A method for preparing an ultra-low platinum cathode catalyst for a fuel cell

Abstract

The present invention relates to the field of fuel cell technology, and in particular to a method for preparing an ultra-low platinum cathode catalyst for fuel cells. The method for preparing an ultra-low platinum cathode catalyst for fuel cells of the present invention comprises the following steps: pyrolyzing nitrogen-containing MOFs to prepare a catalyst carrier, mixing the carrier with a platinum precursor for reaction, and then calcining in an inert atmosphere and an ammonia atmosphere in two steps to obtain a nitrogen-doped carbon catalyst loaded with a platinum-cobalt intermetallic compound. The catalyst carrier prepared by the present invention has a hierarchical pore structure, and the loaded platinum-cobalt intermetallic compound particles have a small particle size and are uniformly loaded. The precious metal loading of the prepared catalyst can be adjusted according to the ratio of different raw materials. The cathode catalyst has a higher power density and mass activity in a fuel cell with an ultra-low platinum load than a commercial Pt / C catalyst with the same platinum loading.

Description

Technical Field

[0001] The present invention relates to the technical field of fuel cells, and in particular to a method for preparing an ultra-low platinum cathode catalyst for a fuel cell. Background Art

[0002] Proton exchange membrane fuel cells (PEMFCs) offer great potential for application due to their high energy density, high conversion efficiency, and environmental friendliness. Currently, commercially available cathode catalysts consist of platinum (Pt) particles supported on a carbon support. However, Pt costs account for over 41% of the total fuel cell stack cost, and Pt also suffers from insufficient activity and stability. Therefore, developing novel catalysts with low Pt loadings, high activity, and stability is crucial for improving fuel cell performance.

[0003] Alloying Pt with transition metals is an ideal choice for preparing low-Pt-loaded catalysts. Due to the presence of electronic and strain effects, the resulting Pt-based alloy-loaded catalysts exhibit superior catalytic performance compared to pure Pt-loaded catalysts. Among them, Pt-based intermetallic compounds (ordered alloys) have a defined stoichiometry and atomic long-range order, exhibiting extremely high activity and electrochemical durability. To improve the utilization of Pt, the synthesis of small and uniform intermetallic compounds is key. However, the ordered alloying process usually requires high-temperature calcination to overcome the kinetic energy barrier of atomic ordering rearrangement, which makes its size and uniformity uncontrollable. Therefore, the synthesis of small-particle intermetallic compounds is relatively difficult. Currently, the agglomeration of the alloy at high temperatures is generally avoided by coating the alloy nanoparticles with carbon, metal oxides, or polymers, but these methods are generally cumbersome. Chemical vapor infiltration effectively avoids the solvent selection problem and the instability of the precursor in the solvent in the liquid phase impregnation method, but its synthesis conditions and process are relatively complex. In addition, at ultra-low Pt loading, oxygen mass transfer resistance is a key factor limiting fuel cell performance. A support with abundant mesopores facilitates rapid mass transfer across the three-phase interface during catalytic reactions. Therefore, the synthesis of porous nitrogen-doped carbon catalysts supported by small-particle intermetallic compounds is of great significance for reducing the amount of Pt used in fuel cells and improving fuel cell performance.

[0004] In view of this, the present invention is proposed. Summary of the Invention

[0005] The first purpose of the present invention is to provide a method for preparing an ultra-low platinum cathode catalyst for a fuel cell, which completely or partially solves the problems existing in the prior art in the preparation of PtCo intermetallic compound supported catalysts, such as difficulty in controlling alloy particle size, poor uniformity, and complex preparation process.

[0006] A second object of the present invention is to provide an ultra-low platinum loading cathode catalyst for a fuel cell, wherein the catalyst comprises uniformly distributed small-sized PtCo intermetallic compound particles and a nitrogen-doped carbon support with a hierarchical pore structure.

[0007] The third object of the present invention is to provide a fuel cell membrane electrode with low Pt loading, comprising the ultra-low Pt cathode catalyst for fuel cells as described above.

[0008] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are adopted:

[0009] The present invention provides a method for preparing an ultra-low platinum cathode catalyst for a fuel cell, comprising the following steps:

[0010] (A) MOFs are synthesized by reacting azole organic ligands with zinc metal salts;

[0011] (B) performing a metal replacement treatment on the mixture of the MOFs and cobalt metal salt using a solvothermal method to obtain a Co-doped MOFs precursor material;

[0012] (C) calcining the Co-doped MOFs precursor material in an inert atmosphere to obtain Co-loaded nitrogen-doped carbon;

[0013] (D) mixing the Co-loaded nitrogen-doped carbon with a Pt precursor to prepare a Co-loaded nitrogen-doped carbon;

[0014] (E) The Co-nitrogen-doped carbon loaded with the Pt precursor is calcined in an inert atmosphere and then calcined in an NH3 atmosphere to obtain the ultra-low platinum cathode catalyst for the fuel cell.

[0015] The present invention also provides an ultra-low platinum cathode catalyst for a fuel cell, which is prepared by the above-mentioned method for preparing the ultra-low platinum cathode catalyst for a fuel cell.

