rGO/CoTiO3 nanocomposite with enhanced gas sensing performance at low working temperature

The CoTiO3 decorated rGO sheet nanocomposites have been prepared by a facile sol-gel method. The obtained rGO/CoTiO3 nanocomposites exhibited enhanced sensitivity to ethanol vapor at relatively low working temperature. The relationship between microstructure and sensing properties of rGO/CoTiO3 was investigated to clarify the sensing mechanism. The results showed that the rGO concentration of the composite influenced the sensing performance significantly. The S4 sample with 3.9 wt% GO is the most sensitive and selective to ethanol gas at optimal working temperature of 195 °C. The response of S4 to 10 ppm ethanol is 5.5 and the response/recovery time is 2 s/4 s. Compared to pure CoTiO3, the operating temperature decreased 150 °C. The enhanced sensitivity is mainly attributed to following aspects. (1) High conductivity at relatively low temperature due to the presence of rGO; (2) The rGO/CoTiO3 p-p nanojunctions facilitate additional chemisorption of oxygen and carrier transfer; (3) More Ti3+ concentration in the crystal lattice which offers more active adsorption sites. Besides, Ti3+ is an effective catalyst for redox reaction between ethanol and the adsorbed oxygen. (4) The rGO nanosheets which contain functional groups (CO and COOH) may catalyze the gas adsorption, desorption process and activate the subsequent gas redox reaction.