Graphene-like holey Co3O4 nanosheets as a highly efficient catalyst for oxygen evolution reaction

•Graphene-like holey Co3O4 nanosheets are prepared via a bottom-up self-assembly approach.•The atomic thickness and mesoporosity provide numerous low-coordinated surface atoms.•The lattice structural distortion leads to the redistribution of surface electron density.•The Co3O4 nanosheets exhibit high catalytic activity towards oxygen evolution reaction.