Preparation method and application of a platinum-based alloy-rare earth oxide La2O3 hybrid interfacial catalyst

Abstract

This invention belongs to the field of fuel cell catalysis, specifically relating to a preparation method and application of a platinum-based alloy-rare earth oxide La2O3 hybrid interface catalyst. The specific preparation method includes the following steps: (1) preparing a carbon support material via oxidative polymerization and high-temperature pyrolysis; (2) loading a metal component onto the carbon support material via co-precipitation-impregnation; (3) subjecting the metal-loaded support to high-temperature heat treatment under a reducing atmosphere to finally obtain the catalyst. The preparation process of this invention is safe, simple, and low-cost. By reducing the platinum loading, the problem of high raw material costs is further solved. The half-wave potential of this invention reaches 0.876V, and the mass activity reaches 1.48 A·mg. ‑1 Pt @0.9V, which is 12.3 times the mass activity of commercial 40% Pt / C catalysts, indicating that it has superior oxygen reduction catalytic activity; in addition, after 60,000 cycles of cyclic voltammetry testing, its half-wave potential only decreased by 13 mV, indicating that the present invention has excellent long-term cycling stability.

Description

Technical Field

[0001] This invention belongs to the field of fuel cell catalysis, specifically relating to a method for preparing and applying a platinum-based alloy-rare earth oxide La2O3 hybrid interface catalyst. Background Technology

[0002] With societal progress and development, human demand for energy is increasing dramatically. While developing more energy sources, environmental pollution and the depletion of traditional fossil fuel reserves have emerged, making the development of sustainable, green, and clean renewable energy sources an urgent priority. Proton exchange membrane fuel cells (PEMFCs) are considered a crucial technology for achieving sustainable energy conversion due to their high energy conversion efficiency and environmental friendliness. The oxygen reduction reaction (ORR) is a key process at the cathode of a fuel cell; however, its reaction kinetics are slow, significantly impacting the overall performance of the cell. Currently, platinum (Pt)-based materials remain the most active metal catalysts for ORR, but their high cost, scarcity, and insufficient long-term operational stability make them unsuitable for the long-term normal operation of fuel cells.

[0003] Alloying Pt with transition metals is an effective strategy to reduce Pt content and modulate its electronic structure. Introducing transition metals generates ligand and lattice strain effects, shifting the d-band center of platinum downwards to enhance its intrinsic oxygen reduction activity. However, unfortunately, under the harsh operating conditions and long-term electrochemical cycling of conventional Pt-based alloy catalyst fuel cells, transition metals are prone to dissolution, leading to catalyst structural collapse and loss of active sites, resulting in a significant decline in catalytic performance and hindering its commercial application.

[0004] Rare earth metals have also attracted widespread attention due to their unique 4f-layer electronic configuration. Among them, patent CN121748421A discloses a carbon-supported platinum-gadolinium (Gd) catalyst, which utilizes the complementary effect of dd orbitals between gadolinium and platinum to enhance the electron transfer efficiency of platinum surface sites, synergistically reduce the energy barrier of the reaction steps, and improve the oxygen reduction reaction performance. Although its catalytic activity is excellent, it still has certain limitations: (1) The porous carbon support used is formed by carbonization of Gd-ZIF precursor, and the synthesis process uses toxic and harmful substances such as methanol and 2-methylimidazole, which is highly dangerous. (2) The amount of precious metal platinum used is large, resulting in high cost.

[0005] Currently, rare earth oxides exhibit significant advantages in catalytic interface regulation due to their unique 4f electron layer structure and extremely high chemical stability. Combining rare earth oxides with Pt-based alloys can form heterojunctions with strong interactions. This not only stabilizes the electronic structure of Pt but also further accelerates the reaction process and reduces electron transfer energy through interfacial charge transfer, thus helping to optimize catalytic performance. However, effectively combining platinum-based alloys with rare earth oxides at the nanoscale to form a stable hybrid interface with strong electronic interactions, thereby synergistically enhancing catalytic activity and durability, remains a challenge that requires further exploration.

[0006] In summary, effectively combining platinum-based alloys with rare earth oxides can regulate the d-band center of platinum and improve catalyst performance through mechanisms such as interfacial charge transfer. Therefore, the use of platinum-based alloy-rare earth oxide composites as electrochemical reaction catalysts warrants further investigation. Summary of the Invention

[0007] The purpose of this invention is to provide a method for preparing and applying a platinum-based alloy-rare earth oxide La2O3 hybrid interfacial catalyst.

