Factors influencing the photocatalytic activity of rutile TiO₂ nanorods with different aspect ratios for dye degradation and Cr(VI) photoreduction.

Shape-controlled rutile TiO2 nanorods (NRs) with large {110} and small {111} exposed facets were prepared by hydrothermal treatment of a peroxo titanic acid (PTA) solution. The aspect ratio of the NRs was controlled by the pH of the PTA solution and the addition of polyvinyl alcohol (PVA) or polyvinyl pyrrolidone (PVP). The spatial separation of reduction and oxidation sites, where {110} facets act as reduction sites and {111} facets as oxidation ones, was revealed by tracking the distribution of Pt and PbO2 deposited on the NR surfaces. The MB degradation activity depended on the aspect ratio of the rutile NRs because of the different separation efficiencies of photo-generated carriers on different facets. Meanwhile, the Cr(VI) reduction activity was governed by the slight shift of the conduction-band potential of the rutile NRs estimated from Mott-Schottky plots, which may be caused by the variation of the content of {110} facets in the rutile NRs. Among the prepared rutile NRs, the sample prepared using a PTA solution at pH 4 containing 10 mg of PVA showed higher activity for photocatalytic Cr(VI) reduction than Degussa P25. These results provide a feasible method to design efficient TiO2 photocatalysts with tunable photoreactivity for environmental applications.