Experimental and numerical efforts to improve oxygen mass transport in porous catalyst layer of proton exchange membrane fuel cells

The effective management of oxygen transport resistance (OTR) within the cathode catalyst layer (CCL) is crucial for achieving a high catalyst performance at low platinum (Pt) loading. Over the past two decades, significant advancements have been made in the development of various high active platinum-based catalysts, aiming at enhancing oxygen mass transport and the oxygen reduction reaction (ORR). However, experimental investigations of transport processes in porous media are often computational costs and restrained by limitations in in-situ measurement capabilities, as well as spatial and temporal resolution. Fortunately, numerical simulation provides a valuable alternative for unveiling the intricate relationship between local transport properties and overall cell performance that remain unresolved or uncoupled through experimental approach. In this review, we elucidate the primary experimental and numerical efforts undertaken to improve OTR. We consolidate the available literature on OTR values and perform a quantitative comparison of the effectiveness of different strategies in mitigating OTR. Furthermore, we analyze the intrinsic limitations and challenges associated with current experimental and numerical methods. Finally, we outline future prospect for advancements in both experimental techniques and modelling methods.