MoO2-Ni-graphene ternary nanocomposite for a high- performance room-temperature ethanol gas sensor

Abstract Synthesis of high-performance room-sensing materials have attracted lots of attention in the gas sensor area. In this work, ternary sensing material of MoO2-Ni-Graphene composite was synthesized by the hydrothermal method. Through X-ray diffraction, Raman spectroscopy and X-ray photoelectron spectroscopy, the existence of chemisorbed oxygen contents introduced by the annealing processes are validated (the intensity of graphene oxide (GO) peak (C (0 0 2)) at 9.90° is increased, and the oxidation state of Mo is changed from 6+ to 4+ and 5+). The gas sensing performance of composites to ethanol, formaldehyde, and ammonia was then tested and response (Rg/Ra) of the sample annealed at 400 °C towards 1000 ppm ethanol was improved to 105 at room temperature and the minimum detection limit was 15 ppm. Meanwhile, it didn’t show response towards formaldehyde. For the enhanced sensitivity and selectivity of sensor towards ethanol, metallic nature of Ni and MoO2 on graphene surface, interaction of hydroxyl species via hydrogen bonding and lower LUMO energy levels (0.13 eV) value of ethanol were the main factors. Moreover, long term stability of 40 ppm ethanol for 30 days with response 21.61 ± 0.96 suggested that proposed sensor could be an ideal candidate for future commercial ethanol sensing.