Computational study of surface orientation effect of rutile TiO2 on H2S and CO sensing mechanism

Abstract

The adsorption of hazardous CO and H2S on four low-index surfaces of rutile TiO2 surfaces was investigated using first-principle calculations, in an effort to distinguish the difference of surface reactivity on these surfaces in sensing process. We predicted that rutile TiO2 possessed excellent capacity for H2S detection than CO based on adsorptive structure, density of states (DOS) analysis and charge density difference (CDD) plots. Particularly, in H2S adsorption, the dissociative adsorption process occurred on the (001) surface of TiO2 with largest adsorption energy as 1.17 eV and noticeable modification in the electronic structure, rendering high sensitivity on this surface. The decomposition of H2S yielded HS and H species, whose bonding features were also analyzed. It was suggested that 3p states of HS were able to mix with surface titanium and the 1 s states of H were considerably overlapped with 2p states of surface bridging oxygen, forming OH radicals on (001) surface. The reason for different sensing properties on these surfaces was pinpointed, and the significance of rutile (100) facet in H2S monitoring was underlined. These preliminary investigations would provide a basic understanding for CO and H2S adsorption for pursuing high-performance sensor toward targeted gas.