LAUSR

Abstract VO2 shows a phase transition from the monoclinic phase at 300 K to the tetragonal rutile phase at 350 K, and both phases present highly selective sensing performance towards methane. However, the atomic-level gas sensing mechanisms for the VO2–based systems remain unclear. In this work, the sensing performance of the monoclinic and tetragonal rutile phases of VO2 towards CH4, H2, CO2 and CO molecules was studied by using a first principles method. From calculation of the adsorption energies, charge transfer and density of states, VO2 was found to show a highly selective sensing performance towards CH4 compared to H2, CO and CO2, which is in accordance with experimental results. CH4 tends to form stable H O bonds with the monoclinic and tetragonal rutile phases of VO2, with lengths of 0.95 A and 1.05 A, respectively. The maximum current in the current–voltage relationship for the VO2-methane system was found to be significantly greater than that obtained for other methane-incorporated systems reported in previous studies. The diffusion of CH4 gas in VO2 is more difficult compared to other gases due to chemical adsorption of CH4. This study provides a theoretical foundation for designing VO2-based high performance gas sensors.