Enhanced photocatalytic degradation of methylene blue dye using eco-friendly synthesized rGO@ZnO nanocomposites

Asfaw Negash; Said Mohammed; Hulugirgesh Degefu Weldekirstos; Abera D Ambaye; Minbale Gashu

doi:10.1038/s41598-023-48826-7

Enhanced photocatalytic degradation of methylene blue dye using eco-friendly synthesized rGO@ZnO nanocomposites

Sci Rep. 2023 Dec 14;13(1):22234. doi: 10.1038/s41598-023-48826-7.

Authors

Asfaw Negash¹, Said Mohammed², Hulugirgesh Degefu Weldekirstos², Abera D Ambaye^{3

4}, Minbale Gashu⁵

Affiliations

¹ Department of Chemistry, Debre Berhan University, P.O. Box 445, Debre Berhan, Ethiopia. asfawnegash@dbu.edu.et.
² Department of Chemistry, Debre Berhan University, P.O. Box 445, Debre Berhan, Ethiopia.
³ Institute for Nanotechnology and Water Sustainability, University of South Africa, Florida Science Campus, Johannesburg, 1710, South Africa.
⁴ Materials Science and Engineering Research, Bio and Emerging Technology Institute, P.O. Box 5954, Addis Ababa, Ethiopia.
⁵ Department of Chemistry, Debre Berhan University, P.O. Box 445, Debre Berhan, Ethiopia. minbalegashu@dbu.edu.et.

Abstract

Industrial chemical pollutants such as methylene blue (MB) dye are released into the water body and potentially cause harm to the human and aquatic biosphere. Therefore, this study aims to synthesize eco-friendly nanocatalysts, i.e., reduced graphene oxide (rGO), zinc oxide (ZnO), and reduced graphene oxide-zinc oxide (rGO@ZnO) nanocomposites, for efficient photocatalytic degradation of MB dye. A graphite rod was obtained from waste dry cell batteries for the electrochemical exfoliation synthesis of graphene oxide (GO) and rGO. For the eco-friendly synthesis of ZnO and rGO@ZnO nanocatalysts, Croton macrostachyus leaf extract was used as a reducing and capping agent. The synthesized nanocatalysts were characterized using a UV-Vis spectrophotometer, Fourier transform infrared spectroscopy, X-ray diffraction, and scanning electron microscopy with energy-dispersive X-ray. The eco-friendly synthesized rGO, ZnO, and rGO@ZnO nanocatalysts were applied for the photocatalytic degradation of MB dye using direct sunlight irradiation. At optimum parameters, photocatalytic degradation of MB dye efficiency reached up to 66%, 96.5%, and 99.0%, respectively. Furthermore, kinetics of the photodegradation reaction based on rGO, ZnO, and rGO@ZnO nanocatalysts follow pseudo-first-order with a rate constant of 2.16 × 10^-3 min^-1, 4.97 × 10^-3 min^-1, and 5.03 × 10^-3 min^-1, respectively. Lastly, this study promotes a low catalyst load (20 mg) for the efficient photodegradation of MB dye.