A method for preparing a high-loading Pt-based oxygen reduction reaction catalyst loaded with mesoporous carbon nanocages
By loading high-load Pt-based catalysts onto mesoporous carbon nanocages and combining them with Mn-Nx single-atom sites, the problem of activity degradation of Pt-based catalysts in proton exchange membrane fuel cell cathodes due to sulfonic acid group poisoning and Pt particle migration was solved, thus improving the stability and activity of high-load Pt catalysts.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- UNIV OF ELECTRONICS SCI & TECH OF CHINA
- Filing Date
- 2026-03-18
- Publication Date
- 2026-06-19
Smart Images
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Abstract
Description
Technical Field
[0001] This invention relates to a high-loading Pt-based oxygen reduction reaction catalyst supported on mesoporous carbon nanocages and its preparation method, belonging to the fields of new energy nanomaterials and catalysis technology. Background Technology
[0002] Proton exchange membrane fuel cells (PEMFCs), as a clean energy conversion technology, possess advantages such as high energy conversion efficiency, rapid response, and zero greenhouse gas emissions, and are considered one of the key technologies for achieving deep decarbonization in the transportation sector (such as heavy-duty trucks and passenger cars) and stationary power generation systems. However, the widespread application of PEMFCs is still limited by the slow kinetics of the cathode ORR (Orbital Reduction), a complex process involving multi-step electron transfer that highly relies on Pt-based catalysts to lower its activation energy barrier. Despite extensive research, two long-standing challenges hinder its commercialization in demanding scenarios such as heavy-duty vehicles: first, the poisoning effect of sulfonic acid groups (-SO3H) in perfluorosulfonic acid (PFSA) ionomers on Pt active sites; and second, the poor stability of Pt-based catalysts under high Pt loading conditions.
[0003] To ensure efficient proton transport, perfluorosulfonic acid (PFSA) ionomers must be added to the cathode catalyst layer of PEMFCs. However, the terminal -SO3H groups of PFSA strongly and specifically adsorb onto the Pt catalyst surface under electrochemical conditions, blocking active sites and leading to a decrease in intrinsic catalyst activity. This poisoning effect is more severe under high current density operation or complex operating conditions; uneven ionomer distribution further blocks mass transfer channels, reducing Pt accessibility. Recent studies have shown that such interfacial interactions can reduce Pt utilization to below 20% and lead to a significant decline in catalytic activity. Meanwhile, to meet the high power output demands of heavy-duty vehicles, the cathode often needs to increase the Pt loading to provide sufficient active sites. However, in actual PEMFC operation, the cathode potential fluctuates frequently and experiences high potentials (e.g., during start-up and shutdown), which exacerbates the degradation of traditional carbon-supported platinum catalysts. The main degradation mechanisms include: electrochemical corrosion of the carbon support at high potentials, leading to the loss of support and detachment or aggregation of Pt nanoparticles; and Ostwald ripening (dissolution and re-deposition of smaller particles onto larger particles) and migration and aggregation of the Pt nanoparticles themselves during potential cycling. These limitations collectively result in low mass activity (typically approximately 0.1 A mg at 0.9 V vs. RHE). Pt -1The catalyst exhibits rapid performance degradation (MA loss >40% after 30,000 cycles), far below the US Department of Energy's (DOE) 2025 target. However, under high Pt loading conditions, current mitigation strategies still struggle to simultaneously address the sulfonic acid group poisoning effect and maintain the long-term stability of the Pt-based catalyst structure. We have independently invented a novel catalyst structure by constructing mesoporous carbon nanocages that confine highly loaded Pt nanoparticles and combining them with Mn-N... x Single-atom site integration (the catalyst is denoted as Pt-MnNC) is used to synergistically address the aforementioned intertwined challenges. Summary of the Invention
[0004] The purpose of this invention is to solve the technical problems of poor accessibility of active sites, rapid decay of mass activity, insufficient long-term durability and low Pt utilization rate of high-loading Pt-based oxygen reduction reaction catalysts in proton exchange membrane fuel cell cathode applications. These problems are caused by the specific adsorption and poisoning of active sites by sulfonic acid groups (-SO3H) in perfluorosulfonic acid ionomers, migration and agglomeration of Pt nanoparticles during electrochemical cycling (Ostwald ripening), and uneven particle distribution under high loading conditions.
