Favorable Energy Band Alignment of TiO2 Anatase/Rutile Heterophase Homojunctions Yields Photocatalytic Hydrogen Evolution with Quantum Efficiency Exceeding 45.6%

Developing the technology for high yielding photocatalytic hydrogen evolution reactions is an important challenge. Development and optimization of photocatalytic junctions is a likely route for achieving this if heterojunctions with suitable band alignments can be achieved in sufficiently high-density form. Here, a novel anatase-TiO2/H-rutile-TiO2 heterophase homojunction system with near optimum energy band alignment is reported. The resulting as-prepared catalyst exhibits an excellent photocatalytic hydrogen evolution rate of 29.63 mmol g–1 h–1 under UV–vis light irradiation and an outstanding apparent quantum efficiency of 45.6% at 365 nm. The significant improvement is ascribed to near perfect lattice matching in combination with the rapid separation and transfer of photogenerated carriers in anatase-TiO2/H-rutile-TiO2 heterophase homojunctions. In situ X-ray photoelectron spectroscopy, electron spin resonance spin-trapping tests, femtosecond transient absorption spectroscopy, steady-state surface photovoltage spectroscopy, and transient-state surface photovoltage with additional ex situ characterizations and theoretical calculations show that the mechanism is enhanced transfer of photogenerated carriers in the anatase-TiO2/H-rutile-TiO2 catalyst. This work provides a pathway for enhancing photocatalytic performance through optimization of heterojunctions.