Increased 1T-MoS2 in MoS2 @CoS2/G composite for high-efficiency hydrogen evolution reaction

Metallic 1 T-MoS 2 exhibits higher conductivity and electrocatalytic activity for hydrogen evolution reaction (HER) than semiconductor 2 H-MoS 2 . However, 1 T-MoS 2 is a metastable state on thermodynamics, which hinder its further application as catalyst for HER. In this work, we report a new strategy to prepare MoS 2 @CoS 2 /G electrocatalysts (G=graphene) with high-percentage metallic 1 T-MoS 2 phase through a simple hydrothermal method followed by sulfurization treatment. We show that the introduction of CoS 2 and the sulfurization can both promote the formation of 1 T-MoS 2 phase (87.94%) in the MoS 2 @CoS 2 /G electrocatalysts, which leads to improved charge transfer efficiency and electrochemical conductivity, larger surface area, and extensive active sites. These properties ultimately lead to the significantly enhanced catalytic activity of MoS 2 @CoS 2 /G for HER with a small overpotential of 118 mV at 10 mA cm −2 , and a small Tafel slope of 53 mV dec −1 , as well as excellent durability and cycling stability in acidic electrolyte. MoS 2 @CoS 2 /G composite for High-Efficiency Hydrogen Evolution Reaction • High-percentage metallic 1 T-MoS 2 in CoS 2 @MoS 2 /Graphene obtained by a sample sulfurization treatment. • Proper sulfurization conditions could reduce the overpotential of CoS 2 @MoS 2 /Graphene to 118 mV. • The mechanism was systematically studied.