Designing noble-metal-free and highly active bifunctional electrocatalysts for overall water splitting is extremely desirable. Herein, we apply a facile method to fabricate cobalt nitride porous nanowires with a length of 7 mm and a diameter of 135 nm on carbon cloth (CC) as a bifunctional electrocatalyst for overall water splitting. The self-supported cobalt nitride porous nanowire arrays exhibit superior catalytic activities with a current density of 10 mAcm(-2) at an overpotential of 97 mV for hydrogen evolution reaction and at an overpotential of 251 mV for oxygen evolution reaction. The alkaline water electrolyzer with the self-supported porous nanowire arrays as cathode and anode requires a cell voltage of 1.587 V to achieve a current density of 10 mAcm(-2) and shows long-term stability at the high current density(similar to 360 mAcm(-2)) over 37 h, favorably comparable to the integrated performance of commercial Pt and IrO2. (C) 2018 Elsevier Ltd. All rights reserved.