Hexagonal CoSe2 nanosheets stabilized by nitrogen-doped reduced graphene oxide for efficient hydrogen evolution reaction

CoSe 2 is considered as a promising candidate among non-noble metal electrocatalysts for the hydrogen evolution reaction (HER) due to its intrinsic metallicity and low Gibbs free energy for hydrogen adsorption. Recently, the hexagonal CoSe 2 becoming increasingly popular owing to its chemically favorable basal plane , which provides more active sites, but remains limited by the poor stability. In this study, we design a small-molecule-amine-assisted hydrothermal method to in situ anchor the hexagonal CoSe 2 nanosheets (NSs) on nitrogen-doped reduced graphene oxides (RGO) as an advanced electrode material for HER. Due to the existence of abundant functional groups and high specific surface area of RGO, the hexagonal CoSe 2 NSs could be stably formed on RGO. As a result, only a small overpotential of 172 mV is needed for the optimized sample to drive a current density of 10 mA cm −2 in 0.5 M H 2 SO 4 and the Tafel slope is 35.2 mV dec −1 , which is comparable with the state-of-the-art Pt catalyst (32.3 mV dec −1 ). Therefore, the facile and low-cost method for synthesizing hexagonal TMDs with robust electrical and chemical coupling developed in this work is promising in promoting the large-scale application of non-precious electrocatalysts.