell, comprising the following steps: S1. Mix 100 mL of water, 40 mL of ethanol, and 0.2 mL of ammonia water, stir evenly in an oil bath at 70 °C, then add 2 g of cetyltrimethylammonium bromide, stir evenly, and then sequentially add 0.55 g of resorcinol and 0.74 mL of formaldehyde. After stirring evenly, quickly add 1 mL of tetraethyl orthosilicate, continuously stir and react for 24 h. After the reaction is completed, centrifuge the stirred solution, wash it five times with ethanol, and dry it in a vacuum oven at 80 °C for 24 h to obtain brown nitrogen-doped mesoporous carbon sphere precursor powder.

[0058] S2. Grind the nitrogen-doped mesoporous carbon sphere precursor powder, then heat it to 800 °C at a rate of 5 °C / min under a nitrogen atmosphere for calcination, hold for 3 h, and then cool it with the furnace to obtain spherical porous carbon / silica composite. React the spherical porous carbon / silica composite in 2 mol / L NaOH solution for 24 h to remove silica in the sample. Filter the reacted solution by suction, wash it 5 times with deionized water, and dry it in a vacuum oven at 80 °C for 24 h to obtain nitrogen-doped mesoporous carbon spheres.

[0059] S3. Weigh 40 mg of NMCS and add it to a mixed solvent of 40 mL of ethylene glycol and 10 mL of isopropanol, and ultrasonically oscillate to make it uniform. Weigh 2.409 mL of chloroplatinic acid and 3.8 mg of cobalt chloride and add them to the mixed solution, ultrasonically and stir to make it uniform. Adjust the pH value of the mixed solution to 10 with KOH / ethylene glycol solution (the mass fraction of KOH in the KOH / ethylene glycol solution is 5 wt.%), and carry out microwave reaction at a power of 800 W for 90 s. Take out the reaction solution and let it cool naturally. After the solution cools, adjust the pH value of the solution to 4 with nitric acid solution and stir overnight. Filter by suction, wash it three times with ethanol and deionized water respectively, and dry it in a vacuum oven at 60 °C for 24 h to obtain a low-temperature direct ammonia fuel cell catalyst.

[0060] Example 7 A preparation method of a low-temperature direct ammonia fuel cell catalyst, comprising the following steps: S1. Mix 100 mL of water, 40 mL of ethanol and 0.2 mL of ammonia water, stir evenly in an oil bath at 70 °C, then add 2 g of cetyltrimethylammonium bromide, stir evenly, then add 0.55 g of resorcinol and 0.74 mL of formaldehyde in sequence, stir evenly and quickly add 5 mL of tetraethyl orthosilicate, and continuously stir and react for 24 h. After the reaction, centrifuge the stirred solution, wash it five times with ethanol, and dry it in a vacuum oven at 80 °C for 24 h to obtain brown nitrogen-doped mesoporous carbon sphere precursor powder.

[0061] S2. Grind the nitrogen-doped mesoporous carbon sphere precursor powder, then heat it to 800 °C at a rate of 5 °C / min under a nitrogen atmosphere for calcination, hold for 3 h, and then cool it with the furnace to obtain spherical porous carbon / silica composite. React the spherical porous carbon / silica composite in 2 mol / L NaOH solution for 24 h to remove silica in the sample. Filter the reacted solution by suction, wash it 5 times with deionized water, and dry it in a vacuum oven at 80 °C for 24 h to obtain nitrogen-doped mesoporous carbon spheres.

[0062] S3. Weigh 40 mg of NMCS and add it to a mixed solvent of 40 mL of ethylene glycol and 10 mL of isopropanol, and ultrasonically oscillate to make it uniform; weigh 2.409 mL of chloroplatinic acid and 3.8 mg of cobalt chloride and add them to the mixed solution, ultrasonically mix and stir evenly, adjust the pH value of the mixed solution to 10 with KOH / ethylene glycol solution, and carry out microwave reaction at a power of 800 W for 90 s; take out the reaction solution and let it cool naturally; after the solution cools, adjust the pH value of the solution to 4 with nitric acid solution and stir overnight; carry out suction filtration separation, wash three times with ethanol and deionized water respectively, and dry in a vacuum oven at 60 °C for 24 h to obtain a catalyst for low-temperature direct ammonia fuel cells.

