The Study Of Gas Sensors Based On Wo₃with3D Mesoporous Structure

In the process of the sustained society industry rapid development, a large amountof harmful gas NO₂was produced because of taking too much fossil fuel. Research tomonitor harmful gases in the environment fast, in time and accuracy is very important.This paper was aimed to realize high sensitivity at low temperature, studied thepreparation of3D mesoporous WO₃gas sensing material with highly active surface,evaluated and analyzed the sensitive property of the corresponding sensing elements.In this paper two types of typical mesoporous structure SiO2SBA-15and KIT-6were synthesized firstly, we duplicated two kinds of3D structure WO₃gas sensitivematerials in a two-step impregnation process when mesoporous SiO2（SBA-15andKIT-6） acted as hard template, silicotungstic acid as tungsten source precursor.WO₃-SBA-15obtained has a structure of parallel nanowires constituted aquasi-three-dimensional structure by bridging structures that distributed amongnano-wires randomly. While WO₃-kit-6has a more complex3D grid structures, thechannels are multiple through holes. Its specific surface area is135.2m2/g.The gas sensors based on WO₃-SBA-15had higher response sensitivity at125oC,while sensors based on WO₃-KIT-6showed excellent ability to work near roomtemperature at50oC. Both sensors had high sensing response to rare NO₂of ppb levelat their optimum operating temperatures. The response time of gas sensors based onmesoporous structure WO₃to NO₂of ppb and sub-ppm levels was2-3mins, whilerecovery time was a little longer. The Gas sensing test experiment compared to NH3and C2H5OH showed that the both sensors had good selectivity to NO₂.It is unsuitable for the mesoporous tungsten oxide materials to vary property bydoping because of their small mesopore size. Suitable vario-property method andproper doping metal type are important influence factors to the sensing properties ofmesoporous WO₃. In the process of structure cloning, the heat treatment durationwould have significant influence to completeness of mesoporous structure, themorphology would be incomplete without enough time, and sensing properties ofmesoporous structure materials would be affected after on.