Fluorine-doped titanium dioxide nanorod arrays for efficient photoelectrochemical water splitting

TiO₂ is a well-known photocatalyst due to its excellent photocatalytic activity, low cost, and stability. However, its practical applications are limited by its poor charge transport and wide bandgap. In this study, F-doped TiO₂ nanorod arrays were synthesized using a simple chemical bath annealing method, which resulted in significantly improved properties. Among the samples, 0.05F-T exhibited the best performance, with a photocurrent of 7.34 mA/cm² at 1.8 V vs. RHE, which is 4.61 times higher than that of pure TiO₂ nanorods (1.59 mA/cm²). IPCE measurements showed prominent photocurrent responses in the 325–375 nm range and a slight redshift towards the visible region around 425 nm, indicating improved light absorption. The electron-hole separation efficiency was enhanced, and bandgap and flat-band potential measurements confirmed optimizing the energy band structure. The photoelectrochemical performance for water splitting was also evaluated, with 0.05F-T achieving the highest hydrogen production of 842.28 µmol/cm² in 5 hours at 1.8 V vs. RHE, which is 6.58 times higher than that of pure TiO₂ (128.05 µmol/cm²). These results demonstrate that F-doped TiO₂  nanorods are promising for enhancing photocatalytic hydrogen production.