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 TiO2 nanofibers (TiO2-NF) by electrospinning of TiO2 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.