Application of a piezo-photocatalytic thin film (FTO/BaTiO₃/SnO₂) for enhanced degradation of organic pollutants and disinfection of wastewater

In recent years, the removal of organic pollutants (dyes and pharmaceuticals) and microbes from polluted water has remained a significant concern. We report a novel biosynthesized SnO₂ loaded fluorine-doped tin oxide/barium titanate (FTO/BTO) thin film for piezo-photocatalytic degradation of methyl orange (MO), methylene blue (MB) and ciprofloxacin (CIP), as well as for the removal of gram-negative E. coli and gram-positive S. aureus bacteria from water. Piezo-photocatalyst thin films were characterised using XRD, FTIR, FE-SEM, TEM, TGA, BET, XPS, PL and UV-DRS spectroscopy. The deposition of the small spherically shaped SnO₂ nanoparticles on the surface of BaTiO₃ was confirmed by TEM, EDS and FTIR. Chronoamperometry and electrochemical impedance spectroscopy (EIS) were employed to determine piezo-electrochemical properties of the prepared piezo-photocatalyst thin films. The results showed that BaTiO₃ loaded with SnO₂ on its surface, exhibited a higher piezo-electrochemical current than pure BaTiO₃ (BTO). FTO/BaTiO₃@0.2%SnO₂ generated about 1.3 mA current under ultrasonic vibration, which is more than 6 times that of pure FTO/BaTiO₃. Furthermore, FTO/BaTiO₃@0.2%SnO₂ showed a better degradation efficiency of 94, 92 and 64% for MO, MB and CIP, respectively. Additionally, BaTiO₃@0.2%SnO₂ was shown to have a higher antibacterial activity against gram-negative E. coli bacteria than against gram-positive S. aureus bacteria. Overall, this study showed that the piezo-photocatalytic activity of BaTiO₃ could be improved through SnO₂ loading. Moreover we were able to demonstrate that BaTiO₃/SnO₂ composites may be employed as multifunctional catalysts based on their ability to break down various organic contaminates (dyes and pharmaceutical pollutants), and to remove bacteria from wastewater.