Facile synthesis of ZnO/SnO2 hybrids for highly selective and sensitive detection of formaldehyde

One of the on-going problems with formaldehyde sensors is poor selectivity. In this study, 2D ZnO/0D SnO2 hybrids are prepared via a simple hydrothermal process with a subsequent heat treatment. The purity, morphology, crystallographic information and surface chemical composition of the as-obtained ZnO-SnO2 hybrids are characterized by XRD, SEM, TEM and XPS, respectively. The gas sensing performance of the ZnO-SnO2 hybrids is discussed in detail. The results show that the ZnO-SnO2 hybrids not only exhibit excellent formaldehyde selectivity (S-HCHO/S-ethanol = 10.6), but also show a high response of 70.8 to 100 ppm of formaldehyde, which is 32 and 35 times higher than those of pure ZnO nanosheets and SnO2 nanoparticles, respectively. In addition, the ZnO-SnO2 hybrids display short response and recovery time (1 and 9 s) to 100 ppm of formaldehyde. The enhanced sensing performance is mainly attributed to the creation of defects and the formation of n-N heterojunctions. Thus, it can be regarded as a promising material to detect formaldehyde effectively.