Carbon supported platinum-cobalt alloy oxygen reduction electrocatalyst and method for preparing the same

Abstract

This application discloses a carbon-supported platinum-cobalt alloy oxygen reduction electrocatalyst, wherein the catalyst is composed of PtCo alloy nanoparticles supported on a carbon support. The catalyst of this application exhibits excellent catalytic activity, stability, and active site utilization. After rigorous 30,000 cycles of accelerated voltammetry aging test, the ECSA and MA decay rates of the catalyst are both controlled within 10%, showing almost no decay. Compared with commercial Pt / C catalysts, the mass activity and areal activity of the catalyst in this application are significantly improved. Furthermore, this application provides a one-pot preparation method, greatly simplifying the preparation process.

Description

Technical Field

[0001] This invention belongs to the field of catalyst materials and relates to a high-performance catalyst for the oxygen reduction reaction (ORR) at the cathode of a proton exchange membrane fuel cell (PEMFC) and its preparation method. Background Technology

[0002] With the increasing severity of the global energy crisis and environmental pollution, the development of clean and efficient energy conversion technologies has become a focal point of global technological competition. Proton exchange membrane fuel cells (PEMFCs), due to their outstanding advantages such as high energy conversion efficiency, low operating temperature, zero emissions, and rapid start-up, are considered one of the ideal power sources to replace traditional internal combustion engines in the future, showing great application potential in transportation, stationary power plants, and portable power supplies.

[0003] However, the commercialization of PEMFCs still faces many challenges, one of the most critical being the exceptionally slow kinetics of its cathode oxygen reduction reaction (ORR). ORR is a complex four-electron transfer process with a high activation energy barrier, leading to significant potential loss, which directly limits the overall performance and efficiency of fuel cells. To overcome this bottleneck, highly efficient electrocatalysts must be used to accelerate ORR. Currently, platinum (Pt)-based catalysts, especially carbon-supported platinum nanoparticles (Pt / C), remain the most effective ORR catalysts.

[0004] Although commercially available Pt / C catalysts (e.g., those produced by Johnson Matthey, Tanaka TKK, etc., typically with platinum loadings of 20 wt% to 60 wt%) exhibit good initial activity in ORR, their large-scale application is limited by two key issues: High cost: Platinum is a precious metal, scarce in the Earth's crust, and expensive. Fuel cell cathodes require high platinum loading (typically greater than 0.4 mg / cm²) to achieve the desired power density, which makes catalyst costs account for nearly 30-40% of the total fuel cell stack cost. Reducing the amount of platinum used, i.e., increasing the mass activity (MA) of platinum, is one of the keys to promoting the commercialization of PEMFCs.

[0005] Insufficient stability: Under the harsh conditions of acidic, high-potential, and electrochemical cycling in actual fuel cell operation, Pt / C catalysts undergo a series of degradation processes. These processes mainly include: dissolution and redeposition of platinum nanoparticles (Ostwald ripening), leading to increased particle size and reduced electrochemically active surface area (ECSA); migration and agglomeration of platinum particles, also resulting in loss of active surface area; and electrochemical oxidation and corrosion of the carbon support, especially under high-potential transient conditions such as vehicle start-up / stop, where corrosion of the carbon support can cause platinum particles to detach, leading to permanent degradation of catalyst performance.

