Two-dimensional ZnI2 monolayer as a photocatalyst for water splitting and improvement its electronic and optical properties by strains

Abstract

We investigate the electronic and optical properties of zinc iodide (ZnI 2 ) under the effect of the biaxial strains. It has been emphasized that ZnI 2 monolayer is stable based on the molecular dynamics simulations, phonon dispersion curve and binding energy calculations. In the equilibrium state, the results revealed that the ZnI 2 monolayer is a semiconductor with the indirect bandgap value of 2.018 eV/2.94 eV using PBE/HSE06 methods. In addition, the ZnI 2 monolayer has appropriate band-edge positions for the oxidation and reduction reactions of water splitting at pH = 0. Besides, it is disclosed that the energy bandgap varies extremely with the influence of biaxial strain reaching about 1.631 eV with the compressive strain of −6%. Generally, the change in the bandgap is higher with the compressive strain state than that with the tensile strain state. However, all energy gaps are located in the visible region and distributed in wide range regions which can have extensive nanodevices applications. Most importantly, a remarkable enhancement in the optical properties can be perceived under the strain effect. Precisely, the absorption coefficient achieves a maximum value of 16.6 × 10 4 cm −1 at −6% within the ultraviolet range. Finally, our perusal highlights that the effect of the biaxial strain on the ZnI 2 monolayer presents effectual guidance to design highly effective optoelectronic materials for nanoscale devices. • ZnI 2 monolayer is semiconductor with a bandgap of 2.018/2.94 eV using PBE/HSE06 methods. • The energy bandgap is tuning considerably under the biaxial strain effect. • Tensile strain results in significant red-shifting in the absorption edge. • The ZnI 2 monolayer can act as a high-efficiency photocatalyst for water splitting. • Control of the electronic and optical properties is beneficial in nanoelectronic applications.