Non-precious metal catalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) are the cost-effective materials for overall water splitting. Here, we report that the core-shell structured Ni12P5/Ni-3(PO4)(2) hollow spheres (Ni12P5/Ni-3(PO4)(2)-HS) exhibits high activity and stability towards both HER and OER in strong alkaline media. A current density of 10 mA cm(-2) is generated at an overpotential of 0.114V and 0318 V in 1 M KOH for HER and OER, respectively. The high activity is attributed to the hollow core-shell (Ni12P5/Ni-3(PO4)(2)) structure that the material adopts under catalytic conditions. The Ni12P5/Ni-3(PO4)(2)-HS can serve as both cathode and anode catalysts for a real water electrolysis cell, which generates a current density of 357.6mA cm(-2) at 1.8V and stable at 300mA cm(-2) for at least 100h, the potential catalytic degradation mechanism has been systematically studied and discussed. (C) 2016 Elsevier B.V. All rights reserved.