Topochemical Preparation of WO3 Nanoplates through Precursor H2WO4 and Their Gas-Sensing Performances

Size- and shape-controllable preparation of WO3 nanoplates has been successfully realized through topochemical transformation of corresponding H2WO4 precursors synthesized by a facile solution-phase method. The fluoroboric acid was found to not only provide acid source but also act as a structure-directing agent during the growth process of H2WO4 nanoplates in the solution phase. WO3 nanoplates could be obtained by the two different topochemical transformation methods, hydrothermal treatment of H2WO4 nanoplates at the temperature (above 160 °C) and calcination at higher temperatures in air, based on their similarity of the W–O octahedral layers in both H2WO4 and WO3. Furthermore, the enhanced ethanol-sensing performance could be attributed to the plate-like morphology, especially the high crystallinity, due to the advantages of the effective adsorption and rapid diffusion of the ethanol molecules.