Light-harvesting TiO₂ nanotube arrays decorated with functional photo- And electrocatalysts

TiO₂ nanotube arrays (TiNT) have received growing attentions from various research fields such as hydrogen-sensing, photoelectrochemical water splitting, solar cells, and biological applications. The synthesis of TiNT is rather simple and straightforward; DC-anodizataion of Ti foil in fluoride-based electrolytes results in highly ordered and vertically self-aligned TiNT. Since TiNT provides a unique and robust nanoporous tubular architectures, it can serve as a platform for anchoring various photo- and electrocatalyst nanomaterials. This study presents applications of TiNT as a support for iron oxide nanoparticles. Alpha-Fe₂O₃ (hematite) nanoparticles were electrodeposited at TiNT, which was subsequently annealed at 550 degree Celsius for 6 hours in the presence of air. For comparison, TiO₂ nanoparticles (TiNP) were obtained via oxidative annealing of Ti foil. As-prepared hematite/TiNT was found to have much higher photoelectrochemical performances than hematite/TiNP under visible light (> 420 nm) whereas its performances decreased at AM 1.5 condition as compared to hematite/TiNP. Such behaviors are likely to be attributed to site-selective photocatalytic activities of TiNT. More detailed surface characterization for TiNT and TiNP without or with hematite particles via TEM, SEM, XPS, XRD, UV-vis, EDX, Raman, etc will be presented and discussed. Finally, other applications of TiNT hybrids with Co-phosphate and polyoxometalates will be presented.