Platinum monatomic-platinum nanoparticle synergistic dispersion catalyst as well as preparation method and application thereof

Abstract

The invention discloses a platinum single atom-platinum nanoparticle synergistic dispersion catalyst as well as a preparation method and application thereof. According to the invention, nano SiO2 is used as a template agent, a zinc source, a carbon source and a nitrogen source are introduced, and the carrier nitrogen-doped porous carbon of the catalyst is obtained after drying, ball milling and two times of high-temperature treatment. According to the optimized carrier, the activity and long-term stability of the catalyst can be improved under the condition that the dosage of precious metal platinum is not increased. The catalyst prepared by the invention contains rich micro-mesoporous-large hierarchical communicated pore structures, platinum single atoms and platinum nanoparticles are double-embedded in a mesoporous carbon network and are loaded on the surface of the mesoporous carbon network to form Pt-N3 high-activity sites. The preparation method disclosed by the invention is simple, the existence form of platinum is controllable, large-scale preparation can be realized, and the preparation method has important application potential in proton exchange membrane fuel cells.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of catalyst materials, and particularly relates to a platinum monatomic-particle and platinum nanoparticle synergistically dispersed catalyst as well as a preparation method and application thereof. BACKGROUND

[0002] The noble metal platinum (Pt) based catalysts exhibit important value in the field of electrochemical energy storage and conversion (such as fuel cells and water electrolysis for hydrogen production) and organic catalytic reactions due to their high catalytic activity and stability. However, the traditional platinum-based catalysts have the bottleneck problems of low active site utilization, high noble metal consumption, and insufficient long-term stability.

[0003] In order to optimize the dispersion and atomic efficiency of platinum, single-atom catalysts (SACs) have attracted much attention due to their nearly 100% atomic utilization. However, a single single-atom site is often difficult to meet the multi-step electron transfer of complex catalytic reactions, and the activity is insufficient under high current density, which is difficult to meet the actual application requirements. At the same time, although platinum nanoparticle catalysts have high intrinsic activity, the particles are prone to agglomeration or Ostwald ripening, resulting in performance degradation.

[0004] The carrier material is the key to improve the performance of platinum catalysts. Carbon materials are widely used due to their high electrical conductivity, adjustable pore structure, and chemical stability. However, the single pore size distribution of traditional carbon carriers (such as carbon black) limits the mass transfer efficiency, and the surface chemical inertness leads to weak metal-carrier interaction, which is difficult to synergistically load platinum species of different sizes. In addition, the disordered pore structure in the traditional carrier easily leads to uneven loading of platinum, and the structure is prone to collapse during high-temperature treatment or electrochemical cycling, which affects the catalytic stability.

[0005] In view of the above problems, it is urgent to develop a new composite catalyst with high activity, high stability and low platinum loading to meet the application in the field of electrochemical energy storage and conversion. SUMMARY

[0006] In order to solve the problems of low active site utilization, high noble metal consumption, and insufficient long-term stability of the existing platinum carbon catalysts, the application provides a nitrogen-doped porous carbon supported platinum monatomic-particle and platinum nanoparticle synergistically dispersed catalyst as well as a preparation method and application thereof.

[0007] By constructing a nitrogen-doped porous carbon carrier and synergistically loading platinum monatomic particles and platinum nanoparticles, the following breakthroughs are expected to be achieved: 1) multi-level pores promote mass transfer and active site exposure; 2) nitrogen species precisely control the dispersion and electronic state of platinum; 3) the interface of platinum monatomic particles and platinum nanoparticles optimizes the reaction path.

[0008] The purpose of the application is achieved by the following technical solutions.

[0009] In a first aspect, the present application provides a preparation method of a platinum single atom-platinum nanoparticle synergistic dispersion catalyst, characterized in that the method comprises the following steps:

[0010] S1, dissolving a zinc salt in deionized water, adding a SiO2 template agent with a particle size of 50-100 nm and a polyquaternary ammonium salt, the mass ratio of the zinc salt, the SiO2 template agent and the polyquaternary ammonium salt being 1:(5-7):(2-3); after sufficient stirring, a uniformly dispersed mixed solution is obtained;

[0011] S2, drying the mixed solution at 75-90°C for 10-14h to obtain a block, and then performing planetary ball milling at a rotation speed of 280-350rpm for 1-4h to obtain a uniform powder;

