Characterization and comparison of WO₃ with hybrid Mo-WO₃ and TiO₂ with hybrid Zn-TiO₂ nanostructures as a photoanodes

Tungsten oxide (WO₃) and zinc oxide (ZnO) are n-type semiconductor with numerous applications in photocatalysis due to its abundance, non-toxicity, versatility and photoelectrical properties. The objective of this study is to synthesize and characterize different types of nanostructures (WO₃, hybrid WO₃-Mo, TiO₂ and TiO₂-Zn) for a comparison of hybrid and pure nanostructures in order to use them as a photoanodes for removing emerging contaminants from wastewater by photoelectrocatalysis (PEC).

WO₃ nanostructures were synthesized using electrochemical anodization in acidic electrolytes. In order to improve the properties of WO₃ nanostructures, different concentrations of sodium molybdate were added to the electrolyte to create hybrid WO3-Mo nanostructures. Furthermore, TiO₂ nanostructures were synthesized by anodization method in a fluoride electrolyte and following the same procedure mentioned above, TiO2-Zn nanostructures were obtained by adding different concentrations of zinc nitrate to the electrolyte. In all cases, an annealing treatment was carried out after the anodization process.

With the aim of analyzing accurately and comparing the properties of both samples, Field Emission Scanning Electron Microscopy (FE-SEM) and Confocal Laser-Raman Spectroscopy have been used to study the morphology and composition and crystallinity, respectively. Finally, water splitting measurements were performed using the synthesized nanostructures in order to compare the photoelectrochemical properties of the photoanodes.