Morphology engineering of rutile/anatase-TiO2 heterophase junctions for enhanced photoelectrochemical properties

TiO2 is a promising photoelectrochemical (PEC) material as photoanodes for photoelectric conversion. However, severe charge recombination issues in TiO2 significantly hinder the PEC efficiency and thus its application. It has been reported that the construction of rutile/anatase (R/A) heterophase junctions benefits fast charge transfer via interfaces and improves the efficiency of conversion. However, the evolution of R and/or A phases and their morphology and phase-transition effect on the PEC properties have not been investigated. In this study, unique TiO2 heterophase junctions consisting of R-phase nanorods on the titanate-coexisting-phase (CO-phase) truncated octahedral particles were fabricated through a two-step hydrothermal method, where the morphology and phase transition of a titanate-coexisting phase was meticulously controlled and carefully monitored. The heterophase junctions exhibited superior PEC performances with a photocurrent density of 1.62 +/- 0.05 mA cm-2 at 1.23 V, which was 4.3 times and 1.6 times greater than that of pure R phase and R-nanorod/A-nanosheet, respectively. This work demonstrates the potential of morphology engineering and phase transition of photo-anodes for highly efficient photoelectric conversion.