Development of porous ceramic coatings via the PEO process: The key role of CuO nanoparticles in methylene blue photodegradation under visible light illumination

The TiO2/CuO coatings were applied on pure titanium via PEO, observing the photocatalytic capacity for methylene blue (MB) degradation. Additionally, the effect of the ionization process at room temperature on the photocatalytic efficiency of the coatings was studied. A coating containing CuO nanoparticles (NPs) presented a more porous morphology. Phase analysis results proved that coatings containing CuO NPs were comprised of anatase and CuO phases, while the addition of ionized-CuO NPs into the electrolyte led to the formation of anatase, rutile, CuO, and TiP2O7. The CuO-incorporated coating exhibited 76 % efficient MB photodegradation. Most importantly, the introduction of 1 g/L CuO-ionized NPs at 25 degrees C increased photocatalytic efficiency to 90 % after 6 h of visible light illumination. Moreover, the optimum coating satisfied photocatalytic efficiency even after 3 runs. A deep investigation into the effect of photocatalytic parameters, including concentrations (2.5, 5, 10 and 15 ppm) and pH of pollutants (3 and 9), was also performed. Furthermore, appropriate scavengers such as isopropanol (0.1 mM), ascorbic acid (0.1 mM), and potassium bromate (0.1 mM) were employed to scrutinize the role of various photogenerated reactive species and to detail the photocatalytic mechanism.