Mixed Titanium Oxide Strategy for Enhanced Photocatalytic Hydrogen Evolution.

Titanium dioxide is a promising photocatalyst material for water splitting, but is limited by its low utilization of solar energy and rapid recombination of electron-hole pairs. Herein, a mixed titanium oxide strategy, utilizing TiO/TiO heterostructures consisting of in situ grown TiO nanotubes with mixed anatase and rutile phases on bulk TiO materials, is demonstrated for efficient and recyclable hydrogen evolution from photocatalytic water splitting. Taking advantage of the formed heterostructures and the created porous structures, the photogenerated electrons from the conduction band of anatase TiO can be first delivered to rutile TiO and then transferred to TiO. Meanwhile, the presence of TiO in TiO/TiO heterostructures can substantially promote the charge mobility and suppress the recombination of photogenerated electron-hole pairs. Hence, with a tuned band gap structure that enables rapid electron-hole separation, increased charge carrier density, and enhanced light absorption, the TiO/TiO heterostructures provide an enhanced photocatalytic hydrogen evolution rate as high as 1440 μmol g h under full-sunlight irradiation and without any other cocatalyst. This mixed titanium oxide strategy may open up new avenues for designing and constructing highly efficient TiO-based photocatalytic materials for various applications.