High-spin Co³⁺ in cobalt oxyhydroxide for efficient water oxidation

Cobalt oxyhydroxide (CoOOH) is a promising catalytic material for oxygen evolution reaction (OER). In the traditional CoOOH structure, Co³⁺ exhibits a low-spin state configuration (t2g6), with electron transfer occurring in face-to-face t2g orbitals. In this work, we report the successful synthesis of high-spin state Co³⁺ CoOOH structure, by introducing coordinatively unsaturated Co atoms. As compared to the low-spin state CoOOH, electron transfer in the high-spin state CoOOH occurs in apex-to-apex eg orbitals, which exhibits faster electron transfer ability. As a result, the high-spin state CoOOH performs superior OER activity with an overpotential of 226 mV at 10 mA cm⁻², which is 148 mV lower than that of the low-spin state CoOOH. This work emphasizes the effect of the spin state of Co³⁺ on OER activity of CoOOH based electrocatalysts for water splitting, and thus provides a new strategy for designing highly efficient electrocatalysts.

Xin Zhang, Haoyin Zhong, Qi Zhang, Qihan Zhang, Chao Wu, Junchen Yu, Yifan Ma, Hang An, Hao Wang, Yiming Zou, Caozheng Diao, Jingsheng Chen, Zhi Gen Yu, Shibo Xi, Xiaopeng Wang, Junmin Xue