MoO3 nanoflakes coupled reduced graphene oxide with enhanced ethanol sensing performance and mechanism

In this paper, MoO3 nanoflakes coupled reduced graphene oxide (MoO3-rGO) composites were fabricated by annealing the MoS2-GO nanosheet, and the MoO3-rGO shows high sensitivity, fast response, and good selectivity to ethanol. The response towards 100, 200, 500, and 8000 ppm of ethanol is 53, 68.98, 117.0, and 702, respectively, which are 5.4, 4.83, 5.05, and 3.64 times higher than the MoO3 at the working temperature of 310 (sic)C. Besides, the response time of MoO3-rGO to 100 ppm of ethanol at 280, 310, and 350 (sic)C is 7 s, 6 s, and 4 s, respectively. In addition, the MoO3-rGO shows good selectivity to ethanol over n-propanol, methanol, isopropanol, xylene, acetone, and benzene. ESR and XPS spectra of samples before and after exposed in ethanol have been used to detect the vacancy oxygen and chemical state of the MoO3 in the responding process, and the possible sensing mechanism of the MoO3 to ethanol has also been discussed. Both the adsorbed oxygen and lattice oxygen participate in the reaction process, and the adsorbed ethanol molecules is catalytically oxidized into H2O and CO2 molecules, and in this process the resistance has changed. And the results indicate that the Mo5+ also plays an important role in the sensing process.