Grain Boundary Engineering in Multicomponent Metal Oxides for the Simultaneous Generation of Effective Chlorine and Reactive Oxygen Species

Effective chlorine and reactive oxygen species (ROS) are vital for oxidative wastewater remediation, yet conventional electrocatalysts often face activity and selectivity trade-offs. Here, a grain boundary (GB) engineering strategy is used to construct RuIrSnCoNbOx multicomponent oxides, achieving 97.0% Faradaic efficiency (FE) and over 1400 h of stability for chlorine evolution under acidic conditions. The electrocatalyst also enables simultaneous generation of effective chlorine and ROS in simulated tap water, sustaining 87.7% FE with stability approaching 160 h. Density functional theory (DFT) reveals that the RuIrSnCoNbOx GB structure facilitates dual pathways, with chlorine produced via OCl* (ηTD = 0.96 V) and ROS via the adsorbate evolution mechanism (ηTD = 1.08 V), consistent with in situ *OOH detection. Integrated into a continuous flow electrolyzer, the system ensures efficient mass transport and active zone utilization, achieving around 99% pollutant removal. This work highlights a GB engineering route to efficient and durable electrocatalysts for water treatment.