Thin Films (FTO/BaTiO₃/AgNPs) for Enhanced Piezo-Photocatalytic Degradation of Methylene Blue and Ciprofloxacin in Wastewater

In this study, we investigate the ability of barium titanate/silver nanoparticles (BaTiO₃/AgNPs) composites deposited on a fluorine-doped tin oxide (FTO) glass using tape-casting method to produce piezoelectric thin film (FTO/BaTiO₃/AgNPs) for piezocatalytic, photocatalytic, and piezo-photocatalytic degradation of methylene blue (MB) and ciprofloxacin (CIP) in wastewater. The prepared piezoelectric materials (BaTiO₃and BaTiO₃/AgNPs) were characterized using XRD, SEM, TEM, EDS, UV-DRS, TGA, PL, BET, EIS, and chronoamperometry. The UV-DRS showed the surface plasmon resonance (SPR) of Ag nanoparticles on the surface of BaTiO₃at a wavelength of 505 nm. The TEM images revealed the average Ag nanoparticle size deposited on the surface of BaTiO₃to be in the range of 10-15 nm. The chronoamperometry showed that the photoreduction of silver nanoparticles (AgNPs) onto BaTiO₃(BTO) resulted in a piezo-electrochemical current enhancement from 0.24 to 0.38 mA. The composites (FTO/BaTiO₃/AgNPs) achieved a higher degradation of MB and CIP when the photocatalysis and piezocatalysis processes were merged. Under both ultrasonic vibration and UV light exposure, FTO/BTO/AgNPs degraded about 72 and 98% of CIP and MB from wastewater, respectively. These piezoelectric thin films were shown to be efficient and reusable even after five cycles, suggesting that they are highly stable. Furthermore, the reactive oxygen species studies demonstrated that hydroxyl radicals (·OH) were the most effective species during degradation of MB, with minor superoxide radicals (·O₂^-) and holes (h⁺). From this study, we were able to show that these materials can be used as multifunctional materials as they were able to degrade both the dye and pharmaceutical pollutants. Moreover, they were more efficient through the piezo-photocatalytic process.