Symmetric synergy of hybrid CoS2–WS2 electrocatalysts for the hydrogen evolution reaction

A highly active and stable hybrid electrocatalyst 3D hierarchical CoS2 nanosheets incorporated with WS2 (CoS2@WS2) has been developed via a one-step sulfurization method for the first time, where the contents of WS2 can be adjusted easily. We first prove that the addition of small amounts of WS2 enhances the hydrogen evolution reaction (HER) performance of CoS2, and vice versa. In other words, we validated the symmetric synergy for the HER between the Co- and W-based sulfide hybrid catalysts. In addition, we confirmed that the formation of nanointerfaces of Co–S–W between CoS2 and WS2 was responsible for the excellent HER activity (an overpotential of −97.2 mV at −10 mA cm−2, a small Tafel slope of 66.0 mV dec−1, and prominent electrochemical stability) of the hybrid electrocatalyst CoS2@WS2.