Nickel selenides with different Ni/Se atomic ratio have been successfully synthesized by a simple solvothermal method. Among them, the nonstoichiometric compound (Ni0.85Se) (A-10) behaved excellent electrochemical catalytic activity towards hydrogen evolution reaction. Furthermore, it presents an ultra-low overpotential (ii) of 190 mV and extremely small Tafel slope of 57 mV/dec when the current density j(A) reaches similar to 10 mA/cm(2). At the same time, it has large effective electrochemical active surface area and shows outstanding stability after a long time chronoamperometry testing. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.