Lanthanum-doped high-stability ordered platinum alloy fuel cell cathode catalyst and preparation method thereof

Abstract

The invention discloses a lanthanum-doped high-stability ordered platinum alloy fuel cell cathode catalyst and a preparation method thereof, and belongs to the technical field of cell cathode catalysts. Atomic-scale dispersion of lanthanide elements on the porous carbon substrate is achieved through a metal-organic framework derivation strategy, abundant anchoring points are provided for nucleation growth of the platinum-based ordered alloy, and the strong interaction between the platinum-based alloy and lanthanum is ensured. Lanthanum is doped into platinum-based alloy crystal lattices through a high-temperature annealing method in a reducing atmosphere, the strong bonding effect of lanthanum and platinum is achieved, meanwhile, agglomeration of platinum-based nano-particles is restrained through the anchoring effect of lanthanum in a carrier and the confinement effect of the carrier, the formed ordered platinum-based alloy nano-particles are small in particle size, and the high platinum utilization rate is guaranteed. The preparation method is simple, low in cost and good in reproducibility, and compared with an existing commercial catalyst, the prepared lanthanum-doped platinum-based ordered alloy fuel cell cathode catalyst is lower in platinum dosage, higher in catalytic activity and better in stability.

Description

Technical Field

[0001] This invention belongs to the field of battery cathode catalyst technology, specifically relating to a lanthanum-doped, highly stable, ordered platinum alloy fuel cell cathode catalyst and its preparation method. Background Technology

[0002] Proton exchange membrane fuel cells (PEMFCs) have become highly promising energy conversion devices due to their excellent energy conversion efficiency and environmentally friendly, pollution-free characteristics. However, the oxygen reduction reaction (ORR) kinetics at the cathode is very slow, requiring large-scale platinum-based catalytic reactions. But platinum-based metals are scarce and extremely expensive, significantly hindering the commercial application of PEMFCs. Therefore, developing highly active and stable low-platinum catalysts has become a current international research hotspot.

[0003] Previous studies have shown that the activity and stability of platinum-based fuel cell cathode catalysts can be effectively improved by preparing alloys with transition metals and controlling the catalyst geometry. For example, Xia Baoyu's team designed a one-dimensional PtNi nanocage with a Pt shell structure, which achieved a mass activity of 3.52 A / m with a relatively low platinum loading. Pt -1 This is 17 times that of commercial Pt / C catalysts. Simultaneously, the catalyst exhibits high stability, with negligible activity decay after 50,000 cycles. (Tian,XL; Zhao,X.; Su,YQ; Wang,LJ; Wang,HM; Dang,D.; Chi,B.; Liu,HF; Hensen,EJM; Lou,XW; Xia,BY, Engineeringbunched Pt-Ni alloy nanocages for efficient oxygen reduction in practical fuel cells. Science 2019,366(6467),850-856); Huang Yu's team reported a graphene nanobag-protected and pore-limited Pt@Gnp catalyst, exhibiting 0.74 A mg at low loading. Pt -1 Mass activity and 1.08W cm -2The catalyst exhibits a high rated power. After 90,000 square wave cycles, the rated power loss is only 1.1%. With a fuel cell lifetime exceeding 200,000 hours and a peak density retention rate of up to 71.9%, this catalyst holds significant potential for heavy-duty fuel cell applications. (Liu, Zeyan; Peng, Bosi; Tsai, Yu-Han, Joseph; Zhang, Ao; Xu, Mingjie; Zang, Wenjie; Yan, Xing Xu; Xing, Li; Pan, Xiaoqing; Duan, Xiangfeng; Huang, Yu, Pt catalyst protected by graphene nanopockets enables lifetimes of over 200,000 h for heavy-duty fuel cell applications. Nat. Nanotechnol 2025.) Although the modified Pt-M (M = Fe, Co, Ni) alloy has high oxygen reduction activity, under the actual operating temperature and voltage conditions of fuel cells, the transition metals will undergo severe oxidation and dissolution as the reaction proceeds, resulting in a rapid decline in the performance of proton exchange membrane fuel cells.

