Photocatalytic evaluation of hierarchical TiO2/WO3 hybrid coating created by PEO/hydrothermal method

The practical application of powder photocatalysts for visible light catalysis can be limited due to the accumulation of nanoparticles and the complexity of their recovery. Therefore, photocatalytic coatings are suitable candidates for pollutant degradation. In this study, a hierarchical TiO2/WO3 hybrid coating was created on a Ti substrate using plasma electrolytic oxidation (PEO) followed by hydrothermal treatment as a post-treatment. The TiO2/WO3 hybrid coating exhibits superior photocatalytic performance for methylene blue removal under visible light compared to the pure TiO2 coating, increasing MB removal from 41 to 88.3 %. The morphology of the hybrid coating consists of a combination of nanoparticles and nanorods. The decrease in photoluminescence (PL) intensity of the TiO2/WO3 coating indicates that the hybrid coating inhibits photo-induced e--h+ recombination. The optimal coating revealed exceptional stability and efficiency even after four cycles. The impact of photocatalytic parameters such as pollutant concentration and pH was investigated as well. The scavenging test results reveal that the main active radicals in photocatalysis are hydroxyl (HO center dot) and holes (h+) species. According to the Mott-Schottky and DRS (Diffuse Reflectance Spectroscopy) results, the MB photodegradation mechanism was proposed.