In situ reversible assembly of atomic interfacial structure in BiOI/Bi₅O₇I p-n heterojunctions to promote visible-light photocatalysis

Constructing efficient p-n heterojunctions holds great potential in the realm of photocatalysis for promoting the sustainable development of the environment and energy industries. However, traditional p-n heterojunctions suffer from limited interfacial interaction which severely restricts the effectiveness of the built-in electric field in boosting charge separation. Herein, we present an in situ reversible assembly approach to fabricate functional p-n junction in BiOI/Bi₅O₇I composites at room temperature. By controlling the reaction time or the amount of KI precursor added, we attain the as-designed BiOI@Bi₅O₇I and Bi₅O₇I@BiOI heterojunctions with large specific surface area and ample interfacial electric field. Subsequent application of the optimized heterojunction material as visible-light photocatalyst achieves efficient photoreduction of CO₂ reactant into CO product (0.46 μmol g⁻¹h⁻¹), even without using any sacrificial agent in the gas–solid reaction system. This catalytic performance is notably ∼ 6.6 times and 15.3 times higher than that of standalone BiOI and Bi₅O₇I materials, respectively. In situ XPS, in situ Kelvin probe force microscopy, and theoretical calculations reveal that the built-in electric field induces directional charge transfer to greatly boosts the efficiency of separating photogenerated electron-hole pairs at the interface of BiOI and Bi₅O₇I. This study provides valuable insights for the rational design and straightforward fabrication of next-generation, integrated heterostructured photoelectronic materials for efficient energy, environmental, and chemical applications.