Stability/Durability Challenges of Cathode Catalysts for PEM Fuel Cells: Experiments, Mechanisms, and Perspectives Beyond Three-Electrode System

Abstract

The sluggish oxygen reduction reaction (ORR) determines the performance and lifetime of Proton Exchange Membrane (PEM) fuel cells. The commercialized cathodic ORR catalyst is synthesized with platinum-group-metal (PGM)-based chemicals, which suffers from low geological reserves; As alternatives, PGM-free catalysts are emerging. However, both PGM and PGM-free catalysts suffer from insufficient stability/durability. The stability/durability test protocols for ORR catalysts, especially for PGM-free catalysts, have not been well agreed—different groups using different stability/durability test protocols in their experiments, particularly in membrane electrode assembly (MEA) tests; some false-comparison maybe overlooked by researchers. On the other hand, deep understanding of degradation mechanisms and developing efficient strategies to improve the stability/durability have become the research frontier in this field. In this regard, we herein discuss the key experimental factors influencing the accuracy of stability/durability tests in three-electrode system and MEA, and touch the critical knowledge of degradation mechanisms and materials-based solutions to improve the catalyst stability/durability. We hope such discussion will highlight the importance of stability/durability studies and promote the PEM fuel cell development.