Highly enhanced gas sensing properties of porous SnO2-CeO2 composite nanofibers prepared by electrospinning

Porous SnO2-CeO2 (Ce/(Sn + Ce) = 3, 5, 7, and 10% (in molar ratio)) composite nanofibers (NFs) were fabricated by the electrospinning method and characterized by various techniques, such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), UV-vis absorption and X-ray photoelectron spectroscopy (XPS). The results indicated that, as the content of Ce gradually increased, the as prepared NFs showed a mixed phase of SnO2 and CeO2. The band gaps of the composite NFs gradually decreased, and the ratio of Sn2+ and Sn4+ increased, and Ce3+ and Ce4+ also existed, implying the improvement of surface oxygen vacancies. They were then explored to fabricate the bifunctional gas sensors and the gas sensing test revealed that in comparison to the pure SnO2 sensor, all the composite sensors demonstrated highly improved sensing performance to ethanol, and for the optimum sensor (7%), the response was improved more than one order at 370 °C. When the content of Ce was appropriate (3%), the response to dilute H2S was also improved ∼2.5 times at 210 °C. These enhanced gas sensing properties are closely related to the role change of Ce in different composite NFs, and their mechanisms were carefully discussed.