Semiconductor photocatalysts have attracted much research attention because of their applications to solar energy conversion and environmental purification in the past decades. Among photocatalysts, TiO2 is one of the most important transition metal oxides owning a favorable band edge position, nontoxicity, a strong optical absorption, and an inexpensive cost. The photocatalytic performance of TiO2 has been influenced by many factors such as the phase structure, the surface area, the crystallite size, and the amount of surface hydroxyl groups, and so on. Among them, the restriction of recombination between electrons and holes is one of the key issues so as to enhance photocatalytic efficiency. So it is highly desirable to develop approaches that can validly promote charge separation in TiO2. Among various methods, fabrication surface-phase junctions of TiO2 particles, has been demonstrated to be a valid strategy in photocatalytic performance. Besides, for photoelectrochemical (PEC) water splitting, the traditional photoanode is made by TiO2 nanoparticles, which suffers from high charge recombination loss. Thus, it is highly desirable to synthesize a 1D nanostructure owning the two phases (rutile or anatase), which can certainly enhance the charge separation and transportation.
Branched TiO2 nanorod arrays (NRs) which own the surface anatase/rutile junctions were successfully synthesized via a simple modified hydrothermal method by researchers from Institute of Process Engineering (IPE), Chinese Academy of Sciences. PEC measurement shows that the photoelectrical response was increased significantly with the surface phase junction and the highest photocurrent density of 1.02 mA/cm2 is observed at 0.8 V vs. RHE when the photoelectrode is illuminated by solar simulator (AM 1.5G). The enhanced charge separation and transportation on surface-phase junctions of TiO2 NRs contribute to the high efficient photoelectrochemical water splitting. Thus, the branched TiO2 NRs owning surface-phase junctions could emerge as viable alternatives to traditional single-crystalline TiO2 NRs for photoanode materials.