[0004] In contrast, early transition metals, especially lanthanides, exhibit significant potential to suppress metal dissolution. For example, Xing Wei's team (Yang,L.;Bai,J.;Zhang,N.;Jiang,Z.;Wang,Y.;Xiao,M.;Liu,C.;Zhu,S.;Xu,ZJ;Ge,J.;Xing,W.,Rare Earth Evoked Subsurface Oxygen Species in Platinum Alloy Catalysts Enable Durable Fuel Cells.Angewandte Chemie International Edition 2024,63(7),e202315119) developed a highly stable and active Gd-O-Pt3Ni catalyst. The introduced Gd-O dipole effectively reduced the dissolution of the noble metal platinum. After accelerated aging at 40k, the mass activity retention rate reached 67.8%, demonstrating good stability.

[0005] However, due to the significant difference between the standard reduction potentials of lanthanides and the noble metal platinum, the synthesis of ordered lanthanide alloys using traditional wet chemical methods is quite difficult. Therefore, overcoming the problem of noble and transition metal dissolution in proton exchange membrane fuel cell cathode catalysts, and achieving stable lanthanide doping to prepare highly stable and highly active ordered lanthanide platinum-based alloy catalysts are urgent problems to be solved. Summary of the Invention

[0006] The purpose of this section is to outline some aspects of embodiments of the present invention and to briefly describe some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of this application, to avoid obscuring the purpose of these documents; however, such simplifications or omissions should not be construed as limiting the scope of the invention.

[0007] To address the problems of low catalytic activity and poor catalytic stability in existing proton exchange membrane fuel cell (PEMFC) cathode catalysts due to the dissolution and particle agglomeration of platinum and the second transition metal, this invention provides a method for preparing a lanthanum-doped, highly stable, ordered platinum alloy fuel cell cathode catalyst. This method utilizes a metal-organic framework (MOF) derivatization strategy to achieve atomic-level dispersion of lanthanum on a porous carbon substrate, providing abundant anchoring sites for the nucleation and growth of the platinum-based ordered alloy, ensuring strong interaction between the platinum-based alloy and lanthanum. Lanthanum is incorporated into the platinum-based alloy lattice through high-temperature annealing in a reducing atmosphere, achieving strong bonding between lanthanum and platinum. Simultaneously, the anchoring effect of lanthanum in the support and the confinement effect of the support inhibit the agglomeration of platinum-based nanoparticles, resulting in smaller ordered platinum-based alloy nanoparticles and ensuring high platinum utilization. This preparation method is simple, low-cost, and reproducible. Compared with existing commercial catalysts, the prepared lanthanum-doped platinum-based ordered alloy fuel cell cathode catalyst requires less platinum, exhibits higher catalytic activity, and demonstrates better stability. It effectively solves the aforementioned technical problems.

[0008] This invention provides a lanthanum-doped, highly stable, ordered platinum alloy fuel cell cathode catalyst and its preparation method, which solves the technical problems of low catalytic activity and poor catalytic stability in existing proton exchange membrane fuel cell (PEMFC) cathode catalysts due to the dissolution and particle agglomeration of platinum and the second transition metal.

[0009] In view of the problems existing in the above and / or prior art, the present invention is proposed.

[0010] Therefore, the purpose of this invention is to overcome the shortcomings of the prior art and provide a method for preparing a lanthanum-doped, highly stable, ordered platinum alloy fuel cell cathode catalyst.

[0011] To solve the above-mentioned technical problems, the present invention provides the following technical solutions, including:

[0012] The lanthanum salt and 1,3,5-benzenetricarboxylic acid were dissolved in a mixed solvent of N,N-dimethylformamide and ultrapure water. The mixture was heated and stirred in an oil bath, centrifuged, washed and dried to obtain a flocculent white solid. After high-temperature annealing, a carbon support rich in lanthanum dispersion sites was obtained.

[0013] A platinum-containing aqueous solution and a second metal salt containing iron, cobalt, or nickel were sequentially added to a carbon support, stirred overnight, and then obtained as a catalyst precursor by rotary evaporation.

[0014] The catalyst precursor was subjected to high-temperature annealing and acid treatment in sequence to obtain a lanthanum-doped, highly stable, ordered platinum alloy fuel cell cathode catalyst.

[0015] The molar ratio of the lanthanum salt and 1,3,5-benzenetricarboxylic acid is 0.5:1 to 1:10.

[0016] In a preferred embodiment of the method for preparing the lanthanum-doped, highly stable, ordered platinum alloy fuel cell cathode catalyst of the present invention, the lanthanum salt comprises lanthanum chloride hexahydrate.

