Optimized Mo–doped cobalt selenides coupled carbon nanospheres for efficient hydrogen evolution.

• The optimized MoCoSe x @NC is prepared by a facile two-step method. • The uniform NC provides the growth space and fast electron transfer of active sites. • Mo doping can improve the intrinsic activity of CoSe x for HER. • The obtained MoCoSe x @NC exhibits excellent activity and stability for HER. Transition metal selenides have attracted wide attention owing to the unique structure and electron distribution in the field of electrocatalysis. However, adopting the suitable strategy to further improve the intrinsic activity and exposure of transition metal selenides is still a challenge. Herein, the optimized MoCoSe x encapsulated in N–doped hollow carbon nanosphere (MoCoSe x @NC) has been synthesized for hydrogen evolution reaction (HER) through a simple two–step method. Firstly, the uniform porous NC has been obtained through carbonization at 900 °C, which provides the growth space and fast electron transfer of active sites. Secondly, the optimized MoCoSe x @NC with excellent dispersion has been synthesized through the following hydrothermal process. Moreover, the synergistic effect of Mo doping can improve the intrinsic activity of CoSe x for HER. The obtained MoCoSe x @NC exhibited excellent low over potential of 60 mV at 10 mA cm−2 and great stability for HER. The enhanced activity may attribute to the good dispersion of MoCoSe x and NC substrate. After optimized synthesis process, we found that the first carbonization of NC is the base for constructing the good dispersion of MoCoSe x. This work provides a new design strategy for transition metal selenides supported on carbon substrate as electrocatalysts for HER. [ABSTRACT FROM AUTHOR]