[0006] To address these challenges, researchers have focused on developing novel, highly active, and stable ORR electrocatalysts. Among these, alloying platinum with one or more inexpensive 3d transition metals (such as iron, cobalt, and nickel) has proven to be a highly effective technical approach. Pt-M (M = Fe, Co, Ni) alloy catalysts exhibit significantly enhanced intrinsic ORR activity compared to pure Pt catalysts. This enhanced activity is primarily attributed to the following mechanisms: Electronic Effect: The introduction of transition metals alters the d-band electronic structure of Pt atoms. Typically, transition metals donate electrons to Pt, causing the d-band center of Pt to shift downwards, thereby weakening the adsorption strength of oxygen-containing intermediates (such as *OH) on the Pt surface. In the ORR process, the strong adsorption of intermediates such as *OH at Pt active sites is one of the rate-determining steps; weakening this adsorption effectively releases the active sites, thus significantly improving the ORR kinetic rate. Geometric Effect: The introduction of transition metal atoms alters the atomic arrangement on the Pt surface. On the one hand, the entry of smaller-radius atoms such as Co into the Pt lattice leads to lattice contraction and a reduction in Pt-Pt atomic spacing. This strain effect also modulates the d-band structure, optimizing the adsorption energy for reaction intermediates. On the other hand, on the surface of alloy nanoparticles, Pt atoms may exhibit a unique arrangement, providing more highly active reaction sites. Structural stability: The formation of alloy structures, especially highly ordered intermetallic compound structures (such as L10 phase PtCo), can significantly improve the structural stability of the catalyst. The alternating arrangement of Pt and Co atoms in the ordered structure enhances the interatomic bonding, thereby inhibiting the leaching of Co and the dissolution of Pt in acidic environments, resulting in superior durability of the catalyst during long-term operation.

[0007] Among numerous Pt-M alloy systems, PtCo alloys have attracted considerable attention due to their excellent ORR activity and relatively good stability. Currently, various methods exist for preparing PtCo / C alloy catalysts, including impregnation reduction, hydrothermal / solvothermal methods, microwave-assisted methods, and polyol reduction methods. However, these methods still present challenges in controlling the size, morphology, elemental distribution, and alloying degree of nanoparticles, often requiring complex multi-step synthesis or stringent post-treatment (such as high-temperature annealing) to obtain ideal performance, which is detrimental to industrial-scale production.

[0008] The direct synthesis of supported, highly alloyed PtCo / C catalysts and the systematic optimization of their electrochemical performance remain a challenging yet highly valuable research topic. In particular, achieving simultaneous reduction and uniform alloying of Pt and Co precursors within this system, efficiently and firmly loading the resulting nano-alloy particles onto the carbon support surface, and ensuring the final catalyst exhibits excellent electrochemical activity and unprecedented stability are pressing technical challenges that need to be addressed in this field. Summary of the Invention

[0009] This invention provides a highly active and stable carbon-supported platinum-cobalt alloy oxygen reduction electrocatalyst. The catalyst comprises PtCo alloy nanoparticles supported on a carbon support, wherein the atomic molar ratio of Pt to Co (Pt / Co) is 1:2-6:1, preferably 1:1-3:1; the average particle size of the PtCo alloy nanoparticles is 5 nm-12 nm, preferably 6 nm-8 nm; the carbon support is activated carbon with high specific surface area and good conductivity, wherein the specific surface area of ​​the activated carbon is 218-254 m² / g, and the conductivity is 2.5-2.8 S / cm, preferably Ketjen Black or Vulcan XC-72 carbon black. In a preferred embodiment of this invention, Cabot 72R carbon powder is used. In this document, "carbon support" and "carbon" are used interchangeably.

[0010] The present invention also provides a method for preparing the catalyst, the method comprising: S1: Mix platinum precursor, cobalt precursor and carbon support to form a suspension mixture, and add organic solvent and surfactant to the mixture; S2: Heat the mixture system obtained in S1 to 120~160 ℃, preferably 140-150 ℃, and stir for 1 hour under open conditions or with a small amount of air introduced; S3: Under an inert atmosphere, raise the temperature of the reaction system to 260-290 ℃, preferably 270-285 ℃, and react for 1-5 hours, preferably 1.5-3 hours; S4: Solid-liquid separation, washing and drying the solid product to obtain a black solid product.

[0011] in, Step S1: This step involves mixing and pretreating the reactants. The platinum precursor is selected from platinum acetylacetonate, chloroplatinic acid, and diaminodinitroplatinum, preferably chloroplatinic acid; the cobalt precursor is an organometallic salt with good solubility in organic solvents, selected from cobalt acetylacetonate(II), cobalt acetylacetonate(III), cobalt oleate, or cobalt carbonyl. In one specific embodiment, cobalt acetylacetonate(II) was used.