[0008] Based on the unique electronic structure of rare earth metals, the applicant proposed that Pt-based alloys can be combined with rare earth metal oxides to form hybrid interfaces, inducing a redistribution of interfacial charges, which is expected to effectively promote oxygen reduction performance and long-term cycling stability.

[0009] To achieve the objectives of the invention described above, the technical solution adopted by the present invention is as follows:

[0010] A method for preparing a platinum-based alloy-rare earth oxide La2O3 hybrid interface catalyst includes the following steps: (1) preparing a carbon support material by oxidative polymerization and high-temperature pyrolysis; (2) loading a metal component onto the carbon support material by co-precipitation-impregnation method; (3) subjecting the support loaded with the metal component to high-temperature heat treatment under a reducing atmosphere to finally obtain the catalyst.

[0011] Further, step (1) specifically includes:

[0012] (a) Aniline and melamine were dispersed together in dilute hydrochloric acid, and ammonium persulfate was added as an oxidant under ice bath conditions to carry out the reaction;

[0013] (b) The product was centrifuged, washed with a large amount of deionized water, and then vacuum dried to obtain the melamine / polyaniline composite.

[0014] (c) The above composite is pyrolyzed in a tube furnace under nitrogen atmosphere protection to obtain nitrogen-doped carbon support material.

[0015] Furthermore, step (2) specifically includes:

[0016] (a) Dissolve a metal salt containing a platinum source, an iron source, a manganese source, a copper source and a lanthanum source in deionized water to prepare a mixed metal salt solution, wherein the molar ratio of the platinum source, the iron source, the manganese source, the copper source and the lanthanum source is (0.8)∶1∶1∶1∶(0.25-1);

[0017] (b) The carrier material is added to the mixed metal salt solution and stirred. During the stirring process, a precipitant KOH solution is added dropwise, followed by ultrasonic treatment to obtain an ultrasonically mixed solution. Finally, the solution is dried under vacuum to obtain a carbon carrier loaded with metal components.

[0018] Further, step (3) specifically involves placing the carbon support loaded with metal components in a tube furnace, pyrolyzing it for 1 h in a hydrogen-argon mixed atmosphere at 700°C, cooling it, washing it with deionized water, filtering it, and then drying it under vacuum to finally obtain the catalyst.

[0019] Furthermore, the concentration of the dilute hydrochloric acid is 0.75 mol / L, the mass ratio of aniline, melamine, and ammonium persulfate is 2:1:5, the polymerization reaction time is 18 h, and the pyrolysis conditions are pyrolysis at 900 ℃ for 1 h.

[0020] Furthermore, the concentration of the precipitant KOH solution is 0.1 mol / L; the platinum source, iron source, manganese source, copper source and lanthanum source are potassium chloride platinum sulfite, copper chloride dihydrate, ferric chloride hexahydrate, manganese chloride tetrahydrate and lanthanum chloride heptahydrate, respectively.

[0021] Furthermore, the hydrogen-argon mixture consists of 5% hydrogen and 95% argon by volume.

[0022] This invention also provides the application of the platinum-based alloy-rare earth oxide La2O3 hybrid interfacial catalyst obtained by the above preparation method in electrocatalytic oxygen reduction reaction.

[0023] Compared with the prior art, the present invention has the following advantages:

[0024] (1) The catalyst of this invention is applied to the oxygen reduction catalyst in hydrogen fuel cells and has excellent performance, with high half-wave potential (0.876 V) and high mass activity (1.48 A·mg). -1 Pt The catalyst exhibits significantly better performance than commercial 40% Pt / C catalysts at 0.9V. Furthermore, in long-term electrochemical cycling tests, after 60,000 CV cycles, the half-wave potential only decreased by 13 mV, demonstrating excellent long-term stability and effectively solving the problem of poor stability of conventional platinum-based alloy catalysts.

[0025] (2) The preparation process of this invention is simple. The aniline and melamine used as carrier synthesis materials are abundant and inexpensive. In addition, compared with the commercial 40% platinum carbon catalyst, this invention greatly reduces the amount of Pt used, thus saving costs.

[0026] (3) This invention realizes the effective composite of rare earth metal oxides and Pt-based alloys, and further promotes the research on rare earth-based materials as catalysts for electrochemical reactions. Attached Figure Description

[0027] Figure 1 This is the XRD pattern obtained in Embodiment 1 of the present invention;

[0028] Figure 2 These are oxygen reduction polarization curves of the catalysts obtained in Examples 1-3 of this invention and a commercial 40% Pt / C catalyst on a rotating disk electrode.

