Uniformly and controllably introducing oxygen vacancy (Ov) into spinel electrocatalysts is still a great challenge for the oxygen evolution reaction (OER). Herein, we demonstrate the synthesis of spinel Co3O4 mesoporous nanosheets aggregation with tunable Ov by a simple phosphorus (P) doping strategy. It is found that a trade-off between Ov and electronic conductivity plays an important role in improving OER electrocatalytic activity. The optimized Co3O4-xP0.15 electrocatalyst delivers a current density of 20 mA cm(-2) in alkaline media within a small overpotential of only 338 mV, which is much lower than the corresponding Co3O4 (395 mV) and the commercial RuO2 (368 mV) catalysts. The Tafel slope is 52 mV dec(-1) and the overpotential gives negligible increase even through 8 h OER at 10 mA cm(-2). The superior OER catalytic activity is mainly attributed to the 2D mesoporous nanosheets (rich active sites) and appropriate Ov (fast electrons transfer). This work provides a simple and effective strategy to control Ov concentration in spinel electrocatalysts for enhancing water oxidation capability. (C) 2017 Elsevier Ltd. All rights reserved.