[0012] S3, high-temperature treatment of the above powder, heating to 800-1000°C at a rate of 5°C / min under N2 atmosphere, maintaining for 1h to obtain a template agent-containing nitrogen-doped carbon material;

[0013] S4, sequentially performing alkali washing, acid washing and deionized water washing of the template agent-containing nitrogen-doped carbon material until neutral, then drying at a temperature of 50-70°C for 10-14h, and then performing second high-temperature treatment, heating to 800-1000°C at a rate of 5°C / min under N2 atmosphere, maintaining for 1h to obtain a nitrogen-doped porous carbon;

[0014] S5, mixing anhydrous sodium carbonate, ethylene glycol and a platinum-containing precursor, then adding the nitrogen-doped porous carbon prepared in step S4, and performing a reduction reaction at a pH of 8-10 and a temperature of 120-160°C; after the reaction is completed, the reaction precipitate is centrifuged, washed and dried to obtain a platinum single atom-platinum nanoparticle synergistic dispersion catalyst Pt SA-NP @N-MPC.

[0015] Further, in step S1, the zinc salt is zinc sulfate, zinc chloride or zinc nitrate. The mass ratio of the zinc salt, the SiO2 template agent and the polyquaternary ammonium salt is preferably 1:5:2.

[0016] Further, in step S2, the drying condition is to dry at a temperature of 85°C for 12h; and the ball milling condition is to use a rotation speed of 300rpm for ball milling for 4h.

[0017] Further, in step S3, the high-temperature treatment is to heat to 950°C at a rate of 5°C / min, maintaining for 1h.

[0018] Further, in step S4, the drying condition is to dry at a temperature of 60°C for 12h.

[0019] Further, in step S5, the platinum-containing precursor is an aqueous solution of chloroplatinic acid, ammonium chloroplatinate or platinum nitrate.

[0020] Further, in step S5, the centrifugal washing and drying conditions are: first centrifugal washing with deionized water and anhydrous ethanol each three times, and then drying at a temperature of 50-70 DEG C for 10-14h.

[0021] In a second aspect, the present application provides a platinum single atom-platinum nanoparticle synergistic dispersion catalyst, which is prepared by the method of the first aspect.

[0022] The carrier nitrogen-doped porous carbon of the catalyst has a micropore-mesopore hierarchical structure, and the pore size distribution is 2-50nm; and platinum is anchored in the interior and surface of the carrier in the form of single atom and nanoparticle.

[0023] The catalyst of the present application optimizes mass transfer through hierarchical pores, enhances platinum anchoring capacity through nitrogen species, and improves catalytic activity and long-term stability without increasing the amount of noble metal Pt by utilizing the interface synergistic effect of Pt single atom and nanoparticle.

[0024] In a third aspect, the present application provides the application of the platinum single atom-platinum nanoparticle synergistic dispersion catalyst of the second aspect in a proton exchange membrane fuel cell.

[0025] The platinum single atom-platinum nanoparticle synergistic dispersion catalyst of the present application is induced by Zn evaporation to form platinum single atom from Pt particles, so as to fix the platinum single atom on the nitrogen-doped porous carbon, and form a synergistically enhanced composite catalyst material. Compared with the prior art, the present application has the following beneficial effects.

[0026] (1) Carrier optimization: the carrier nitrogen-doped porous carbon of the catalyst of the present application is obtained by introducing zinc source, carbon source and nitrogen source, drying and ball milling, and then twice high-temperature treatment with nano-SiO2 as a template agent. With nano-SiO2 as a template agent, the macropore-mesopore-micropore structure is constructed, the reaction diffusion kinetics and the accessibility of active sites are significantly improved; at the same time, the polyquaternary ammonium salt is used as the carbon source and the nitrogen source, the nitrogen doping can introduce rich functional groups, which not only can enhance the surface polarity of the carbon carrier to anchor the metal species, but also can regulate the electronic structure of platinum to optimize its adsorption energy barrier; the introduction of zinc source, Zn evaporation provides metal active sites to induce Pt particles to form platinum single atom, so as to fix the platinum single atom on the nitrogen-doped porous carbon, enhance the platinum-carrier electronic coupling, and promote mass transfer and active site exposure by the multi-level pores. The catalyst of the present application prepared by the optimized carrier may cause the strong adsorption of specific intermediates to lead to the increase of reaction energy barrier, and the continuous active sites of nanoparticles are helpful for the multi-electron reaction process; the rich pore structure of the nitrogen-doped porous carbon inhibits the migration and aggregation of platinum, and the activity attenuation is ≤8% after 50000 cycles.

