Unusual double ligand holes as catalytic active sites in LiNiO2

Abstract

AbstractDesigning 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 LiNiO2with a dominant 3d8Lconfiguration (Lis a hole at O 2p) under high oxygen pressure, and achieve a double ligand holes 3d8L2under OER since one electron removal occurs at O 2porbitals for NiIIIoxides. LiNiO2exhibits super-efficient OER activity among LiMO2,RMO3(M = transition metal,R = rare earth) and other unary 3d catalysts. Multiple in situ/operando spectroscopies reveal NiIII→NiIVtransition together with Li-removal during OER. Our theory indicates that NiIV(3d8L2) 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.