Effect of growth time on photoelectrochemical performance of TiO₂ nanotubes

This study investigates how the duration of anodization influences the structural and morphological characteristics and photoelectrochemical (PEC) performance of titanium dioxide (TiO₂) nanotube arrays (TNTs) fabricated via electrochemical anodic oxidation. Four different growth times, 0.5, 1, 1.5, and 2 hours, were tested to optimize the nanotubes’ morphology and structure for PEC applications. X-ray diffraction (XRD) analysis confirmed the presence of the anatase phase across all samples, with increased phase intensity observed with longer anodization periods. Field emission scanning electron microscopy (FESEM) revealed that TNTs anodized for one hour exhibited a uniform, vertically aligned, and crack-free structure; however, extended anodization times introduced structural irregularities. Energy-dispersive X-ray spectroscopy (EDS) verified that all samples maintained a stoichiometric TiO₂ composition, with higher oxidation levels correlating with longer anodization durations. Diffuse reflectance spectroscopy (DRS) indicated a slight decrease in band gap energy as anodization time increased, implying enhanced visible-light absorption. Under illumination of 100 mW/cm², photoelectrochemical testing showed that TNTs anodized for one hour achieved the highest photocurrent density of 0.15 mA/cm² at 0 V vs. Ag/AgCl, with a corresponding photoconversion efficiency of 0.18%. These findings suggest that a one-hour anodization period produces TNTs with optimal structural and optoelectronic properties, making them highly suitable for efficient solar-driven water splitting and other PEC energy conversion technologies.