Unfolding the temperature induced dual bandgap in TiO₂ nanotubes with improved photocatalytic application

Since the discovery of photocatalytic water splitting, TiO₂ has gained enormous interest in improving efficiency by generating stable electron-hole (e-h) pairs upon proper light illumination [1]. In particular, anodic TiO₂ nanotubes have attracted wide interest not only for their high surface-to-volume ratio with scalable structures [2]. However, the overall efficiency is limited by the recombination of the photo-generated (e-h) pairs in the bulk and electrode/electrolyte interfaces. To overcome this tuning the crystallinity and the bandgap of them are required. Among various approaches, thermal annealing dependent control over the anatase/rutile phase ratio of TiO₂ and their inter-granular charge transfer process exhibit a relatively high photocatalytic performance. Here, we report the efficacy of dual-phase mediated bandgap modulation and the subsequent improvement of photocatalytic activity of TiO2 nanotubes as a function of temperature by various complementary techniques like UV-Vis, XRD, XPS, XAS, Raman, etc. and supported by DFT calculations.
References
1. P. Roy et al. Angew. Chem. 50, 2904 (2011)
2. J.M. Macak et al. Small, 3, 300 (2007).