Developing low cost co-catalysts is crucial for both fundamental research and practical application of g-C3N4. In this work, we prepared ternary Ni2P/rGO/g-C3N4 nanotubes with different Ni2P contents for visible-light-driven photocatalytic H-2 generation from triethanolamine aqueous solution. The optimal Ni2P/rGO/g-C3N4 produced H-2 at a rate of 2921.9 mu mol h(-1) g(-1), which is about 35, 16 and 9 times as large as that of g-C3N4, binary rGO/g-C3N4 and Ni2P/g-C3N4, respectively. The apparent quantum efficiency of optimal Ni2P/rGO/g-C3N4 was 5.6% at lambda = 420 nm. We believe that the improved photocatalytic performance of Ni2P/rGO/g-C3N4 originates from the synergistic effect of rGO as electron transfer medium and Ni2P as reaction site, which is supported by photoelectrochemical and photoluminescence measurements. Cyclic experiment demonstrated an excellent stability of Ni2P/rGO/g-C3N4. Moreover, we further studied the effect of other nickel-based compounds by replacing Ni2P with NiS, Ni3C, and Ni3N, respectively. The order of the H-2-generation rate is Ni2P/rGO/CNNT > NiS/rGO/CNNT > Ni3C/rGO/CNNT > Ni3N/rGO/CNNT, which could be reasonably explained based on Mott-Schottky plots. Our work reveals that Ni2P can be used as a promising cocatalyst for photocatalytic H-2 evolution. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.