Transition metal phosphides represent a class of promising electrocatalysts for electrochemical water oxidization and other energy conversion reactions. In this work, we report a novel seal strategy, followed by a second step phosphorization treatment, produces Ni-Fe-P heterostructure directly grown on nickel foam that shows highly catalytic activity for electrochemical water oxidation. The as-prepared catalyst exhibits an excellent electrocatalytic activity, manifested by a current density of 20 mA cm(-2) with a very low overpotential (260 mV) for oxygen evolution reaction along with an extremely small Tafel slope of 27 mV decade(-1) and a very excellent durability of 120 h in alkaline solution. The excellent performance with exceptional durability owe much to the synergistic effect between the Ni-Fe-P heterostructure and the outer oxidized layer. Remarkably, a current density of 10 mA cm(-2) was reached at a low cell voltage of 1.63 V when the original electrode and surface oxidized electrode are used as cathode and anode, respectively. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.