Novel ZnO blended SnO2 nanocatalysts exhibiting superior degradation of hazardous pollutants and enhanced visible photoemission properties

Abstract

Hazardous dyes mixed with water bodies are causing a big threat to human life and need to be degraded effectively. Heterogeneous photocatalysis is the most promising method and has been found to be efficacious in dealing the above issue. Herein, we present an extensive study on the development of ZnO/SnO2 nanocomposites (NCs) towards the degradation of a series of harmful dyes such as; methyl orange, methylene blue and Congo red. X-ray diffraction (XRD) measurement confirmed the formation of the NCs comprised of tetragonal rutile phased SnO2 and wurtzite phased ZnO without the presence of any impurity phases. Disappearance of the excitonic emission of ZnO in the photoluminescence (PL) emission spectra of NCs manifests an inhibition in the direct recombination of electron-hole pairs. Introduction of defect centers also hinders the recombination of charge carriers acting as trapping sites and leads to an improvisation in the visible emissions and visible light photocatalytic activity. ZnO-SnO2 manifests enhanced photodegradation efficiency owing to the availability of large number of active sites and increased electron-hole separation efficiency in the coupled system. Accumulated electrons on SnO2 and holes on ZnO surfaces lead to an increased carrier life limiting the fast recombination of carriers. Formation of highly reactive OH� and super-oxide O2�? radicals is also responsible for effective decomposition of the dyes. The effect of photocatalyst loading and initial dye concentration along with pH on the degradation efficiency has also been studied and discussed mechanistically. ZnO-SnO2 NCs are also highly stable and reusable after different cycles of experiment. � 2021