The state-of-the-art and stable electrocatalysts with non-noble metal elements are exceedingly desirable for hydrogen/oxygen production from water splitting. Herein, three-dimensional (3D) iron-nickel nitride nanoparticles grown on carbon cloth (Ni3FeN-NPs) are developed as a flexible bifunctional electro-catalyst for overall water splitting. The as-prepared Ni3FeN-NPs show outstanding electrocatalytic activities toward both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in 1 M KOH solution, with low overpotentials of 238 and 241 mV at 10 mA/cm(2), Tafel slopes of 46 and 59 mV/dec, respectively. Moreover, an advanced water electrolyzer based on the Ni3FeN-NPs electrodes as anode and cathode is assembled and could achieve overall water splitting with a cell voltage of 1.81 V at 10 mA/cm(2). Also, the as-fabricated water electrolyzer exhibits stable electrocatalytic performance without decreasing in 1 M KOH after 130 h even at the foldable state. (C) 2017 Elsevier Ltd. All rights reserved.