CoS 2 -MoS 2 nanoflakes decorated MoO 2 (CoMoOS) hybrid submicro-wires with rich active interfaces were synthesized via the sulfuration of CoMoO 4 . They showed excellent activity while synergistically catalyzing the hydrogen evolultion reaction (HER) in basic media by promoting both the water dissociation and hydrogen absorption steps. Thus, the CoMoOS catalysts only needed 123 mV to achieve 10 mA cm -2 with a small Tafel slope in alkaline solutions, and required 1.68 V to obtain the same current density when assembled into an alkaline electrolyser.