[0016] The present invention also provides a fuel cell membrane electrode with ultra-low Pt loading, comprising the ultra-low Pt cathode catalyst for fuel cells as described above.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] (1) The present invention provides a method for preparing an ultra-low platinum cathode catalyst for a fuel cell. The method is conducive to forming small and uniform PtCo intermetallic compound particles; the precious metal loading of the prepared catalyst can be adjusted according to the ratio of different raw materials.

[0019] (2) The present invention promotes the ordering of PtCo intermetallic compounds by calcining with NH3, thereby improving the intrinsic activity of the catalytic sites and further enhancing the stability of the catalyst.

[0020] (2) The present invention requires simple equipment and is easy to operate. The MEA prepared with ultra-low Pt loading exhibits high mass activity and stability in fuel cell performance testing, providing a new approach for constructing low-cost, high-performance fuel cell catalysts. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0022] Figure 1 PXRD spectra of MET(Zn) and Co-doped MET(Zn) prepared in Example 1 of the present invention.

[0023] Figure 2 The SEM image (a), STEM image (b) and EDS surface distribution image (c) of Co-doped MET(Zn) prepared in Example 1 of the present invention.

[0024] Figure 3 The STEM image (a), HRTEM image (b), EDS surface distribution image (c) and AC HAADF-STEM image (d) of Co SAs / NC prepared in Example 1 of the present invention.

[0025] Figure 4 N2 adsorption-desorption curves (a) and QSDFT pore size distribution curves (b) of Co SAs / NC and MeCpPtMe3@Co SAs / NC prepared in Example 1 of the present invention.

[0026] Figure 5 STEM image (a) and EDS surface distribution map (b) of MeCpPtMe3@Co SAs / NC prepared in Example 1 of the present invention.

[0027] Figure 6 This is the PXRD spectrum of L10 PtCo / NC prepared in Example 1 of the present invention.

[0028] Figure 7 STEM image (a) and TEM image (b) of L10 PtCo / NC prepared in Example 1 of the present invention.

[0029] Figure 8AC HAADF-STEM image (a), arrangement diagram of Pt and Co atoms (b), and EDS element distribution diagram (c) of L10 PtCo / NC prepared in Example 1 of the present invention.

[0030] Figure 9 N2 adsorption-desorption curve (a) and QSDFT pore size distribution curve (b) of L10 PtCo / NC prepared in Example 1 of the present invention.

[0031] Figure 10 The STEM image (a), TEM image (b) and AC HAADF-STEM image (c) of Pt / NC prepared in Comparative Example 1 of the present invention.

[0032] Figure 11 Polarization curves (a) and mass activity and specific activity comparison (b) of L10 PtCo / NC prepared in Example 1 of the present invention, Pt / NC prepared in Comparative Example 1, and commercial Pt / C catalysts.

[0033] Figure 12 Polarization curves of L10 PtCo / NC prepared in Example 1 of the present invention and commercial Pt / C catalysts in H2-O2 fuel cells.

[0034] Figure 13 Figure 1 shows the polarization curves and power density curves of the L10 PtCo / NC prepared in Example 1 of the present invention in a H2-O2 fuel cell after initial and cycle testing, and a comparison of the MA of the L10PtCo / NC prepared in Example 1 and a commercial Pt / C catalyst before and after durability testing (b). DETAILED DESCRIPTION

[0035] The technical scheme of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and specific embodiments, but it will be understood by those skilled in the art that the following described embodiments are part of embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention, and should not be considered as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of the present invention. Those who do not specify specific conditions in the embodiments are carried out according to normal conditions or the conditions recommended by the manufacturer. Those whose reagents or instruments are not specified by the manufacturer are conventional products that can be purchased commercially.

[0036] The following is a detailed description of a method for preparing an ultra-low platinum cathode catalyst for a fuel cell according to an embodiment of the present invention.

[0037] In some embodiments of the present invention, a method for preparing an ultra-low platinum cathode catalyst for a fuel cell is provided, comprising the following steps:

[0038] (A) MOFs are synthesized by reacting azole organic ligands with zinc metal salts;

[0039] (B) A mixture of MOFs and cobalt metal salts was subjected to a solvothermal metal exchange treatment to obtain Co-doped MOFs precursor material;

[0040] (C) Co-doped MOFs precursor material was calcined in an inert atmosphere to obtain Co-loaded nitrogen-doped carbon;

[0041] (D) Co-loaded nitrogen-doped carbon is mixed with a Pt precursor to prepare Co-loaded nitrogen-doped carbon;

[0042] (E) Co-nitrogen-doped carbon loaded with Pt precursor was calcined in an inert atmosphere and then calcined in an NH3 atmosphere to obtain an ultra-low Pt cathode catalyst for fuel cells.