[0012] The atomic molar ratio of Pt to Co in the final product can be precisely controlled by adjusting the amounts of chloroplatinic acid and cobalt acetylacetonate. This invention can cover a wide range of Pt / Co = 0.5 to 6, preferably within the range of Pt / Co = 1 to 3.

[0013] The carbon support has a specific surface area of ​​218-254 m² / g and a conductivity of 2.5-2.8 S / cm. It is preferably Ketjen Black or Vulcan XC-72 carbon black. In one specific embodiment, Cabot 72R toner was used.

[0014] For carbon supports, acid treatment can be performed. For example, reflux treatment in concentrated nitric acid can remove metallic impurities and introduce oxygen-containing functional groups as anchoring sites for nanoparticles, but this is not a necessary step.

[0015] The organic solvent is 1-octadecene (ODE), 9-octadecene, n-hexadecane, or squalane. The amount of solvent added is sufficient to form a stirable slurry. In one specific embodiment, 100 mL of 1-octadecene is added.

[0016] The surfactant is oleylamine (OAm), hexadecylamine, or octadecylamine. In one specific embodiment, 10 mL of oleylamine is added. The ratio (volume ratio) of surfactant to organic solvent is 1:5 to 1:20.

[0017] Step S2 is a low-temperature dehydration and solvent preheating step. The main purpose of this step is to evaporate and remove moisture and other potential low-boiling-point impurities introduced into the chloroplatinic acid aqueous solution. In high-temperature organic phase reactions, the presence of water can interfere with the reaction mechanism, potentially leading to the formation of metal oxides or affecting the nucleation process of nanoparticles. Step S2 also ensures that the carbon powder is adequately wetted and dispersed in the solvent and surfactant system (such as oleylamine and octadecene), providing a foundation for the uniform loading of nanoparticles. It may also allow the metal precursor to undergo initial coordination with organic amine molecules (surfactants), forming more stable metal-amine complexes, which facilitates subsequent simultaneous thermal decomposition at higher temperatures.

[0018] Step S3 is a high-temperature co-reduction and alloying step. The inert gas is selected from nitrogen or argon. In step S3, the precursors of platinum and cobalt (which may have been converted into complexes with oleylamine) undergo thermal decomposition, releasing metal ions. Besides acting as a surfactant, oleylamine also acts as the main reducing agent, reducing the metal ions generated during decomposition to zero-valent metal atoms. In this stage, zero-valent Pt and Co atoms undergo heterogeneous nucleation on the carbon support surface, subsequently growing through atomic deposition to form PtCo alloy nanoparticles.

[0019] The dynamic adsorption-desorption equilibrium of oleylamine molecules effectively controls the particle growth rate and final size, preventing uncontrolled particle growth and agglomeration. The high-temperature environment promotes the interdiffusion and lattice intercalation of Pt and Co atoms, forming a highly alloyed solid solution structure, which is key to achieving high performance. Reaction time and temperature are important parameters for controlling the degree of alloying and particle crystallinity.

[0020] Step S4 is the post-processing step, including product separation, purification, and drying. The solid-liquid separation uses conventional methods, such as filtration or centrifugation, to separate the solid product from the liquid phase. The washing operation employs a solvent gradient washing method: first, washing 2-10 times with a non-polar solvent (such as n-hexane, toluene, or cyclohexane), for example, washing with 50-100 mL of n-hexane and centrifuging 3-5 times. Then, washing 2-10 times with a polar solvent (such as ethanol, acetone, or isopropanol) to remove oleylamine and other polar impurities. For example, washing with 50-100 mL of anhydrous ethanol and centrifuging 3-5 times. Finally, washing 1-5 times with deionized water to remove water-soluble impurities such as inorganic salts. After each wash, solid-liquid separation is performed to collect the solid. For example, centrifugation (e.g., 5000-8000 rpm, 10 minutes) is used to collect the solid and decan the supernatant. The drying process involves placing the cleaned catalyst powder in a vacuum oven and drying it under vacuum at 60-80°C overnight (at least 12 hours) to obtain the final PtCo / C catalyst powder.

