Adjusting the intrinsic activity and conductivity of electrocatalysts may be a crucial way for excellent performance for water splitting.Herein,the rational design of vanadium element doped cobalt phosphide (V-doped CoP) nanoparticles has been investigated through a facile gaseous phosphorization using cobalt vanadium oxide or hydroxide (Co-V hydr(oxy)oxide) as precursor.The physical characterization shows that the homogeneous dispersion of V element on V-doped CoP nanoparticles have obtained,which may imply the enhanced electrocatalytic activity for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER).The electrochemical measurements of the prepared V-doped CoP in alkaline electrolyte demonstrate the superior electrocatalytic activity for both HER (overpotential of 235mV@10mA cm-2) and OER (overpotential of 340 mV@10 mA cm-2).Further,V-doped CoP nanoparticles used as anode and cathode simultaneously in a cell require only 370 mV to achieve a current density of 10 mA cm-2.The outstanding electrocatalytic activity may be ascribed to the improved conductivity and intrinsic activity owing to phosphating and the doping of V element.In addition,the long-term stability of V-doped CoP has been obtained.Therefore,metal doping into transition metal-based phosphides may be a promising strategy for the remarkable bifunctional electrocatalyst for water splitting.