Nickel phosphide has been shown to be active toward hydrogen evolution reaction (HER). In this paper, we demonstrate the phase and composition controllable synthesis of nickel phosphide-based nanoparticles (Ni-P-based NPs) via a low-temperature phosphidation reaction (250 degrees C) using NaH2PO2 as the phosphorus source and the as-prepared Ni(OH)(2) precursor as the nickel source. Interestingly, by changing the NaOH concentration and nickel source used to fabricate Ni(OH)(2) precursors, we could adjust the phases and compositions of as-synthesized Ni-P-based nanocatalysts from Ni5P4, Ni2P to Ni12P5. The different steric hindrance and the electrostatic repulsion of synthesized beta-Ni(OH)(2) precursors result in the formation of three Ni-P phases with various Ni:P ratios. Electrochemical characterizations reveal that the Ni-P-based NPs with P-rich phase (Ni5P4+Ni2P) exhibit remarkable electrocatalytic HER property, with low overpotential (eta) of 111 mV to reach a current density of 10 mA cm(-2) in a 0.5 M H2SO4 media, which is superior than those of pure Ni2P (eta = 118 mV) and the Ni-rich Ni-P-based counterpart (Ni12P5+Ni2P) (eta = 131 mV). This is attributed to the stronger ensemble effect of P and more active sites provided by P-rich Ni-P-based NPs. Our results demonstrate that by tailoring the surface properties of Ni(OH)(2) precursors, the phases and compositions of Ni-P-based nanoparticles could be easily tuned, which provides a simple, economic, and green strategy to optimize the HER performance of transition metal phosphide-based electrocatalysts. (C) 2017 Elsevier Ltd. All rights reserved.