Roles of cobalt doping on ethanol-sensing mechanisms of flame-spray-made SnO<inf>2</inf>nanoparticles−electrolytically exfoliated graphene interfaces

Abstract

© 2017 Elsevier B.V. In this work, the roles of cobalt (Co) and electrolytically exfoliated graphene additives on ethanol gas-sensing properties of flame-spray-made SnO2nanoparticles were systematically studied. Structural characterizations indicated that Co dopants formed solid solution with SnO2nanoparticles while multilayer graphene sheets were well dispersed within the Co-doped SnO2matrix at low graphene loading contents. The sensing films were fabricated by a spin coating process and tested towards 50–1000 ppm ethanol at 150–400 °C. It was found that the response to 1000 ppm ethanol at the optimal working temperature of 350 °C was enhanced from 91 to 292 and to 803 by 0.5 wt% graphene loading and 0.5 wt% Co-doping, respectively. The combination of Co-doping and graphene loading with the same concentration of 0.5 wt% led to a synergistic enhancement of ethanol response to 2147 at 1000 ppm with a short response time of ∼0.9 s and fast recovery stabilization at 350 °C, proving the significance of dopant on the gas-sensing performances of graphene/SnO2composites. Furthermore, the optimal sensor exhibited high ethanol selectivity against C3H6O, NO2, H2S, H2,CH4and humidity. The mechanisms for the ethanol response enhancement were proposed on the basis of combinative effects of catalytic substitutional p-type Co dopants and active graphene−Co-doped SnO2M-S junctions with highly accessible surface area of micropores and mesopores in the composites. Therefore, the graphene loaded Co-doped SnO2sensor is highly potential for responsive and selective detection of ethanol vapor at ppm levels and may be practically useful for drunken driving applications.