[0043] The present invention provides a method for preparing an ultra-low platinum cathode catalyst for a fuel cell, using MOFs as a precursor material, and 2+ After a replacement treatment, pyrolysis was performed to prepare uniformly Co-loaded nitrogen-doped carbon. This Co-loaded nitrogen-doped carbon was then used as a support for a Pt precursor. The uniform distribution of Co atoms and Pt precursor on the nitrogen-doped carbon support was key to preparing a uniform PtCo intermetallic compound. Finally, a small-particle PtCo intermetallic compound-supported catalyst on nitrogen-doped carbon was prepared through high-temperature thermal reduction and NH3 calcination. Compared to a pure Pt-loaded catalyst, the PtCo intermetallic compound-supported nitrogen-doped carbon catalyst of the present invention exhibited superior catalytic activity and stability in disc potentiometry tests.

[0044] The present invention provides a method for preparing an ultra-low platinum cathode catalyst for a fuel cell, which effectively solves the problems of difficulty in synthesizing small-particle Pt-based intermetallic compounds, poor uniformity, and complex preparation process in the preparation of Pt-based intermetallic compound-supported catalysts.

[0045] In some embodiments of the present invention, in step (A), the preparation of MOFs comprises: reacting an azole organic ligand with a zinc metal salt to synthesize MOFs.

[0046] The MOFs prepared in the present invention are named after the names of MOFs, for example, MOFs prepared with 2-methylimidazole and zinc nitrate hexahydrate are named ZIF-8; MOFs prepared with 1H-1,2,3-triazole and zinc chloride are named MET(Zn).

[0047] In some embodiments of the present invention, in step (A), the azole organic ligand includes one or more of imidazole, 2-methylimidazole, 2-nitroimidazole, benzimidazole, 1H-1,2,3-triazole, and 1H-1,2,4-triazole; preferably, the azole organic ligand includes 1H-1,2,3-triazole.

[0048] In some embodiments of the present invention, in step (A), the zinc metal salt comprises zinc nitrate hexahydrate and / or zinc chloride.

[0049] In some embodiments of the present invention, in step (A), the molar ratio of the azole organic ligand to the zinc metal salt is 2 to 4:1.

[0050] In some embodiments of the present invention, in step (A), a mixed solution of an azole organic ligand, a zinc metal salt, and a solvent A is reacted and then centrifuged to obtain a solid, which is then washed, solvent replaced, vacuum dried, and pretreated to obtain MOFs.

[0051] In some embodiments of the present invention, in step (A), solvent A comprises at least one of N,N-dimethylformamide, methanol, water and ethanol.

[0052] In some embodiments of the present invention, in step (A), the reaction comprises a room temperature stirring method or a solvothermal method.

[0053] In some embodiments of the present invention, in step (A), the room temperature stirring method comprises stirring the reaction at 20-30° C.; preferably, the stirring reaction time is 10-24 h.

[0054] In some embodiments of the present invention, in step (A), the temperature of the solvothermal method is 80 to 120° C.; preferably, the reaction time of the solvothermal method is 12 to 48 hours.

[0055] In some embodiments of the present invention, in step (A), the solvent for solvent replacement comprises methanol and / or ethanol.

[0056] In some embodiments of the present invention, in step (A), the temperature for solvent replacement is 20 to 60° C., and the time for solvent replacement is 24 to 72 hours.

[0057] In some embodiments of the present invention, in step (A), drying comprises vacuum drying; preferably, the drying time is 20 to 30 hours.

[0058] In some embodiments of the present invention, in step (A), the pretreatment temperature is 90 to 150° C.; and the pretreatment time is 6 to 24 hours.

[0059] In some embodiments of the present invention, in step (A), the concentration of zinc metal salt in the mixed solution is 0.1 to 0.3 mol L -1 .

[0060] In some embodiments of the present invention, in step (B), the cobalt metal salt comprises cobalt nitrate hexahydrate and / or cobalt chloride.

[0061] In some embodiments of the present invention, in step (B), the mass ratio of MOFs to cobalt metal salt is 50 to 90:1; typically but not limitatively, for example, in step (B), the mass ratio of the precursor material to the cobalt salt is 50:1, 55:1, 60:1, 65:1, 70:1, 75:1, 80:1, 85:1 or 90:1, etc.

[0062] In some embodiments of the present invention, in step (B), a mixture of MOFs and cobalt metal salts is subjected to a solvent thermal method to perform metal replacement treatment, followed by centrifugation to obtain a solid, which is then washed, solvent replaced, vacuum dried, and pretreated to obtain a Co-doped MOFs precursor material.

[0063] The Co-doped MOFs precursor material prepared in the present invention is named Co-doped MET(Zn).

[0064] In some embodiments of the present invention, in step (B), the solvent for the metal replacement treatment comprises N,N-dimethylformamide and / or N,N-dimethylacetamide.

[0065] In some embodiments of the present invention, in step (B), the temperature of the metal replacement treatment is 80-130° C., and the reaction time is 6-16 h. Typically, but not limiting, for example, in step (B), the reaction temperature is 80° C., 90° C., 100° C., 110° C., 120° C., or 130° C., and the like; and the reaction time is 6 h, 8 h, 9 h, 12 h, 14 h, or 16 h, and the like.

[0066] In some embodiments of the present invention, in step (B), the solvent for solvent replacement comprises methanol and / or ethanol.

[0067] In some embodiments of the present invention, in step (B), the temperature for solvent replacement is 20 to 60° C., and the time for solvent replacement is 24 to 72 hours.