[0017] In a preferred embodiment of the method for preparing the lanthanum-doped high-stability ordered platinum alloy fuel cell cathode catalyst of the present invention, the oil bath heating is performed at a temperature of 50–130°C for a time of 1–6 hours.

[0018] As a preferred embodiment of the preparation method of the lanthanum-doped high-stability ordered platinum alloy fuel cell cathode catalyst of the present invention, the centrifugation separation is carried out at a speed of 10,000 rpm for 3 min; the drying is carried out at a temperature of 50-80℃ for 12-24 h.

[0019] In a preferred embodiment of the method for preparing the lanthanum-doped high-stability ordered platinum alloy fuel cell cathode catalyst of the present invention, the platinum-containing aqueous solution includes an aqueous solution of chloroplatinic acid; the second metal salt includes chlorides or nitrates of iron, cobalt, or nickel.

[0020] In a preferred embodiment of the method for preparing the lanthanum-doped, highly stable, ordered platinum alloy fuel cell cathode catalyst of the present invention, the molar ratio of platinum to iron, cobalt, or nickel is 3:1.

[0021] In a preferred embodiment of the method for preparing the lanthanum-doped high-stability ordered platinum alloy fuel cell cathode catalyst of the present invention, the high-temperature annealing includes a heating rate of 0.5–10 °C / min, a treatment temperature of 500–1100 °C, and a treatment time of 0.5–6 h; the atmosphere includes argon, nitrogen, and an argon-hydrogen mixture.

[0022] In a preferred embodiment of the method for preparing the lanthanum-doped high-stability ordered platinum alloy fuel cell cathode catalyst of the present invention, the hydrogen volume content in the argon-hydrogen mixed gas is 5-10 vol%.

[0023] In a preferred embodiment of the method for preparing the lanthanum-doped high-stability ordered platinum alloy fuel cell cathode catalyst of the present invention, the acid treatment solution is a 0.1 mol / L perchloric acid, dilute hydrochloric acid, or dilute sulfuric acid solution.

[0024] The purpose of this invention is to overcome the shortcomings of the prior art and provide a lanthanum-doped, highly stable, ordered platinum alloy fuel cell cathode catalyst.

[0025] Beneficial effects of this invention:

[0026] (1) In this invention, lanthanum salt is first reacted with a complex to form a lanthanum complex, which is then carbonized to form a carbon support containing lanthanum salt. Platinum and a second metal are loaded and then annealed to introduce lanthanum into an ordered alloy lattice. The provided lanthanum-doped, highly stable ordered platinum alloy fuel cell cathode catalyst has good nanoparticle dispersion, high utilization of noble metal atoms, high catalytic activity, and good stability.

[0027] (2) The method for preparing the lanthanum-doped high-stability ordered platinum alloy fuel cell cathode catalyst provided by this invention achieves atomic-level dispersion of lanthanides on a porous carbon substrate through a metal-organic framework (MOF) derivation strategy, providing abundant anchoring sites for the nucleation and growth of the platinum-based ordered alloy and ensuring strong interaction between the platinum-based alloy and lanthanum. Lanthanum is incorporated into the platinum-based alloy lattice by high-temperature annealing under a reducing atmosphere, achieving strong bonding between lanthanum and platinum. At the same time, the anchoring effect of lanthanum in the support and the confinement effect of the support inhibit the agglomeration of platinum-based nanoparticles. The resulting ordered platinum-based alloy nanoparticles have a small particle size, ensuring high platinum utilization.

[0028] (3) The preparation method is simple, low-cost, and reproducible. Compared with existing commercial catalysts, the prepared lanthanum-doped platinum-based ordered alloy fuel cell cathode catalyst has a lower platinum content, higher catalytic activity, and better stability. Attached Figure Description

[0029] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein:

[0030] Figure 1 This is a transmission electron microscopy (TEM) characterization image of the lanthanum-doped, highly stable, ordered platinum alloy fuel cell cathode catalyst prepared in Example 1 of this invention.

[0031] Figure 2 This is a statistical distribution diagram of the nanoparticle size supported on the lanthanum-doped, highly stable, ordered platinum alloy fuel cell cathode catalyst prepared in Example 1 of the present invention.

[0032] Figure 3 This is an elemental distribution diagram of the nanoparticles supported on the lanthanum-doped, highly stable, ordered platinum alloy fuel cell cathode catalyst prepared in Example 1 of this invention.

