The effects of polymorphism and lithium intercalation on the hydrogen evolution reaction for the basal planes of MoS2

The activity of Li-intercalated MoS2 phases for the hydrogen evolution reaction is investigated using density functional theory. The most stable semiconducting 2H phase, the metallic 1T' phase, and a polymorphous surface composed of alternating H and T' phases (1T″) are investigated. The local structure of the MoS2 surface is found to define its reactivity. In all cases, active sites for the hydrogen evolution process are restricted to T-like sulphur sites. Li-intercalation is found to promote hydrogen evolution reaction reactivity for the H phase whilst having little effect on the T phase. While improved compared to the non-intercalated phase, the Li-intercalated H phase MoS2 still has minimal activity for the hydrogen evolution reaction. The same effect of intercalation is also found for another transition metal dichalcogenide, MoSe2. The ability to improve reactivity in this way makes ion intercalation a promising space for designing new 2D catalysts for the hydrogen evolution reaction.