[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:
[0006] This invention provides a method for preparing a highly loaded Pt-based oxygen reduction reaction catalyst supported on mesoporous carbon nanocages, comprising the following steps:
[0007] Step (1) The Mn source was introduced into the zeolite imidazolium ester framework material ZIF-8 by adsorption method to obtain the Mn-doped zeolite imidazolium ester framework material Mn / ZIF-8.
[0008] Step (2) The Mn / ZIF-8 obtained in step (1) is mixed and ground with NaCl salt at a mass ratio of 1:(8-12), and then subjected to high-temperature carbonization treatment at 800-1000℃ under an inert atmosphere to form a mesoporous structure using NaCl molten salt as a template; the carbonization product is then acid-washed to remove residual metal elements and salt template to obtain a mesoporous carbon nanocage MnNC support, wherein the MnNC support contains atomically dispersed Mn-Nx sites;
[0009] Step (3) Disperse the MnNC support obtained in step (2) in a solvent, add Pt precursor solution to mix and impregnate, so that Pt precursor enters the pores of MnNC support, and obtain precursor complex after drying.
[0010] Step (4) The precursor complex obtained in step (3) is subjected to high-temperature thermal reduction at 200-400℃ in a reducing atmosphere to reduce the platinum precursor to Pt nanoparticles, thereby obtaining a mesoporous carbon nanocage supported high-load Pt-based oxygen reduction reaction catalyst.
[0011] In the above scheme, the preparation of ZIF-8 in step (1) includes: dissolving zinc nitrate hexahydrate and 2-methylimidazole in an alcohol solvent at a mass ratio of 1:(1.1-1.3) and mixing and reacting, and then centrifuging, washing and drying to obtain the zeolite imidazole ester skeleton material ZIF-8.
[0012] In the above scheme, the preparation of Mn / ZIF-8 includes:
[0013] Step 1.1: Disperse 1.487 g of zinc nitrate hexahydrate evenly in 40 mL of methanol solution to obtain methanol mixture A;
[0014] Step 1.2: Disperse 1.741 g of 2-methylimidazole evenly in 40 mL of methanol solution to obtain methanol mixture B;
[0015] Step 1.3: Slowly pour methanol mixture A into methanol mixture B which is stirred at a constant speed and continue stirring at room temperature for 15 minutes. Then let it stand for 12 hours, then centrifuge, wash with methanol, and dry to obtain zeolite imidazole ester framework material ZIF-8.
[0016] Step 1.4: Disperse 0.2 g of zeolite imidazolium ester framework material ZIF-8 in 20 mL of ethanol solution, and add 0.03 g of manganese acetylacetone. Stir continuously at room temperature for 24 hours, and then transfer the mixed solution to an 80℃ oil bath for drying to obtain Mn-doped zeolite imidazolium ester framework material Mn / ZIF-8.
[0017] In the above scheme, step 2 includes:
[0018] Step 2.1: Mix and grind the Mn / ZIF-8 precursor with NaCl salt at a mass ratio of 1:(8-12) to make NaCl uniformly coat the surface of the precursor.
[0019] Step 2.2: Transfer the sample obtained in step 2.1 to a crucible, and then calcine it in a tube furnace under high-temperature argon atmosphere for 2 hours at a heating rate of 2℃ / min;
[0020] Step 2.3: Take out the sample after the treatment in step 2.2, and wash it with acid in 1M HNO3 solution to remove the residual zinc and manganese particles in the material. After filtration, washing and drying, the supported mesoporous carbon nanocage MnNC carrier is obtained.
