Density functional theory study of the NO2-sensing mechanism on a WO3 (001) surface: the role of surface oxygen vacancies in the formation of NO and NO3

The trapping and detection of nitrogen oxide with tungsten trioxide has become a popular research topic in recent years. Knowledge of the complete reactionmechanism for nitrogen oxide adsorption is necessary to improve detector performance. In this work, we used density functional theory (DFT) calculations to study the adsorption characteristics and electron transfer of nitrogen dioxide on an oxygen-deficient monoclinic WO3 (001) surface. We observed different reactions of NO2 on slabs with different O- and WO-terminated WO3 (001) surfaces with oxygen vacancies. Our calculations show that the bridging oxygen atom on an oxygen defect on an O-terminated WO3 (001) surface is the active site where an NO2 molecule is oxidised into nitrate and is adsorbed onto the surface. On a WO-terminated (001) surface, one of the oxygen atoms from the NO2 molecule fills the oxygen vacancy, and the resulting NO fragment is adsorbed onto a W atom. Both of these adsorption models can cause an increase in the electrical resistance of WO3. We also calculated the adsorption energies of NO2 on slabs with different oxygen-deficient WO3 surfaces. [GRAPHICS] .