Enhanced Photocatalysis from Truncated Octahedral Bipyramids of Anatase TiO2 with Exposed {001}/{101} Facets

In this study, we develop a new synthetic method to grow anatase TiO2 crystals composed of truncated octahedral bipyramids (TOBs) with exposed {001} and {101} facets by a vapor–solid reaction growth (VSRG) method. The VSRG method employs TiCl4(g) to react with CaO(s)/Ca(OH)2(s) at 823–1043 K under atmospheric pressure. The O-deficient pale-blue TOB TiO2 crystals display high amount of both {001} and {101} facets. Together, they decompose methylene blue photocatalytically under UV–visible (UV–vis) light irradiation. The most-efficient TOB catalyst VT923 (grown at 923 K, average edge length 400 nm, average thickness 200 nm, and surface area 4.20 m2/g) shows a degradation rate constant k, 0.0527 min–1. This is close to that of the P25 standard 0.0577 min–1. However, the surface area of P25 (46.8 m2/g) is about 12 times that of VT923. The extraordinary performance of VT923 is attributed to the presence of high amount of coexisting {001} and {101} facets to form effective surface heterojunctions. They would se...