[0021] In the above scheme, step 3 includes:
[0022] Step 3.1: Disperse 500 mg of mesoporous carbon nanocage MnNC support in 200 mL of deionized water by ultrasonication for 30 minutes. Impregnate the Pt precursor into the pores of the mesoporous carbon nanocage MnNC support and stir continuously at room temperature for 12 hours. Collect the product by freeze drying to obtain the precursor complex MnNC@H2PtCl6.
[0023] In the above scheme, the drying temperature in step 1.3 is 60℃, the drying time is 12 h, and the average particle size of ZIF-8 is 200 nm.
[0024] In the above scheme, the pyrolysis temperature in step 2.2 is 800-1000℃.
[0025] In the above scheme, the pickling conditions in step 2.3 are 1M HNO3, 80℃, stirring at 200 rpm for 12 h; after pickling, the mixture is filtered and washed with deionized water until neutral; the vacuum drying temperature is 60℃ and the drying time is 12 h.
[0026] In the above scheme, the impregnation conditions are as follows: 500 mg of MnNC carrier is ultrasonically dispersed in 200 mL of deionized water for 30 minutes. Subsequently, 30 mL of a solution containing 1350 mg of H2PtCl6 is added dropwise to the dispersion, and the mixture is continuously stirred at room temperature for 12 h.
[0027] In the above scheme, the high-temperature thermal reduction temperature in step 4 is 300℃, the heating rate is 2℃ / min, the heat treatment time is 2h, and the atmosphere is Ar / H2 mixed gas; the obtained mesoporous carbon nanocage supported high-load Pt-based oxygen reduction reaction catalyst Pt-MnHNC has high specific surface area and high accessibility of active sites, and the Pt loading of Pt-MnHNC is as high as 51.8 wt%.
[0028] The present invention has the following advantages:
[0029] 1) This invention utilizes mesoporous nanocages constructed through molten salt-assisted pyrolysis to achieve atomic-level (Mn-N) nanoporous structure construction. x Multi-scale confinement from the pore size to the nanoscale (mesoporous channels). Mn-N x The introduction of sites not only provides additional oxygen reduction activity, but also optimizes the d-band center of Pt through electronic effects, strengthening the anchoring force and enabling the catalyst to exhibit long-term durability that surpasses that of commercial Pt / C during cycling.
[0030] 2) The mesoporous carbon wall designed in this invention plays a key physical barrier role in the catalyst structure. It establishes a physical barrier to perfluorosulfonic acid ionomer (Nafion) by utilizing the spatial confinement effect, effectively blocking the specific adsorption of sulfonic acid groups to Pt active sites.
[0031] 3) Utilizing the pore environment confined by the mesoporous carbon nanocage framework, and taking advantage of Mn-N x The metal-support interaction enables Pt nanoparticles to be uniformly fixed on mesoporous carbon nanocages. The Pt mass fraction of this material is as high as 51.8 wt%, and the size of the Pt nanoparticles can be uniformly controlled (2.0-2.2 nm), thereby significantly improving the stability and intrinsic activity of Pt-based catalysts. Attached Figure Description
[0032] Figure 1 This is the SEM image of the Pt-MnHNC catalyst obtained in Example 1;
[0033] Figure 2 These are the (a) SEM and (b) STEM images of the same region of the Pt-MnHNC catalyst obtained in Example 1;
[0034] Figure 3 These are (a) TEM images and (b) HR-TEM images of the Pt-MnHNC catalyst obtained in Example 1;
[0035] Figure 4 These are (a) TEM images and (b) EDX elemental mapping images of the Pt-MnHNC catalyst obtained in Example 1;
[0036] Figure 5 The XRD pattern of the Pt-MnHNC catalyst obtained in Example 1 is shown below.
[0037] Figure 6 This is the TGA spectrum of the Pt-MnHNC catalyst obtained in Example 1;
[0038] Figure 7 The images show (a) N2 adsorption-desorption curves and (b) pore size distribution diagrams of the Pt-MnHNC catalyst obtained in Example 1.
