Photoelectrochemical and spectroscopical surface analysis of TiO₂ nanorods/Ag nanoparticles toward organic carboxylic acids oxidation

The photoelectrochemical interaction of TiO₂-based heterostructures was evaluated in an alkaline medium. These structures were fabricated by attaching silver nanoparticles (NPs) onto TiO₂ nanorods (NRs), synthesized using hydrothermal methodology, by electrodeposition as a time function. Field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV-vis analysis, and electrochemical techniques were used to characterize the synthesized materials. SEM analysis showed the formation of vertically oriented ca. 150-nm-diameter NRs, in turn constituted by 10-nm-diameter nanowires. On the other hand, the analysis of XRD indicated the formation of a TiO₂ rutile phase. TEM images revealed ca. 5-nm-diameter silver nanoparticles attached to the TiO₂ NR surface. The photoelectrochemical properties of the synthesized materials were evaluated in 0.1 M KOH using cyclic voltammetry, linear voltammetry, chronoamperometry, and electrochemical impedance spectroscopy (EIS) under dark and UV radiation at 365 nm. The photoelectrochemical oxidations of oxalic and formic acids were carried out under UV and visible irradiations on the material with the best photoeletrochemical performance. The obtained results demonstrated that the amount of silver increases both the light absorption and the faradic current during the oxygen evolution reaction as a result of an intrinsic-electric modification. During photoelectrochemical oxidation of the carboxylic acids, photocurrents of saturation were obtained, a condition suitable for photoelectrochemical cell (PEC) applications, representing 100% of photoexited electrons collected.