Tailoring the interface engineering of the catalysts-membrane electrode assembly for advanced hydrogen fuel cells

Enhancing both the intrinsic activity of catalysts and the apparent activity of the catalytic layer within the membrane electrode assembly (MEA) is pivotal for improving the power density and cycling longevity of hydrogen fuel cells. However, major challenges remain in the precise construction of catalytic active sites, full exposure of these sites, and effective reduction of mass transport resistance at the electrode interfaces. This review provides a systematic overview of catalyst and catalytic layer design strategies for advanced hydrogen fuel cells. We begin by outlining the fundamental working principles of fuel cells, with a particular focus on the mechanisms of the oxygen reduction reaction (ORR). We then comprehensively summarize cutting-edge strategies in catalyst design, including metal-free catalysts, metal-nitrogen-carbon (M-Nx-C) catalysts, metal compound electrocatalysts, and pyrolysis-free covalent organic polymer (COP)-based catalysts. Furthermore, we explore advanced construction strategies for self-supporting catalytic layers, such as templating methods, electrospinning, and 3D printing. The review also delves into mechanistic investigation techniques crucial for boosting membrane electrode performance, encompassing theoretical calculations, data-driven machine learning, atomic-scale characterization, and in situ monitoring. Finally, we discuss the current challenges and future research directions in this field, aiming to guide the development of next-generation high-performance fuel cells.