[0033] Figure 4 The image shows the X-ray diffraction pattern of the lanthanum-doped, highly stable, ordered platinum alloy fuel cell cathode catalyst prepared in Example 1 of this invention.

[0034] Figure 5 The image shows the accelerated aging performance of the lanthanum-doped, highly stable, ordered platinum alloy fuel cell cathode catalyst prepared in Example 1 of this invention under three-electrode conditions.

[0035] Figure 6 The peak power density test performance of the lanthanum-doped high-stability ordered platinum alloy fuel cell cathode catalyst prepared in Example 1 of the present invention, when assembled into a single cell as a cathode catalyst.

[0036] Figure 7 The figure shows the stability test results of the lanthanum-doped high-stability ordered platinum alloy fuel cell cathode catalyst prepared in Example 1 of the present invention when assembled into a single cell.

[0037] Figure 8 The three-electrode test performance diagrams are for lanthanum-doped, highly stable, ordered platinum alloy fuel cell cathode catalysts with different feed ratios prepared in Example 2 of this invention.

[0038] Figure 9 The three-electrode test performance diagram shows the lanthanum-doped, highly stable, ordered platinum alloy fuel cell cathode catalysts with different second metal particle element types prepared in Example 3 of this invention.

[0039] Figure 10 The image shows the accelerated aging performance of the three-electrode cathode catalyst of the lanthanum-free platinum-based fuel cell prepared in Comparative Example 1 of this invention. Detailed Implementation

[0040] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0041] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0042] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0043] Unless otherwise specified, all raw materials used in this invention are common commercially available analytical grade chemicals.

[0044] Example 1

[0045] This embodiment provides a method for preparing a lanthanum-doped, highly stable, ordered platinum alloy fuel cell cathode catalyst, specifically as follows:

[0046] 1) Weigh 725.5 mg of lanthanum chloride hexahydrate and 428.85 mg of 1,3,5-benzenetricarboxylic acid (BTC), add 50 mL of ultrapure water and N,N-dimethylformamide (N,N-dimethylformamide to ultrapure water volume ratio 1:1) and stir until clarified (i.e., the molar ratio of lanthanum salt to 1,3,5-benzenetricarboxylic acid is 1:1). Stir at 90 °C for 3 h, let stand at room temperature for 12 h, centrifuge, wash three times with a mixed solvent of water and ethanol (volume ratio 1:1), and then dry in a drying oven at 60 °C for 24 h to obtain a flocculent white solid. Place the obtained flocculent white solid in a tube furnace and perform high-temperature annealing under an argon atmosphere. The heating rate is 5 °C / min, the high-temperature annealing temperature is 800 °C, and the holding time is 1 h. After natural cooling, a carbon support rich in lanthanum dispersion is obtained.

[0047] 2) Disperse 200 mg of lanthanum-rich carbon support in 50 mL of ultrapure water, and add 1.5 mL of chloroplatinic acid solution (concentration 7.4 mg). Pt 2.3 mL of cobalt chloride solution (concentration 0.495 mg / mL) and 2.3 mL of cobalt chloride solution (concentration 0.495 mg / mL). Co / mL), then sonicated for 30 min, stirred at room temperature for 12 h to obtain a suspension, and the suspension was rotary evaporated at 60 °C to obtain the catalyst precursor (i.e., the molar ratio of platinum to cobalt is 3:1).

[0048] 3) The precursor was placed in a tube furnace and heat-treated in a 5 vol% argon-hydrogen mixed gas at a heating rate of 5 °C / min, a heat treatment temperature of 1000 °C, and a time of 3 h. The temperature was then reduced to 400 °C within 1 h and allowed to cool naturally to room temperature. After that, it was acid-washed with 0.1 M HClO4 solution for 12 h, filtered, and dried to obtain a highly stable ordered platinum alloy fuel cell cathode catalyst doped with 20% metal loading.

[0049] The highly stable ordered platinum alloy fuel cell cathode catalyst prepared in Example 1 was characterized by transmission electron microscopy, and the results are as follows: Figure 1 As shown, the lanthanum-doped alloy nanoparticles in the obtained catalyst are uniformly loaded on the surface of the support.

