Roles of Phase Junction in Photocatalysis and Photoelectrocatalysis

Photogenerated charge separation is one of the key factors determining the solar energy conversion efficiency in photocatalysis and photoelectrocatalysis. Fabrication of phase junction has been demonstrated to be an effective strategy to construct the internal electric field for the charge separation. Phase junction is essentially a heterojunction, but more common in semiconductor-based photoelectric conversion systems, because most semiconductors exhibit the polymorphous structures. Because of the similar crystal structure between the two phases, phase junctions are more easily formed. The application of phase junction in photo-catalysis and photoelectrocatalysis, especially the anataserutile TiO2 and alpha-beta Ga2O3 phase junction, are summarized in this Feature Article. The internal electrical field across the phase junction provides enough driving force for the improved charge separation, evidenced by the time and spatial resolved characterizations. We conclude with a summary and perspectives on the design and application of phase junction in solar energy conversion systems.