Symmetrical synergy of hybrid Co9S8-MoSx electrocatalysts for hydrogen evolution reaction

Abstract There exists a strong demand to replace expensive noble metal catalysts with efficient and earth-abundant catalysts for hydrogen evolution reaction (HER). Recently the Co- and Mo-based sulfides such as CoS 2 , Co 9 S 8 , and MoS x have been considered as several promising HER candidates. Here, a highly active and stable hybrid electrocatalyst 3D flower-like hierarchical Co 9 S 8 nanosheets incorporated with MoS x has been developed via a one-step sulfurization method. Since the amounts of Co 9 S 8 and MoS x are easily adjustable, we verify that small amounts of MoS x promotes the HER activity of Co 9 S 8 , and vise versa. In other words, we validate that symmetric synergy for HER in the Co- and Mo-based sulfide hybrid catalysts, a long-standing question requiring clear experimental proofs. Meanwhile, the best electrocatalyst Co 9 S 8 -30@MoS x /CC in this study exhibits excellent HER performance with an overpotential of −98 mV at −10 mA/cm 2 , a small Tafel slope of 64.8 mV/dec, and prominent electrochemical stability.