Three dimensional porous CoP nanosheet arrays grown on nickel foam composite were designed and constructed through a combination of electrodeposition and phosphatization. Nanosheet arrays of cobalt (II) hydroxide were firstly formed on nickel foam via electrodeposition which is further phosphatized to form defect-rich porous CoP nano sheets. The as-prepared CoP nanosheets exhibit high activity as a catalyst for the hydrogen evolution reaction, and the overpotentials of generating a current density of 10 mA cm(-2) are 79.5 mV and 86.6 mV in acidic and basic electrolytes, respectively. In addition, the as prepared CoP nanosheet catalyst shows excellent stability in acidic electrolyte, and no obvious degradation was observed at 10 mA cm(-2) for 50 h. The high activity is attributed to the unique three dimensional structure of the material as well as the metalloid characteristics of CoP. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.