Improved growth rate of anodized TiO₂ nanotube arrays under reduced pressure field and light illumination

The one-dimensional titanium oxide (TiO₂) nanotubes (TONT) can be rationally fabricated in the fluoride-containing electrolyte by electrochemical anodization. The high-speed growth of TONT for elongated nanotubes is highly desirable because the undesirable chemical etching will induce "nanograss" on the top of nanotubes and restrain the continued elongation of nanotubes. Herein, the external fields were employed to accelerate the growth of TONTs and obtain the elongated TONT arrays. A growth rate up to 18μm/h was achieved under the presence of reduced pressure (0.07MPa) and UV light (365nm) stimulation. The generation of longer nanotube arrays could be attributed to the applied fields, which facilitate timely gas pumping out and induce chemical equilibrium shift forward. The TONT films obtained under different parameters were subsequently employed as anodes for photoelectrochemical (PEC) water splitting. The photocurrent (at 0V vs Ag/AgCl) of TONT electrode obtained under external fields represented a 50% enhancement compared with the photoanode produced by the conventional method.