Analysis of Ionomer Distribution and Reaction Mechanisms on Polymer Electrolyte Fuel Cell Pt Catalysts Supported on Mesoporous Carbon under Various Humidity Conditions

High Resolution Image Download MS PowerPoint Slide Mesoporous carbon-based catalysts have attracted considerable interest as promising materials for proton exchange membrane fuel cells (PEFCs), evidenced by their implementation in the Toyota MIRAI II fuel cell vehicle (FCV). This study involves the fabrication of membrane electrode assemblies (MEAs) with various ionomer-to-carbon ratios (I/C) for Pt/mesoporous carbon (MPC) catalysts, followed by an analysis of their pore formation, electrochemical properties, and polarization curve behavior. The study examines ionomer distribution, including both primary particles and the entire catalyst layer, and reveals the presence of specific adsorption via the appearance of a step in the Tafel plot. The findings clarify the reaction mechanisms of Pt/MPC catalysts under both high and low humidity conditions. They highlight the challenges associated with MPCs for FCVs, particularly under high temperature and low humidity operational conditions anticipated for heavy-duty commercial vehicles and allow us to propose strategic considerations to address these issues.