Ultrathin SnO2 nanosheets with dominant high-energy {001} facets for low temperature formaldehyde gas sensor

Semiconducting metal oxides (SMO) have been investigated as important gas sensing materials for detecting various inflammable and toxic gases; however most of them are suffered from low response and high operation temperature. Ultrathin SnO2 nanosheets with dominant high-energy {001} facets were synthesized by a facile hydrothermal method, and the gas sensing properties to formaldehyde (HCHO) were systemically studied. The structure, morphology, specific surface area, band gap and chemical state of the ultrathin SnO2 nanosheets were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscope (TEM), N-2 adsorption-desorption, UV-Vis diffuse reflectance spectrum and X-ray photoelectron spectroscopy (XPS), respectively. Sensors based on SnO2 nanosheets show outstanding gas sensing properties to HCHO vapor at the optimum operating temperature (OOT) of 200 degrees C. The nanosheet sensor exhibit a response of 207.7 to 200 ppm HCHO at 200 degrees C with the response-recovery time of 30 s and 57 s, respectively. Notably, as low as 1 ppm HCHO can be readily detected with a high response value (S-r = 6.1). The excellent HCHO sensing performance is mainly originated from the structural sensitization of large specific surface area, characteristically small thickness and dominant high-energy {001} facets.