Liquid flame spray fabrication of WO3-reduced graphene oxide nanocomposites for enhanced O3-sensing performances

Abstract

WO3 is one of the inspiring sensing materials that show high response to O3; an efficient fabrication of WO3 film with incorporation of complementary additives is essential for enhanced sensitivity. Here we report film deposition by liquid flame spraying, characterization of nanostructured WO3-reduced graphene oxide (rGO) composites and their gas-sensing activities to O3. The starting feedstock was prepared from WCl6 and rGO for pyrolysis synthesis by flame spraying. Nano-porous WO3-rGO films were successfully fabricated and characterized by transmission electron microscopy, field emission scanning electron microscopy, Raman spectrometry, thermal analyses and X-ray diffraction. Nanosized WO3 grains exhibited oriented nucleation on rGO flakes whereas rGO retained intact its nano-structural features after spraying. Constrained grain growth of WO3 of 60–70 nm in size was realized in the rGO-containing films with as compared to ~220 nm in the pure WO3 film. The WO3-rGO film sensors showed quicker response to O3 and faster recovery than rGO-free WO3 film sensors. Addition of rGO in 1.0 wt% or 3.0 wt% in the films caused a significantly reduced effective working temperature of the film sensors from ~ 250 °C to ~ 150 °C.