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

Cobalt-doped MoS 2 /graphene (Co-MoS 2 /G) hybrids are fabricated through a one-pot hydrothermal method by reacting Na 2 MoO 4 and graphene oxide with l -cysteine in the presence of Co(CH 3 COO) 2 ·4H 2 O. It is found that the rational Co-doping not only changes the morphology and microstructure of the Co-MoS 2 /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-MoS 2 /G-3 hybrid prepared with 0.15 mmol Co(CH 3 COO) 2 ·4H 2 O displays numerous Co-MoS 2 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-MoS 2 /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-MoS 2 /G-3 catalyst electrode displays a greatly reduced charge-transfer resistance for HER, indicating its favorable reaction kinetics. Co-Doped MoS 2 /graphene hybrids with more exposed active sites and a Tafel slope of 44.3 mV dec −1 for HER were prepared.