Alumina Coatings Containing Niobium Pentoxide Polymorphs Prepared by Plasma Electrolytic Oxidation of Aluminum

This study explores the experimental parameters related to the production of Nb2O5 over alumina coatings produced by plasma electrolytic oxidation (PEO) and evaluates its use in photocatalytic applications. The influence of niobium precursor concentration and the electrolyte temperature on the electrochemical, morphological, and compositional responses are investigated using chemometric tools. The experimental design provides a geometrical representation of experimental parameters and shows the effect of the anodizing conditions on the pore density and the anodization curves. The samples are prepared at a constant current (10 mA cm(-2)) under the PEO regime. The coatings reveal a porous structure and crystalline phases of Nb2O5 and gamma-Al2O3. A preliminary photodegradation test under UV radiation and utilizing Rhodamine B (RhB) solution shows the best photocatalytic performance for the sample produced by the highest Nb salt concentration (16.0 g L-1) and highest temperature (18.7 degrees C). These results are attributed to a higher niobium content in this sample and crystalline phases of Nb2O5 over the Al substrate.