[0050] Statistical analysis was performed on the particle size of the nanoparticles loaded in the high-stability ordered platinum alloy fuel cell cathode catalyst prepared in Example 1. The results are as follows: Figure 2 As shown, the average particle size of the nanoparticles is 4.89 nm. The small particle size and uniform distribution are beneficial for exposing more catalytic active sites.

[0051] Elemental analysis was performed on the nanoparticles loaded in the high-stability ordered platinum alloy fuel cell cathode catalyst prepared in Example 1, and the results are as follows: Figure 3 As shown, the particles contain platinum, cobalt, and lanthanum simultaneously, confirming the successful doping of lanthanum.

[0052] The highly stable ordered platinum alloy fuel cell cathode catalyst prepared in Example 1 was characterized by X-ray diffraction, and the results are as follows: Figure 4 As shown in the figure, the diffraction peaks of the obtained catalyst match those of the platinum-cobalt alloy, indicating the successful synthesis of the alloy.

[0053] The high-stability ordered platinum alloy fuel cell cathode catalyst prepared in this embodiment was tested in a three-electrode system to assess its performance and stability. A standard hydrogen electrode was used as the reference electrode, a carbon rod as the counter electrode, and a rotating disk electrode covered with a catalyst film as the working electrode. A 0.1M HClO4 solution was used as the electrolyte. The results are as follows: Figure 5 As shown, the catalyst exhibited no significant performance degradation after undergoing 40,000 cycles of accelerated aging testing, demonstrating excellent stability.

[0054] Figure 6The graph shows the peak power density performance of a single cell assembled with the lanthanum-doped, highly stable, ordered platinum alloy fuel cell cathode catalyst prepared in Example 1 of this invention. It can be seen that the peak power of the single cell prepared by the lanthanum-doped, highly stable, ordered platinum alloy fuel cell cathode catalyst under different back pressure conditions is significantly higher than that of a commercial Pt / C catalyst with the same loading, indicating that the catalyst prepared by this invention has superior electrocatalytic activity compared to the commercial Pt / C catalyst.

[0055] Figure 7 The figure shows the stability test results of the lanthanum-doped, highly stable ordered platinum alloy fuel cell cathode catalyst prepared in Example 1 of this invention when assembled into a single cell. It can be seen that the lanthanum-doped, highly stable ordered platinum alloy fuel cell cathode catalyst prepared in this invention exhibits high stability under hydrogen-air conditions, maintaining 88% of its peak power density even after accelerated aging at 50K. This demonstrates the excellent stability of the lanthanum-doped, highly stable ordered platinum alloy fuel cell cathode catalyst prepared in this invention within the fuel cell.

[0056] Example 2

[0057] The difference between this embodiment and Example 1 is that the amount of chloroplatinic acid solution added is adjusted to 0.375 mL and the amount of cobalt chloride solution added is 0.575 mL. The rest of the preparation process is the same as in Example 1, and a cathode catalyst is obtained.

[0058] The lanthanum-doped high-stability ordered platinum alloy fuel cell cathode catalyst of Example 2 was characterized by transmission electron microscopy, particle size analysis, elemental analysis, three-electrode stability testing, and single-cell performance and stability testing. The results were similar to those of Example 1.

[0059] Example 3

[0060] The difference between this embodiment and Example 1 is that the amount of chloroplatinic acid solution added is adjusted to 0.75 mL and the amount of cobalt chloride solution added is 1.15 mL. The rest of the preparation process is the same as in Example 1, and a cathode catalyst is obtained.

[0061] The lanthanum-doped high-stability ordered platinum alloy fuel cell cathode catalyst of Example 3 was characterized by transmission electron microscopy, particle size analysis, elemental analysis, three-electrode stability testing, and single-cell performance and stability testing. The results were similar to those of Example 1.

[0062] Figure 8The figures show the three-electrode performance of lanthanum-doped, highly stable, ordered platinum alloy fuel cell cathode catalysts prepared in Examples 2 and 3 of this invention with different feed ratios. It can be seen that the catalyst with a 5% metal feed ratio exhibits superior three-electrode performance compared to those with 2.5% and 5%, indicating that the feed ratio should not be too high or too low. Too low a feed ratio leads to uneven distribution of active sites, while too high a feed ratio easily leads to nano-metal agglomeration.

[0063] Example 4

[0064] The difference between this embodiment and Example 1 is that the cobalt chloride solution is changed to a nickel chloride solution, while the rest of the preparation process is the same as in Example 1, and a cathode catalyst is obtained.

