Variable dimensional structure and interface design of g-C₃N₄/BiOI composites with oxygen vacancy for improving visible-light photocatalytic properties

It is still challenging to adjust the desired structure and heterojunction interface of photocatalytic materials by a facile and efficient strategy. In this manuscript, variable dimensional structured BiOI with surface oxygen vacancies (OVs) were prepared via an in-situ growth on mesoporous g-C₃N₄ nanosheets through one-pot synthesis at room temperature, which possesses the p-n heterojunction required for the high-performance photocatalysis. By reducing the amount of the precursor of BiOI during the reaction, the morphology of BiOI gradually changed from 3D microspheres to 2D nanosheets and even 0D nanoparticles, which were conjugated with ultrathin g-C₃N₄ nanosheets forming the composites with 2D/3D, 2D/2D, and 2D/0D structure, respectively. The catalyst with the best performance was determined to be the g-C₃N₄/BiOI with 2D/2D structure, which provides a larger contact surface, appropriate bandgap, and the higher utilization of visible light. The synergies between heterostructure and OVs can promote both the production and the separation of electron-hole effectively, and hence producing more oxidizing ^•O₂⁻ and h⁺ with the energy input. Thereby, under visible light, the optimized combination of g-C₃N₄/BiOI heterojunction can exhibit the outstanding photocatalytic performance of degrading 99% rhodamine B within 2 h, which was 2.6 and 12.8 times faster than pure g-C₃N₄ and pure BiOI, respectively. In addition, our work provides a feasible and adjustable approach to regulate the structure and heterojunction interface of photocatalysts as well as the discussion about the variable dimensional structure-activity relationship in photocatalysis.