A first-principles study of electronic structure and photocatalytic performance of GaN-MX2 (M = Mo, W; X= S, Se) van der Waals heterostructures.

Fawad Khan,Bin Amin,Iftikhar Ahmad,C Nguyen,M Idrees

doi:10.1039/d0ra04082g

Abstract

Modeling novel van der Waals (vdW) heterostructures is an emerging field to achieve materials with exciting properties for various devices. In this paper, we report a theoretical investigation of GaN–MX2 (M = Mo, W; X= S, Se) van der Waals heterostructures by hybrid density functional theory calculations. Our results predicted that GaN–MoS2, GaN–MoSe2, GaN–WS2 and GaN–WSe2 van der Waals heterostructures are energetically stable. Furthermore, we find that GaN–MoS2, GaN–MoSe2 and GaN–WSe2 are direct semiconductors, whereas GaN–WS2 is an indirect band gap semiconductor. Type-II band alignment is observed through PBE, PBE + SOC and HSE calculations in all heterostructures, except GaN–WSe2 having type-I. The photocatalytic behavior of these systems, based on Bader charge analysis, work function and valence and conduction band edge potentials, shows that these heterostructures are energetically favorable for water splitting.

Highlights

Developing material with desired characteristics for speci c applications is the most challenging aspect of modern science and technology
The photocatalytic behavior of these heterostructures that based on Bader charge analysis, work function and valence and conduction band edge potentials, show that these heterostructures are energetically favorable for water splitting
In stacking (III) the Ga atom placed on the top of M/W atom while the N atom is in the hexagonal site

Summary

Introduction

Developing material with desired characteristics for speci c applications is the most challenging aspect of modern science and technology. For an efficient photocatalyst several requirements must be critically satis ed, such as the band gap of the semiconductor must be suitable and with respect to water redox potential such that the conduction band minimum and the valance band maximum must have reasonable positions.[47,48] In layered material the optical absorption can be tuned by adjusting its band gap and can be considered advantageous as a photocatalyst in comparison to other conventional materials, while the recombination of photogenerated holes and electrons are much decreased due to high carrier mobility and ultrathin nature. A large number of vertically stacked vdW heterostructures are experimentally and theoretically investigated, and they are found with good properties for electronic and optoelectronic applications.[52] Heterostructure photocatalysts are promising materials with better photocatalytic properties than that of the individual layers.[53] In a formed heterostructure, the band gap width and positions are effectively tuned to reach the requirement of a photocatalyst. The photocatalytic behavior of these heterostructures that based on Bader charge analysis, work function and valence and conduction band edge potentials, show that these heterostructures are energetically favorable for water splitting

Computational details

Findings

Result and discussion

Conclusion