Fe3O4/ZnO/L-lysine functionalized graphene oxide a promising nanocomposite with double Z-scheme visible photocatalytic and dark catalytic activity for water remediation

Abstract

Developing multifunctional catalysts for efficient pollutant degradation in dark and visible light conditions represents a significant advancement in water remediation technology. This study reports the synthesis of a novel Fe3O4/ZnO/Lys-rGO nanocomposite via environmentally friendly methods that exhibit catalytic-photocatalytic activity for efficient degradation of organic pollutants. The synergistic effect of compositing Lys-rGO, a bio-organic component with a narrow band gap (1.08 eV), into the Fe3O4/ZnO inorganic composite induces a double Z-scheme mechanism by providing two pathways for effective charge separation in the visible photocatalytic activity of the nanocomposite. Additionally, the stored electrons in the very conductive Lys-rGO layers offer active sites for the catalytic activity of the nanocomposite in the dark. Meanwhile, ZnO generates reactive oxygen species (ROS) through surface oxygen vacancies, further contributing to the nanocomposite’s dark catalytic activity. The degradation of various organic pollutants (Methylene Blue, Tetracycline, Ciprofloxacin, Rhodamine B, and their mixture), as well as Congo Red, with low catalyst dosage and visible light irradiation time, demonstrates the high performance and versatility of this nanocomposite. This research highlights the potential of Lys-rGO in compositing with semiconductors to design multifunctional catalysts for cost-effective sustainable water purification technologies.