Oxygen evolution reaction (OER) is crucial for hydrogen production as well as other energy storage technologies. CoFe-layered double hydroxide (CoFe-OH) has been widely considered as one of the most efficient electrocatalysts for OER in basic aqueous solution. However, it still suffers from low activity in neutral electrolyte. This paper describes partially oxidized CoFe-OH (PO-CoFe-OH) with enhanced covalency of M-O bonds and displays enhanced OER performance under mild condition. Mechanism studies reveal the suitably enhanced M-O covalency in PO-CoFe-OH shifts the OER mechanism to lattice oxygen oxidation mechanism and also promotes the rate-limiting deprotonation, providing superior OER performance. It just requires the overpotentials of 186 and 365 mV to drive the current density densities of 1 and 10 mA·cm⁻² in 0.1 M KHCO₃ aqueous solution (pH = 8.3), respectively. It provides a new process for rational design of efficient catalysts for water oxidation in mild conditions.