Photochemical Deposition of Ag, Cu, Cu@Ag, and Ag@Cu on TiO2 Nanotubes and their Optical Properties and Photoelectrochemical Activity

A combined electrochemical anodization and ultraviolet light-assisted photochemical preparation technique has been used to prepare Cu/TiO₂, Ag/TiO₂, Cu@Ag/TiO₂, and Ag@Cu/TiO₂ nanotubes. X-ray diffraction (XRD) and scanning electron microscopy (SEM) with energy-dispersive spectroscopy (EDS) were used to systematically characterize the crystalline phase and morphology, respectively, of the prepared nanotube films. The optical absorption properties of the samples were also studied using ultraviolet-visible (UV-Vis) absorption spectroscopy. The photoelectrochemical activity and photocathodic protection properties of 403 stainless steel were investigated using photogenerated open circuit potential, photogenerated current density, Tafel curves, and J-V curves. The effects of the type of particles deposited and the deposition sequence on their photocathodic protection properties were also studied. According to the results, the morphology and photoelectrochemical and photocathodic protection properties of the prepared samples are affected by the photodeposition sequence of the particles. The results also show that photodeposited TiO₂ nanotubes enhance the light absorption and photoelectrochemical properties under light illumination, thus greatly increasing the photocurrent density of the Cu/TiO₂ and Ag/TiO₂ nanotubes in comparison with bare TiO₂ nanotubes. In addition, the photogenerated potential drop of the photodeposited TiO₂ was greater than that of bare TiO₂. The open circuit potential (OCP) values of 403SS coupled with Cu/TiO₂, Ag/TiO₂, Cu@Ag/TiO₂, and Ag@Cu/TiO₂ under irradiation were −695 mV, −665 mV, −594 mV, and −574 mV, respectively. Silver- and copper-photodeposited TiO₂ nanotubes can be applied as new photoanode materials to provide good photogenerated cathodic protection for metals under light illumination.