[0039] Figure 8 The graphs are (a) oxygen reduction reaction polarization curves and (b) corresponding Tafel curves of the Pt-based catalyst and the commercial Pt / C catalyst obtained in Example 1.
[0040] Figure 9 LSV curves of the Pt-based catalyst (a) and the commercial Pt / C catalyst (b) obtained in Example 1 before and after the accelerated durability test (ADT) cycle in oxygen-saturated 0.1 MHClO4.
[0041] Figure 10 The cathode was Pt-MnHNC and 40% Pt / C as described in Example 1 (both with a loading of 0.3 mg). Pt cm -2Commercial 40% Pt / C was used as the anode (loading 0.05 mg). Pt cm -2 Test results of assembling a proton exchange membrane fuel cell. Detailed Implementation
[0042] The invention will be further explained below with reference to specific implementation examples.
[0043] First, Mn-doped zeolite imidazole ester framework material Mn / ZIF-8 was obtained by adsorption. Then, it was mixed and ground with NaCl salt, followed by carbonization under argon atmosphere and acid washing to obtain a supported mesoporous carbon nanocage MnNC support. The MnNC support was then mixed with chloroplatinic acid H2PtCl6·6H2O and then subjected to high-temperature thermal reduction to prepare a high-load Pt nanoparticle catalyst with ordered structure, uniform size and distribution supported by mesoporous carbon nanocage support.
[0044] The principle is as follows: Mn-doped zeolite imidazolium ester framework material Mn / ZIF-8 is obtained by adsorption method, and then mixed and ground with NaCl salt. Utilizing the confinement effect of molten salt, most Mn atoms can be separated and bonded to nitrogen atoms on the carbon support. A mesoporous carbon nanocage MnNC support with high specific surface area is obtained through molten salt-assisted pyrolysis. The anchoring of Pt nanoparticles is enhanced through metal-support interaction, effectively limiting the migration and aggregation of Pt nanoparticles at high temperatures, ensuring the structural integrity and activity durability of the catalyst during long-term operation. Through the confined pore environment of the mesoporous carbon nanocage framework, the Mn-N... x The metal-support interaction was successfully demonstrated, and Pt nanoparticles were uniformly fixed on mesoporous carbon nanocages. The Pt mass fraction of the material was as high as 51.8 wt%, and the size of the Pt nanoparticles was uniformly controlled (2.0-2.2 nm), thereby significantly improving the stability and intrinsic activity of Pt-based catalysts.
[0045] The preparation process of the above-mentioned mesoporous carbon nanocage-supported Pt-based oxygen reduction reaction catalyst is as follows:
[0046] Step 1) Disperse 1.487 g of zinc nitrate hexahydrate evenly in 40 mL of methanol solution to obtain methanol mixture A;
[0047] Step 2) Disperse 1.741 g of 2-methylimidazole evenly in 40 mL of methanol solution to obtain methanol mixture B;
[0048] Step 3) Slowly pour methanol mixture A into methanol mixture B which is stirred at a constant speed and continue stirring at room temperature for 15 minutes. Then let it stand for 12 hours, then centrifuge, wash with methanol, and dry to obtain zeolite imidazole ester framework material ZIF-8.
[0049] Step 4) Disperse 0.2 g of zeolite imidazolium ester framework material ZIF-8 in 20 mL of ethanol solution and add 0.03 g of manganese acetylacetone. Stir continuously at room temperature for 24 hours. Then transfer the mixed solution to an 80℃ oil bath for drying to obtain Mn-doped zeolite imidazolium ester framework material Mn / ZIF-8.
[0050] Step 5) Collect the sample obtained in step 4 and add 10 times the mass of NaCl to grind it together for a certain period of time;
[0051] Step 6) Transfer the sample obtained in Step 5 to a crucible, and then calcine it in a tube furnace under high temperature argon atmosphere for 2 hours at a heating rate of 2℃ / min;
[0052] Step 7) Take out the sample after step 6 and acid wash it in 1M HNO3 solution to remove the residual zinc and manganese particles in the material. After filtration, washing and drying, the supported mesoporous carbon nanocage MnNC carrier is obtained.