[0065] The lanthanum-doped high-stability ordered platinum alloy fuel cell cathode catalyst of Example 4 was characterized by transmission electron microscopy, particle size analysis, elemental analysis, three-electrode stability test, and single-cell performance and stability test. The three-electrode performance was slightly lower than that of Example 1, while the yield, metal loading, particle size, and stability were similar to those of Example 1.

[0066] Example 5

[0067] The difference between this embodiment and Example 1 is that the cobalt chloride solution is changed to an iron chloride solution, while the rest of the preparation process is the same as in Example 1, and a cathode catalyst is obtained.

[0068] The lanthanum-doped high-stability ordered platinum alloy fuel cell cathode catalyst of Example 5 was characterized by transmission electron microscopy, particle size analysis, elemental analysis, three-electrode stability test, and single-cell performance and stability test. The three-electrode performance was slightly lower than that of Example 1, while the yield, metal loading, particle size, and stability were similar to those of Example 1.

[0069] Figure 9 The figures show the three-electrode performance of lanthanum-doped high-stability ordered platinum alloy fuel cell cathode catalysts with different second metal particle elements prepared in Examples 4 and 5 of this invention. It can be seen that the three-electrode performance of the lanthanum-doped high-stability ordered platinum alloy fuel cell cathode catalysts with different second metals is superior to that of commercial Pt / C, and the performance order is cobalt > nickel > iron. This indicates that different transition metal elements have a significant impact on the performance of the prepared catalysts. This is because the reduction temperature and phase transition temperature of different metals have different effects on the incorporation of lanthanum.

[0070] Example 6

[0071] The difference between this embodiment and Example 1 is that the heat treatment temperature in step 3) is adjusted to 900℃, while the rest of the preparation process is the same as in Example 1, and a cathode catalyst is obtained.

[0072] Example 7

[0073] The difference between this embodiment and Example 1 is that the heat treatment temperature in step 3) is adjusted to 1100℃, while the rest of the preparation process is the same as in Example 1, and a cathode catalyst is obtained.

[0074] The electrochemical performance of the materials prepared in Examples 6 and 7 was tested, and the results compared with those in Example 1 are shown in Table 1.

[0075] Table 1

[0076] Temperature Half-wave potential (V) mass active (Amg Pt -1 )]]> Example 1 1000℃ 0.945 1.41 Example 6 900℃ 0.905 0.32 Example 7 1100℃ 0.908 0.30

[0077] As shown in the table above, different heat treatment temperatures have a significant impact on the prepared catalyst. At lower temperatures, lanthanum cannot diffuse into the platinum alloy to form ordered intermetallic compounds, resulting in poor performance. As the temperature increases further, lanthanum diffuses into the platinum alloy lattice to form ordered intermetallic compounds, and the performance is greatly improved. However, when the temperature is too high, the ordered intermetallic compound particles agglomerate, the specific surface area decreases, and the performance actually declines.

[0078] Comparative Example 1

[0079] The difference between this comparative example and Example 1 is that lanthanum chloride hexahydrate is replaced with zinc nitrate hexahydrate, while the rest of the preparation process is the same as in Example 1, and a cathode catalyst is obtained.

[0080] The three-electrode stability test was performed on the lanthanum-free platinum-based fuel cell cathode catalyst of Comparative Example 1, and the results are as follows: Figure 10 As shown, it can be seen that due to the lack of lanthanum doping, the activity and stability of the comparative sample 1 are significantly reduced.

[0081] Comparative Example 2

[0082] The difference between this comparative example and Example 1 is that no second metal salt is added; all other preparation processes are the same as in Example 1 to obtain the cathode catalyst. Step 2) specifically involves:

[0083] 200 mg of lanthanum-rich carbon support was dispersed in 50 mL of ultrapure water, and 1.5 mL of chloroplatinic acid solution (concentration 7.4 mg) was added. Pt / mL), followed by sonication for 30 min, and stirring at room temperature for 12 h to obtain a suspension. The suspension was then rotary evaporated at 60 °C to obtain the catalyst precursor.

[0084] Comparative Example 3

[0085] The difference between this comparative example and Example 1 is that lanthanum chloride hexahydrate is replaced with zinc nitrate hexahydrate, and no second metal salt is added. The rest of the preparation process is the same as in Example 1, and a cathode catalyst is obtained.

