A porous multilayered TiO2/Bi2WO6 hierarchical hybrid coating was fabricated on a titanium substrate via consecutive plasma electrolytic oxidation (PEO) and hydrothermal reactions. The impact of hydrothermal parameters on the morphology of hydrothermally treated PEO coatings and the photodegradation of metformin (MET) were considered. In this regard, excellent PA was obtained for the needle-shaped morphology with a high aspect ratio owing to the higher light scattering and absorption, lower photoluminescence intensity, lower contact angle, and narrower band gap. Phase analysis confirmed the presence of rutile, anatase, Bi2WO6, and Bi6Ti3WO18 in the composite coating. The MET photodegradation rate with the optimum coating reached 90 % within 180 min of visible-light irradiation, which was 14.6 times higher than that with the TiO2 coating. The coating exhibited remarkable stability and efficiency, and its performance was successfully enhanced by peroxymonosulfate (PMS) activation. By exploiting the band alignment of the composite coating and performing scavenging tests, an Type II mechanism was proposed. Furthermore, photo-produced reactive intermediates (PPRIs) were identified during degradation mediated by appropriate scavengers, allowing us to propose a mechanism for MET degradation. Finally, recycling tests confirmed the stability of the catalysts presented in this study.
