As the pivotal half-reaction of electrolytic water for energy conversion devices, the oxygen evolution reaction (OER) with sluggish multistep electron transfer kinetics calls for the development of highly active electrocatalysts. Till now, the most widely studied OER catalysts are metal (hydro)oxides, such as IrOx , Co3O4 and NiFe layered double hydroxides (LDHs) , which usually generate amorphous layers on the surface during oxidation.