Unveiling the Structure-Performance Relationship in Ruthenium-Based Anode Catalysts for PEM Water Electrolyzers

Ruthenium (Ru) based electrocatalysts are considered cost-effective alternatives to expensive iridium (Ir)-based anode catalysts in proton exchange membrane water electrolyzers (PEMWEs), due to their lower cost and high catalytic activity. However, these catalysts suffer from poor stability mainly due to metal dissolution, overoxidation, and lattice oxygen activation. Therefore, a detailed understanding of structure-performance relationships in Ru-based catalysts is crucial to develop robust catalysts for PEMWEs. Herein, a comprehensive discussion on geometric and electronic structural parameters reveals a direct correlation with catalyst performance. A detailed analysis of dynamic intrinsic structural transformation related to Ru-O bonding under different reaction mechanisms provides understanding of Ru catalyst degradation. Similarly, recent advances in Ru-based catalysts, including Ru single atoms, Ru alloys with noble and non-noble metals, heteroatom doping strategies, and strong metal support interactions, demonstrate a significant impact of structural and compositional tuning on catalytic performance. These modifications influence active-site dynamics, Ru-O covalency, and surface regeneration, which play crucial roles in enhancing catalytic performance. More importantly, single-cell performance combined with reaction mechanistic insights helps to identify the key stabilizing factors to develop robust catalysts for long-term durability in PEMWEs. Finally, future perspectives are outlined to design durable and cost-effective Ru-based catalysts for PEMWEs.