Hierarchical binary metal sulfides nanoflakes decorated on graphene with precious-metal-like activity for water electrolysis

Construction of cost-efficient and high-performance overall water splitting electrocatalysts for generating hydrogen and oxygen has recently received increasing research attention. Herein, hierarchical CoS2/MoS2 (CMS) nanoflakes were successfully decorated on graphene (denoted as CMSGr) as an efficient electrocatalyst for overall water splitting. Owing to the distinct hierarchical flakes morphology, and optimized interfacial microenvironment between CoS2 and MoS2, the fabricated CMSGr composites exhibit enhanced hydrogen and oxygen evolution reaction (HER/OER) activity. In particular, the optimized CMSGr-3 electrocatalyst presents the small overpotentials of 53 and 255 mV for HER and OER, and a low voltage of 1.55 V for overall water splitting in alkaline media under 10 mA cm−2. Theoretical calculations confirm that introducing CoS2 into MoS2 can greatly tune the electronic structure and optimize the adsorption energy during the water splitting. This work demonstrates that tuning the interfacial microenvironment of the binary metal sulfide composites is an effective route for developing high-performance water splitting electrocatalysts.