Understanding on the ethanol sensing mechanism of atmospheric plasma sprayed 25 wt. % WO3-75 wt. % SnO2 coating

Publication date: 1 July 2019Source: Sensors and Actuators B: Chemical, Volume 290Author(s): V. Ambardekar, P.P. Bandyopadhyay, S.B. MajumderAbstractAtmospheric plasma spray was utilized to fabricate 25 wt. % WO3-75 wt. % SnO2 composite coating on alumina substrate for ethanol sensing. Analyzing the conductance transients we have demonstrated that the response transients follow Freundlich adsorption isotherm. From isotherm analyses we have estimated the activation energy of the adsorption of test vapors (Ea) and heat of adsorption (Q) as a function of concentration and reported that maximum response % of ethanol among acetone and isopropanol matches well with lowering of (Ea + Q) for ethanol sensing. Though the composite sensor exhibits superior ethanol sensing characteristics, it is cross-sensitive to acetone and isopropanol vapors. Two dominant factors namely nature of sensing surface and formation of hetero-junction are postulated to control the ethanol sensing characteristics in WO3-SnO2 composites. Relatively basic nature of the composite surface catalyzes dehydrogenation reaction during ethanol sensing. This, together with the formation of n(WO3)-n(SnO2) hetero-junction is explained to adsorb more oxygen to yield superior ethanol sensing characteristics as compared to acetone and isopropanol.

Source: Sensors and Actuators B: Chemical - April 10, 2019 Category: Chemistry Source Type: research