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

The basal plane of MoS 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 MoS surface using a graphene oxide (GO) support (MoS/GOs). The chemical bonding of the functional groups (CH and NH) on the MoS-GO hybrid is stronger than that in freestanding MoS or MoS-graphene. Upon increasing the oxygen group concentration or introducing N heteroatoms into the GO support, the stability of the chemically functionalized MoS is improved. Furthermore, use of GOs to support pristine and defective MoS with a S vacancy (S-MoS) can greatly promote the HER activity of the basal plane. The catalytic activity of S-MoS is further enhanced by doping N into GOs; this results in a hydrogen adsorption free energy of almost zero (ΔG = ∼-0.014 eV). The coupling interaction with the GO substrate reduces the p-type Schottky barrier heights (SBH) of S-MoS 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 MoS-based nanosheets and HER catalysts.