Hydrogen evolution reaction catalyzed by nickel/nickel phosphide nanospheres synthesized through electrochemical methods

Nickel/Nickel phosphides electrodes are prepared through in-situ reduction of NiSO4 and NaH2PO2 on carbon cloth substrates using square-wave and cyclic voltammetry methods. Nickel/nickel phosphide nanospheres prepared with the pulse deposition procedure exhibits higher activity in the hydrogen evolution reaction (HER), outperforming those prepared through cyclic voltammetry approach. Scanning electron microscopy measurements indicate that pulse-deposition offers a better control on the nucleation process and the size of nanospheres, leading to the formation of nano-cracks within the spheres and creating more active sites for the HER. The as-obtained nickel/nickel phosphide/carbon cloth electrodes exhibit cathodic currents of 10 mA cm(-2) at the overpotential of 164 mV in a 0.5 M H2SO4 solution and the obtained Tafel plot has a slope of 76 mV dec(-1). (C) 2018 Elsevier Ltd. All rights reserved.