[0021] The catalyst disclosed in this application exhibits the following electrochemical performance: In a 0.1 M perchloric acid (HClO4) electrolyte, the electrochemically active surface area (ECSA), measured by cyclic voltammetry, ranged from 50 m² / g Pt to 70 m² / g Pt. The oxygen reduction reaction half-wave potential (E0) in a 0.1 M HClO4 electrolyte, measured by rotating disk electrode (RDE) at 1600 rpm, was also measured. 1 / 2The maximum value is preferably above 910 mV, within the range of 900 mV to 930 mV (relative to the reversible hydrogen electrode RHE). The mass activity (MA) at 0.9 V vs. RHE is in the range of 0.5 A / mg_Pt to 1.5 A / mg_Pt. After 30,000 cyclic voltammetric scans (e.g., accelerated stability testing at a rate of 500 mV / s within a potential window of 0.6 V to 1.0 V vs. RHE), both the ECSA and MA exhibit a decay rate of less than 10%.

[0022] (III) Beneficial Effects Compared with the prior art, the PtCo / C electrocatalyst and its preparation method provided by the present invention have the following significant advantages: 1. Superior Catalytic Activity: The PtCo / C catalyst prepared in this invention exhibits a high half-wave potential of 900-930 mV and a mass activity of 0.5-1.5 A / mgPt (at 0.9 V vs. RHE). This performance far surpasses that of currently available commercial Pt / C catalysts (whose half-wave potential is typically around 850-870 mV and mass activity is approximately 0.1-0.3 A / mgPt). For example, compared to commercial catalysts such as Johnson Matthey's HiSPEC4000 or TKK's TEC10E50E under the same conditions, the catalyst of this invention demonstrates a positive half-wave potential shift of at least 20 mV and a 2-5 times increase in mass activity. This means that while achieving the same battery output power, the amount of platinum used can be significantly reduced, thereby significantly lowering the cost of fuel cells.

[0023] 2. Unprecedented Stability: After rigorous 30,000 cycles of accelerated voltammetry aging test, the ECSA and MA degradation rates of the catalyst of this invention were both controlled within 10%, or even almost non-existent. In contrast, commercial Pt / C catalysts typically experience performance degradation of more than 30-50% under the same or milder conditions (e.g., 5000-10000 cycles). This exceptional stability is attributed to: (a) the highly alloyed structure inhibiting the dissolution of Co and Pt; (b) the larger particle size of 5-12 nm, which, according to the Kelvin equation, has a lower surface energy and stronger resistance to dissolution and aging compared to the 3-5 nm small particles commonly found in commercial Pt / C; and (c) the high-temperature organic phase synthesis method may have formed stronger interactions between the nanoparticles and the carbon support, enhancing the resistance to particle shedding.

[0024] 3. Optimized Active Site Utilization: Although the particle size of the catalyst in this invention (5-12 nm) is larger than that of commercial Pt / C catalysts (3-5 nm), resulting in a slightly lower ECSA (50-70 m² / g_Pt) compared to the latter (typically 70-90 m² / g_Pt), its mass activity and specific activity (SA) are significantly improved. This indicates that this invention successfully enhances the intrinsic catalytic capacity (i.e., turnover rate) of each exposed Pt active site through alloying, achieving a shift from "quantity-based" to "quality-based" approaches, representing a more efficient strategy for utilizing precious metals.