[0063] Example 8 A preparation method of a catalyst for low-temperature direct ammonia fuel cells, comprising the following steps: S1. Mix 117 mL of water, 23 mL of ethanol and 0.2 mL of ammonia water, stir evenly in an oil bath at 70 °C, then add 2 g of cetyltrimethylammonium bromide, stir evenly, then add 0.55 g of resorcinol and 0.74 mL of formaldehyde in sequence, stir evenly and quickly add 3 mL of tetraethyl orthosilicate, continuously stir and react for 24 h. After the reaction ends, centrifuge the stirred solution, wash five times with ethanol, and dry in a vacuum oven at 80 °C for 24 h to obtain brown nitrogen-doped mesoporous carbon sphere precursor powder.

[0064] S2. Grind the nitrogen-doped mesoporous carbon sphere precursor powder, then heat it to 800 °C at a rate of 5 °C / min in a nitrogen atmosphere and calcine for 3 h, and then cool it with the furnace to obtain spherical porous carbon / silica composite. React the spherical porous carbon / silica composite in 2 mol / L NaOH solution for 24 h to remove silica in the sample. Carry out suction filtration separation on the reacted solution, wash 5 times with deionized water, and dry in a vacuum oven at 80 °C for 24 h to obtain nitrogen-doped mesoporous carbon spheres.

[0065] S3. Weigh 40 mg of NMCS and add it to a mixed solvent of 40 mL of ethylene glycol and 10 mL of isopropanol, and ultrasonically oscillate to make it uniform; weigh 2.409 mL of chloroplatinic acid and 3.8 mg of cobalt chloride and add them to the mixed solution, ultrasonically mix and stir evenly, adjust the pH value of the mixed solution to 10 with KOH / ethylene glycol solution (the mass fraction of KOH in the KOH / ethylene glycol solution is 5 wt.%), and carry out microwave reaction at a power of 800 W for 90 s; take out the reaction solution and let it cool naturally; after the solution cools, adjust the pH value of the solution to 4 with nitric acid solution and stir overnight; carry out suction filtration separation, wash three times with ethanol and deionized water respectively, and dry in a vacuum oven at 60 °C for 24 h to obtain a catalyst for low-temperature direct ammonia fuel cells.

[0066] Example 9 A preparation method of a catalyst for a low-temperature direct ammonia fuel cell, comprising the following steps: S1. Mix 78 mL of water, 62 mL of ethanol and 0.2 mL of ammonia water, stir evenly in an oil bath at 70 °C, then add 2 g of cetyltrimethylammonium bromide, stir evenly, then add 0.55 g of resorcinol and 0.74 mL of formaldehyde in sequence, stir evenly, and quickly add 3 mL of tetraethyl orthosilicate, continuously stir and react for 24 h. After the reaction, centrifuge the stirred solution, wash it five times with ethanol, and dry it in a vacuum oven at 80 °C for 24 h to obtain brown nitrogen-doped mesoporous carbon sphere precursor powder.

[0067] S2. Grind the nitrogen-doped mesoporous carbon sphere precursor powder, then heat it to 800 °C at a rate of 5 °C / min in a nitrogen atmosphere and calcine it for 3 h, and then cool it with the furnace to obtain spherical porous carbon / silica composite. React the spherical porous carbon / silica composite in 2 mol / L NaOH solution for 24 h to remove silica in the sample. Filter the reacted solution by suction, wash it 5 times with deionized water, and dry it in a vacuum oven at 80 °C for 24 h to obtain nitrogen-doped mesoporous carbon spheres.

[0068] S3. Weigh 40 mg of NMCS, add it to a mixed solvent of 40 mL of ethylene glycol and 10 mL of isopropanol, and ultrasonically oscillate to make it uniform; weigh 2.409 mL of chloroplatinic acid and 3.8 mg of cobalt chloride and add them to the mixed solution, ultrasonically stir and mix evenly, adjust the pH value of the mixed solution to 10 with KOH / ethylene glycol solution (the mass fraction of KOH in the KOH / ethylene glycol solution is 5 wt.%), and carry out microwave reaction at a power of 800 W for 90 s; take out the reaction solution and let it cool naturally; after the solution cools, adjust the pH value of the solution to 4 with nitric acid solution, and stir overnight; filter by suction, wash it three times with ethanol and deionized water respectively, and dry it in a vacuum oven at 60 °C for 24 h to obtain a catalyst for a low-temperature direct ammonia fuel cell.

