Operando Insights into Bridging Oxygen-Driven RuO_x Lattice Collapse and its Mitigation Strategy for Durable...

Ruthenium oxide (RuO_x) is a promising anode catalyst for proton exchange membrane water electrolysis (PEMWE), but its degradation mechanism, especially under practical ampere-level operation, remains elusive. Herein, we established a device-level diagnostic framework to investigate the evolution of RuO_x. Operando PEMWE-based X-ray absorption spectroscopy (XAS) revealed a progressive negative shift of the Ru K-edge. Extended X-ray absorption fine structure (EXAFS) analysis further showed a pronounced decrease in both Ru-O and Ru-O-Ru coordination, revealing that irreversible loss of bridging oxygen (O_bridge) triggers the final catalyst deactivation. Guided by these insights, we demonstrated that low-level Ir doping in Ru_0.9Ir_0.1O_x could notably increase the O_bridge vacancy formation energy and thus stabilize the Ru-O framework. Under identical PEMWE operating conditions, the Ru valence state and coordination environment in Ru_0.9Ir_0.1O_x remain relatively stable. In-cell electrochemical impedance spectroscopy (EIS) and distribution of relaxation time (DRT) analyses confirmed that this structural stabilization strategy effectively maintains low electrode kinetic and proton transport resistances across a range of cell voltages, enabling stable operation at industrially relevant ampere-level current densities. Finally, the resulting Ru_0.9Ir_0.1O_x catalyst achieves 1.74 V at 3 A cm^-2 and stably operates for 500 h at 1 A cm^-2, outperforming most reported Ru-based anodes.