Alkali metal-mediated interfacial charge redistribution toward near-optimal water oxidation

The optimal oxidation state and electronic structure of active sites in an electrocatalyst are critical factors for maximizing water-oxidation kinetics. To this end, we developed a heterostructured electrocatalyst for oxygen evolution reaction (OER) comprising La_0.5Sr_0.5CoO_3−δ and Li₂MoO₄ (LSC/LMO) with optimized oxidation states for active metal sites using an alkali metal mediator. The LSC/LMO system exhibited excellent OER performance (overpotential: 1.45 V at 10 mA cm⁻²) and operational durability (chronoamperometric and cyclic voltammetry stabilities of 200 h at 1.52 V and 5000 cycles). The experimental and computational analyses revealed that lithium atoms accumulated at the LSC/LMO interface exhibit a mediating function toward optimizing the oxidation state and electronic structure of OER active metal elements (cobalt and molybdenum), minimizing the free energy barrier of the rate-determining step in OER. This study provides a new insight for boosting sluggish OER kinetics in water oxidation through in situ oxidation state modulation for heterostructured electrocatalysts.