[0053] Step 8) Disperse 500 mg of the sample obtained in Step 7 in 200 mL of deionized water by ultrasonication for 30 minutes. Impregnate the Pt precursor into the pores of the MnNC support and stir continuously at room temperature for 12 hours. Collect the product by freeze drying to obtain MnNC@H2PtCl6.
[0054] Step 9) The sample obtained in step 8 was calcined in an argon-hydrogen atmosphere at 300℃ for in-situ reduction, and finally a Pt-MnNC catalyst with highly loaded Pt nanoparticles spatially confined in a carbon matrix was obtained.
[0055] In step 3) above, the drying temperature is 60℃, the drying time is 12 h, and the average particle size of ZIF-8 is 200 nm.
[0056] In step 6) above, the pyrolysis temperature is 900℃.
[0057] In step 7) above, the pickling conditions are 1M HNO3, 80℃, and stirring at 200 rpm for 12 h; after pickling, the mixture is filtered and washed with deionized water until neutral; the vacuum drying temperature is 60℃ and the drying time is 12 h.
[0058] In step 8) above, the impregnation conditions are as follows: 500 mg of MnNC carrier is ultrasonically dispersed in 200 mL of deionized water for 30 minutes. Subsequently, 30 mL of a solution containing 1350 mg of H2PtCl6 is added dropwise to the dispersion, and the mixture is stirred continuously at room temperature for 12 h.
[0059] In step 9) above, the heat treatment temperature is 300℃, the heating rate is 2℃ / min, the heat treatment time is 2 h, and the atmosphere is Ar / H2 mixed gas; the obtained mesoporous carbon nanocage supported high-load Pt-based oxygen reduction reaction catalyst Pt-MnHNC has high specific surface area and high accessibility of active sites, and the Pt loading of Pt-MnHNC is as high as 51.8 wt%.
[0060] The specific preparation steps for Example 1 are as follows:
[0061] 1) Disperse 1.487 g of zinc nitrate hexahydrate evenly in 40 mL of methanol solution to obtain methanol mixture A;
[0062] 2) 1.741 g of 2-methylimidazole was uniformly dispersed in 40 mL of methanol solution to obtain methanol mixture B;
[0063] 3) Slowly pour methanol mixture A into methanol mixture B which is stirred at a constant speed and continue stirring at room temperature for 15 minutes. Then let it stand for 12 hours, then centrifuge, wash with methanol, and dry in an oven at 60℃ for 12 hours to obtain zeolite imidazole ester framework material ZIF-8 with an average particle size of 200 nm.
[0064] 4) Take 0.2 g of zeolite imidazolium ester framework material ZIF-8 and disperse it in 20 mL of ethanol solution, add 0.03 g of manganese acetylacetone, stir continuously at room temperature for 24 hours, and then transfer the mixed solution to an 80℃ oil bath for drying to obtain Mn-doped zeolite imidazolium ester framework material Mn / ZIF-8.
[0065] 5) Collect the sample obtained in step 4, and add 1:(8-12) times the mass of NaCl and grind for a certain period of time;
[0066] 6) Transfer the sample obtained in step 5 to a crucible, and then calcine it in a tube furnace at a high temperature of 800-1000℃ under argon atmosphere for 2 hours, with a heating rate of 2℃ / min;
[0067] 7) Take out the sample after step 6, and acid wash it in 1M HNO3 solution in an oil bath at 80℃, stirring at 200 rpm for 12 h to remove residual zinc and manganese particles in the material. After filtration, washing and drying, the supported mesoporous carbon nanocage MnNC carrier is obtained.
[0068] 8) Disperse 500 mg of the sample obtained in step 7 in 200 mL of deionized water by ultrasonication for 30 minutes. Then, add 30 mL of solution containing 1350 mg of H2PtCl6 dropwise to the dispersion and stir continuously at room temperature for 12 hours. Collect the product by freeze drying to obtain MnNC@H2PtCl6.
