Metal oxyhydroxides are regarded as active catalysts for oxygen evolution reaction (OER). Herein, we creatively report NiFeOOH is greatly activated by N-doping to get an efficient OER catalyst. The effect of N-doping in the resulted metal oxyhydroxides for the OER is revealed for the first time. N-doped NiFeOOH (N-NiFeOOH) is in-situ derived from N-(NiFe)(3)S-2 precatalyst by electrochemical oxidation. N-NiFeOOH exhibits superior performance with a low overpotential of 278 mV at the current density of 100 mA cm(-2) and a small Tafel slope of 35.3 mV dec(-1), which is comparable to the most excellent non-noble catalysts. DFT calculations reveal that N-doping would lower the d-band center of the surface metal atoms and in turn increase the adsorption ability of *OH on NiFeOOH, thereby reducing the OER overpotential. The key role of N-doping in the NiFeOOH for enhancing OER performance is reported for the first time, which will shed light on the design of catalysts. (C) 2020 Elsevier Inc. All rights reserved.