LAUSR

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 °C) using NaH 2 PO 2 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 Ni 5 P 4 , Ni 2 P to Ni 12 P 5 . The different steric hindrance and the electrostatic repulsion of synthesized β-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 (Ni 5 P 4 +Ni 2 P) exhibit remarkable electrocatalytic HER property, with low overpotential ( η ) of 111 mV to reach a current density of 10 mA cm −2 in a 0.5 M H 2 SO 4 media, which is superior than those of pure Ni 2 P ( η  = 118 mV) and the Ni-rich Ni P-based counterpart (Ni 12 P 5 +Ni 2 P) ( η  = 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.