Photocatalytic comparison of TiO₂ nanoparticles and electrospun TiO₂ nanofibers: Effects of mesoporosity and interparticle charge transfer

The development of a high-efficiency TiO₂ photocatalyst is of great importance to a variety of solar light conversion and application fields; the desired high efficiency can be achieved by employing well-controlled TiO₂ nanoarchitectures. In this study, we have successfully synthesized well-ordered and aligned high surface area mesoporous TiO ₂ nanofibers (TiO₂-NF) by electrospinning of TiO ₂ powder dispersed in viscous polymer solution and subsequent calcination. For comparison, TiO₂ nanoparticles (TiO₂-NP) are also prepared from calcination of the same TiO₂ powder. The TiO₂-NF of ca. 500 nm in diameter and a few micrometers in length consist of compactly and densely packed spherical nanoparticles of ca. 20 nm in size and have mesopores of 3-4 nm in radius. Photocatalytic comparison between TiO₂-NF and TiO₂-NP indicated that the former had far higher photocatalytic activities in photocurrent generation by a factor of 3 and higher hydrogen production by a factor of 7. The photocatalytic superiority of TiO₂-NF is attributed to effects of mesoporosity and nanoparticle alignment, which could cause efficient charge separation through interparticle charge transfer along the nanofiber framework. Finally, various surface characterization experiments were conducted and included to understand the photocatalytic behaviors of TiO₂-NF and TiO₂-NP.