[0029] Figure 3 These are oxygen reduction polarization curves of the catalysts obtained in Examples 1, 4-5 of this invention and a commercial 40% Pt / C catalyst on a rotating disk electrode.

[0030] Figure 4 This is a test graph of the long-term cycle stability of the catalyst prepared in Example 1 of the present invention;

[0031] Figure 5 This is a mass activity diagram of the catalyst of Example 1 of the present invention and a commercial 40% Pt / C catalyst under a potential of 0.9 V. Detailed Implementation

[0032] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] Example 1:

[0034] A method for preparing a platinum-based alloy-rare earth oxide La2O3 hybrid interfacial catalyst includes the following steps:

[0035] Step (1): Measure aniline, melamine and ammonium persulfate in a mass ratio of 2:1:5. Add aniline and melamine together to 0.75 mol / L dilute hydrochloric acid. Under ice bath stirring conditions, slowly add ammonium persulfate solution that is also soluble in dilute hydrochloric acid and keep it for 18 h. Then centrifuge, wash with deionized water, dry at 60 ℃, and then place in a tube furnace for pyrolysis at 900 ℃ for 60 min under nitrogen atmosphere. Cool naturally to room temperature to obtain the carrier material (PM).

[0036] Step (2): Add five metal salts, potassium chloroplatinate, copper chloride dihydrate, ferric chloride hexahydrate, manganese chloride tetrahydrate and lanthanum chloride heptahydrate, in a molar ratio of (0.8):1:1:1:(0.5), to 10 ml of deionized water. Weigh 40 mg of the above carrier material and add it to the solution. Stir for 30 min and then sonicate for 40 min. During the stirring process, slowly add 3 ml of 0.1 mol / L KOH solution. After sonication, place it in a vacuum drying oven at 60 °C and dry it. Take the bottom layer product.

[0037] Step (3): The dried product was pyrolyzed in a tube furnace at 700 °C under a hydrogen-argon mixed atmosphere (hydrogen volume percentage 5%, argon volume percentage 95%) for 60 min to obtain the final product catalyst, named PM-Pt. 0.8 Fe1Cu1Mn1La 0.5 -700.

[0038] To investigate the material structure and composition of Example 1, XRD tests were performed. The test results are as follows: Figure 1 As shown, the characteristic diffraction peaks at positions 19.5°, 27.2°, and 31.6° of the sample belong to the (211), (222), and (400) crystal planes of La2O3 (PDF#22-0369), indicating that La exists in the catalyst as the La2O3 phase. Meanwhile, the diffraction peaks at positions 41.3°, 47.9°, and 70.4° belong to the face-centered cubic (FCC) Pt-based alloy phase. Compared with the pure Pt standard card (PDF#04-0802, 2θ=39.76°, 46.24°, 67.45°), the 2θ values ​​of these peaks are shifted to higher angles by about 1.5°, 1.6°, and 2.9°, respectively. This is attributed to the solid solution of metals such as Fe, Cu, and Mn into the Pt lattice. Since the atomic radius is smaller than that of Pt, the Pt lattice shrinks. The above confirms that the catalyst obtained by this invention consists of two phases: a Pt-based alloy and La2O3, and the composite of the two phases has been successfully achieved.

[0039] To demonstrate the performance of this invention, electrochemical tests were conducted, and the specific test methods are as follows:

[0040] Take 5 mg of the prepared PM-Pt 0.8Fe1Cu1Mn1La 0.5 -700 catalyst was dispersed in 1 mL of 0.25% Nafion / ethanol solution and sonicated for 20 min. 10 μL of the catalyst-containing solution was drop-coated onto a glassy carbon electrode using a three-electrode system: an Ag / AgCl electrode as the reference electrode, a platinum wire as the counter electrode, and a glassy carbon electrode as the working electrode. 0.1 mol / L HClO4 was used as the electrolyte. Initially measured potentials relative to Ag / AgCl (saturated KCl) were converted to potentials relative to the reversible hydrogen electrode (E). RHE =E Ag / AgCl +0.266 V). Before conducting electrochemical tests, O2 or N2 should be continuously passed through the electrolyte for 40 minutes to saturate the electrolyte with O2 or N2.

[0041] To compare with commercial 40% Pt / C, electrochemical tests were also performed on commercial 40% Pt / C. The test method was the same as that for Pt / C. Unless otherwise specified, the steps were the same as those described above. The difference was that for the electrochemical test of commercial 40% Pt / C, 5 μL of a solution containing commercial 40% Pt / C catalyst was dropped onto a glassy carbon electrode.