[0027] (2) Platinum is better dispersed on the carbon carrier: Nitrogen-doped porous carbon is used as a bifunctional material in the present application. Nitrogen-doped porous carbon is a catalyst itself and also serves as a carbon carrier for platinum single atom-platinum nanoparticle synergistic dispersion catalysts. In the present application, anhydrous sodium carbonate is dissolved in water to produce hydroxyl ions through hydrolysis, making the solution alkaline, thereby improving the reducing ability of ethylene glycol and the efficiency and selectivity of the reduction reaction. Meanwhile, anhydrous sodium carbonate can cause certain changes in the chemical properties of the surface of the nitrogen-doped porous carbon carrier, increasing the active sites on the surface of the nitrogen-doped porous carbon, making it easier for platinum ions to be uniformly adsorbed on the surface of the nitrogen-doped porous carbon, and helping to improve the uniform dispersion of platinum on the carrier and the specific surface area and activity of the catalyst.

[0028] (3) Synergistic improvement of catalytic efficiency of platinum single atoms and platinum nanoparticles: The present application improves the catalytic activity by embedding and loading platinum single atoms (Pt-SA) and nanoparticles (Pt-NP) in the interior and on the surface of nitrogen-doped porous carbon. Pt-SA provides high intrinsic activity, and Pt-NP enhances charge transport, and the two synergistically improve the catalytic efficiency.

[0029] (4) Stability: The anhydrous sodium carbonate in the present application helps to stabilize the catalyst reaction system, inhibits the hydrolysis and oxidation of metal ions, and keeps the catalyst active and stable in the reaction system. Meanwhile, the coexistence of platinum single atoms and platinum nanoparticles makes full use of the synergistic effect of platinum species of different sizes, thereby improving the stability in the oxygen reduction reaction.

[0030] The catalyst Pt SA-NP N-MPC contains rich micro-meso-macro hierarchical interconnected pore structures, platinum single atoms and platinum nanoparticles are doubly embedded in the mesoporous carbon network and loaded on its surface to form Pt-N3 high active sites, significantly improving the activity and stability of the catalyst. Without increasing the amount of noble metal platinum, the catalytic activity and long-term stability of the catalyst can be improved. The preparation method of the present application is simple, the existence form of platinum is controllable, and it can be prepared on a large scale, and has good application prospect. The catalyst of the present application shows excellent performance in proton exchange membrane fuel cells, especially in fuel cell cathode oxygen reduction (ORR), electrocatalytic hydrogen evolution (HER) and other clean energy fields, and has important application potential. BRIEF DESCRIPTION OF DRAWINGS

[0031] Fig. 1a SEM image of N-MPC prepared in Example 1 x .

[0032] Fig. 1b SEM image of N-MPC prepared in Example 2 x .

[0033] Fig. 1c SEM image of N-MPC prepared in Example 3x SEM image.

[0034] Fig. 1d N-MPC prepared in Example 4 x SEM image.

[0035] Fig. 2 Pt prepared in Example 3 SA-NP @N-MPC 950 SEM image.

[0036] Fig. 3 Pt prepared in Example 3 SA-NP @N-MPC 950 TEM image.

[0037] Fig. 4 The carrier N-MPC prepared in Example 3 950 Pt catalyst SA-NP @N-MPC 950 Adsorption-desorption isotherms.

[0038] Fig. 5a Four types of N-MPC carriers prepared in Examples 1-4 x ORR performance comparison chart at 0.1M HClO4.

[0039] Fig. 5b Four types of N-MPC carriers prepared in Examples 1-4 x ORR performance comparison chart at 0.1 M KOH.

[0040] Fig. 6a N-MPC prepared in Example 3 950 Pt SA-NP @N-MPC 950 Comparison of ORR performance between the commercial Pt / C(JM) catalyst and Comparative Example 1 in 0.1M HClO4.

[0041] Fig. 6b N-MPC prepared in Example 3 950 Pt SA-NP @N-MPC 950 Comparison of ORR performance between the commercial Pt / C(JM) catalyst and Comparative Example 1 at 0.1 M KOH. Detailed Implementation

[0042] In order to make the technical problems, technical solutions and beneficial effects solved by the present application clearer, the present application will be further described in detail below in combination with specific embodiments. It should be understood that the embodiments described herein are part of the embodiments of the present application, rather than all the embodiments, and are only used to explain the present application, and do not limit the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the protection scope of the present application.

