Time-Controlled Photoassisted Deposition of Silver on Tio2 Nanotube Arrays: Tuning Plasmonic for Enhanced Photoelectrochemical Performance

This study demonstrates that time-controlled photoassisted deposition of silver (Ag) nanoparticles can effectively tune the plasmonic and photoelectrochemical behavior of TiO2 nanotube arrays (TNTs/Ti foil). Structural analyses confirmed the preservation of phase-pure anatase TiO2 and revealed progressive Ag loading with deposition time. FESEM observations showed that early deposition (5–15 min) primarily thickened tube walls, increasing the outer diameter from ~210 to ~250 nm, while distinct Ag nanoparticles were not yet resolved. At longer deposition times (20–25 min), well-defined Ag particles appeared, growing from ~450 to ~750 nm, indicating coalescence and aggregation. These morphological changes corresponded with optical responses, where a pronounced LSPR band emerged at ~620 nm and the apparent band gap decreased from 3.20 eV for pristine TNTs to 2.7 eV at 10 min Ag coverage. Photoelectrochemical measurements highlighted the importance of deposition time: photocurrent density increased from 0.11 mA cm-2 for pristine TNTs to a maximum of 0.39 mA cm⁻² at 10 min, over 3.5-fold enhancement, before declining due to aggregation-induced recombination. Overall, these results show that precise control of Ag deposition time governs nanoparticle nucleation, growth, plasmonic behavior, and interfacial charge transfer, providing a scalable strategy for designing high-performance plasmonic photoelectrodes.