Enhancing the hydrogen evolution activity of MoS2 basal planes and edges using tunable carbon-based supports

摘要

The hydrogen adsorption free energy (Delta G(Hads)) on the basal plane and edges of MoS2 is studied using periodic density functional theory, with the catalyst supported by a range of two-dimensional carbon-based materials. Understanding how Delta G(Hads) can be tuned with support gives insight into MoS2 as a catalyst for the hydrogen evolution reaction. The supports studied here include graphene oxide materials, heteroatom doped (S, B, and N) graphene, and some insulator materials (hexagonal boron nitride and graphitic carbon nitride). For the basal plane of MoS2, a wide range of values for Delta G(Hads) are observed (between 1.4 and 2.2 eV) depending on the support material used. It is found that Delta G(Hads) relates directly to the energy of occupied p-orbital states in the MoS2 catalyst, which is modified by the support material. On the Mo-edge of MoS2, different supports induce smaller variations in Delta G(Hads), with values ranging between -0.27 and 0.09 eV. However, a graphene support doped with graphitic N atoms produces a Delta G(Hads) value of exactly 0 eV, which is thermodynamically ideal for hydrogen evolution. Furthermore, Delta G(Hads) is found to relate closely and linearly to the amount of charge transfer between MoS2 and support when they adhere together. The support-induced tuning of Delta G(Hads) on MoS2 observed here provides a useful tool for improving current MoS2 catalysts, and the discovery of variables which mediate changes in Delta G(Hads) contributes to the rational design of new hydrogen evolution catalysts.