A DFT study on WO3 nanowires with different orientations for NO2 sensing application

The adsorption of NO2 molecule on the surface of WO3 nanowires with [0 0 1] and [0 1 0] orientations were investigated using density functional theory (DFT) calculations with aim to explore their potential sensing abilities theoretically. It is found that NO2 molecule can adsorb in multiple stable configurations for the WO3 nanowires with the two orientations, and the NO2 adsorption on the surface tunes the electronic structures of WO3 nanowires, giving rise to new impurity electronic states and then changing the band gap and the Fermi level position. The sensitive electronic structures as well as the multiple stable configurations to NO2 adsorption highlight the potential of WO3 nanowires as a sensor to detect NO2 gas. Further calculations about the atomic Mulliken charge population, planar averaged charge density differences, and electron localization functions (ELF) indicate that NO2 adsorption on [0 1 0]-oriented WO3 nanowire induces much stronger adsorbate-surface interaction and much more electrons extracted from the surface than on [0 0 1] nanowire, hinting a much higher sensitivity expectable for a NO2 gas sensor based on WO3 nanowire with [0 1 0] orientation.