Clarifying the structure-reactivity relationship of non-noble-metal electrocatalysts is one of the decisive factors for the practical application of water electrolysis. In this field, the anodic oxygen evolution reaction (OER) with a sluggish kinetic process has become a huge challenge for large-scale production of high-purity hydrogen. Here we synthesize a layered quasi-nevskite metastable-phase cobalt oxide (LQNMP-Co2O3) nanosheet via a simple molten alkali synthesis strategy. The unit-cell parameters of LQNMP-Co2O3 are determined to be a = b = 2.81 Å and c = 6.89 Å with a space group of P3̅m1 (No. 164). The electrochemical results show that the LQNMP-Co2O3 electrocatalyst enables delivering an ultralow overpotential of 266 mV at a current density of 10 mA cmgeo-2 with excellent durability. The operando XANES and EXAFS analyses clearly reveal the origin of the OER activity and the electrochemical stability of the LQNMP-Co2O3 electrocatalyst. Density functional theory (DFT) simulations show that the energy barrier of the rate-determining step (RDS) (from *O to *OOH) is significantly reduced on the LQNMP-Co2O3 electrocatalyst by comparing with simulated monolayered CoO2 (M-CoO2).
Keywords: Cobalt oxide; Electrochemistry; Metastable phase; Operando XANES; Oxygen evolution reaction; Two-dimensional materials.