Ultrathin CeO 2 nanosheets as bifunctional sensing materials for humidity and formaldehyde detection

Abstract Issues like morphology control and further multifunctional applications are of significant importance for rare earth nano‐oxides, e.g., cerium dioxide (CeO 2 ) nanostructures, however, relevant results in this respect are rather limited up to now. In the present work, ultrathin CeO 2 nanosheets were synthesized through a facile low‐temperature hydrothermal method. The structure, morphology and specific surface area of these CeO 2 nanosheets were characterized by X‐ray diffraction (XRD), field emission scanning electron microscope (FESEM) and N 2 adsorption–desorption. Significantly, CeO 2 nanosheets have the potential as bifunctional sensing materials to detect both humidity and formaldehyde vapor. The CeO 2 nanosheet humidity sensor exhibited excellent sensing characteristics in the relative humidity range of 11%–97% with the response value as high as 3.1 × 10 4 . Meanwhile, the CeO 2 nanosheet gas sensor showed superior sensitivity and repeatability with fast response/recovery speed toward formaldehyde vapor at 300 °C. Finally, the humidity and formaldehyde sensing mechanism were discussed as well.