RGO supported ZnO/SnO 2 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-SnO ₂ 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-SnO ₂ 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-SnO ₂ heterojunction-reduced graphene oxide nanocomposites were investigated systematically. XRD, Raman and FT-IR confirmed the hexagonal wurtzite and tetragonal rutile structures of ZnO and SnO ₂ crystals in different nanocomposites. Cube and spherical-shaped surface structures were demonstrated by TEM and FE-SEM analysis for ZnO and SnO ₂ , 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-SnO ₂ 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 and ofloxacin. In this study, the results illustrated that the photocatalytic degradation of p-bromophenol, bisphenol A and ofloxacin using n-ZnO/n-SnO ₂ heterojunction-reduced graphene oxide nanocomposites is predominantly based on the hydroxyl radicals and superoxide radical anion as main reactive oxygen species as compared to ¹ O ₂ . A reasonable photodegradation mechanism using prepared nanocomposites under investigation has also been proposed.
Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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