[0069] Step 9) The sample obtained in step 8 was calcined in 300℃ in an argon-hydrogen atmosphere for 2 h at a heating rate of 2℃ / min to carry out in-situ reduction, and finally a Pt-MnNC catalyst with highly loaded Pt nanoparticles spatially confined in a carbon matrix was obtained.
[0070] Figure 1 This is a SEM image of the Pt-MnHNC catalyst prepared in Example 1. It can be observed that the prepared Pt-MnHNC catalyst exhibits a porous carbon nanocage structure with an average diameter of approximately 200 nm.
[0071] Figure 2 The images show SEM and STEM characterizations of the same region of the Pt-MnHNC prepared in Example 1. Figure 2 The SEM image of a shows only a few scattered bright spots, indicating that the number of Pt nanoparticles exposed on the outermost surface of the carbon support is extremely small. Figure 2 The STEM image in image b clearly shows a high density of bright Pt nanoparticles uniformly distributed within the hollow carbon particles. This direct visual contrast provides conclusive evidence that the vast majority of Pt nanoparticles are successfully confined within the mesoporous carbon matrix. This intentional internal spatial positioning is a core strategy in our catalyst design. Its fundamental purpose is to physically isolate the catalytically active Pt surface from direct contact with the sulfonic acid groups in the Nafion ionomer during MEA preparation, thereby significantly mitigating the catalyst active site poisoning problem caused by the specific adsorption of -SO3H groups.
[0072] Figure 3 These are TEM and HR-TEM images of the Pt-MnHNC prepared in Example 1. From... Figure 3 In section a, fine and high-density Pt nanoparticles can be observed to be uniformly dispersed throughout the porous carbon matrix, without obvious agglomeration; from Figure 3 In the middle b, a clear lattice fringe spacing of 0.223 nm is observed, corresponding to the (111) crystal plane of the face-centered cubic Pt structure;
[0073] Figure 4 The images show TEM images and corresponding EDX elemental mappings of the Pt-MnHNC prepared in Example 1. The images further confirm that Pt nanoparticles are uniformly dispersed on mesoporous carbon nanocages, and that Mn elements have been successfully doped into the carbon support.
[0074] Figure 5 This is the XRD pattern of Pt-MnHNC prepared in Example 1. The XRD pattern confirms that Pt nanoparticles were formed after calcination of the metal precursor.
[0075] Figure 6This is the TGA image of the Pt-MnHNC prepared in Example 1. Pt-MnNC exhibits a 5.8 wt% mass loss below 150 °C, attributed to the removal of adsorbed water; a significant 51.1 wt% mass loss occurs between 150 and 500 °C, corresponding to the oxidative decomposition of the carbon matrix. Therefore, the total metal content is calculated to be approximately 54.2 wt%. Furthermore, inductively coupled plasma atomic emission spectrometry (ICP-AES) further quantifies the Pt and Mn loadings in Pt-MnNC to be 51.8 wt% and 0.2 wt%, respectively, which is largely consistent with the thermogravimetric analysis results. This confirms the catalyst's ultra-high Pt loading and indicates that the Mn doping is extremely low and atomically dispersed.
[0076] Figure 7 This is a specific surface area and pore size distribution diagram of the Pt-MnHNC prepared in Example 1. According to the test results, this Pt-MnHNC has a high specific surface area (454.3 m²). 2 g -1 Furthermore, it possesses a rich mesoporous structure, which can anchor and constrain the size of Pt nanoparticles and facilitate the transport of reactants and products in the oxygen reduction reaction, thereby improving catalyst activity.
