Tuning the activity of the inert MoS2 surface via graphene oxide support doping towards chemical functionalization and hydrogen evolution: a density functional study

Abstract

The basal plane of MoS₂ provides a promising platform for chemical functionalization and the hydrogen evolution reaction (HER); however, its practical utilization remains challenging due to the lack of active sites and its low conductivity. Herein, using first principles simulations, we first proposed a novel and effective strategy for significantly enhancing the activity of the inert MoS₂ surface using a graphene oxide (GO) support (MoS₂/GOs). The chemical bonding of the functional groups (CH₃ and NH₂) on the MoS₂–GO hybrid is stronger than that in freestanding MoS₂ or MoS₂–graphene. Upon increasing the oxygen group concentration or introducing N heteroatoms into the GO support, the stability of the chemically functionalized MoS₂ is improved. Furthermore, use of GOs to support pristine and defective MoS₂ with a S vacancy (S-MoS₂) can greatly promote the HER activity of the basal plane. The catalytic activity of S-MoS₂ is further enhanced by doping N into GOs; this results in a hydrogen adsorption free energy of almost zero (ΔG_H = ∼−0.014 eV). The coupling interaction with the GO substrate reduces the p-type Schottky barrier heights (SBH) of S-MoS₂ and modifies its electronic properties, which facilitate charge transfer between them. Our calculated results are consistent with the experimental observations. Thus, the present results open new avenues for the chemical functionalization of MoS₂-based nanosheets and HER catalysts.