Effect of ZnO Nanostructure Morphology on the Sensing of H2S Gas

Detection of pollutant gases, such as H2S, is of high importance for health reasons. We examine the effect of ZnO nanostructure morphology on the sensing mechanism of H2S, using density functional theory calculations. The effect of nanostructure size and shape, gas coverage, and reaction temperature are analyzed in order to determine the effect that each has on the gas surface reaction. We show that H2S dissociatively chemisorbs on the nanowire and faceted-nanotube as H and SH, while H2S molecularly physisorbs on the nanotube. H2S can adsorb in multiple locations and orientations on the nanowire and faceted-nanotube with the faceted-nanotube providing a greater number of surface sites due to its larger outer surface area and the fact that H2S can also adsorb on the inside of the structure. H2S acts as a charge donor, causing a decrease in the band gap after adsorption on the nanowire and faceted-nanotube, while the band gap for the nanotube remained almost unchanged after H2S adsorption. Using ab initio molecular dynamics simulations, we show that H2S may poison the nanowire and faceted-nanotube surface, while H2S causes the nanotube structure to distort significantly.