Electrochemical and microscopic characterization of fuel cell catalyst layer degradation during accelerated stress tests: a review

The catalyst layer is an essential component of fuel cells, exerting a decisive influence on performance, particularly under degradation processes. Characterization derived from accelerated stress tests (ASTs) provide valuable insights into the long-term degradation from the perspective of changes in physical and chemical properties, thereby offering a scientific foundation for evaluating advanced materials and strategies. In this review, multidimensional and multi-characterization application scenarios based on ASTs data are systematically summarized. Firstly, the degradation mechanism of catalyst layer (CL) under AST conditions is discussed, with an emphasis on platinum aging and carbon support corrosion. In addition, electrochemical and microphysical characterization tools applicable to different AST test protocols, such as electrochemical surface area (ECSA), electrochemical impedance spectrum (EIS) mapping combined with distribution of relaxation times (DRT), and microscopic physical evolution and tracking techniques for each internal chemical component, are also presented in detail. Finally, through the existing research progress and hotspots, the application prospect of data fusion is elaborated and the important research direction of material optimization and performance prediction based on AST data is emphasized, aiming to provide insights into the study of catalytic layer degradation in fuel cells and promote the continuous development of the field.