Cobalt oxyhydroxide (CoOOH) is a promising catalytic material for oxygen evolution reaction (OER). This work reports the synthesis of high-spin state Co³⁺ CoOOH, exhibiting faster electron transfer than low-spin CoOOH due to electron transfer in apex-to-apex eg orbitals. High-spin CoOOH shows superior OER activity (overpotential of 226 mV at 10 mA cm⁻², 148 mV lower than low-spin CoOOH), highlighting the impact of Co³⁺ spin state on OER activity and offering a new strategy for designing efficient electrocatalysts.
