Here, we demonstrate the enhanced water splitting activity of CoFe-LDH by vanadium substitution. Volcano plots are obtained for intrinsic water oxidation and hydrogen evolution with increasing vanadium substitution, and the best catalyst V0.3-CoFe-LDH achieved 10 mA cm-2 current density for H2 and O2 evolution merely at 98 mV and 240 mV overpotential, respectively.