[0043] In a first aspect, the present application provides a preparation method of a platinum single atom-platinum nanoparticle synergistic dispersion catalyst, characterized in that the method comprises the following steps:

[0044] S1, dissolving a zinc salt in deionized water, adding a SiO2 template agent with a particle size of 50-100 nm and a polyquaternary ammonium salt, the mass ratio of the zinc salt, the SiO2 template agent and the polyquaternary ammonium salt being 1:(5-7):(2-3); after sufficient stirring, a uniformly dispersed mixed solution is obtained;

[0045] S2, drying the mixed solution at 75-90℃ for 10-14h to obtain a block-shaped material, and then performing planetary ball milling at a rotation speed of 280-350rpm for 1-4h to obtain a uniform powder;

[0046] S3, performing high-temperature treatment on the above-mentioned powder, heating to 800-1000℃ at a rate of 5℃ / min under N2 atmosphere, and maintaining for 1h to obtain a template agent-containing nitrogen-doped carbon material;

[0047] S4, sequentially performing alkali washing, acid washing and deionized water washing to neutralize the template agent-containing nitrogen-doped carbon material, then drying at a temperature of 50-70℃ for 10-14h, and performing second high-temperature treatment, heating to 800-1000℃ at a rate of 5℃ / min under N2 atmosphere, and maintaining for 1h, to obtain a nitrogen-doped porous carbon;

[0048] S5, mixing anhydrous sodium carbonate, ethylene glycol and a platinum-containing precursor, and then adding the nitrogen-doped porous carbon prepared in step S4, to perform a reduction reaction at a pH of 8-10 and a temperature of 120-160℃; after the reaction is completed, the reaction precipitate is centrifuged, washed and dried to obtain a platinum single atom-platinum nanoparticle synergistic dispersion catalyst Pt SA-NP @N-MPC.

[0049] In some embodiments, in step S1, the zinc salt is zinc sulfate, zinc chloride or zinc nitrate. The mass ratio of the zinc salt, the SiO2 template agent and the polyquaternary ammonium salt is preferably 1:5:2.

[0050] In some embodiments, in step S2, the drying condition is drying at 85℃ for 12h; and the ball milling condition is ball milling at 300rpm for 4h.

[0051] In some embodiments, in step S3, the high temperature treatment is heating to 950℃ at a rate of 5℃ / min and keeping for 1h.

[0052] In some embodiments, in step S4, the drying condition is drying at 60℃ for 12h.

[0053] In some embodiments, in step S5, the platinum-containing precursor is an aqueous solution of chloroplatinic acid H2PtCl6, ammonium chloroplatinate (NH4)2PtCl6 or platinum nitrate Pt(NO3)2.

[0054] In step S5, the amounts of ethylene glycol, platinum-containing precursor and nitrogen-doped porous carbon can be adjusted according to the platinum loading. The platinum single atom-platinum nanoparticle synergistic dispersion catalyst prepared by the method of the application has low platinum loading but high catalytic efficiency. The catalytic activity and long-term stability of the catalyst can be improved without increasing the amount of noble metal platinum.

[0055] In step S5, the amount of anhydrous sodium carbonate can be adjusted to make the pH value of the system 8-10. After anhydrous sodium carbonate is dissolved in water, hydroxyl ions are generated by hydrolysis, making the solution alkaline, thereby improving the reducing ability of ethylene glycol and the efficiency and selectivity of the reduction reaction. Anhydrous sodium carbonate helps to stabilize the catalyst reaction system, inhibits the hydrolysis and oxidation of metal ions, and makes the catalyst maintain good activity and stability in the reaction system. At the same time, anhydrous sodium carbonate can change the chemical properties of the surface of the nitrogen-doped porous carbon carrier, increase the active sites on the surface of the nitrogen-doped porous carbon, make platinum ions more easily and uniformly adsorbed on the surface of the nitrogen-doped porous carbon, help the uniform dispersion of platinum on the carrier, and improve the specific surface area and activity of the catalyst.

[0056] In some embodiments, in step S5, the centrifugal washing and drying condition is centrifugal washing with deionized water and anhydrous ethanol for three times each, and then drying at 50-70℃ for 10-14h.

[0057] In a second aspect, the application provides a platinum single atom-platinum nanoparticle synergistic dispersion catalyst, which is prepared by the method of the first aspect.

