High Electrocatalytic Activity of Defected MX2/Graphene Heterostructures (M = Mo, W; X = S, Se) for Hydrogen Evolution Reaction

Two-dimensional transition metal dichalcogenides have been regarded as cheap and abundant catalysts for driving electrolysis of water. Using density functional theory methods, we systematically investigate the hydrogen evolution reduction of metal dichalcogenides/ graphene heterostructures (MX2/Gs, M = Mo, W; X = S, Se) with various defects, MX2/G_V-X, MX2/G_V-M, and MX2/G_V(M+X). We find that such defected MX2/Gs show better hydrogen evolution reactive activities than pure MX2/Gs as well as freestanding MX2 monolayers, due to the metallic states induced by the defects. Particularly, MX2/G_V(X)s with a S(Se) vacancy display catalytic performance comparable to that of Pt. Moreover, the catalytic performance for the hydrogen evolution reaction of most defected MX2/G_V(M)s and MX2/G_V((M+X))s varies with H coverage and the M vacancy concentration. Our results provide a feasible way to apply MX2/graphene heterostructures to water electrolysis for hydrogen production.