Using waste silver metal in synthesis of Z-scheme Ag@WO3-CeO2 heterojunction to increase photodegradation and electrochemical performances

Abstract

Design of a Z-scheme heterojunction structure is eco-friendly due to its multi-nanocatalyst performances like wastewater treatment, antibacterial and electrochemical activity. Herein, Ag was extracted from waste batteries in a nitric acid leaching manner. Also, WO3 nanorods and WO3-CeO2 were synthesized by the surfactant-assisted hydrothermal acidic and sol–gel methods, respectively. Silver nanoparticles were doped by wet impregnation method to prepare ternary (Ag@WO3-CeO2) and binary (Ag@WO3 and Ag@CeO2) heterojunctions. The band gap of the prepared Ag@WO3-CeO2 was remarkably diminished in comparison with the rest of the sample (from 2.73 to 2.59 eV). The Langmuir-Hinslewood model showed that ternary systems can degrade methylene blue twice as much as WO3-CeO2 and seven times more than single-component systems. This was due to the presence of silver as a mediator for the transfer of photogenerated electrons between two semiconductors. Also, methylene blue was degraded by more than 90.8% efficiency. Electrochemical impedance spectroscopy (EIS) analysis confirmed that the charge transfer resistance of Ag@WO3-CeO2 was decreased by more than 50%. The results of bactericidal activeness confirmed elevated inhibition capability of Ag@WO3-CeO2 towards E.coli with 99% degradation. X-ray fluorescence (XRF) results confirmed that 98% of silver can be re-extracted after 5 photocatalytic uses which is a material with green technology.