[0077] Figure 8 The Pt-MnHNC and commercial Pt / C (20%) catalysts of Example 1 were tested in 0.1 M HClO4 electrolyte at a scan rate of 50 mV / s. -1 The LSV curve and the corresponding Tafel curve at 1600 rpm. Figure 8 Figure a shows that Pt-MnNC exhibits a more positive half-wave potential than commercial Pt / C catalysts, indicating that it has superior ORR activity both thermodynamically and kinetically. Figure 8 Further analysis of the Tafel slope curve of the Pt-MnNC catalyst from a kinetic perspective revealed that the Tafel slope is 67.4 mV dec. -1 This is lower than the 76.2 mV dec of commercial Pt / C. -1 The lower Tafel slope indicates that the Pt-MnNC catalyst can provide a higher current density at the same overpotential, suggesting that it has a faster rate-determining step and better kinetic performance.
[0078] Figure 9The LSV curves of Pt-MnHNC (a) and commercial Pt / C (20%) (b) from Example 1 were recorded before and after 6 weeks of ADT cycling in oxygen-saturated 0.1 M HClO4 and at a voltage of 0.6–1.0 V. The results show that, under the same Pt metal loading and number of cycles, the stability of the prepared Pt-based catalyst is significantly higher than that of the commercial Pt / C catalyst. The high-load Pt nanoparticle catalyst supported by mesoporous carbon nanocages, through its unique structural design, utilizes the spatial confinement effect of the mesoporous carbon nanocages to separate most of the Mn atoms and bond them with nitrogen atoms on the carbon support to form Mn-N. x Through metal-support interaction, the anchoring of Pt nanoparticles is enhanced, which can effectively limit the migration and aggregation of Pt nanoparticles at high temperatures, thus ensuring the structural integrity and activity durability of the catalyst during long-term operation.
[0079] Figure 10 The cathode was Pt-MnHNC and 40% Pt / C as described in Example 1 (both with a loading of 0.3 mg). Pt cm -2 Commercial 40% Pt / C was used as the anode (loading 0.05 mg). Pt cm -2 Test results of assembling a proton exchange membrane fuel cell. Figure 10 The results show that under the same test conditions, the H2-Air fuel cell based on the Pt-MnHNC cathode exhibits significantly improved performance, achieving a current density of 1.36 A cm⁻¹ at 0.7 V. -2 , at 2.0 A cm -2 The power density at the current density is 1.26 W / cm². -2 In contrast, a battery using commercially available 40% Pt / C as the cathode achieves only 0.84 A cm⁻¹ at the same voltage (0.7V). -2 , at 2.0 A cm -2 The power density at the current density is 1.02 W / cm². -2 This fully demonstrates the excellent oxygen reduction electrochemical performance of the Pt-MnNC catalyst.
Claims
1. A method for preparing a high-loading Pt-based oxygen reduction reaction catalyst supported on mesoporous carbon nanocages, characterized in that, Includes the following steps: Step 1: The Mn source was introduced into the zeolite imidazolium ester framework material ZIF-8 by adsorption method to obtain the Mn-doped zeolite imidazolium ester framework material Mn / ZIF-8. Step 2: The Mn / ZIF-8 obtained in Step 1 is mixed and ground with NaCl salt at a mass ratio of 1:(8-12), and then subjected to high-temperature carbonization treatment at 800-1000℃ under an inert atmosphere to form a mesoporous structure using NaCl molten salt as a template; the carbonization product is then acid-washed to remove residual metal elements and salt template to obtain a mesoporous carbon nanocage MnNC support, wherein the MnNC support contains atomically dispersed Mn-Nx sites; Step 3: Disperse the MnNC support obtained in Step 2 in a solvent, add a Pt precursor solution and mix to impregnate the MnNC support, so that the Pt precursor enters the pores of the MnNC support, and then dry to obtain the precursor complex. Step 4: The precursor complex obtained in Step 3 is subjected to high-temperature thermal reduction at 200-400℃ under a reducing atmosphere to reduce the platinum precursor to Pt nanoparticles, thereby obtaining a high-load Pt-based oxygen reduction catalyst supported on mesoporous carbon nanocages.
