▎ 摘　　要

An N-doped graphene wrapped metallic Co nanosheet-on-nanosheet structure with a thickness of sub-4 nm and a high percentage of hexagonal Co phase as an efficient water oxidation electrocatalyst is presented. This sample exhibits an onset overpotential of 290 mV and performs comparably to RuO2 at high current density due to the unique hexagonal Co and the wrapped N-doped graphene.