In-situ fabrication of atomic charge transferring path for constructing heterojunction photocatalysts with hierarchical structure

The efficiencies of photocatalytic solar energy conversion systems are significantly limited by the challenging charge separation process, which can be improved via some commonly-used interfacial modulating strategies, e.g., introducing heterojunctions at the interfaces of different semiconductors. However, in many cases, the constructed heterojunctions not always work well mainly due to the serious mismatching of surface and energy structures between different components. In this study, inspired by the similarities in crystalline structures and elemental compositions, a novel heterojunction photocatalyst with hierarchical structure was first fabricated between bismuth-based semiconductors (Bi2Ti2O2 and gamma-Bi2O3) possessing identical cubic phase via a simple insitu transformation method. The resulted Bi2Ti2O7/gamma-Bi2O3 heterojunction photocatalyst (denoted as BT/gamma-Bi2O3) shows extremely high photocatalytic activities in photocatalytic removal of various high concentration environmental pollutants, e.g., phenol, dyes and sulfur containing compounds. An enhancement of more than two orders of magnitude in photocatalytic performances can be achieved for the BT/gamma-Bi2O3 photocatalyst than the single composite, which is possibly attributable to the co-sharing of Bi-O tetrahedra units for the composites in heterojunction structures to provide an atomic charge transferring pathway for facilitating the spatial charge separation. This work provides an effective strategy for rationally constructing charge separation and transfer pathway in semiconductor-based photocatalysts for solar energy conversion.