[0068] In some embodiments of the present invention, in step (B), drying comprises vacuum drying.

[0069] In some embodiments of the present invention, in step (B), the pretreatment temperature is 90 to 150° C., and the pretreatment time is 6 to 24 hours.

[0070] In the preparation method of an ultra-low platinum cathode catalyst for a fuel cell provided by the present invention, the Co 2+ Uniform distribution in MOFs is beneficial to obtain uniformly distributed Co single atoms on the support during the subsequent pyrolysis process.

[0071] In some embodiments of the present invention, in step (C), the calcination is carried out in an inert atmosphere, and the gas of the inert atmosphere includes nitrogen and / or argon.

[0072] In some embodiments of the present invention, in step (C), calcining in an inert atmosphere includes: heating to 700-1000°C and keeping warm for 1-3 hours; typically but not limitatively, for example, the calcining temperature in an inert atmosphere is 700°C, 750°C, 800°C, 850°C, 900°C, 950°C or 1000°C, etc.; the calcining time in an inert atmosphere is 0.5h, 1h, 2h or 3h, etc.

[0073] In a preparation method for an ultra-low platinum cathode catalyst for a fuel cell provided by the present invention, Co-doped MOFs are calcined in an inert atmosphere and, after pyrolysis, a nitrogen-doped carbon loaded with Co with uniform distribution of Co atoms and rich mesoporous structure can be obtained.

[0074] The Co-loaded nitrogen-doped carbon prepared in the present invention is named Co SAs / NC.

[0075] In some embodiments of the present invention, in step (C), during calcination in an inert atmosphere, the heating rate is 2-10°C / min; preferably, in step (C), during calcination in an inert atmosphere, the heating rate is 4-7°C / min.

[0076] In some embodiments of the present invention, in step (D), the Pt precursor includes one or more of chloroplatinic acid hexahydrate, potassium chloroplatinate, platinum acetylacetonate, and trimethyl(methylcyclopentadienyl)platinum.

[0077] In some embodiments of the present invention, in step (D), the mass ratio of the Co-loaded nitrogen-doped carbon to the Pt precursor is 3 to 8:1; typically but not limitatively, for example, the mass ratio of the Co-loaded nitrogen-doped carbon to the Pt precursor is 3:1, 4:1, 5:1, 6:1, 7:1 or 8:1, etc.

[0078] In some embodiments of the present invention, in step (D), the method for preparing the Co-loaded nitrogen-doped carbon by mixing with the Pt precursor includes a liquid phase method or a gas phase method.

[0079] In some embodiments of the present invention, in step (D), the liquid phase method comprises: dispersing the Pt precursor and the Co-loaded nitrogen-doped carbon in solvent B and stirring, then centrifuging to obtain a solid, and the solid is washed and vacuum-dried in turn to obtain the Co-loaded nitrogen-doped carbon.

[0080] In some embodiments of the present invention, in step (D), in the liquid phase method, solvent B comprises at least one of methanol, water, ethanol and oleylamine.

[0081] In some embodiments of the present invention, in step (D), in the liquid phase method, the stirring temperature is 80 to 160° C., and the stirring time is 12 to 24 hours.

[0082] In some embodiments of the present invention, in step (D), in the liquid phase method, the washing solvent includes ethanol and / or water.

[0083] In some embodiments of the present invention, in step (D), in the liquid phase method, the vacuum drying temperature is 40-80°C.

[0084] In some embodiments of the present invention, in step (D), the gas phase method comprises: vacuum sealing the Pt precursor and the Co-loaded nitrogen-doped carbon, and heating the reaction to obtain the Co-loaded nitrogen-doped carbon.

[0085] In some embodiments of the present invention, in step (D), in the gas phase method, the vacuum degree of the heating reaction is -0.1 MPa to 0.1 MPa, the temperature of the heating reaction is 30 to 80° C., and the heating reaction time is 10 to 40 h; typically but not limitatively, for example, the reaction temperature is 30° C., 35° C., 40° C., 45° C., 50° C., 55° C., 60° C., 65° C., 70° C., 75° C. or 80° C., etc.; and the reaction time is 10 h, 15 h, 20 h, 25 h, 30 h, 35 h or 40 h.

[0086] In the preparation method of an ultra-low platinum cathode catalyst for a fuel cell provided by the present invention, a Pt precursor is loaded by a simple liquid phase or gas phase method, which has the characteristic of simple operation.

[0087] The product obtained after the Pt precursor loading treatment of the present invention is named Pt precursor@Co SAs / NC, such as MeCpPtMe3@Co SAs / NC.

[0088] In the Pt precursor@Co SAs / NC of the present invention, the distribution of Co atoms and Pt precursor is uniform, which is conducive to the subsequent formation of PtCo intermetallic compound particles with small and uniform particle size.

[0089] In some embodiments of the present invention, in step (E), during the calcination in an inert atmosphere, the gas of the inert atmosphere includes nitrogen and / or argon.

