The development of noble-metal-free electrocatalysts for water splitting is indispensable for the efficient production of hydrogen fuel.Herein,a Co-doped Ni-Mo phosphide nanorod arrays fabricated on porous Ni foam was shown to be an efficient binder-free electrocatalyst for water splitting.This catalyst featured exceptional activity,exhibiting an overpotential of 29 mV at a current density of 10 mA-cm-2 for the hydrogen evolution reaction,whereas the corresponding precatalyst exhibited an overpotential of 314 mV at a current density of 50 mA·cm-2 for the oxygen evolution reaction.The achieved electrocatalytic performance provided access to a simple water splitting system,affording a current density of 10 mA·cm-2 at 1.47 V in 1 M KOH electrolyte.Density functional theory results indicated that Co doping and phosphorization were responsible for the high electrocatalytic performance.Thus,this work paves the way for the development of novel noble-metal-free electrocatalysts for practical H2 production via water splitting.