Gas-Phase Reactivity Studies of Small Molybdenum Cluster Ions with Dimethyl Disulfide

Molybdenum sulfide is a potent hydrogen evolution catalyst, and is discussed as a replacement of platinum in large-scale electrochemical hydrogen production. To learn more about the elementary steps of MoS₂ production by sputtering in the presence of dimethyl disulfide (DMDS), the reactions of Mo_x ⁺, x = 1-3, with DMDS are studied by Fourier transform ion cyclotron resonance mass spectrometry and density functional theory calculations. A rich variety of products composed of molybdenum, sulfur, carbon and hydrogen was observed. Mo_xS_y ⁺ species are formed in the first reaction step, together with products containing carbon and hydrogen. The calculations indicate that the strong Mo-S bonds are formed preferentially, followed by Mo-C bonds. Hydrogen is exclusively bound to carbon atoms, i.e. no insertion of a molybdenum atom into a C-H bond is observed. The reactions are efficient and highly exothermic, explaining the rich chemistry observed in the experiment.