[0025] 4. The "one-pot" synthesis process greatly simplifies the preparation process, integrating multiple steps such as carbon support loading, metal precursor reduction, and alloy nanoparticle nucleation and growth into a single reactor. The reaction conditions are mild, easy to control, and highly reproducible. This method avoids the additional high-temperature annealing step that may be required in traditional methods, reducing energy consumption and preventing severe particle agglomeration problems that can occur with annealing. Therefore, the method of this invention is not only suitable for precise laboratory-scale preparation but also lays a solid technical foundation for the large-scale production of this high-performance catalyst. Attached Figure Description

[0026] Figure 1 This is a transmission electron microscope (TEM) image of the Catalyst-A catalyst from Example 1.

[0027] Figure 2 This is a transmission electron microscope (TEM) image of the Catalyst-B catalyst in Example 2.

[0028] Figure 3 This is a transmission electron microscope (TEM) image of the JM-40 catalyst.

[0029] Figure 4 The graph shows the electrochemical active surface area (ECSA) test results of Catalyst-A in Example 1.

[0030] Figure 5 The graph shows the electrochemical active surface area (ECSA) test results of Catalyst-B in Example 2.

[0031] Figure 6 The graph shows the electrochemical active surface area (ECSA) test results for JM-40.

[0032] Figure 7 The graph shows the test results of the oxygen reduction reaction (ORR) activity test of Catalyst-A in Example 1.

[0033] Figure 8The graph shows the test results of the oxygen reduction reaction (ORR) activity test of Catalyst-B in Example 2.

[0034] Figure 9 The graph shows the test results of the oxygen reduction reaction (ORR) activity test of JM-40.

[0035] Figure 10 The figure shows the stability test results of the Catalyst-A catalyst in Example 1.

[0036] Figure 11 The figure shows the stability test results of the JM-40 catalyst. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of protection of this invention.

[0038] Experimental raw materials and equipment: Chloroplatinic acid hydrate (H2PtCl6·6H2O, Pt content ≥37.5%), Aladdin reagent.

[0039] Cobalt(II) acetylacetonate (Co(acac)2), analytical grade, TCI Chemicals.

[0040] 1-Octadecene (ODE, 90%), Alfa Aesar.

[0041] Oleylamine (OAm, 80-90%), Sigma-Aldrich.

[0042] Cabot Vulcan XC-72R carbon black (Cabot Corp.).

[0043] Other solvents, such as n-hexane and anhydrous ethanol, were of analytical grade.

[0044] Main equipment: three-necked round-bottom flask, magnetic heating stirrer, condenser, vacuum pump, centrifuge, vacuum drying oven, electrochemical workstation (CHI or Bio-Logic), rotating disk electrode device (PINE Research).

[0045] Example 1: Preparation of a PtCo / C catalyst with a Pt / Co atomic ratio of approximately 1:1 1. Material Preparation and Mixing: Accurately weigh 1.31 g of chloroplatinic acid hydrate (H₂PtCl₆·6H₂O, equivalent to 0.5 g Pt, approximately 2.56 mmol) and dissolve it in 5 mL of deionized water to obtain an orange-yellow solution. Accurately weigh 0.66 g of cobalt(II) acetylacetonate (Co(acac)₂, approximately 0.86 mmol) and 1.0 g of Cabot XC-72R toner. Add all the above solids and solutions together to a 250 mL three-necked flask.

[0046] 2. Add the organic phase: Add 100 mL of 1-octadecene (ODE) and 10 mL of oleylamine (OAm) to the flask. Attach a mechanical stirrer or add a sufficiently large magnetic stir bar.

[0047] 3. Dehydration pretreatment: Place the three-necked flask in an oil bath and connect the condenser (without cooling water to prevent excessive solvent evaporation). Under normal pressure and open conditions, start stirring and slowly heat the system to 140°C, then maintain this temperature and stir for 1 hour. Bubbles will be observed emerging from the system, indicating that water is evaporating.

