Graphene/Rh-doped SnO<inf>2</inf> nanocomposites synthesized by electrochemical exfoliation and flame spray pyrolysis for H<inf>2</inf>S sensing

Abstract

In this study, flame-made Rh-doped SnO2/electrochemically exfoliated graphene hybrid materials were developed and systematically investigated for gas sensing towards H2S. Structural characterizations by various microscopic and spectroscopic techniques demonstrated the dispersion of graphene sheets on Rh-substituted polycrystalline SnO2 nanoparticles with improved specific surface area. The effects of Rh dopants and graphene on gas-sensing behaviors of the hybrid sensors were systematically evaluated towards H2S, H2, CH4, C2H2, C2H4, CH3SH, CO2, C2H5OH, C3H6O and NO2 at 200–400 °C in dry and humidified air with 20–80% RH. It was found that Rh doping at the optimal amount of 0.5 wt% considerably enhances the response and selectivity of flame-made SnO2 nanoparticles toward H2S and additional graphene loading further increases the H2S-sensing performance with the optimum graphene content of 0.5 wt%. Accordingly, the 0.5 wt% graphene-loaded 0.5 wt% Rh-doped SnO2 sensor provided the highest responses of ∼439 and the shortest response time of 6.5 s to 10 ppm H2S with high selectivity against CH3SH, H2, CH4, C2H2, C2H4, CO2, C2H5OH, C3H6O and NO2 at the optimal working temperature of 350 °C. The mechanisms of H2S response enhancement were described by the combinative effects of catalytic p-type substitutional Rh dopants and active graphene–Rh-doped SnO2 junctions.