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 TiO2/Ti2O3 heterostructures consisting of in situ grown TiO2 nanotubes with mixed anatase and rutile phases on bulk Ti2O3 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 TiO2 can be first delivered to rutile TiO2 and then transferred to Ti2O3. Meanwhile, the presence of Ti2O3 in TiO2/Ti2O3 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 TiO2/Ti2O3 heterostructures provide an enhanced photocatalytic hydrogen evolution rate as high as 1440 μmol g-1 h-1 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 TiO2-based photocatalytic materials for various applications.
Keywords: hydrogen evolution; mixed phase strategy; photocatalysis; titanium oxide; water splitting.