[0048] 4. High-temperature synthesis: After 1 hour, immediately introduce high-purity nitrogen gas into the reaction system (flow rate approximately 50 mL / min), and raise the oil bath temperature to 280°C (heating rate approximately 10°C / min). Stir continuously at 280°C and react for 2 hours. During the reaction, the system color will gradually turn into a uniform black.

[0049] 5. Product purification: After the reaction is complete, remove the oil bath and allow the reaction system to cool naturally to room temperature under nitrogen protection. Transfer the black suspension in the flask to multiple 50 mL centrifuge tubes.

[0050] Step 5a: Add approximately 40 mL of n-hexane to each centrifuge tube and vortex vigorously to mix thoroughly. Then centrifuge at 6000 rpm for 10 minutes and carefully discard the dark supernatant. Repeat this n-hexane wash-centrifugation step a total of 3 times.

[0051] Step 5b: Add approximately 40 mL of anhydrous ethanol to the precipitate in the centrifuge tube and sonicate for 15 minutes to form a homogeneous suspension. Then centrifuge at 6000 rpm for 10 minutes and discard the supernatant. Repeat this ethanol washing-centrifugation step a total of 3 times.

[0052] 6. Drying: Collect the cleaned black solid powder in a petri dish, place it in a vacuum oven, and dry it under vacuum at 60°C for 12 hours to obtain the final PtCo / C catalyst powder, denoted as Catalyst-A.

[0053] Example 2: Preparation of a PtCo / C catalyst with a Pt / Co atomic ratio of approximately 1:3 All steps of Example 1 were repeated, except that the amount of cobalt(II) acetylacetonate was adjusted to 1.98 g (approximately 5.94 mmol) in step 1. The resulting catalyst was designated Catalyst-B.

[0054] Comparative Example: Commercial Pt / C Catalyst Commercially available Johnson Matthey Hispec 4000 catalyst (40 wt% Pt / C, average platinum particle size approximately 4 nm), denoted as JM-40, was selected as the benchmark for performance comparison. This type of commercial catalyst has been used as a comparative example in numerous publications.

[0055] Test Example: Characterization of the Physicochemical Properties of Catalysts The catalysts Catalyst-A, Catalyst-B, and the commercial catalyst JM-40 prepared above were characterized in a series of ways.

[0056] Transmission electron microscopy (TEM): Catalyst-A, Catalyst-B, and JM-40 products were tested respectively. See [link to TEM results]. Figure 1-3 The results showed that Catalyst-A (see...) Figure 1 ) and Catalyst-B (see Figure 2 The nanoparticles in Catalyst-A were uniformly dispersed on the carbon support surface, with almost no obvious aggregation observed. Statistical analysis of at least 200 particles yielded an average particle size of 6.5 ± 0.7 nm for Catalyst-A and 10.9 ± 0.8 nm for Catalyst-B, both within the target range of 5–12 nm. In contrast, JM-40 exhibited smaller particle size and a wider distribution, averaging approximately 4 nm (see [link to relevant documentation]). Figure 3 ).

[0057] Inductively coupled plasma atomic emission spectrometry (ICP-AES) was used to determine the actual loading and atomic ratio of Pt and Co in the catalysts. The results showed that the Pt / Co atomic ratio of Catalyst-A was 1:1.1 and that of Catalyst-B was 1:2.9, which was basically consistent with the feed ratio, proving that the preparation method is precise and effective in controlling the composition.

[0058] Performance testing example: Electrochemical performance testing 1. Preparation of catalyst ink Accurately weigh 5.0 mg of catalyst powder into a 2 mL glass bottle. Add 500 μL of isopropanol, 500 μL of deionized water, and 40 μL of 5 wt% Nafion® solution (DuPont). Treat the mixture in an ultrasonic cleaner for at least 60 minutes to form a uniform, stable black catalyst ink.

[0059] 2. Electrochemical testing All tests were performed in a standard three-electrode system. The working electrode was a glassy carbon rotating disk electrode coated with catalyst (GCE-RDE, 5 mm in diameter), the counter electrode was a graphite rod, and the reference electrode was a saturated calomel electrode (SCE). All potentials were ultimately converted to the reversible hydrogen electrode (RHE) scale. The electrolyte was a 0.1 M HClO4 solution.

