Ultrafine particles of Co–P were synthesized by direct ball milling of Co and P powders and also investigated as a reversible hydrogen storage electrode material. The electrochemical results demonstrated that the reversible charge–discharge capacity of the Co–P electrode can reach more than 300mAh/g. In addition, the cycling ability and high rate capability of the Co–P electrode are excellent with only 5% capacity decay after 100 cycles at a high rate of 300mA/g. The temperature-programmed desorption measurements (TPD) of the Co–P electrode revealed that the charge and discharge reactions of the Co–P electrode proceeds predominantly through electrochemical hydrogen storage mechanism and the electrooxidation of cobalt contributes only a negligible part to the reversible electrochemical capacity.