[0090] In some embodiments of the present invention, in step (E), calcining in an inert atmosphere comprises: heating to 600-1000°C and keeping the temperature for 0.5-2 hours; typically but not limitatively, for example, in step (D), the calcining temperature in an inert atmosphere is 600°C, 650°C, 700°C, 750°C, 800°C, 850°C, 900°C, 950°C or 1000°C, etc.; the calcining time in an inert atmosphere is 0.5h, 1h or 2h, etc.

[0091] In some embodiments of the present invention, in step (E), during the calcination in an inert atmosphere, the heating rate is 3 to 10°C / min; preferably, in step (E), during the calcination in an inert atmosphere, the heating rate is 4 to 7°C / min.

[0092] In some embodiments of the present invention, in step (E), calcining in an NH3 atmosphere includes: heating to 400-800°C and keeping warm for 10-60 min; typically but not limitatively, for example, the calcination temperature in an NH3 atmosphere is 400°C, 450°C, 500°C, 550°C, 600°C, 650°C, 700°C, 750°C or 800°C, etc.; the calcination time in an NH3 atmosphere is 10 min, 20 min, 30 min, 40 min, 50 min or 60 min, etc.

[0093] In a method for preparing an ultra-low-platinum cathode catalyst for fuel cells, calcination in NH3 promotes the ordering of a PtCo intermetallic compound, resulting in small PtCo intermetallic compound particles. This enhances the intrinsic activity of the catalytic sites while also improving catalyst stability. Furthermore, the etching effect of NH3 further increases the size of the mesopores in the catalyst.

[0094] The product obtained by calcining the Pt precursor @Co SAs / NC of the present invention in an inert atmosphere and in an NH3 atmosphere is named L10 PtCo / NC.

[0095] In some embodiments of the present invention, in step (E), during the calcination in an NH3 atmosphere, the heating rate is 3 to 10°C / min; preferably, in step (E), during the calcination in an NH3 atmosphere, the heating rate is 4 to 7°C / min.

[0096] In some embodiments of the present invention, an ultra-low platinum cathode catalyst for a fuel cell is also provided, which is obtained by using the preparation method of the ultra-low platinum cathode catalyst for a fuel cell as described above.

[0097] In some embodiments of the present invention, in the ultra-low platinum cathode catalyst for a fuel cell, the particle size of the PtCo intermetallic compound particles is 2 to 6 nm.

[0098] The nitrogen-doped carbon catalyst L10 PtCo / NC loaded with a PtCo intermetallic compound of the present invention has uniformly distributed PtCo intermetallic compound particles with small particle size, and the formation of an intermetallic phase enables it to have excellent activity and stability.

[0099] In some embodiments of the present invention, a fuel cell membrane electrode with low Pt loading is further provided, comprising the ultra-low Pt cathode catalyst for fuel cells as described above.

[0100] The ultra-low platinum cathode catalyst for fuel cells of the present invention is used to produce an ultra-low Pt loading (0.02 mg Pt cm -2 ) Prepare membrane electrodes to test the performance of proton exchange membrane fuel cells, showing excellent mass activity and stability.

[0101] Example 1

[0102] The preparation method of L10 PtCo / NC provided in this embodiment includes the following steps:

[0103] (A) 1 g of zinc chloride, 10 mL of N,N-dimethylformamide, 10 mL of ethanol, 15 mL of water, and 5 mL of 30% aqueous ammonia were mixed to obtain a mixed solution. 1.25 mL (21.6 mmol) of 1H-1,2,3-triazole was added to the mixed solution, and the mixture was reacted at 25°C for 12 h to obtain a reaction solution. The reaction solution was centrifuged and washed to obtain a product. 100 mL of methanol was added to the product, and the product was subjected to a displacement treatment at 25°C for 72 h, with the methanol being replaced every 24 h. After the displacement treatment, the product was vacuum dried for 24 h and then kept at 100°C for 12 h to obtain MET(Zn).

[0104] (B) 7 g of the MET(Zn) from step (A), 96 mg of anhydrous cobalt chloride, and 500 mL of N,N-dimethylformamide were mixed to obtain a mixed solution, and the mixed solution was sonicated until the MET(Zn) was uniformly dispersed; the mixed solution was then reacted at 130° C. for 10 h to obtain a reaction solution; the reaction solution was cooled, centrifuged, and washed to obtain a product, 100 mL of methanol was added to the product, and the product was subjected to a displacement treatment at 25° C. for 72 h, with the methanol being replaced every 24 h during the displacement treatment. After the displacement treatment, the product was vacuum dried for 24 h and then kept at 100° C. for 12 h to obtain co-doped MET(Zn);

[0105] (C) 500 mg of Co-doped MET(Zn) was placed in a quartz boat, which was then placed in a tube furnace. The temperature was raised to 900°C at 5°C / min in an argon atmosphere and held for 1 h to obtain Co SAs / NC.

[0106] (D) 100 mg of Co SAs / NC and 70 mg of trimethyl(methylcyclopentadienyl)platinum(IV) were added to a schlenk tube. The tube was sealed under vacuum at -0.1 MPa and heated in an oven at 50°C for 24 h to obtain MeCpPtMe3@Co SAs / NC.