[0060] 2.1 Electrochemical Active Surface Area (ECSA) Test: High-purity N2 was bubbled into the electrolyte for at least 30 minutes to remove oxygen. Cyclic voltammetry (CV) scans were performed at a scan rate of 100 mV / s within the potential range of 0.05 V to 1.1 V vs. RHE until the curve stabilized. ECSA was calculated by integrating the charge in the hydrogen adsorption / desorption peak (H-upd) region (0.05–0.4 V) and assuming a charge density of 210 μC / cm²_Pt for monolayer hydrogen adsorption.

[0061] Catalyst-A: ECSA = 65.0 m² / gPt.

[0062] Catalyst-B: ECSA = 53.6 m² / gPt.

[0063] JM-40: ECSA =72.4 m² / gPt.

[0064] The results show that, due to the larger particle size, the ECSA value of the alloy catalyst prepared in this invention is slightly lower than that of commercial catalysts, but still remains at a high level (50-70 m² / gPt). See [link to specific test results] for details. Figure 4-6 . 2.2 Oxygen Reduction Reaction (ORR) Activity Test: High-purity O2 was bubbled into the electrolyte for at least 30 minutes until saturation. Linear scan voltammetry (LSV) was performed at 1600 rpm, from 1.1 V to 0.2 V vs. RHE, at a scan rate of 10 mV / s.

[0065] Half-wave potential (E) 1 / 2 ): Catalyst-A: 922 mV Catalyst-B: 912 mV JM-40: 879 mV Mass activity (MA @ 0.9 V): The kinetic current (Ik) was obtained by processing the LSV data using the Koutecky-Levich equation. k ), and then calculate the mass activity.

[0066] Catalyst-A: 1.33A / mgPt Catalyst-B: 0.89 A / mgPt JM-40: 0.29 A / mgPt See test results Figure 7-9 The test results clearly show that the ORR activities of the PtCo / C (Catalyst-A) and PtCo3 / C (Catalyst-B) catalysts prepared in this invention far exceed those of the commercial JM-40 catalyst. Among them, Catalyst-A has the best performance, with its half-wave potential shifted positively by 43 mV compared to JM-40, and its mass activity improved by about 4.6 times.

[0067] 2.3 Stability Testing (Accelerated Aging Test, ADT): Cyclic voltammetry was performed in a N2-saturated 0.1 M HClO4 electrolyte at a scan rate of 500 mV / s for a total of 30,000 cycles within a potential window of 0.6 V to 1.0 V vs. RHE. This test condition simulates the potential fluctuations under the start-stop conditions of a fuel cell vehicle and can effectively evaluate the catalyst durability. ECSA and ORR activities were tested before and after ADT. Figure 10 The results are the stability test results of the Catalyst-A catalyst in Example 1. Figure 11 The test results are for the JM-40 catalyst.

[0068] Catalyst-A: ECSA attenuation: 1.8% E 1 / 2 Negative shift: 1 mV MA (@0.9V) attenuation: 1%.

[0069] JM-40: ECSA attenuation: 40.6% E 1 / 2 Negative shift: 28 mV MA (@0.9V) attenuation: 48.3%.

[0070] The stability test results convincingly demonstrate the exceptional durability of the catalyst of this invention. After undergoing 30,000 rigorous potential cycles, the performance indicators of Catalyst-A showed a decline of less than 10%, while the commercial JM-40 catalyst exhibited severe performance degradation. This fully demonstrates that the PtCo alloy catalyst obtained by the preparation method of this invention has unparalleled advantages in both structure and chemical stability.

