A theoretical study on the electronic and optical properties of M-TiO2/ZnO (M=Li, Na, K, Fe) toward application in photocatalysis

Abstract

This study employs the tight-binding density functional method GFN1-xTB to investigate the structural and electronic properties of TiO₂-ZnO and TiO₂-ZnO composite materials modified by Li, Na, K, and Fe metals. Computational analyses reveal the formation of weak covalent bonds between the TiO₂ and ZnO components within the composite system. Doping TiO₂-ZnO with metals induces significant alterations in the electronic structure, particularly in terms of ionization energy and global electrophilic index. The UV-VIS spectra are calculated using real-time time-dependent density functional theory with xTB Hamiltonians. The obtained results demonstrate minimal impact of metal presence on the absorption spectrum of TiO₂-ZnO, but significant influence on the recombination potential of photogenerated charge carriers. It is suggested that Fe/TiO₂-ZnO and Li/TiO₂-ZnO will demonstrate higher photocatalytic activity than the pristine TiO₂-ZnO material.