50. the size-dependent edge and odd-even effect on single-layered mos2 nanosheets with and without sulfur vacancies

Department: NanoEngineering
Research Institute Affiliation: Agile - Sustainable Power and Energy Center (SPEC)
Faculty Advisor(s): Kesong Yang

Primary Student
Name: Paul Hyunggyu Joo
Email: pjoo@ucsd.edu
Phone: 858-568-8983
Grad Year: 2019

Abstract
We report the size effect on the energetic stability of the triangular MoS2 nanosheets with four different edge-type triangular-shaped nanosheets - ZZ-Mo1, ZZ-Mo2, ZZ-S1, and ZZ-S2. Our DFT results reveal that the two S-terminated edge structures, ZZ-S1 and ZZ-S2, become more favorable while the two Mo-terminated edge sturctures, ZZ-Mo1 and ZZ-Mo2, become less favorable in the transition from S-poor to S-rich conditions. All four edge-type structures decrease in the formation energy with increase in their size. Under S-rich conditions, the ZZ-S2 structures are the most energetically stable thus, taken to further studies with sulfur dimer vacancies. The corner (V@Cnr) and center (V@Cen) vacancy sites on the edges demonstrate an opposite odd-even effect in the formation energies from size, n=4-8, with n being the number of Mo atoms along the edges. The two sites share a consistent odd-even effect from n=9-13. Such effect is caused by the structural variations on the edges after sulfur vacancies. Relatively lower formation energies are caused by a new interaction between the Mo atom at the vacancy site and its adjacent S dimer. Our first-principles electronic structure calculations revealed, in terms of the energetic stability, the reliance of the size-dependent MoS2 nanosheets on the HDS catalytic applications.

Industry Application Area(s)
Energy/Clean technology | Materials

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