Multitasking-Effect Ca Ions Triggered Symmetry-Breaking of RuO₂ Coordination for Acidic Oxygen Evolution Reaction

The development of highly active and stable electrocatalysts for the acid oxygen evolution reaction (OER) is both appealing and challenging. The generation of defects is an emerging strategy for improving the water oxidation efficiency. Herein, we introduced multitasking Ca ions to trigger oxygen vacancies in RuO₂, resulting in vacancy-rich RuO₂ (RuO₂-O_v) nanoparticles with enhanced and sustainable OER activity. The oxygen vacancy in RuO₂-O_v breaks the symmetry of the RuO₆ octahedron, enhancing the d-band center of Ru and reducing the level of 4d-2p hybridization in Ru-O bonds. This effectively optimizes intermediate adsorption and inhibits Ru dissolution. The RuO₂-O_V catalyst achieves a current density of 10 mA/cm² with an overpotential of only 198 mV, stabilizing for over 100 h (degradation rate: 0.2 mV/h). Its mass activity is 17.9 times higher than that of commercial RuO₂. Our work highlights that multitasking atomic construction defect engineering effectively balances the seesaw relationship between catalytic activity and stability.