[0107] (E) MeCpPtMe3@Co SAs / NC was placed in a quartz boat, which was then placed in a tube furnace and heated to 900°C at 5°C / min in an argon atmosphere and held for 1 h. The boat was then heated to 700°C in an NH3 atmosphere at 5°C / min and held for 0.5 h to obtain L10 PtCo / NC.

[0108] Comparative Example 1

[0109] The preparation method of Pt / NC provided in this comparative example comprises the following steps:

[0110] (A) 1 g of zinc chloride, 10 mL of N,N-dimethylformamide, 10 mL of ethanol, 15 mL of water, and 5 mL of 30% ammonia water were mixed to obtain a mixed solution. 1.25 mL (21.6 mmol) of 1H-1,2,3-triazole was added to the mixed solution, and the mixture was reacted at 25°C for 12 h to obtain a reaction solution. The reaction solution was centrifuged and washed to obtain a product. 200 mL of methanol was added to the product, and the product was subjected to a displacement treatment at 25°C for 72 h, with the methanol being replaced every 24 h. After the displacement treatment, the product was vacuum dried for 24 h and then kept at 100°C for 12 h to obtain the product MET(Zn).

[0111] (B) 500 mg of MET(Zn) was placed in a quartz boat, which was then placed in a tube furnace. The temperature was raised to 900°C at 5°C / min in an argon atmosphere and held for 1 h to obtain the product NC.

[0112] (C) 100 mg of NC and 70 mg of trimethyl(methylcyclopentadienyl)platinum(IV) were added to a Schlenk tube. The tube was sealed under vacuum at -0.1 MPa and heated in an oven at 50°C for 24 h to obtain the product MeCpPtMe3@NC.

[0113] (D) MeCpPtMe3@NC was placed in a quartz boat, which was then placed in a tube furnace and heated to 900°C at 5°C / min in an argon atmosphere and held for 1 hour. The boat was then heated to 700°C in an NH3 atmosphere at 5°C / min and held for 0.5 hour to obtain Pt / NC.

[0114] Test Example 1

[0115] Figure 1 : PXRD test was performed on the MET(Zn) and Co-doped MET(Zn) prepared in Example 1. There was no obvious change in the PXRD spectra of MET(Zn) and Co-doped MET(Zn).

[0116] Figure 2 : The Co-doped MET (Zn) prepared in Example 1 was subjected to SEM, STEM and EDS tests. The Co-doped MET (Zn) was octahedral in shape with a particle size of about 200 nm, and Co was uniformly distributed in the Co-doped MET (Zn).

[0117] Figure 3 Scanning electron microscopy and transmission electron microscopy (TEM) tests of the Co SAs / NC prepared in Comparative Example 1 revealed no obvious metal particles in the Co SAs / NC. Co was uniformly distributed as isolated atoms on the nitrogen-doped carbon support.

[0118] Figure 4 N₂ adsorption / desorption tests were performed on the Co SAs / NC and MeCpPtMe₃@Co SAs / NC prepared in Example 1. CoSAs / NC possesses a continuously distributed mesoporous structure. After vapor-phase diffusion loading of MeCpPtMe₃, the BET surface area and pore volume of MeCpPtMe₃@Co SAs / NC decreased.

[0119] Figure 5Scanning electron microscopy (SEM) analysis of the MeCpPtMe3@Co SAs / NC prepared in Example 1 revealed no significant changes in the morphology of the sample after loading MeCpPtMe3, and the Pt element was evenly distributed on the Co SAs / NC.

[0120] Figure 6 : PXRD test of L10 PtCo / NC prepared in Example 1 shows that L10 PtCo / NC exhibits obvious superlattice order peaks at 24°, 33°, 54° and 61°.

[0121] Figure 7 : The L10 PtCo / NC prepared in Example 1 was subjected to STEM and TEM electron microscopy tests. The PtCo intermetallic compound particles were uniformly distributed on the support, and the particle size was about 3.2 nm.

[0122] Figure 8 The L10 PtCo / NC prepared in Example 1 was subjected to spherical aberration-corrected high-angle annular dark-field scanning transmission electron microscopy. The PtCo intermetallic compound particles in the L10 PtCo / NC were L10 PtCo@Pt with a core-shell structure.

[0123] Figure 9 : The L10 PtCo / NC prepared in Example 1 was subjected to N2 adsorption and desorption tests. The BET specific surface area of ​​L10 PtCo / NC was 635 m 2 g -1 .

[0124] Figure 10 : The Pt / NC prepared in Comparative Example 1 was subjected to scanning electron microscopy and transmission electron microscopy tests, and the Pt nanoparticles were evenly distributed on the nitrogen-doped carbon, with a particle size of about 3.1 nm.

[0125] Test Example 2

[0126] Figure 11 Electrochemical tests were performed on the L10 PtCo / NC prepared in Example 1, the Pt / NC prepared in Example 1, and a commercial Pt / C catalyst (supplier: Johnson Matthey, with a Pt content of 40 wt.%). Among them, the L10 PtCo / NC showed the best mass activity (0.797 A mg Pt -1 ) and specific activity (1.25 mA cm -2 ).

