Optimizing the three-phase interface in proton exchange membrane fuel cells: performance bottlenecks and regulation strategies

Proton exchange membrane fuel cells (PEMFCs) hold great promise for low-carbon energy systems, yet their commercial viability is hindered by performance bottlenecks, particularly at the cathode catalyst layer (CCL). Central to the performance of PEMFCs is the triple-phase boundary (TPB), where the oxygen reduction reaction (ORR) occurs. However, achieving an ideal TPB is complicated by ionomer-induced poisoning, oxygen mass transport resistance, proton conduction discontinuities, and water management challenges. This review discusses the challenges associated with the TPB, focusing on ionomer poisoning, oxygen mass transport, proton conduction, and water management, and highlights the strategies to optimize each of these issues. It also covers recent advances in material strategies, including ionomer molecular engineering, surface functionalization of carbon supports, and catalyst design, aimed at improving TPB formation and maintaining optimal transport conditions. The study emphasizes the importance of optimizing the TPB for improving the efficiency and durability of PEMFCs, providing insights into designing next-generation low-Pt catalysts with enhanced performance.