[0042] To further demonstrate the electrochemical performance, the oxygen reduction catalytic activity of the catalyst was evaluated using linear sweep voltammetry. Specifically, the test was conducted in an O2-saturated 0.1 mol / L HClO4 solution using a rotating disk electrode at a rotation speed of 1600 rpm and a scan rate of 10 mV·s. -1 The step size is 5 mV. The test results are as follows: Figure 2 As shown, PM-Pt 0.8 Fe1Cu1Mn1La 0.5 The half-wave potential of the -700 catalyst is 0.876 V, while that of the commercial 40% Pt / C catalyst is 0.874 V. Therefore, PM-Pt... 0.8 Fe1Cu1Mn1La 0.5 The -700 catalyst exhibits better oxygen reduction catalytic activity.

[0043] To investigate the effect of rare earth metal content on catalyst performance, the proportion of lanthanum chloride heptahydrate was adjusted, as shown in Examples 2 and 3:

[0044] Example 2:

[0045] The difference between this embodiment and Example 1 is that in step (2) of Example 1, the molar ratio of lanthanum chloride heptahydrate to other metals is changed from 0.5 to 0.25; the rest is the same as in Example 1. The sample is named PM-Pt. 0.8 Fe1Cu1Mn1La0.25 -700, test results are as follows Figure 2 As shown, the catalyst PM-Pt 0.8 Fe1Cu1Mn1La 0.25 The half-wave potential at -700 is 0.836 V.

[0046] Example 3:

[0047] The difference between this embodiment and Example 1 is that in step (2) of Example 1, the molar ratio of lanthanum chloride heptahydrate to other metals is changed from 0.5 to 1; the rest is the same as in Example 1. The sample is named PM-Pt. 0.8 Fe1Cu1Mn1La1-700, test results are as follows Figure 2 As shown, the catalyst PM-Pt 0.8 The half-wave potential of Fe1Cu1Mn1La1-700 is 0.862 V.

[0048] Examples 2 and 3 show that appropriately increasing the content of lanthanum chloride heptahydrate is beneficial to improving the oxygen reduction half-wave potential of the catalyst. Specifically, when the molar ratio of lanthanum chloride heptahydrate is 0.5, its half-wave potential can reach 0.876 V.

[0049] To investigate the effect of different high-temperature reduction temperatures on catalyst performance, this invention provides Examples 4 and 5, as detailed below:

[0050] Example 4:

[0051] The difference between this embodiment and Embodiment 1 is that the temperature of the tubular furnace in step (3) of Embodiment 1 is changed from 700 ℃ to 650 ℃. The other parts are the same as in Embodiment 1, and the sample is named PM-Pt. 0.8 Fe1Cu1Mn1La 0.5 -650, test results are as follows Figure 3 As shown, the catalyst PM-Pt 0.8 Fe1Cu1Mn1La 0.5 The half-wave potential at -650°C is 0.701 V.

[0052] Example 5:

[0053] The difference between this embodiment and Embodiment 1 is that the temperature of the tubular furnace in step (3) of Embodiment 1 is changed from 700 ℃ to 750 ℃. The other parts are the same as in Embodiment 1, and the sample is named PM-Pt. 0.8 Fe1Cu1Mn1La 0.5 -750, test results are as follows Figure 3 As shown, the catalyst PM-Pt 0.8 Fe1Cu1Mn1La 0.5The half-wave potential at -750 is 0.816 V.

[0054] Examples 4 and 5 show that the high-temperature reduction temperature has a significant effect on the oxygen reduction activity of the catalyst. This may be because different reduction temperatures will form different crystal phase structures, with 700 °C being a better high-temperature reduction temperature.

[0055] To demonstrate the PM-Pt prepared in Example 1 0.8 Fe1Cu1Mn1La 0.5 -700 exhibits excellent long-term stability, and accelerated aging testing (ADT) was performed, with the test results as follows: Figure 4 As shown, after 60,000 CV cycles, its half-wave potential only decreased by 13 mV. This result indicates that the catalyst PM-Pt... 0.8 Fe1Cu1Mn1La 0.5 -700 exhibits very good long-term stability.

