Abstract: Platinum-carbon (Pt/C) catalyst is one of the most promising cathode materials for proton exchange membrane fuel cells (PEMFCs). However, it faces significant durability challenges, primarily due to the growth and agglomeration of platinum nanoparticles (Pt NPs), which results in increased Pt particle size and consequent loss of catalytic activity. In this study, an internally pearl-like mesoporous carbon (IPMC) support with beaded pore channels was constructed to investigate the deposition sites of Pt NPs within carbon supports. Through precisely confining Pt NPs within the pore channels by leveraging the unique pore architecture, efficient confinement and stabilization of Pt NPs were achieved. The average size of Pt NPs in IPMC increased by only 0.46 nm after 30000 cycles of accelerated durability tests (ADT), significantly less than the growth (0.79 nm) observed in conventional solid carbon-supported catalysts. The IPMC-based catalyst also exhibited slower electrochemical performance decay. The electrochemical active area (ECSA) loss rate of the mesoporous carbon catalyst was 24.18%, significantly lower than the 32.33% observed for solid carbon catalysts in comparative testing. This superior durability originates from the unique pore structure of IPMC, which imposes spatial confinement effects that effectively suppress Ostwald ripening and migration of Pt NPs, thereby mitigating the degradation of oxygen reduction reaction (ORR) activity. This work delivers a precise structural blueprint for optimal carbon carriers by revealing how beaded mesopores confine platinum nanoparticles: interconnected pore channels with local constrictions form spatial barriers that hinder dissolved platinum species diffusion while anchoring particles. This work provides a precise structural blueprint for designing optimized carbon supports for high-stability PEMFC catalysts.

Key words: platinum-carbon catalyst, mesoporous carbon, durability, Ostwald ripening, ORR catalytic activity