Synthesis of Co-doped MoS2/graphene hybrids as enhanced electrocatalysts for the hydrogen evolution reaction

Abstract

Cobalt-doped MoS₂/graphene (Co–MoS₂/G) hybrids are fabricated through a one-pot hydrothermal method by reacting Na₂MoO₄ and graphene oxide with L-cysteine in the presence of Co(CH₃COO)₂·4H₂O. It is found that the rational Co-doping not only changes the morphology and microstructure of the Co–MoS₂/G hybrids, but also improves the intrinsic electrocatalytic activity of their active sites. In addition, the highly conductive graphene facilitates the electron transport between active sites and electrodes. In particular, the Co–MoS₂/G-3 hybrid prepared with 0.15 mmol Co(CH₃COO)₂·4H₂O displays numerous Co–MoS₂ short sheets which are well-anchored on the graphene surface, and provide more exposed active edge sites for the hydrogen evolution reaction (HER). With such merits, the Co–MoS₂/G-3 hybrid shows a remarkable catalytic activity toward HER with a low Tafel slope of 44.3 mV dec⁻¹ and excellent durability (minimal performance degradation after 1000 cycles). Also, electrochemical impedance spectroscopy demonstrates that the Co–MoS₂/G-3 catalyst electrode displays a greatly reduced charge-transfer resistance for HER, indicating its favorable reaction kinetics.