Modification Of Porous Tungsten Oxide And Its Application In Gas Sensing And Humidity Sensing

Tungsten oxide(WO3)contains abundant structure defects which are beneficial to gas sensing and humidity sensing performances.Developing an effective method to modify WO3 nanomaterials with better gas sensing performance has raised many concerns.Element doping and structural modifications are two of the most effective methods to improve the sensing property.Element doping not only promotes the generation of structure defects which help the adsorption of NO2 and water molecules but also contributes to the increase of carrier mobility and surface adsorbed oxygen.The investigation on mechanism of alkali metal doped WO3 sensing performance based on the structural and electronic properties has not been reported,and there are only a few researches of 3DOM WO3 nanomaterials on gas sensing sensors and humidity sensing sensors.In this work,alkali metal mono-doped and co-doped 3DOM WO3 are synthesized using a colloidal crystal templating method.And the effect of structural and electronic properties on the gas sensing and humidity sensing performance are further discussed.The specific experimental works are concluded as follows:1.Alkali metal doped 3DOM WO3 were prepared and applied to the test of NO2.Our experimental results indicated that alkali metal especially Li doping remarkably improved NO2 sensing performance.The highest response of 3DOM WO3/Li to 500 ppb NO2 is about 258 at 150 ℃,which was almost 7 times far higher than NO2 response value of pure 3DOM WO3.In addition,3DOM WO3/Li showed excellent sensing property at room temperature(25 ℃).The huge improvement on the NO2 sensing performance was attributed to the optimized structural and electronic properties.Alkali metal doped 3DOM WO3 with abundant structure defects which help the adsorption of NO2 possess the improved gas sensing performance.The increased carrier mobility due to the doping of alkali metals,which could accelerate the surface reaction,is another reason for the improved NO2 sensing performance.2.Li/K co-doped 3DOM WO3 was synthesized and applied to the humidity measurement.Compared with the pure and Li mono-doped samples,the co-doped sample showed better humidity sensing performance.The results of XRD,XPS and UV-vis characterizations demonstrated that structure defects and surface adsorbed oxygen are the main reasons for the improved humidity sensing performance.Meanwhile,Li+ is beneficial to the dissociation of water molecules and K+ could participate in the ion conduction process,leading to the better humidity sensing property.