Roles of cobalt doping on ethanol-sensing mechanisms of flame-spray-made SnO2 nanoparticles−electrolytically exfoliated graphene interfaces

Abstract In this work, the roles of cobalt (Co) and electrolytically exfoliated graphene additives on ethanol gas-sensing properties of flame-spray-made SnO 2 nanoparticles were systematically studied. Structural characterizations indicated that Co dopants formed solid solution with SnO 2 nanoparticles while multilayer graphene sheets were well dispersed within the Co-doped SnO 2 matrix 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/SnO 2 composites. Furthermore, the optimal sensor exhibited high ethanol selectivity against C 3 H 6 O, NO 2 , H 2 S, H 2, CH 4 and 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 SnO 2 M-S junctions with highly accessible surface area of micropores and mesopores in the composites. Therefore, the graphene loaded Co-doped SnO 2 sensor is highly potential for responsive and selective detection of ethanol vapor at ppm levels and may be practically useful for drunken driving applications.