[0058] The carrier of the catalyst, nitrogen-doped porous carbon, has a hierarchical micro-mesoporous structure with a pore size distribution of 2-50nm; and platinum exists as single atoms and nanoparticles and is anchored to the inside and surface of the carrier.

[0059] The catalyst of the present application optimizes mass transfer through hierarchical pores, enhances platinum anchoring capacity through nitrogen species, and simultaneously utilizes the interface synergy effect of Pt monatomic atoms and nanoparticles to improve its catalytic activity and long-term stability.

[0060] In a third aspect, the present application provides use of the platinum monatomic atom-palladium nanoparticle synergistically dispersed catalyst of the second aspect in a proton exchange membrane fuel cell.

[0061] The specific embodiments of the present application will be further explained by the following examples and comparative examples.

[0062] The reagents, materials and instruments used in the following description are all conventional reagents, conventional materials and conventional instruments, which are commercially available, and the reagents involved can also be synthesized by conventional synthesis methods. The methods in the examples are all conventional methods in the art, unless otherwise specified.

[0063] The micro-morphology of the product of the embodiments of the present application is tested by TEM (JEOL JEM-2100F system) and SEM (Hitachi S-4800), the elemental analysis is determined by XPS (Perkin Elmer RBD upgraded PHIe5000C ECSA system), the specific surface and pore size distribution are determined by BET (Brunauer-Emmett-Teller), the electrochemical performance test is tested by a three-electrode system on a Chenhua CHI760D electrochemical workstation, and the single cell performance test is tested on an 850e fuel cell test system.

[0064] Example 1

[0065] This example is used to illustrate the preparation method of the platinum monatomic atom-palladium nanoparticle synergistically dispersed catalyst disclosed by the present application, which comprises the following operation steps:

[0066] S1, dissolve zinc chloride in deionized water and stir until uniform, then add SiO2 template agent with a particle size of 50-100 nm and polyquaternary ammonium salt PQ7, the mass ratio of zinc chloride, SiO2 and polyquaternary ammonium salt PQ7 is 1:5:2; after stirring for 12 h, a uniformly dispersed mixed solution is obtained.

[0067] S2, first dry the mixed solution in an oven at 85℃ for 12h to obtain a block, then use a planetary ball mill at a speed of 300 rpm for 4h to obtain a uniformly distributed light yellow powder.

[0068] S3, transfer the above powder to a tube furnace for high temperature treatment, heat to 800℃ at a rate of 5℃ / min under N2 atmosphere, keep for 1h, and naturally cool to room temperature to obtain the template-containing nitrogen-doped carbon material Zn@SiO2@NC.800 .

[0069] S4, the template-containing nitrogen-doped carbon material is sequentially subjected to alkali washing, acid washing, and washing with deionized water until neutral, and then is first placed in a 60℃ oven for drying for 12h, and then is transferred to a tube furnace for second high-temperature treatment, is heated to 800℃ at 5℃ / min under N2 atmosphere and kept for 1h, and is naturally cooled to room temperature, to obtain nitrogen-doped porous carbon N-MPC 800 .

[0070] S5, anhydrous sodium carbonate, ethylene glycol and chloroplatinic acid are mixed, and the nitrogen-doped porous carbon N-MPC prepared in step S4 is added 800 , a glycol reduction reaction is carried out at pH 8.5 and temperature 130℃, to realize controllable deposition of platinum single atoms and nanoparticles; after the reaction is completed, the reaction precipitate is first washed with deionized water and anhydrous ethanol for three times each by centrifugation, and is then transferred to a 60℃ oven for drying for 12h, to obtain a platinum single atom and platinum nanoparticle synergistically dispersed catalyst Pt SA-NP @N-MPC 800 .

[0071] Example 2

[0072] The embodiment provides a preparation method of a platinum single atom-platinum nanoparticle synergistically dispersed catalyst, and comprises the following operation steps:

[0073] S1, zinc chloride is dissolved in deionized water and stirred uniformly, and then SiO2 template with a particle size of 50-100nm and polyquaternary ammonium salt PQ7 are added, and the mass ratio of zinc chloride, SiO2 and polyquaternary ammonium salt PQ7 is 1:5:2; after stirring for 12h, a uniformly dispersed mixed solution is obtained.

[0074] S2, the mixed solution is first placed in an 85℃ oven for drying for 12h to obtain a block-shaped substance, and then a planetary ball mill with a rotating speed of 300rpm is adopted for 4h to obtain a uniformly distributed light yellow powder.

