Enhanced photoelectrochemical activity of detached TiO₂ nanotube films via time-controlled electrodeposition Au nanoarchitectures

Abstract TiO 2 nanotubes detached films decorated with gold nanoparticles (TiO 2 NTs-AuNPs) represent an effective strategy to enhance light harvesting in photoanodes. The films were characterized by X-ray diffraction (XRD), Raman spectroscopy, field emission gun scanning electron microscopy (FEG-SEM), diffuse reflectance spectroscopy (DRS), transient photocurrent (TP), Mott-Schottky analysis and electrochemical impedance spectroscopy (EIS). XRD and Raman analyses confirmed the anatase phase of TiO 2 NTs, while Raman also revealed shifts in the active modes associated with the stabilization of self-doping states and the formation of vacancies/defects AuNPs incorporation. FEG-SEM images showed well-organized TiO₂NTs with average diameters of 78.1 ± 14.4 nm and globular structures homogeneously distributed on the surface, attributed to AuNPs. DRS spectra and Tauc plot analysis indicated a slight reduction in the bandgap energy as the AuNPs content increased. TP measurements showed that pristine TiO₂NTs reached a photocurrent density of 0.19 mA cm –2 , whereas TiO₂NTs-AuNPs prepared with electrodeposition times of 60 and 80 s achieved values near to 1.00 mA cm –2 , attributed to, according to Mott-Schottky analysis, the smallest energy difference between the Fermi level and the conduction band of TiO₂ for those samples, indicating a close relationship between morphology, (nanoarchitecture) energy levels, and photocurrent efficiency. EIS analysis revealed a significant decrease in charge transfer resistance in TiO 2 NTs-AuNPs, even when not exposed to UV radiation, causing significant changes in the electrode properties. The proposed photoanode exhibited exceptional photocurrent performance while operating under lower applied potential and less powerful radiation sources, demonstrating their strong potential as an efficient photoelectrochemical platform.