[0069] Comparative Example 1 A preparation method of a catalyst for a low-temperature direct ammonia fuel cell, comprising the following steps: S1. Mix 100 mL of water, 40 mL of ethanol and 0.2 mL of ammonia water, stir evenly in an oil bath at 70 °C, then add 2 g of cetyltrimethylammonium bromide, stir evenly, then add 0.55 g of resorcinol and 0.74 mL of formaldehyde in sequence, stir evenly, and quickly add 3 mL of tetraethyl orthosilicate, continuously stir and react for 24 h. After the reaction, centrifuge the stirred solution, wash it five times with ethanol, and dry it in a vacuum oven at 80 °C for 24 h to obtain brown nitrogen-doped mesoporous carbon sphere precursor powder.

[0070] S2. Grind the nitrogen-doped mesoporous carbon sphere precursor powder, then heat it to 800 °C at a rate of 5 °C / min in a nitrogen atmosphere for calcination, hold for 3 h, and then cool it with the furnace to obtain spherical porous carbon / silica composite. React the spherical porous carbon / silica composite in 2 mol / L NaOH solution for 24 h to remove silica in the sample. Filter the reacted solution by suction, wash it 5 times with deionized water, and dry it in a vacuum oven at 80 °C for 24 h to obtain nitrogen-doped mesoporous carbon spheres.

[0071] S3. Weigh 40 mg of NMCS and add it to a mixed solvent of 40 mL of ethylene glycol and 10 mL of isopropanol, and ultrasonically oscillate to make it uniform. Weigh 2.409 mL of chloroplatinic acid and 2.1 mg of nickel chloride and add them to the mixed solution, ultrasonically and stir to make it uniform. Adjust the pH value of the mixed solution to 10 with KOH / ethylene glycol solution (the mass fraction of KOH in the KOH / ethylene glycol solution is 5 wt.%), and carry out microwave reaction for 90 s at a power of 800 W. Take out the reaction solution and let it cool naturally. After the solution cools, adjust the pH value of the solution to 4 with nitric acid solution and stir overnight. Filter by suction, wash it three times with ethanol and deionized water respectively, and dry it in a vacuum oven at 60 °C for 24 h to obtain a low-temperature direct ammonia fuel cell catalyst, named PtNi / NMCS catalyst.

[0072] Comparative Example 2 A preparation method of a low-temperature direct ammonia fuel cell catalyst, comprising the following steps: S1. Mix 100 mL of water, 40 mL of ethanol and 0.2 mL of ammonia water, stir evenly in an oil bath at 70 °C, then add 2 g of cetyltrimethylammonium bromide, stir evenly and then add 0.55 g of resorcinol and 0.74 mL of formaldehyde in sequence, stir evenly and then quickly add 3 mL of tetraethyl orthosilicate, and continuously stir and react for 24 h. After the reaction is completed, centrifuge the stirred solution, wash it 5 times with ethanol, and dry it in a vacuum oven at 80 °C for 24 h to obtain brown nitrogen-doped mesoporous carbon sphere precursor powder.

[0073] S2. Grind the nitrogen-doped mesoporous carbon sphere precursor powder, then heat it to 800 °C at a rate of 5 °C / min in a nitrogen atmosphere for calcination, hold for 3 h, and then cool it with the furnace to obtain spherical porous carbon / silica composite. React the spherical porous carbon / silica composite in 2 mol / L NaOH solution for 24 h to remove silica in the sample. Filter the reacted solution by suction, wash it 5 times with deionized water, and dry it in a vacuum oven at 80 °C for 24 h to obtain nitrogen-doped mesoporous carbon spheres.

[0074] S3. Weigh 40 mg of NMCS and add it to a mixed solvent of 40 mL of ethylene glycol and 10 mL of isopropanol, and ultrasonically oscillate to make it uniform. Weigh 2.409 mL of chloroplatinic acid and 0.287 mL of chloroiridic acid (55.7 mmol / L) and add them to the mixed solution, ultrasonically and stir to make it uniform. Use a KOH / ethylene glycol solution (the mass fraction of KOH in the KOH / ethylene glycol solution is 5 wt.%) to adjust the pH value of the mixed solution to 10, and carry out a microwave reaction at a power of 800 W for 90 s. Take out the reaction solution and let it cool naturally. After the solution cools, use a nitric acid solution to adjust the pH value of the solution to 4, and stir overnight. Carry out suction filtration separation, wash it three times with ethanol and deionized water respectively, and dry it in a vacuum oven at 60 °C for 24 h to obtain a low-temperature direct ammonia fuel cell catalyst, named PtIr / NMCS catalyst.