[0075] S3, the above powder is transferred to a tube furnace for high-temperature treatment, is heated to 900℃ at 5℃ / min under N2 atmosphere and kept for 1h, and is naturally cooled to room temperature, to obtain a template-containing nitrogen-doped carbon material Zn@SiO2@NC 900 .

[0076] S4, the template-containing nitrogen-doped carbon material is sequentially subjected to alkali washing, acid washing, and washing with deionized water until neutral, and then is first placed in a 60℃ oven for drying for 12h, and then is transferred to a tube furnace for second high-temperature treatment, is heated to 900℃ at 5℃ / min under N2 atmosphere and kept for 1h, and is naturally cooled to room temperature, to obtain nitrogen-doped porous carbon N-MPC 900 .

[0077] S5, first mix anhydrous sodium carbonate, ethylene glycol and chloroplatinic acid, then add the nitrogen-doped porous carbon N-MPC prepared in step S4 900 , the glycol reduction reaction is carried out at a temperature of 130 DEG C and a pH of 8.5, thereby realizing the controllable deposition of platinum single atoms and nanoparticles; after the reaction is completed, the reaction precipitate is first washed with deionized water and anhydrous ethanol three times each by centrifugation, then transferred to a 60 DEG C oven for drying for 12 h, thereby obtaining the platinum single atom and platinum nanoparticle synergistically dispersed catalyst Pt SA-NP @N-MPC 900 .

[0078] Example 3

[0079] The present embodiment provides a preparation method of a platinum single atom-platinum nanoparticle synergistically dispersed catalyst, comprising the following operation steps:

[0080] S1, after dissolving zinc chloride in deionized water and stirring uniformly, add SiO2 template agent with a particle size of 50-100 nm and polyquaternary ammonium salt PQ7, the mass ratio of zinc chloride, SiO2 and polyquaternary ammonium salt PQ7 being 1:5:2; after stirring for 12 h, a uniformly dispersed mixed solution is obtained.

[0081] S2, first dry the mixed solution in an 85 DEG C oven for 12 h to obtain a block, then use a planetary ball mill at a rotation speed of 300 rpm for 4 h to obtain a uniformly distributed light yellow powder.

[0082] S3, transfer the above powder to a tube furnace for high-temperature treatment, heat to 950 DEG C at a rate of 5 DEG C / min under N2 atmosphere and keep for 1 h, then naturally cool to room temperature, thereby obtaining the nitrogen-doped carbon material containing a template agent Zn@SiO2@NC 950 .

[0083] S4, sequentially perform alkali washing and acid washing on the nitrogen-doped carbon material containing a template agent, then wash with deionized water until neutral, first dry in a 60 DEG C oven for 12 h, then transfer to a tube furnace for second high-temperature treatment, heat to 950 DEG C at a rate of 5 DEG C / min under N2 atmosphere and keep for 1 h, then naturally cool to room temperature, thereby obtaining the nitrogen-doped porous carbon N-MPC 950 .

[0084] S5, first mix anhydrous sodium carbonate, ethylene glycol and chloroplatinic acid, then add the nitrogen-doped porous carbon N-MPC prepared in step S4 950 , the glycol reduction reaction is carried out at a temperature of 130 DEG C and a pH of 8.5, thereby realizing the controllable deposition of platinum single atoms and nanoparticles; after the reaction is completed, the reaction precipitate is first washed with deionized water and anhydrous ethanol three times each by centrifugation, then transferred to a 60 DEG C oven for drying for 12 h, thereby obtaining the platinum single atom and platinum nanoparticle synergistically dispersed catalyst Pt SA-NPN-MPC 950 .

[0085] Example 4

[0086] The present embodiment provides a preparation method of a platinum monatomic-palladium nanoparticle synergistically dispersed catalyst, comprising the following operation steps:

[0087] S1, after dissolving zinc chloride in deionized water and stirring uniformly, adding SiO2 template agent with a particle size of 50-100 nm and polyquaternary ammonium salt PQ7, the mass ratio of zinc chloride, SiO2 and polyquaternary ammonium salt PQ7 being 1:5:2; after stirring for 12 h, a uniformly dispersed mixed solution is obtained.

[0088] S2, first drying the mixed solution in an oven at 85℃ for 12 h to obtain a block, and then using a planetary ball mill at a rotating speed of 300 rpm for 4 h to obtain a uniformly distributed light yellow powder.