2. The preparation method according to claim 1, characterized in that, The preparation of ZIF-8 in step (1) includes: dissolving zinc nitrate hexahydrate and 2-methylimidazole in an alcohol solvent at a mass ratio of 1:(1.1-1.3) and mixing and reacting, followed by centrifugation, washing and drying to obtain the zeolite imidazole ester framework material ZIF-8.
3. The preparation method according to claim 2, characterized in that, The preparation of Mn / ZIF-8 includes: Step 1.1: Disperse 1.487 g of zinc nitrate hexahydrate evenly in 40 mL of methanol solution to obtain methanol mixture A; Step 1.2: Disperse 1.741 g of 2-methylimidazole evenly in 40 mL of methanol solution to obtain methanol mixture B; Step 1.3: Slowly pour methanol mixture A into methanol mixture B which is stirred at a constant speed and continue stirring at room temperature for 15 minutes. Then let it stand for 12 hours, then centrifuge, wash with methanol, and dry to obtain zeolite imidazole ester framework material ZIF-8. Step 1.4: Disperse 0.2 g of zeolite imidazolium ester framework material ZIF-8 in 20 mL of ethanol solution, and add 0.03 g of manganese acetylacetone. Stir continuously at room temperature for 24 hours, and then transfer the mixed solution to an 80℃ oil bath for drying to obtain Mn-doped zeolite imidazolium ester framework material Mn / ZIF-8.
4. The preparation method according to claim 1, characterized in that, Step 2 includes: Step 2.1: Mix and grind the Mn / ZIF-8 precursor with NaCl salt at a mass ratio of 1:(8-12) to make NaCl uniformly coat the surface of the precursor. Step 2.2: Transfer the sample obtained in step 2.1 to a crucible, and then calcine it in a tube furnace under high-temperature argon atmosphere for 2 hours at a heating rate of 2℃ / min; Step 2.3: Take out the sample after the treatment in step 2.2, and wash it with acid in 1M HNO3 solution to remove the residual zinc and manganese particles in the material. After filtration, washing and drying, the supported mesoporous carbon nanocage MnNC carrier is obtained.
5. The preparation method according to claim 1, characterized in that, Step 3 includes: Step 3.1: Disperse 500 mg of mesoporous carbon nanocage MnNC support in 200 mL of deionized water by ultrasonication for 30 minutes. Impregnate the Pt precursor into the pores of the mesoporous carbon nanocage MnNC support and stir continuously at room temperature for 12 hours. Collect the product by freeze drying to obtain the precursor complex MnNC@H2PtCl6.
6. The preparation method according to claim 3, characterized in that: The drying temperature in step 1.3 is 60℃, the drying time is 12 h, and the average particle size of ZIF-8 is 200 nm.
7. The preparation method according to claim 4, characterized in that: The pyrolysis temperature described in step 2.2 is 800-1000℃.
8. The preparation method according to claim 4, characterized in that: The pickling conditions described in step 2.3 are: 1M HNO3, 80℃, stirring at 200 rpm for 12 h; after pickling, the mixture is filtered and washed with deionized water until neutral; the vacuum drying temperature is 60℃ and the drying time is 12 h.
9. The preparation method according to claim 5, characterized in that: The impregnation conditions described in step 3.1 are as follows: 500 mg of MnNC carrier is ultrasonically dispersed in 200 mL of deionized water for 30 minutes. Then, 30 mL of a solution containing 1350 mg of H2PtCl6 is added dropwise to the above dispersion and stirred continuously at room temperature for 12 h.
10. The preparation method according to claim 5, characterized in that: In step 4, the high-temperature thermal reduction temperature was 300℃, the heating rate was 2℃ / min, the heat treatment time was 2 h, and the atmosphere was an Ar / H2 mixture. The obtained mesoporous carbon nanocage supported high-load Pt-based oxygen reduction reaction catalyst Pt-MnHNC has high specific surface area and high accessibility of active sites. The Pt loading of Pt-MnHNC is as high as 51.8 wt%.