Bridging oxygen reduction performance gaps in half and full cells: challenges and perspectives

Electrocatalytic oxygen reduction is a core reaction in proton exchange membrane fuel cells. Oxygen reduction performance is commonly assessed using rotating disk electrode (RDE) and membrane electrode assembly (MEA) techniques. However, significant differences in experimental procedures, design setup, and operating conditions create a considerable gap in reporting and comparing the reaction kinetics and durability of oxygen reduction electrocatalysts. In this chemistry frontiers article, we discuss the differences between the test protocols and operating conditions of RDE and MEA evaluation methods and highlight their limitations. Additionally, we review intermediary techniques that can advance the half-cell evaluations, which mimic actual fuel cell conditions and have the potential to bridge the performance gaps between RDE and MEA. Finally, potential perspectives are discussed to overcome the shortcomings of individual methods and bridge the gaps for broader applications of fuel cells. We believe, this overview will provide insightful guidance toward universal evaluation and comparison of oxygen reduction performance and pave the way for broader applications of fuel cells.