Layered Quasi-Nevskite Metastable-Phase Cobalt Oxide Accelerates Alkaline Oxygen Evolution Reaction Kinetics.

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-Co 2 O 3 ) nanosheet via a simple molten alkali synthesis strategy. The unit-cell parameters of LQNMP-Co 2 O 3 are determined to be a = b = 2.81 Å and c = 6.89 Å with a space group of P 3̅ m 1 (No. 164). The electrochemical results show that the LQNMP-Co 2 O 3 electrocatalyst enables delivering an ultralow overpotential of 266 mV at a current density of 10 mA cm geo -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-Co 2 O 3 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-Co 2 O 3 electrocatalyst by comparing with simulated monolayered CoO 2 (M-CoO 2 ).