[0075] Comparative Example 3 Commercial 40% Pt / C catalyst.

[0076] Comparative Example 4 Commercial 30% PtRu / C catalyst.

[0077] Comparative Example 5 A preparation method of a low-temperature direct ammonia fuel cell catalyst, comprising the following steps: S1. Mix 78 mL of water, 62 mL of ethanol and 0.2 mL of ammonia water, stir evenly in an oil bath at 70 °C, then add 2 g of cetyltrimethylammonium bromide, stir evenly and then add 0.55 g of resorcinol and 0.74 mL of formaldehyde in sequence, stir evenly and then quickly add 3 mL of tetraethyl orthosilicate, continuously stir and react for 24 h. After the reaction ends, centrifuge the stirred solution, wash it five times with ethanol, and dry it in a vacuum oven at 80 °C for 24 h to obtain brown nitrogen-doped mesoporous carbon sphere precursor powder.

[0078] S2. Grind the nitrogen-doped mesoporous carbon sphere precursor powder, then heat it to 800 °C at a rate of 5 °C / min in a nitrogen atmosphere, keep it warm for 3 h, and then cool it with the furnace to obtain a spherical porous carbon / silica composite. React the spherical porous carbon / silica composite in a 2 mol / L NaOH solution for 24 h to remove the silica in the sample. Carry out suction filtration separation on the reacted solution, wash it 5 times with deionized water, and dry it in a vacuum oven at 80 °C for 24 h to obtain nitrogen-doped mesoporous carbon spheres.

[0079] S3. Weigh 40 mg of NMCS, add it to a mixed solvent of 40 mL of ethylene glycol and 10 mL of isopropanol, and shake it evenly with ultrasound; weigh 2.650 mL of chloroplatinic acid, add it to the mixed solution, shake it evenly with ultrasound, adjust the pH value of the mixed solution to 10 with KOH / ethylene glycol solution (the mass fraction of KOH in the KOH / ethylene glycol solution is 5 wt.%), and react it with microwaves at a power of 800 W for 90 s; take out the reaction solution and let it cool naturally; after the solution is cooled, adjust the pH value of the solution to 4 with nitric acid solution, and stir it overnight; separate it by suction, wash it three times with ethanol and deionized water respectively, and dry it in a vacuum oven at 60°C for 24 hours to obtain a low-temperature direct ammonia fuel cell catalyst, named Pt / NMCS catalyst.

[0080] The structure and performance of the nitrogen-doped mesoporous carbon spheres and catalyst prepared in Example 1 were tested, wherein the catalyst prepared in Example 1 was named PtCo / NMCS catalyst, and the results were as follows: Figure 1 This is the SEM morphology structure diagram of the nitrogen-doped mesoporous carbon sphere of the present invention. Figure 1 Figure a is the morphology structure diagram of nitrogen-doped mesoporous carbon spheres at 1 μm in size, and figure b is the morphology structure diagram of nitrogen-doped mesoporous carbon spheres at 200 nm in size. Figure 1 As shown, the size of the synthesized nitrogen-doped mesoporous carbon spheres is about 400 nm.

[0081] Figure 2 X-ray diffraction and X-ray photoelectron spectroscopy spectra of the PtCo / NMCS catalyst prepared in Example 1 of the present invention, Figure 2 (a) is the X-ray diffraction spectrum, (b) is the full spectrum of X-ray photoelectron spectrum, (c) is the X-ray photoelectron spectrum of Pt, (d) is the X-ray photoelectron spectrum of C, and (e) is the X-ray photoelectron spectrum of Co. Figure 2 As shown, in Example 1, carbon exists in the form of carbon-nitrogen double bonds, carbon-oxygen double bonds, and carbon-carbon single bonds and double bonds, and Pt exists in the form of platinum element at 70.7eV and 74.1eV and divalent platinum at 71.9eV and 75.3eV respectively.

[0082] The contents of Pt and Co elements in the PtCo / NMCS catalyst prepared in Example 1 were detected by ICP test. The results are shown in Table 1. The content of Pt accounts for 28.39% of the catalyst, and the content of cobalt accounts for 0.3% of the catalyst.

