Development and Challenges of Electrode Ionomers Used in the Catalyst Layer of Proton-Exchange Membrane Fuel Cells: A Review

The electrode ionomer plays a crucial role in the catalyst layer (CL) of a proton-exchange membrane fuel cell (PEMFC) and is closely associated with the proton conduction and gas transport properties, structural stability, and water management capability. In this review, we discuss the CL structural characteristics and highlight the latest advancements in ionomer material research. Additionally, we comprehensively introduce the design concepts and exceptional performances of porous electrode ionomers, elaborate on their structural properties and functions within the fuel cell CL, and investigate their effect on the CL microstructure and performance. Finally, we present a prospective evaluation of the developments in the electrode ionomer for fabricating CL, offering valuable insights for designing and synthesizing more efficient electrode ionomer materials. By addressing these facets, this review contributes to a comprehensive understanding of the role and potential of electrode ionomers for enhancing PEMFC performance.