In situ growth of single-crystal TiO₂ nanorod arrays on Ti substrate: Controllable synthesis and photoelectrochemical water splitting

Despite one-dimensional (1D) semiconductor nanostructure arrays attracting increasing attention due to their many advantages, highly ordered TiO₂ nanorod arrays (TiO₂ NR) are rarely grown in situ on Ti substrates. Herein, a feasible method to fabricate TiO₂ NRs on Ti substrates by using a through-mask anodization process is reported. Self-ordered anodic aluminum oxide (AAO) overlaid on Ti substrate was used as a nanotemplate to induce the growth of TiO₂ NRs. The NR length and diameter could be controlled by adjusting anodization parameters such as electrochemical anodization voltage, anodization time and temperature, and electrolyte composition. Furthermore, according to the proposed NR formation mechanism, the anodized Ti ions migrate and deposit in the AAO nanochannels to form Ti(OH)₄ or amorphous TiO₂ NRs under electric field, owing to the confinement effect of the template. Photoelectrochemical tests indicated that, after hydrogenation, the TiO₂ NRs presented higher photocurrent density under simulated sunlight and visible light illuminations, suggesting their potential use in photoelectrochemical water splitting, photocatalysis, solar cells, and sensors.