[0083] Table 1 Pt and Co element contents of PtCo / NMCS catalyst prepared in Example 1 The catalysts prepared in Example 1 and Comparative Examples 1 to 5 were used for performance testing in a three-electrode system. The establishment of this testing system included the following steps: Step 1: Respectively take 2 mg of the PtCo / NMCS catalyst prepared in Example 1, the PtNi / NMCS catalyst prepared in Comparative Example 1, the PtIr / NMCS catalyst prepared in Comparative Example 2, the commercial 40% Pt / C catalyst in Comparative Example 3, and the commercial 30% PtRu / C catalyst in Comparative Example 4. Add 38 μL of deionized water, 12 μL of Nafion solution, and 950 mL of isopropanol solution thereto, and ultrasonically disperse in ice water for 2 h to prepare catalyst slurries.

[0084] Step 2: Prepare 200 ml of a KOH solution with a molar concentration of 1 mol / L.

[0085] Step 3: Divide 20 μL of the catalyst slurry into 4 portions and coat them on a glassy carbon electrode with an electrode area of 0.196 cm 2 respectively.

[0086] Step 4: Take a platinum wire, fix one end of the platinum wire at the gas outlet of the hydrogen generator so that stable and continuous hydrogen bubbles cover the platinum wire, and connect the other end to the three-electrode testing system. Connect the Hg / HgO reference electrode to the three-electrode testing system simultaneously, and measure the potential difference between the Hg / HgO reference electrode and the standard hydrogen electrode.

[0087] Step 5: Use the glassy carbon electrode as the working electrode, Hg / HgO as the reference electrode, and a graphite rod as the counter electrode to test the AOR performance of the catalyst in a 1 mol / L KOH solution.

[0088] Figure 3 This is the CV comparison chart of the catalysts prepared in Examples 1 to 9 of the present invention. As Figure 3As shown, the performance of the catalyst prepared under the conditions of Example 1 is significantly better than that of the catalysts prepared under other conditions. It can be seen from Example 2 that the concentration of ammonia water is too low, resulting in a relatively large particle size of the nitrogen-doped mesoporous carbon sphere support and poor electrochemical performance of the catalyst. It can be seen from Example 3 that the concentration of ammonia water is too high, and the aggregation phenomenon of the nitrogen-doped mesoporous carbon sphere support is aggravated, resulting in the electrochemical performance of the catalyst being lower than that of Example 1. It can be seen from Example 4 that the calcination temperature is too low, the specific surface area of the nitrogen-doped mesoporous carbon sphere support is small, and the electrochemical performance of the catalyst is poor. It can be seen from Example 5 that the calcination temperature is too high, the spherical structure of the nitrogen-doped mesoporous carbon sphere support is damaged, and the electrochemical performance of the catalyst is poor. It can be seen from Examples 6 and 7 that as the amount of TEOS increases, the pore structure on the surface of the nitrogen-doped mesoporous carbon sphere support gradually becomes dense, resulting in the electrochemical performance of Example 6 being lower than that of Example 1. However, when the amount of TEOS exceeds a certain value, the spherical structure of the nitrogen-doped mesoporous carbon sphere support begins to be damaged, resulting in the electrochemical performance of Example 7 being lower than that of Example 1. It can be seen from Example 8 that the ratio of ethanol / water is too low, the hydrolysis rate of TEOS is too fast, and it is difficult for the NMCS support to form a monodisperse spherical structure, resulting in the electrochemical performance of the catalyst being much lower than that of Example 1. It can be seen from Example 9 that the ratio of ethanol / water is too high, the particle size of the nitrogen-doped mesoporous carbon sphere support is too large and agglomeration occurs, resulting in the electrochemical performance of the catalyst being much lower than that of Example 1.

[0089] Figure 4 This is a CV comparison chart of the catalysts prepared in Example 1 of the present invention and Comparative Examples 1 to 5. As Figure 4 shown, the AOR performance of the PtCo / NMCS catalyst is significantly better than that of the commercial Pt / C and PtRu / C catalysts, and the AOR performance reaches 254% of the Pt / C catalyst. At the same time, the performance of the PtCo / NMCS catalyst is also significantly better than that of the PtNi / NMCS and PtIr / NMCS catalysts loaded with bimetallic elements and the Pt / NMCS catalyst loaded with only a single metallic element..

[0090] Figure 5 This is an i-t curve comparison chart of the catalysts prepared in Example 1 of the present invention and Comparative Examples 1 to 5. As Figure 5 shown, the stability of the PtCo / NMCS catalyst is also relatively excellent. The catalyst stability within 600 s is slightly better than that of the traditional commercial Pt / C catalyst and significantly better than that of the PtNi / NMCS, PtIr / NMCS, PtRu / C, and Pt / NMCS catalysts.

