Interplays between preparation and processing of the catalyst ink in the manufacturing of a proton exchange membrane fuel cell catalyst layer

Catalyst inks are essential for the fabrication of Catalyst Layers (CLs) in Proton Exchange Membrane Fuel Cell (PEMFC) electrodes. While the fabrication process appears straightforward and numerous innovations have emerged in both research and industry, a comprehensive and openly accessible framework for rational ink formulation and CL fabrication is still developing. This gap is largely due to limited public insight into the links between ink and CL properties, structure, and performance, as much industrial know-how remains proprietary. This paper first examines the preparation of catalyst inks—primarily composed of an ionomer, catalyst, solvent, and sometimes additives such as antioxidants—highlighting recent advances in understanding their properties, interactions and influence on ink behaviour and processability. The discussion then turns to ink coating techniques, such as spraying and printing, and explores how these methods impact the structural, mechanical, and chemical characteristics of the resulting CL. Drying processes are also considered, with attention to how different approaches affect final CL properties. By analysing the interplay between ink formulation, coating, and drying, this work sheds light on the feedback-driven, iterative dynamics that underpin CL fabrication in PEMFCs, aiming to guide more rational and effective design strategies.