The Theoretical Study On Sensitivity And Selectivity Of WO₃ Nanowire Concluding Oxygen Vacancy ?WO₃?Vo??

This paper based on the calculation method of first-principles density functional,using MS?Materials Studio?software,studied the effected of the oxygen vacangas in WO₃ nanowires on its gas sensitivity and selectivity.Based on the experiments of [010]-oriented WO₃ nanowires model,we analysed the non-equivalent oxygens on the surface of nanowires.After removal of the oxygen,thus we could build three vacancy-defective WO₃ nanowire models.Than we established the adsorption model of NO₂ molecules on ideal and defected WO₃ nanowire surface,calculation the adsorption energy,electronic structure,atomc Mulliken charge,analysed the NO₂ gas adsorption performance of the ideal and defected WO₃ nanowires growth direction.It showed the adsorption energy Eads when NO₂ molecule adsorbed on the position of Oa of NW_Vb model is smaller than on the stoichiometric surface of WO₃ nanowire.The bandgap decreased from 2.25 eV to 1.42 eV,which has a larger improvement compared with the adsorption on ideal model.Also the captured electrons of NO₂ molecule are 0.84 e which is larger than it captured from ideal model.According to all elements,we got that the existed of oxygen vacancy could improve the gas sensitivity of WO₃ for adsorption of NO₂.Therefore,to improve the sensitivity of WO₃ nanowire gas sensor,the introducing of oxygen vacancy is a good idea.Than we continue to study the effect of oxygen vacancy on the selectivity of multiple gas.Firstly we built NH₃?CH₄?H₂ and CO molecule adsorption model based on the defected WO₃ nanowire.Calculated energy shows the ideal adsorption model The DOS analyzing shows,nanowire has a larger chang of energy level between bandgap when adsorped NO₂ and NH₃.The transferred electrons?|?q|?after adsorption could response the sensitivity of different molecule adsorbed on WO₃ nanowire,and also could know which gas behaved most selectivity.Compared with CH₄?H₂?CO,NO₂ and NH₃ adsorbed on defected nanowires showed higher sensitivity.But NO₂ and NH₃ have an opposite phenomenon that we could easily being distinguished.So according to the above theory,we could get that defected WO₃ nanowire has a better selectivity for NO₂.Thus the present work provides theoretical understanding for the effect of vacancy on NO₂ sensing mechanism of WO₃ nanowire-based sensor and theoretical hints for the development of high sensitive NO₂ gas sensor using WO₃ nanowire as the base sensing material.