[0127] Figure 12: MEA was prepared by using L10 PtCo / NC and commercial Pt / C catalyst (JM, 40 wt.%) of Example 1 for polarization curve and power density curve test. L10 PtCo / NC showed higher current density than commercial Pt / C catalyst, 0.9V iR-free The MA under is 2.2A mg Pt -1 .

[0128] Figure 13 The polarization curves and power density curves of the L10 PtCo / NC prepared in Example 1 were tested in a H2-O2 fuel cell at the initial and post-cycle stages. After 30k cycles of accelerated stress testing, the MA of the L10 PtCo / NC still reached 1.57 A mg Pt -1 , the decay rate is 29%, while the decay rate of commercial Pt / C catalyst is as high as 82%.

[0129] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing an ultra-low platinum cathode catalyst for a fuel cell, characterized in that: The steps include: (A) Synthesis of MOFs by reacting azole organic ligands with zinc metal salts; (B) The mixture of the MOFs and cobalt metal salt is subjected to a metal replacement treatment using a solvothermal method to obtain a Co-doped MOFs precursor material; (C) calcining the Co-doped MOFs precursor material in an inert atmosphere to obtain Co-loaded nitrogen-doped carbon; (D) mixing the Co-loaded nitrogen-doped carbon with a Pt precursor to prepare a Co-loaded nitrogen-doped carbon; (E) The Co-nitrogen-doped carbon loaded with the Pt precursor is calcined in an inert atmosphere and then calcined in an NH 3 atmosphere to obtain the ultra-low platinum cathode catalyst for the fuel cell.

2. The method for preparing an ultra-low platinum cathode catalyst for a fuel cell according to claim 1, wherein: In step (A), the azole organic ligand includes imidazole, 2-methylimidazole, 2-nitroimidazole, benzimidazole, 1 H -1,2,3-triazole and 1 H -1,2,4-triazole or more.

3. The method for preparing an ultra-low platinum cathode catalyst for a fuel cell according to claim 1, wherein: In step (A), the zinc metal salt includes zinc nitrate hexahydrate and / or zinc chloride.

4. The method for preparing an ultra-low platinum cathode catalyst for a fuel cell according to claim 1, wherein: In step (A), the molar ratio of the azole organic ligand to the zinc metal salt is 2-4:

1.

5. The method for preparing an ultra-low platinum cathode catalyst for a fuel cell according to claim 1, wherein: In step (A), a mixed solution of the azole organic ligand, the zinc metal salt and solvent A is reacted and then centrifuged to obtain a solid. The solid is sequentially washed, solvent replaced, vacuum dried and pretreated to obtain the MOFs.

6. The method for preparing an ultra-low platinum cathode catalyst for a fuel cell according to claim 5, characterized in that: In step (A), the solvent A comprises at least one of N,N-dimethylformamide, methanol, water and ethanol.

7. The method for preparing an ultra-low platinum cathode catalyst for a fuel cell according to claim 5, wherein: In step (A), the reaction comprises a room temperature stirring method or a solvent thermal method.

8. The method for preparing an ultra-low platinum cathode catalyst for a fuel cell according to claim 7, wherein: In step (A), the room temperature stirring method comprises stirring the reaction at 20-30°C.

9. The method for preparing an ultra-low platinum cathode catalyst for a fuel cell according to claim 7, wherein: In step (A), the temperature of the solvothermal method is 80-120°C.

10. The method for preparing an ultra-low platinum cathode catalyst for a fuel cell according to claim 5, characterized in that: In step (A), the solvent for the solvent replacement includes methanol and / or ethanol.

11. The method for preparing an ultra-low platinum cathode catalyst for a fuel cell according to claim 5, wherein: In step (A), the temperature of the solvent replacement is 20-60° C., and the time of the solvent replacement is 24-72 h.

12. The method for preparing an ultra-low platinum cathode catalyst for a fuel cell according to claim 5, wherein: In step (A), the pretreatment temperature is 90-150° C. and the pretreatment time is 6-24 h.

13. The method for preparing an ultra-low platinum cathode catalyst for a fuel cell according to claim 5, wherein: In step (A), the concentration of zinc metal salt in the mixed solution is 0.1-0.3 mol L -1 .

14. The method for preparing an ultra-low platinum cathode catalyst for a fuel cell according to claim 1, wherein: In step (B), the cobalt metal salt includes cobalt nitrate hexahydrate and / or cobalt chloride.

15. The method for preparing an ultra-low platinum cathode catalyst for a fuel cell according to claim 1, wherein: In step (B), the mass ratio of the MOFs to the cobalt metal salt is 50-90:

1.

16. The method for preparing an ultra-low platinum cathode catalyst for a fuel cell according to claim 1, wherein: In step (B), the mixture of the MOFs and the cobalt metal salt is subjected to a solvent thermal method to perform metal replacement treatment, and then centrifuged to obtain a solid. The solid is sequentially washed, solvent replaced, vacuum dried and pretreated to obtain the Co-doped MOFs precursor material.