[0091] It should be noted that when the present invention involves numerical ranges, it should be understood that both endpoints of each numerical range and any value between the two endpoints can be selected. Since the adopted step methods are the same as those in the embodiments, in order to prevent repetition, the present invention describes preferred embodiments. Although the preferred embodiments of the present invention have been described, those skilled in the art can make additional changes and modifications to these embodiments once they know the basic creative concept. Therefore, the appended claims are intended to be construed as including the preferred embodiments and all changes and modifications falling within the scope of the present invention.

[0092] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention is also intended to include these modifications and variations.

Claims

1. A preparation method of a catalyst for a low-temperature direct ammonia fuel cell, characterized in that, It includes the following steps: Using cetyltrimethylammonium bromide as a templating agent and nitrogen source, resorcinol and formaldehyde resin as carbon sources, and tetraethyl orthosilicate as a silicon source, in a system of an alkaline catalyst and a solvent, a nitrogen-doped mesoporous carbon sphere precursor is obtained by a method combining soft templating and hard templating methods; Under the atmosphere of a protective gas, the nitrogen-doped mesoporous carbon sphere precursor is calcined at 700 - 900 °C, and then the silicon dioxide is removed to obtain nitrogen-doped mesoporous carbon spheres; The nitrogen-doped mesoporous carbon spheres are dissolved in an ethylene glycol solution to form a nitrogen-doped mesoporous carbon sphere solution. A platinum salt solution and a soluble cobalt salt are added to the nitrogen-doped mesoporous carbon sphere solution to form a reaction solution, and a microwave reaction is carried out to load platinum and cobalt on the nitrogen-doped mesoporous carbon spheres, obtaining a low-temperature direct ammonia fuel cell catalyst.

2. The preparation method of the catalyst for a low-temperature direct ammonia fuel cell according to claim 1, characterized in that, The molar ratio of cetyltrimethylammonium bromide, resorcinol, formaldehyde, and tetraethyl orthosilicate is 0.18 - 1.54:0.2 - 1.23:0.4 - 2.45:

1.

3. The preparation method of the catalyst for the low-temperature direct ammonia fuel cell according to claim 1, characterized in that, The concentration of the nitrogen-doped mesoporous carbon sphere solution is 0.07 wt% - 0.1 wt%.

4. The preparation method of the catalyst for the low-temperature direct ammonia fuel cell according to claim 1, wherein, The platinum salt solution is a chloroplatinic acid solution, the concentration of the chloroplatinic acid solution is 18 mmol / L - 20 mmol / L, the soluble cobalt salt is cobalt chloride, the molar ratio of chloroplatinic acid and cobalt chloride is 2.5 - 3.5:1, the ethylene glycol solution is a mixed solution of ethylene glycol and isopropyl alcohol, and the volume ratio of ethylene glycol and isopropyl alcohol is 3 - 5:

1.

5. The preparation method of the catalyst for a low-temperature direct ammonia fuel cell according to claim 1, characterized in that, Before the microwave reaction, the pH of the reaction solution is adjusted to 9 - 11, the power of the microwave reaction is 480 W - 800 W, and the microwave time is 90 s - 150 s.

6. The preparation method of the catalyst for a low-temperature direct ammonia fuel cell according to claim 1, characterized in that, The heating rate of the calcination is 5 °C / min - 10 °C / min, and the heat preservation time is 1 h - 3 h.

7. The preparation method of the catalyst for a low-temperature direct ammonia fuel cell according to claim 1, characterized in that, In the method combining soft templating and hard templating methods, the reaction temperature is 60 °C - 80 °C, and the time is 20 h - 30 h.

8. The preparation method of the catalyst for the low-temperature direct ammonia fuel cell according to claim 1, characterized in that, The volume ratio of the alkaline catalyst and the solvent is 0.5 - 4:700, the molar ratio of the alkaline catalyst and resorcinol is 1:0.8 - 4.1, the alkaline catalyst is ammonia water, the volume concentration of ammonia water is 25% - 28%, and the solvent is a mixture of water and ethanol with a volume ratio of 500:100 - 400.

9. A catalyst for a low-temperature direct ammonia fuel cell, characterized in that, It is prepared by using the preparation method described in any one of claims 1 - 8.

10. Use of the low-temperature direct ammonia fuel cell catalyst described in claim 9 in a low-temperature direct ammonia fuel cell.

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