[0086] Comparative Example 4

[0087] Commercial Pt / C catalysts produced by Johnson Matthey in the UK.

[0088] The electrochemical performance of the materials prepared in Comparative Examples 2, 3 and 4 was tested, and the results compared with those in Example 1 are shown in Table 2.

[0089] Comparative Example 5

[0090] The difference between this comparative example and Example 1 is that the order of lanthanum salt addition was adjusted; all other preparation processes were the same as in Example 1 to obtain the cathode catalyst. Specifically:

[0091] 1) Weigh 428.85 mg of 1,3,5-benzenetricarboxylic acid (BTC), add it to 50 mL of ultrapure water and N,N-dimethylformamide (N,N-dimethylformamide to ultrapure water volume ratio 1:1), stir until clear, stir at 90 °C for 3 h, let stand at room temperature for 12 h, centrifuge, wash three times with a mixed solvent of water and ethanol (volume ratio 1:1), and then dry in a drying oven at 60 °C for 24 h to obtain a flocculent white solid. Place the obtained flocculent white solid in a tube furnace and perform high-temperature annealing under an argon atmosphere. The heating rate is 5 °C / min, the high-temperature annealing temperature is 800 °C, and the holding time is 1 h. After natural cooling, the carbon support is obtained.

[0092] 2) Disperse 200 mg of carbon support in 50 mL of ultrapure water, add 725.5 mg of lanthanum chloride hexahydrate and 1.5 mL of chloroplatinic acid solution (concentration 7.4 mg). Pt 2.3 mL of cobalt chloride solution (concentration 0.495 mg / mL) and 2.3 mL of cobalt chloride solution (concentration 0.495 mg / mL). Co / mL), then sonicated for 30 min, stirred at room temperature for 12 h to obtain a suspension, and the suspension was rotary evaporated at 60 °C to obtain the catalyst precursor (i.e., the molar ratio of platinum to cobalt is 3:1).

[0093] 3) The precursor was placed in a tube furnace and heat-treated in a 5 vol% argon-hydrogen mixed gas at a heating rate of 5 °C / min, a heat treatment temperature of 1000 °C, and a time of 3 h. The temperature was then reduced to 400 °C within 1 h and allowed to cool naturally to room temperature. After that, it was acid-washed with 0.1 M HClO4 solution for 12 h, filtered, and dried to obtain a lanthanum-containing ordered platinum alloy fuel cell cathode catalyst with a metal loading of 20% without complexation reaction.

[0094] This comparative example changed the order of lanthanum salt addition, adding it together with platinum and the second transition metal after carbonization. The reason for this is that lanthanum is difficult to introduce, which illustrates the superiority of the method of first fixing lanthanum in the support in this invention.

[0095] Comparative Example 6

[0096] The difference between this comparative example and Example 1 is that lanthanum chloride hexahydrate is replaced with thulium chloride hexahydrate, while the rest of the preparation process is the same as in Example 1, and a cathode catalyst is obtained.

[0097] The electrochemical performance of the materials prepared in the above comparative example was tested, and the results compared with those of Example 1 are shown in Table 1.

[0098] Table 2

[0099]

[0100]

[0101] As shown in Table 2, the activities of Comparative Examples 1-4 decreased to varying degrees compared to the Examples. This indicates that the addition of lanthanum and the second metal particles has a significant impact on the prepared catalysts. Without the addition of lanthanum or the second metal, the binary intermetallic compound exhibits less lattice compression compared to the ternary intermetallic compound, resulting in a decrease in activity. When only platinum is present, an intermetallic compound cannot be formed, and the activity is lower than that of the ordered intermetallic compounds in Examples 1, 1, and 2.

[0102] Comparative Example 5 showed a decrease in activity compared to the Examples, indicating that the form of lanthanum incorporation has a significant impact on the prepared catalyst. The fact that lanthanum did not enter the support in the form of a complex makes it difficult for it to enter the alloy lattice, resulting in less lattice compression and decreased activity.

[0103] The activity of Comparative Example 6 decreased compared to the Example, indicating that the choice of lanthanide elements has a significant impact on the prepared catalyst. Thulium, which is also a lanthanide element, has greater electronegativity than lanthanum and is less likely to lose electrons to enter the crystal lattice and form bonds with platinum. The electron interaction is smaller, the lattice compression is smaller, and the activity decreases.