[0089] S3, transferring the above powder to a tube furnace for high-temperature treatment, heating to 1000℃ at a rate of 5℃ / min under N2 atmosphere and keeping for 1 h, and naturally cooling to room temperature, to obtain a nitrogen-doped carbon material Zn@SiO2@NC containing a template agent. 1000 .

[0090] S4, sequentially performing alkali washing and acid washing on the nitrogen-doped carbon material containing a template agent, washing to neutral with deionized water, first drying in an oven at 60℃ for 12 h, and then transferring to a tube furnace for second high-temperature treatment, heating to 1000℃ at a rate of 5℃ / min under N2 atmosphere and keeping for 1 h, to obtain a nitrogen-doped porous carbon N-MPC. 1000 .

[0091] S5, first mixing anhydrous sodium carbonate, ethylene glycol and chloroplatinic acid, then adding the nitrogen-doped porous carbon prepared in step S4, and performing ethylene glycol reduction reaction at a pH of 8.5 and a temperature of 130℃, to realize controllable deposition of platinum monatomic and nanoparticles; after the reaction is completed, centrifugally washing the reaction precipitate with deionized water and anhydrous ethanol each three times, transferring to a 60℃ oven for drying for 12 h, to obtain a platinum monatomic and palladium nanoparticle synergistically dispersed catalyst Pt. SA-NP N-MPC 1000 .

[0092] Comparative Example 1

[0093] Commercial Pt / C catalyst: Pt / C catalyst from Johnson Matthey (JM).

[0094] The catalysts of the above examples and comparative examples are subjected to performance characterization, specifically as follows:

[0095] From Fig. 1a~1d N-MPC prepared in Examples 1-4x The SEM images show that the nitrogen-doped porous carbon N-MPC of this invention... x All of them contain abundant pore structures with pore sizes ranging from 2 to 50 nm. As the high-temperature treatment temperature in the range of 800 to 1000 °C increases, a small number of macropores experience pore wall collapse, and the pore size mainly tends to be mesopores (which is beneficial for enhancing active sites) and micropores.

[0096] N-MPC prepared in Example 3 950 Platinum is added to a solution composed of ethylene glycol, anhydrous sodium carbonate, and chloroplatinic acid, and then supported on mesoporous carbon via ethylene glycol reduction. Fig. 2 The SEM images show that the prepared Pt SA-NP @N-MPC 950 It still maintains a rich porous morphology, with pore sizes between 20 and 30 nm. Fig. 3 The TEM image shows that in Pt SA-NP @N-MPC 950 In this process, Pt particles are uniformly loaded onto nitrogen-doped porous carbon N-MPC950.

[0097] Depend on Fig. 4 The adsorption-desorption isotherms show that the nitrogen-doped porous carbon (N-MPC) support prepared in this invention... 950 and catalyst Pt SA-NP @N-MPC 950 Both materials exhibited a type IV isotherm, with a significant increase in adsorption at relatively low nitrogen partial pressures (<0.1) and a significant hysteresis loop at higher nitrogen pressures (relative pressures from 0.65 to 1.0), indicating the coexistence of micropores and mesopores.

[0098] Depend on Fig. 5a , 5b Examples 1-4: Four types of N-MPC carriers prepared under different conditions (high temperature treatment at 800~1000℃) x The ORR performance comparison charts under 0.1M HClO4 and 0.1M KOH show that N-MPC 950 It is the carrier material with the best ORR performance under both acidic and alkaline conditions.

[0099] Nitrogen-doped porous carbon N-MPC x It can function as both a carbon catalyst and a carbon support, making it a bifunctional material. The nitrogen-doped porous carbon N-MPC prepared according to this invention... 950 Pt catalyst SA-NP @N-MPC 950 ORR performance of the catalyst and a commercial Pt / C catalyst were compared under 0.1 M HClO4 and 0.1 M KOH conditions, respectively; Fig. 6a ,6b It can be seen that the half-wave potential (E SA-NP ) of ORR of Pt 950 / N-MPC 1 / 2 is 0.9 V and 0.94 V respectively, especially E 1 / 2 is higher than that of Pt / C (JM) by nearly 120 mV, and the catalytic performance is significantly superior to that of the commercial Pt / C (JM) catalyst, especially to that of nitrogen-doped porous carbon. This also shows that the platinum anchoring ability can be enhanced by nitrogen species, and the catalytic activity of the catalyst can be significantly improved by utilizing the interface synergistic effect of platinum monatomic and platinum nanoparticles.

