Insight into the structure and energy of Mo₂₇S_xO_y clusters

Oxygen incorporated molybdenum sulfide (MoS₂) nanoparticles are highly promising materials in hydrodesulfurization catalysis, mechanical, electric, and optical applications. We report a systematic theoretical study of the successive oxidation reactions of the Mo₂₇S_xO_y nanoparticles and the reaction network, along with the electronic structure changes caused by the oxygen substitution. The replacement of surface sulfur by oxygen atoms is thermodynamically favorable. Our results indicate that the oxidation on the S edge with 100% and 50% coverage is more favored than on the Mo edge. Meanwhile, it is found that the oxidation on the S edge with 100% coverage has similar replacement ability by oxygen as on the S edge with 50% coverage. Thus, sulfur coverage does not play an important role in the oxidation on the S edge. Further comparison shows that the oxidation on corner sites is more favorable than on edge sites. In addition, the replacement of the bulky sulfur on the Mo edge is equally as favored as those of sulfur on the S edge. This work provides important information on the thermodynamics of the Mo₂₇S_xO_y nanoparticles, and gives new insights into the mechanism of the oxidation of MoS₂ and the sulfidation of MoO₃.