Abstract
Designing efficient catalyst for the oxygen evolution reaction (OER) is of importance for energy conversion devices. The anionic redox allows formation of O-O bonds and offers higher OER activity than the conventional metal sites. Here, we successfully prepare LiNiO(2) with a dominant 3d(8)L configuration (L is a hole at O 2p) under high oxygen pressure, and achieve a double ligand holes 3d(8)L(2) under OER since one electron removal occurs at O 2p orbitals for Ni(III) oxides. LiNiO(2) exhibits super-efficient OER activity among LiMO(2), RMO(3) (M = transition metal, R = rare earth) and other unary 3d catalysts. Multiple in situ/operando spectroscopies reveal Ni(III)→Ni(IV) transition together with Li-removal during OER. Our theory indicates that Ni(IV) (3d(8)L(2)) leads to direct O-O coupling between lattice oxygen and *O intermediates accelerating the OER activity. These findings highlight a new way to design the lattice oxygen redox with enough ligand holes created in OER process.