Contemporaneous Inverse Manipulation Of The Valence Configuration To Preferred Co2+ And Ni3+ For Enhanced Overall Water Electrocatalysis

Valence configurations of active sites are essential for modulating the electronic structure of the non-noble metal electrocatalysts in water splitting. However, synchronously engineering the valence states of different elements to inverse ones has been a key challenge in the integrated synthesis environment. Herein, for the first time, a novel superstructure of inverse spinel NiCoFe oxide nanocubes with contemporaneous valence regulation to preferred Co2+ and Ni3+ ((NiCoFe)-Co-III-Fe-II-O@NF, NF stands for nickel foam), has been developed by in situ topotactic chemical transformation. (NiCoII)-Co-III Fe-O@NF can attain a current density of 10 mA cm(-2) at a low cell voltage of 1.455 V in 1 M KOH when used as bifunctional catalysts. Density functional theory calculations suggested that the favorable Co2+ and Ni3+ act synergistically to lower down Delta G(H)* for HER and the OER overpotential in an optimal pathway. Our study probes the construction and understanding of the heterogeneous valence configuration in a single phase.