Atomic-level insights of enhanced interfacial charge transfer and active sites on self-assembly p-p heterostructure based on BiVO4/SnO2 for highly selective NO2 sensing

Abstract

Even though there are several reports on gas detectors, the issue that remains unaddressed is selective sensing. In this work, a selective sensor is made by using well-ordered spherical shape BiVO4 and self-assembled p-p heterojunctions based on BiVO4/SnO2 nanocomposites. The self-assembly of SnO2 NPs on the defect sites of BiVO4 can easily be seen by the FESEM and HRTEM images. XPS spectrums indicate that the nanocomposite shows more active sites to adsorb gas molecules. The sensing characteristics of BiVO4/SnO2 as well as pristine BiVO4 and SnO2 reveal the p-type characteristics and confirm the formation of p-p heterojunctions. The sensing performance of the self-assembled BiVO4/SnO2 thin film gas sensor has been significantly improved by incorporating SnO2 and the sensor response of the self-assembled BiVO4/SnO2 is 1.98 which is much higher than pure BiVO4 and SnO2 and the lowest detection limit (LOD) was found as 7.8 ppb. Various configurations for the different heterostructures of BiVO4/SnO2 have been analyzed by using density functional theory and the results of p-p heterostructure are quite analogous with the experimental results. Enhancement in the number of active sites by the addition of SnO2 was also observed in the DFT interpretation.