[0104] In summary, this invention achieves atomic-level dispersion of lanthanides on a porous carbon substrate through a metal-organic framework (MOF) derivation strategy, providing abundant anchoring sites for the nucleation and growth of platinum-based ordered alloys and ensuring strong interactions between the platinum-based alloys and lanthanum. Lanthanum is incorporated into the platinum-based alloy lattice through high-temperature annealing in a reducing atmosphere, achieving strong bonding between lanthanum and platinum. Simultaneously, the anchoring effect of lanthanum in the support and the confinement effect of the support suppress the aggregation of platinum-based nanoparticles, resulting in ordered platinum-based alloy nanoparticles with small particle size, ensuring high platinum utilization. This preparation method is simple, low-cost, and reproducible. Compared with existing commercial catalysts, the prepared lanthanum-doped platinum-based ordered alloy fuel cell cathode catalyst has lower platinum content, higher catalytic activity, and better stability.

[0105] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for preparing a lanthanum-doped, highly stable, ordered platinum alloy fuel cell cathode catalyst, characterized in that: include, The lanthanum salt and 1,3,5-benzenetricarboxylic acid were dissolved in a mixed solvent of N,N-dimethylformamide and ultrapure water. The mixture was heated and stirred in an oil bath, centrifuged, washed and dried to obtain a flocculent white solid. After high-temperature annealing, a carbon support rich in lanthanum dispersion sites was obtained. A platinum-containing aqueous solution and a second metal salt containing iron, cobalt, or nickel were sequentially added to a carbon support, stirred overnight, and then obtained as a catalyst precursor by rotary evaporation. The catalyst precursor was subjected to high-temperature annealing and acid treatment in sequence to obtain a lanthanum-doped, highly stable, ordered platinum alloy fuel cell cathode catalyst. The molar ratio of the lanthanum salt and 1,3,5-benzenetricarboxylic acid is 0.5:1 to 1:

10.

2. The method for preparing the lanthanum-doped, highly stable, ordered platinum alloy fuel cell cathode catalyst as described in claim 1, characterized in that: The lanthanum salt includes lanthanum chloride hexahydrate.

3. The method for preparing the lanthanum-doped, highly stable, ordered platinum alloy fuel cell cathode catalyst as described in claim 1, characterized in that: The oil bath heating is performed at a temperature of 50–130°C for a duration of 1–6 hours.

4. The method for preparing the lanthanum-doped, highly stable, ordered platinum alloy fuel cell cathode catalyst as described in claim 1, characterized in that: The centrifugation is carried out at a speed of 10,000 rpm for 3 minutes; the drying is carried out at a temperature of 50–80°C for 12–24 hours.

5. The method for preparing the lanthanum-doped, highly stable, ordered platinum alloy fuel cell cathode catalyst as described in claim 1, characterized in that: The platinum-containing aqueous solution includes an aqueous solution of chloroplatinic acid; the second metal salt includes chlorides or nitrates of iron, cobalt, or nickel.

6. The method for preparing the lanthanum-doped, highly stable, ordered platinum alloy fuel cell cathode catalyst as described in claim 5, characterized in that: The molar ratio of platinum to iron, cobalt, or nickel is 3:

1.

7. The method for preparing the lanthanum-doped, highly stable, ordered platinum alloy fuel cell cathode catalyst as described in claim 1, characterized in that: The high-temperature annealing process includes a heating rate of 0.5–10 °C / min, a processing temperature of 500–1100 °C, and a processing time of 0.5–6 h; the atmosphere comprises argon, nitrogen, and an argon-hydrogen mixture.

8. The method for preparing the lanthanum-doped, highly stable, ordered platinum alloy fuel cell cathode catalyst as described in claim 7, characterized in that: The hydrogen volume content in the argon-hydrogen mixture is 5-10 vol%.

9. The method for preparing the lanthanum-doped, highly stable, ordered platinum alloy fuel cell cathode catalyst as described in claim 1, characterized in that: The acid treatment uses a 0.1 mol / L solution of perchloric acid, dilute hydrochloric acid, or dilute sulfuric acid.

10. A lanthanum-doped, highly stable, ordered platinum alloy fuel cell cathode catalyst prepared by any one of the preparation methods described in claims 1 to 9.

Images