The development of an efficient, robust and low cost catalyst for photocatalytic H-2 evolution is an uphill challenge and has attracted plenty of researchers ' interest. Herein, we report g-C3N4/Ni2P composite photocatalyst for H-2 evolution reaction in which Ni2P acts as a noble-metal-free cocatalyst for g-C3N4. The gC(3)N(4)/Ni2P is prepared based on two-step hydrothermal and phosphidation method. The optimum H-2 evolution ability is obtained when the loaded weight percent of Ni2P is 0.48% (g-C3N4/Ni2P-0.48%), along with a corresponding H-2 evolution rate of 5.67 mu mol h(-1). This value is about 1418 times more than pure gC(3)N(4) and obviously higher than that of Pt modified g-C3N4 (3.78 itmol h(-1)). In addition, the g-C3N4/Ni2P-0.48% catalyst demonstrates almost negligible photocatalytic degradation capability even after eight repeated cycles (a reaction time of 12 h per cycle). The introduction of Ni2P cocatalyst significantly accelerates the separation and transfer of photogenerated electrons of g-C3N4, hence resulting in enhanced H-2 evolution efficiency. In addition, the Ni and P in Ni2P cocatalyst act as the hydride-acceptor and proton acceptor centers, respectively, which synergistically facilitate the fast generation of H-2. (C) 2017 Elsevier B.V. All rights reserved.