Unveiling the acetone sensing mechanism by {WO}3 chemiresistors through a joint theory-experiment approach

The acetone sensing mechanism by WO3 was investigated through a combined experimental and theoretical approach. The γ−monoclinic WO3 powder was synthesized by a template-mediated sol-gel method and characterized on struc- tural, surface, morphological and optical points of view. A thin film of WO3 was deposited on interdigitated Au electrodes by hot-spray method and tested at 300 ◦C (while applying a bias of 1.0 V) for acetone gas sensing, both in presence and absence of oxygen in the gas carrier. Interestingly, the absence of oxygen had no significant effect on the sensor response intensity but it dramat- ically increased the recovery times (from 120 s to 2700 s). In order to explain these experimental results, by means of ab initio density functional theory cal- culations, we modeled a defective γ−WO3 surface structure and simulated the adsorption of acetone and oxygen molecules on top of it. We unprecedentedly evidenced that, in presence of surface oxygen vacancies, both acetone adsorption and its oxidation reaction can occur. However, their contribution to the sen- sor response strictly depends on the inert/oxidative atmosphere present in the sensing chamber, which in turn strongly affects the surface oxygen population. Our findings can either be the guidelines for future studies aimed at delineating the possible reaction products or pave the way for the engineering of tailored nanomaterials having specific surface features and enhanced sensing properties.