Excited States Calculations of MoS2@ZnO and WS2@ZnO Two-Dimensional Nanocomposites for Water-Splitting Applications

Yin-Pai Lin,Edgars Butanovs,Dmitry Bocharov,Boris Polyakov,Aleksandr A Popov,Maksim Sokolov,Sergei Piskunov

doi:10.3390/en15010150

Yin-Pai Lin, Edgars Butanovs + Show 5 more

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https://doi.org/10.3390/en15010150

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Abstract

Transition metal dichalcogenide (TMD) MoS2 and WS2 monolayers (MLs) deposited atop of crystalline zinc oxide (ZnO) and graphene-like ZnO (g-ZnO) substrates have been investigated by means of density functional theory (DFT) using PBE and GLLBSC exchange-correlation functionals. In this work, the electronic structure and optical properties of studied hybrid nanomaterials are described in view of the influence of ZnO substrates thickness on the MoS2@ZnO and WS2@ZnO two-dimensional (2D) nanocomposites. The thicker ZnO substrate not only triggers the decrease of the imaginary part of dielectric function relatively to more thinner g-ZnO but also results in the less accumulated charge density in the vicinity of the Mo and W atoms at the conduction band minimum. Based on the results of our calculations, we predict that MoS2 and WS2 monolayers placed at g-ZnO substrate yield essential enhancement of the photoabsorption in the visible region of solar spectra and, thus, can be used as a promising catalyst for photo-driven water splitting applications.

Highlights

It is reported that the Zn–O bond length between pseudo-planes in the w-zinc oxide (ZnO) (d’Zn−O )
The excess of O states does not lead to further improvement of absorption. These results indicate that the crystal-like ZnO substrate with MoS2 (WS2 ) composites fails to sustain the strong peak around 400 nm induced in the MoS2 @graphene-like ZnO (g-ZnO) and WS2 @g-ZnO
MoS2 and WS2 monolayers deposited at ZnO and g-ZnO substrates are studied by means of density functional theory (DFT) and excited-state time-independent DFT

Summary

Introduction

Zinc oxide (ZnO), one of the potential photocatalysts for water-splitting applications, has been extensively studied at nanoscale for photocatalysis [1], photosensorics [2,3,4,5], and for other industrial applications [6,7,8,9,10,11,12,13], including energy generation by transformation of waste heat energy to electricity through thermoelectric power generation using Al-doped. Based on data available in the literature [25,26,27,29], one knows that the monolayered ZnO combined with MoS2 or WS2 ML, irrespective of mutual layer orientation, keeps the constant band gap, as well as fulfills the condition of band edge alignment with respect to the water splitting redox levels. Taking this into account, in our study, we have chosen two configurations of ZnO substrate orientation relative to MoS2 and WS2 ML, with the rotation angle of 0◦ and 180◦ , as it is described in Refs. A brief summary and conclusions on photocatalytic properties of studied heterostructures are given at the end of this paper

Computational Details and Models of Heterostructures

Results and Discussion

Electronic Structure

Optical Absorption

Differential Charge Density Maps

Conclusions