PEFC catalyst layer: Recent advances in materials, microstructural characterization, and modeling

The cost, performance, and durability of polymer electrolyte fuel cells (PEFCs) are strongly linked to its catalyst layer. In this review, the state of the art of the three Ms—Materials, Microstructure, and Modeling—of catalyst layer research are summarized. Recent advances in catalyst layer materials including shape- and composition-controlled catalysts and two- or three-dimensional catalyst support materials are highlighted. The application of rapidly emerging high-resolution, three-dimensional imaging capabilities of X-ray and electron microscopy for the characterization of the microstructure of the catalyst layer as well as its precursor catalyst ink is presented. Recent advances and key challenges in the transport and kinetic modeling of catalyst layer are also discussed.