[0071] In summary, this invention discloses an innovative technical solution for preparing carbon-supported platinum-cobalt alloy ORR electrocatalysts based on an octadecene-oleylamine high-temperature liquid-phase method. This method features a simple process flow, strong controllability, and can stably prepare PtCo / C alloy catalysts with particle sizes of 5-12 nm and tunable compositions. Detailed physicochemical characterization and rigorous electrochemical performance evaluation, along with comparisons with commercial catalysts, demonstrate that the catalyst prepared by this invention exhibits significant and groundbreaking advantages in both ORR activity (half-wave potential and mass activity) and stability. The success of this invention provides a practical technical route for developing next-generation high-performance, low-cost, and long-life fuel cell cathode catalysts, possessing significant scientific value and broad commercial application prospects.

Claims

1. A carbon-supported platinum-cobalt alloy oxygen reduction electrocatalyst, wherein the catalyst is composed of PtCo alloy nanoparticles supported on a carbon support, wherein, The atomic molar ratio of Pt to Co (Pt / Co) is 1:2-6:1, and the average particle size of the PtCo alloy nanoparticles is 5 nm-12 nm; the carbon support is activated carbon with high specific surface area and good conductivity, the specific surface area of ​​which is 218-254 m² / g and the conductivity is 2.5-2.8 S / cm.

2. The catalyst according to claim 1, characterized in that, The catalyst is composed of PtCo alloy nanoparticles supported on a carbon support, wherein the atomic molar ratio of Pt to Co (Pt / Co) is 1:1-3:1; the average particle size of the PtCo alloy nanoparticles is 6 nm-8 nm; and the carbon support is Ketjen black or Vulcan XC-72 carbon black.

3. A method for preparing the carbon-supported platinum-cobalt alloy oxygen reduction electrocatalyst as described in claim 1 or 2, the method comprising: S1: Mix platinum precursor, cobalt precursor and carbon support to form a suspension mixture, and add organic solvent and surfactant to the mixture; S2: Heat the mixture system obtained in S1 to 120~160 ℃, preferably 140-150 ℃, and stir for 1 hour under open conditions or with a small amount of air introduced; S3: Under an inert atmosphere, raise the temperature of the reaction system to 260-290 ℃, preferably 270-285 ℃, and react for 1-5 hours, preferably 1.5-3 hours; S4: Solid-liquid separation, washing and drying the solid product to obtain a black solid product; The platinum precursor is selected from platinum acetylacetonate, chloroplatinic acid and diaminodinitroplatinum, and the cobalt precursor is an organometallic salt with good solubility in organic solvents. The carbon carrier is activated carbon with a specific surface area of ​​218-254 m² / g and a conductivity of 2.5-2.8 S / cm. The organic phase solvent is 1-octadecene, 9-octadecene, n-hexadecane, or squalane; the surfactant is oleylamine, hexadecamine, or octadecamine.

4. The method as described in claim 3, characterized in that: The platinum precursor is chloroplatinic acid; the cobalt precursor is cobalt acetylacetonate (II), cobalt acetylacetonate (III), cobalt oleate, or cobalt carbonyl. The carbon carrier is Ketjen black or Vulcan XC-72 carbon black; The volume ratio of surfactant to organic solvent is 1:5 to 1:

20.

5. The method as described in claim 3 or 4, wherein, The carbon support is pretreated with acid.

6. The method as described in claim 3 or 4, wherein, In step S3, the inert gas is selected from nitrogen or argon.

7. The method as described in claim 3 or 4, wherein, In step S4, the solid-liquid separation is a conventional separation method that separates the solid product from the liquid phase; The washing operation employs a solvent gradient washing method, which includes: first, washing 2-10 times with a non-polar solvent; then, washing 2-10 times with a polar solvent; and finally, washing 1-5 times with deionized water. The drying process involves placing the cleaned catalyst powder in a vacuum oven and drying it overnight at 60-80°C to obtain the final PtCo / C catalyst powder.

8. The method of claim 7, wherein, Nonpolar solvents are selected from n-hexane, toluene, or cyclohexane; polar solvents are selected from ethanol, acetone, or isopropanol.

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