[0056] To evaluate the catalyst PM-Pt 0.8 Fe1Cu1Mn1La 0.5 The oxygen reduction catalytic activity of the PM-Pt catalyst is -700. 0.8 Fe1Cu1Mn1La 0.5 The mass activity of -700 and commercial 40% Pt / C was calculated, and the results are as follows: Figure 5 As shown, the mass activity of commercial 40% Pt / C is only 0.12 A·mg. -1 Pt @0.9V, while PM-Pt 0.8 Fe1Cu1Mn1La 0.5 The mass activity of -700 is as high as 1.48 A·mg. -1 Pt At 0.9V, it is 12.3 times that of commercial 40% Pt / C, demonstrating superior catalytic performance.

[0057] The above XRD test results ( Figure 1 ) and electrochemical performance results ( Figure 4 , Figure 5All results indicate that this catalyst achieves effective composite formation of platinum-based alloy rare earth oxides and exhibits excellent oxygen reduction activity and stability. The significant performance improvement can be attributed to two main factors: First, the ligand effect and lattice strain effect generated by the alloying of Pt with Fe, Cu, and Mn optimize the electronic structure of Pt. Second, and most importantly, the hybrid interface formed between La2O3 and the Pt-based alloy induces a redistribution of interfacial charges, further modulating the electronic environment of the active sites and stabilizing the alloy nanoparticles. This effectively inhibits the dissolution of transition metals and Ostwald ripening of the particles, thus achieving a balance between high activity and high stability.

[0058] The above description is a detailed description of the preferred embodiments of the present invention. However, the embodiments are not intended to limit the scope of the patent application of the present invention. All equivalent changes or modifications made under the technical spirit of the present invention should fall within the patent scope covered by the present invention.

Claims

1. A method for preparing a platinum-based alloy-rare earth oxide La2O3 hybrid interfacial catalyst, characterized in that, The preparation process includes the following steps: (1) preparing carbon support material by oxidative polymerization and high-temperature pyrolysis; (2) loading metal components onto carbon support material by co-precipitation-impregnation method; (3) subjecting the support loaded with metal components to high-temperature heat treatment under a reducing atmosphere to finally obtain the catalyst.

2. The production method according to claim 1, characterized by, The specific steps (1) are as follows: (a) Aniline and melamine were dispersed together in dilute hydrochloric acid, and ammonium persulfate was added as an oxidant under ice bath conditions to carry out the reaction; (b) The product was centrifuged, washed with a large amount of deionized water, and then vacuum dried to obtain the melamine / polyaniline composite. (c) The above composite is pyrolyzed in a tube furnace under nitrogen atmosphere protection to obtain nitrogen-doped carbon support material.

3. The production method according to claim 1, characterized by, Step (2) specifically involves: (a) Dissolve a metal salt containing a platinum source, an iron source, a manganese source, a copper source and a lanthanum source in deionized water to prepare a mixed metal salt solution, wherein the molar ratio of the platinum source, the iron source, the manganese source, the copper source and the lanthanum source is (0.8)∶1∶1∶1∶(0.25-1); (b) The carrier material is added to the mixed metal salt solution and stirred. During the stirring process, a precipitant KOH solution is added dropwise, followed by ultrasonic treatment to obtain an ultrasonically mixed solution. Finally, the solution is dried under vacuum to obtain a carbon carrier loaded with metal components.

4. The method of claim 1, wherein, The specific steps (3) are as follows: placing the carbon support loaded with metal components in a tube furnace, pyrolyzing it for 1 h in a hydrogen-argon mixed atmosphere at 700 °C, cooling it, washing it with deionized water, filtering it, and then drying it under vacuum to finally obtain the catalyst.

5. The method of claim 2, wherein: The concentration of the dilute hydrochloric acid is 0.75 mol / L, the mass ratio of aniline, melamine and ammonium persulfate is 2:1:5, the polymerization reaction time is 18 h, and the pyrolysis conditions are pyrolysis at 900 ℃ for 1 h.

6. The method of claim 3, wherein: The precipitant KOH solution is 0.1 mol / L; the platinum source, iron source, manganese source, copper source and lanthanum source are potassium chloride platinum sulfite, copper chloride dihydrate, ferric chloride hexahydrate, manganese chloride tetrahydrate and lanthanum chloride heptahydrate, respectively.

7. The method of claim 4, wherein: The hydrogen-argon mixture consists of 5% hydrogen and 95% argon by volume.

8. The application of the platinum-based alloy-rare earth oxide La2O3 hybrid interfacial catalyst prepared according to claims 1-7 in the oxygen reduction reaction at the cathode of a proton exchange membrane fuel cell.

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