[0100] The above further describes the present application with specific examples, but it should be understood that the specific description herein should not be understood as limiting the essence and scope of the present application, and various modifications made to the above examples by those of ordinary skill in the art after reading the present specification are within the scope of the present application.

Claims

1. A method for preparing a platinum monoatom-palladium nanoparticle synergistic dispersion catalyst, characterized by, The method comprises the following steps: S1, dissolving a zinc salt in deionized water, adding a SiO2 template agent with a particle size of 50-100 nm and a polyquaternary ammonium salt, the mass ratio of the zinc salt, SiO2 template agent and polyquaternary ammonium salt being 1:(5-7):(2-3); after sufficient stirring, a uniformly dispersed mixed solution is obtained; S2, drying the mixed solution at 75-90℃ for 10-14h to obtain a block, and then performing planetary ball milling at a rotation speed of 280-350rpm for 1-4h to obtain a uniform powder; S3, performing high-temperature treatment on the powder, heating to 800-1000℃ at a rate of 5℃ / min under a N2 atmosphere, and maintaining for 1h to obtain a nitrogen-doped carbon material containing a template agent; S4, sequentially performing alkali washing, acid washing and deionized water washing to neutralize the nitrogen-doped carbon material containing the template agent, then drying at a temperature of 50-70℃ for 10-14h, and then performing a second high-temperature treatment, heating to 800-1000℃ at a rate of 5℃ / min under a N2 atmosphere, and maintaining for 1h to obtain a nitrogen-doped porous carbon; S5, first mix anhydrous sodium carbonate, ethylene glycol and a precursor containing platinum, then add the nitrogen-doped porous carbon prepared in step S4, and perform a reduction reaction at a pH of 8-10 and a temperature of 120-160°C; after the reaction is completed, centrifuge and wash the reaction precipitate, and dry it to obtain platinum monatomic-particle-platinum nanoparticle synergistically dispersed catalyst Pt SA-NP @N-MPC.

2. The method for preparing a platinum monatomic-palladium nanoparticle synergistic dispersion catalyst according to claim 1, characterized by, In step S1, the zinc salt is zinc sulfate, zinc chloride or zinc nitrate.

3. The method for preparing the platinum single-atom-platinum nanoparticle synergistic dispersion catalyst according to claim 1, characterized in that, In step S2, the drying condition is drying at a temperature of 85℃ for 12h; and the ball milling condition is ball milling at a rotation speed of 300rpm for 4h.

4. The method for preparing the platinum single-atom-platinum nanoparticle synergistic dispersion catalyst according to claim 1, characterized in that, In steps S3 and S4, the high-temperature treatment is heating to 950℃ at a rate of 5℃ / min and maintaining for 1h.

5. The method for preparing the platinum single-atom-platinum nanoparticle synergistic dispersion catalyst according to claim 1, characterized in that, In step S4, the drying condition is drying at a temperature of 60℃ for 12h.

6. The method of claim 1, wherein the platinum single-atom-particle and platinum nanoparticle synergistically dispersed catalyst is prepared by the steps of: (a) preparing a platinum nanoparticle catalyst; (b) preparing a platinum single-atom-particle catalyst; and (c) mixing the platinum nanoparticle catalyst and the platinum single-atom-particle catalyst. In step S5, the platinum-containing precursor is an aqueous solution of chloroplatinic acid, ammonium chloroplatinate or platinum nitrate.

7. The method for preparing the platinum single-atom-platinum nanoparticle synergistic dispersion catalyst according to claim 1, characterized in that, In step S5, the centrifugal washing and drying condition is centrifugal washing with deionized water and anhydrous ethanol each three times, and then drying at a temperature of 50-70℃ for 10-14h.

8. A platinum monoatom-palladium nanoparticle synergistic dispersion catalyst, characterized by, The catalyst is prepared by the method of any one of claims 1-7.

9. The platinum monoatom-nanoparticle cooperative dispersion catalyst of claim 8, wherein, The carrier nitrogen-doped porous carbon of the catalyst has a micropore-mesopore hierarchical structure, and the pore size distribution is 2-50nm; platinum is co-anchored in the interior and surface of the carrier in the form of single atoms and nanoparticles.

10. A platinum single atom-platinum nanoparticle synergistically dispersed catalyst prepared by the method of any one of claims 1-7 for use in a proton exchange membrane fuel cell.

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