RGO supported ZnO/SnO2 Z-scheme heterojunctions with enriched ROS production towards enhanced photocatalytic mineralization of phenolic compounds and antibiotics at low temperature

In the present study, the excellent photocatalytic activity of n-ZnO/n-SnO2 heterojunction integrated with reduced graphene oxide nanosheets was explored towards the elimination of different organic pollutants viz. p-bromophenol, bisphenol A, and ofloxacin from water. n-ZnO/n-SnO2 heterojunction was decorated with a different weight percentage of reduced graphene oxide via a facile refluxing method. The structural, morphological and optical properties of the as-prepared n-ZnO/n-SnO2 heterojunctionreduced graphene oxide nanocomposites were investigated systematically. XRD, Raman and FT-IR confirmed the hexagonal wurtzite and tetragonal rutile structures of ZnO and SnO2 crystals in different nanocomposites. Cube and spherical-shaped surface structures were demonstrated by TEM and FESEM analysis for ZnO and SnO2, respectively. The maximum photocatalytic productivity of nanocomposite with 5 wt% reduced graphene oxide was observed at about 98.64 % and 98.50 % towards the elimination of p-bromophenol and bisphenol A, respectively after 180 min exposure of UV light. Similarly, this productivity was also observed at about 99.13 % towards the elimination of ofloxacin after 120 min irradiation of UV light. The outstanding photocatalytic activity of nanocomposite with 5 wt% reduced graphene oxide has been proven by the presence of homotypic n-ZnO/n-SnO2 and reduced graphene oxide nanosheets owing to the synergistic effect amongst them resulting in remarkable separation of charge carriers, which is responsible for the larger rate of reactive oxygen species generation and enhanced photodegradation of p-bromophenol, bisphenol A , ofloxacin. In this study, the results illus-trated that the photocatalytic degradation of p-bromophenol, bisphenol A and ofloxacin using n-ZnO/n-SnO2 heterojunction-reduced graphene oxide nanocomposites is predominantly based on the hydroxyl radicals and superoxide radical anion as main reactive oxygen species as compared to 1O2. A reasonable photodegradation mechanism using prepared nanocomposites under investigation has also been proposed. (c) 2022 Elsevier Inc. All rights reserved.

Automated summary

In this study, the excellent photocatalytic activity of n-ZnO/n-SnO2 heterojunction integrated with reduced graphene oxide nanosheets was investigated for the removal of various organic pollutants from water. The nanocomposites with different weight percentages of reduced graphene oxide were synthesized and characterized. The results showed that the nanocomposite with 5 wt% reduced graphene oxide exhibited the highest photocatalytic productivity towards the elimination of different organic pollutants. The synergistic effect between n-ZnO/n-SnO2 heterojunction and reduced graphene oxide nanosheets contributed to the enhanced photodegradation.