Symmetrical synergy of hybrid Co<inf>9</inf>S<inf>8</inf>-MoS<inf>x</inf> 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 , Co S , and MoS have been considered as several promising HER candidates. Here, a highly active and stable hybrid electrocatalyst 3D flower-like hierarchical Co S nanosheets incorporated with MoS has been developed via a one-step sulfurization method. Since the amounts of Co S and MoS are easily adjustable, we verify that small amounts of MoS promotes the HER activity of Co S , 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 S -30@MoS /CC in this study exhibits excellent HER performance with an overpotential of −98 mV at −10 mA/cm , a small Tafel slope of 64.8 mV/dec, and prominent electrochemical stability. 2 9 8 x 9 8 x 9 8 x x 9 8 9 8 x 2