High-Valence Metals Accelerate the Reaction Kinetics for Boosting Water Oxidation

The transition metal with high valence state in oxyhydroxides can accelerate the reaction kinetics, enabling highly intrinsic OER activity. However, the formation of high-valence transition-metal ions is thermodynamically unfavorable in most cases. Here, a novel strategy is proposed to realize the purpose and reveal the mechanism by constructing amorphous phase and incorporating of elements with the characteristic of Lewis acid or variable charge state. A model catalyst, CeO₂-NiFeO_xH_y, is presented to achieve the modulation of valence state of active site (Ni²⁺→Ni³⁺→Ni⁴⁺) for improved OER, leading to dominant active sites with high valence state. The CeO₂-NiFeO_xH_y electrode exhibits superior OER performance with overpotential of 214 and 659 mV at 10 and 500 mA cm^-2, respectively (without IR correction), and high stability, which are much better than those of NiO_xH_y, NiFeO_xH_y and CeO₂-NiO_xH_y. These findings provide an effective strategy to achieve the active metals with high-valence state for highly efficient OER.