Structural and electronic engineering of 3DOM WO3 by alkali metal doping for improved NO2 sensing performance

Abstract

Novel alkali metal doped 3DOM WO₃ materials were prepared using a simple colloidal crystal template method. Raman, XRD, SEM, TEM, XPS, PL, Hall and UV-Vis techniques were used to characterize the structural and electronic properties of all the products, while the corresponding sensing performances targeting ppb level NO₂ were determined at different working temperatures. For the overall goal of structural and electronic engineering, the co-effect of structural and electronic properties on the improved NO₂ sensing performance of alkali metal doped 3DOM WO₃ was studied. The test results showed that the gas sensing properties of 3DOM WO₃/Li improved the most, with the fast response–recovery time and excellent selectivity. More importantly, the response of 3DOM WO₃/Li to 500 ppb NO₂ was up to 55 at room temperature (25 °C). The especially high response to ppb level NO₂ at room temperature (25 °C) in this work has a very important practical significance. The best sensing performance of 3DOM WO₃/Li could be ascribed to the most structure defects and the highest carrier mobility. And the possible gas sensing mechanism based on the model of the depletion layer was proposed to demonstrate that both structural and electronic properties are responsible for the NO₂ sensing behavior.