17. The method for preparing an ultra-low platinum cathode catalyst for a fuel cell according to claim 16, wherein: In step (B), the solvent for the metal replacement treatment includes N,N-dimethylformamide and / or N,N-dimethylacetamide.

18. The method for preparing an ultra-low platinum cathode catalyst for a fuel cell according to claim 16, wherein: In step (B), the temperature of the metal replacement treatment is 80-130° C., and the time of the metal replacement treatment is 6-16 hours.

19. The method for preparing an ultra-low platinum cathode catalyst for a fuel cell according to claim 16, wherein: In step (B), the solvent for the solvent replacement includes methanol and / or ethanol.

20. The method for preparing an ultra-low platinum cathode catalyst for a fuel cell according to claim 16, wherein: In step (B), the temperature of the solvent replacement is 20-60° C., and the time of the solvent replacement is 24-72 h.

21. The method for preparing an ultra-low platinum cathode catalyst for a fuel cell according to claim 16, wherein: In step (B), the pretreatment temperature is 90-150° C. and the pretreatment time is 6-24 h.

22. The method for preparing an ultra-low platinum cathode catalyst for a fuel cell according to claim 1, wherein: In step (C), the inert atmosphere includes nitrogen and / or argon.

23. The method for preparing an ultra-low platinum cathode catalyst for a fuel cell according to claim 1, wherein: In step (C), the calcination in an inert atmosphere includes: heating to 700-1000°C and keeping the temperature for 1-3 hours; the heating rate is 2-10°C / min.

24. The method for preparing an ultra-low platinum cathode catalyst for a fuel cell according to claim 1, wherein: In step (D), the Pt precursor includes one or more of chloroplatinic acid hexahydrate, potassium chloroplatinate, platinum acetylacetonate, and trimethyl(methylcyclopentadienyl)platinum.

25. The method for preparing an ultra-low platinum cathode catalyst for a fuel cell according to claim 1, wherein: In step (D), the mass ratio of the Co-loaded nitrogen-doped carbon to the Pt precursor is 3-8:

1.

26. The method for preparing an ultra-low platinum cathode catalyst for a fuel cell according to claim 1, wherein: In step (D), the method for preparing the Co-loaded nitrogen-doped carbon by mixing with a Pt precursor includes a liquid phase method or a gas phase method.

27. The method for preparing an ultra-low platinum cathode catalyst for a fuel cell according to claim 26, wherein: In step (D), the liquid phase method comprises: dispersing the Pt precursor and the Co-loaded nitrogen-doped carbon in solvent B and stirring, then centrifuging to obtain a solid, and sequentially washing and vacuum drying the solid to obtain the Co-loaded Pt precursor nitrogen-doped carbon.

28. The method for preparing an ultra-low platinum cathode catalyst for a fuel cell according to claim 27, wherein: In step (D), the solvent B comprises at least one of methanol, water, ethanol and oleylamine.

29. The method for preparing an ultra-low platinum cathode catalyst for a fuel cell according to claim 27, wherein: In step (D), the stirring temperature is 80-160° C., and the stirring time is 12-24 h.

30. The method for preparing an ultra-low platinum cathode catalyst for a fuel cell according to claim 27, wherein: In step (D), the vacuum drying temperature is 40-80°C.

31. The method for preparing an ultra-low platinum cathode catalyst for a fuel cell according to claim 26, wherein: In step (D), the gas phase method comprises: vacuum sealing the Pt precursor and the Co-loaded nitrogen-doped carbon, and heating them for reaction to obtain the Co-loaded Pt precursor nitrogen-doped carbon.

32. The method for preparing an ultra-low platinum cathode catalyst for a fuel cell according to claim 31, wherein: In step (D), the vacuum degree of the vacuum seal is -0.1 to 0.1 MPa, the temperature of the heating reaction is 30 to 80° C., and the time of the heating reaction is 10 to 40 hours.

33. The method for preparing an ultra-low platinum cathode catalyst for a fuel cell according to claim 1, wherein: In step (E), the inert atmosphere gas includes nitrogen and / or argon.

34. The method for preparing an ultra-low platinum cathode catalyst for a fuel cell according to claim 1, wherein: In step (E), the calcination in an inert atmosphere includes: heating to 600-1000°C and keeping the temperature for 0.5-2 hours; the heating rate is 3-10°C / min.

35. The method for preparing an ultra-low platinum cathode catalyst for a fuel cell according to claim 1, wherein: In step (E), the calcination in an NH3 atmosphere includes: heating to 400-800°C and keeping the temperature for 10-60 min; the heating rate is 3-10°C / min.

36. An ultra-low platinum cathode catalyst for a fuel cell, characterized in that: The catalyst is prepared by the method for preparing an ultra-low platinum cathode catalyst for a fuel cell according to any one of claims 1 to 35.

37. The ultra-low platinum cathode catalyst for fuel cells according to claim 36, characterized in that In the ultra-low platinum cathode catalyst for fuel cells, the particle size of PtCo intermetallic compound particles is 2-6 nm.

38. A fuel cell membrane electrode with low Pt loading, characterized in that: Including the ultra-low platinum cathode catalyst for fuel cell according to claim 36 or 37.

Images