title: Predicting Single-Layer Technetium Dichalcogenides (TcX₂, X = S, Se) with Promising Applications in Photovoltaics and Photocatalysis.
abstract: One of the least known compounds among transition metal dichalcogenides (TMDCs) is the layered triclinic technetium dichalcogenides (TcX2, X = S, Se). In this work, we systematically study the structural, mechanical, electronic, and optical properties of TcS2 and TcSe2 monolayers based on density functional theory (DFT). We find that TcS2 and TcSe2 can be easily exfoliated in a monolayer form because their formation and cleavage energy are analogous to those of other experimentally realized TMDCs monolayer. By using a hybrid DFT functional, the TcS2 and TcSe2 monolayers are calculated to be indirect semiconductors with band gaps of 1.91 and 1.69 eV, respectively. However, bilayer TcS2 exhibits direct-bandgap character, and both TcS2 and TcSe2 monolayers can be tuned from semiconductor to metal under effective tensile/compressive strains. Calculations of visible light absorption indicate that 2D TcS2 and TcSe2 generally possess better capability of harvesting sunlight compared to single-layer MoS2 and ReSe2, implying their potential as excellent light-absorbers. Most interestingly, we have discovered that the TcSe2 monolayer is an excellent photocatalyst for splitting water into hydrogen due to the perfect fit of band edge positions with respect to the water reduction and oxidation potentials. Our predictions expand the two-dimensional (2D) family of TMDCs, and the remarkable electronic/optical properties of monolayer TcS2 and TcSe2 will place them among the most promising 2D TMDCs for renewable energy application in the future.
authors: School of Chemistry, Physics, and Mechanical Engineering, Science and Engineering Faculty, Queensland University of Technology , Gardens Point Campus, 4001 Brisbane, QLD, Australia.
authors: Yalong
authors: Y
authors: Jiao
authors: Bremen Center for Computational Materials Science, University of Bremen , 28359 Bremen, Germany.
authors: Liujiang
authors: L
authors: Zhou
authors: School of Chemistry, Physics, and Mechanical Engineering, Science and Engineering Faculty, Queensland University of Technology , Gardens Point Campus, 4001 Brisbane, QLD, Australia.
authors: Fengxian
authors: F
authors: Ma
authors: School of Chemistry, Physics, and Mechanical Engineering, Science and Engineering Faculty, Queensland University of Technology , Gardens Point Campus, 4001 Brisbane, QLD, Australia.
authors: Guoping
authors: G
authors: Gao
authors: School of Chemistry, Physics, and Mechanical Engineering, Science and Engineering Faculty, Queensland University of Technology , Gardens Point Campus, 4001 Brisbane, QLD, Australia.
authors: Liangzhi
authors: L
authors: Kou
authors: School of Chemistry, Physics, and Mechanical Engineering, Science and Engineering Faculty, Queensland University of Technology , Gardens Point Campus, 4001 Brisbane, QLD, Australia.
authors: John
authors: J
authors: Bell
authors: School of Physics and CRANN, Trinity College , Dublin 2, Ireland.
authors: Stefano
authors: S
authors: Sanvito
authors: School of Chemistry, Physics, and Mechanical Engineering, Science and Engineering Faculty, Queensland University of Technology , Gardens Point Campus, 4001 Brisbane, QLD, Australia.
authors: Aijun
authors: A
authors: Du
keywords: photocatalysis; photovoltaics; strain effect; technetium dichalcogenides; two-dimensional materials