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Ab Initio Calculations on the Electronic Structure and Photocatalytic Properties of Two‐Dimensional WS 2 (0001) Nanolayers of Varying Thickness
Author(s) -
Bocharov Dmitry,
Piskunov Sergei,
Zhukovskii Yuri F.,
Evarestov Robert A.
Publication year - 2019
Publication title -
physica status solidi (rrl) – rapid research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.786
H-Index - 68
eISSN - 1862-6270
pISSN - 1862-6254
DOI - 10.1002/pssr.201800253
Subject(s) - materials science , ab initio , density functional theory , band gap , photocatalysis , hybrid functional , ab initio quantum chemistry methods , visible spectrum , electronic structure , graphene , electronic band structure , molecular physics , condensed matter physics , computational chemistry , nanotechnology , optoelectronics , chemistry , molecule , physics , biochemistry , organic chemistry , catalysis
2D layered transition metal dichalcogenides (TMDC) structurized in hexagonal 2H c phase possess space group P 6 3 / mmc and graphite‐type morphology (e.g., WS 2 bulk), as well as strong chemical bonds and weak coupling between S‐W‐S three‐plane monolayers (MLs). Ab initio calculations on pristine WS 2 (0001) nanolayers are performed using CRYSTAL14 code within the formalism of hybrid density functional theory and Hartree–Fock method (HSE06 Hamiltonian properly adapted to describe tungsten disulphide bulk). An ordered stack of graphene‐type WS 2 (0001)‐oriented MLs (in absence of any point defects including dopants) with thikness varies from 1 to 40 MLs is found to be suitable for photocatalysis since irrespectively of this thickness the bandgap corresponds to the varied range of visible spectrum between its violet and red edges, respectively. The authors calculate the electronic structure of these nanolayers. The highest photocatalytic efficiency is achieved for WS 2 2 ML with band gap △ ϵ gap ≈ 2.06 eV (yellow range of the visible spectrum). Additionally, all the edges of ordered pristine 2H c WS 2 (0001) nanosheets ( ϵ VB and ϵ CB levels corresponding to the top of the valence band and the bottom of the conduction band) are properly aligned relative to the oxidation and reduction potentials ( ϵ O 2 / H 2 Oandϵ H +/ H 2): ϵ VB < ϵ O 2 / H 2 O < ϵ H +/ H 2 < ϵ CB , which means that probability of photocatalytic electron‐hole recombination is rather minimal, being reduced with a decrease of stack thickness.