Effect of shape-driven intrinsic surface defects on photocatalytic activities of titanium dioxide in environmental application

Highlights: • Different-shaped TiO₂ particles (granular (TiNP) and tubular (TiNT)) were applied. • Relatively more intrinsic oxygen defect sites in TiNP, whereas more interstitial oxygen in TiNT. • Relatively rapid reduction of Cr(VI) by TiNP due to facile electron transfer through oxygen defect sites. - Abstract: This study investigated the effect of TiO₂ morphology-driven intrinsic oxygen defects on photocatalytic activities for removal of Cr(VI). To do so, two different-shaped TiO₂ particles, nano-granular TiO₂ particles (TiNP) and TiO₂ nanotube particles (TiNT), were prepared and applied. The surface analyses indicated that TiNP was found to have a greater photocatalytic activity than TiNT because of its more crystallinity and lower bandgap energy, more oxygen vacancies closer to the conduction band (CB), and its resulting more amounts of photogenerated electrons. Accordingly, these photocatalytic properties of TiO₂ particles were more evident in experimental result for photocatalytic reduction of Cr(VI) that was tested as a model target compound. The batch system showed that TiNP completely reduced Cr(VI) to Cr(III) at acidic and neutral pH, whereas TiNT were less effective even at low pH.