Flower-like MoS-Induced α-FeO/Fe(MoO) Nanocomposite as an Ultrafast Sensor for Ethanol Detection.

An ultrafast-responsive α-FeO/Fe(MoO) nanocomposite was developed for the detection of ethanol vapor. The α-FeO/Fe(MoO) nanocomposite was synthesized utilizing a green, normal-pressure, microwave-assisted method followed by an in situ solid-state reaction process with flower-like MoS as a unique precursor. The resulting α-FeO/Fe(MoO) composite presents a porous, agminated petal-like structure with α-FeO nanoparticles homogeneously attached to the surfaces of Fe(MoO) nanosheets. Systematic analyses have demonstrated that the α-FeO/Fe(MoO) composite excels in gas-sensing performance, exhibiting an ultrafast response/recovery, high sensitivity, and selectivity for ethanol vapor concentrations ranging from 1 to 50 ppm. The 5-FeO/Fe(MoO) sensor exhibits the best gas-sensing properties in comparison with sensors of other ratios. At an optimal temperature of 200 °C, the 5-FeO/Fe(MoO) sensor achieves a peak response to 50 ppm ethanol with an ultrafast response time of 5 s and a high response of 12.8. Notably, the sensor boasts a response time of an impressive 3 s to 50 ppm ethanol at 240 °C, while maintaining response times of under 6 s and recovery times within 1 min across the temperature range of 160 to 240 °C. In addition, the 5-FeO/Fe(MoO) sensor demonstrates good selectivity and long-term stability. The enhanced ethanol-sensing properties of the α-FeO/Fe(MoO) nanocomposite could be attributed to its unique three-dimensional porous structure, the synergistic effect between α-FeO and Fe(MoO) species, and the presence of oxygen vacancy defects.