Boosting Carrier Separation on a BiOBr/Bi₄O₅Br₂ Direct Z-Scheme Heterojunction for Superior Photocatalytic Nitrogen Fixation

Photocatalytic dinitrogen (N₂) fixation is regarded as an achievable technology for ammonia (NH₃) production. However, the poor separation efficiency of the photoinduced carriers and ineffective N₂ activation remain grand obstacles to high-performance NH₃ photosynthesis. Designing advanced heterostructured systems to accelerate charge separation and activate the N₂ molecule is a feasible strategy to optimize the photocatalytic N₂ fixation activity. Herein, a direct Z-scheme configuration is established between BiOBr and Bi₄O₅Br₂ through a facile one-step solvothermal reaction. This configuration enables effective spatial separation of electron-hole pairs and preserves the robust redox ability of carriers, concurrently promoting N≡N bond activation and diminishing the energy barrier for the rate-determining step. The formation of direct Z-scheme BiOBr/Bi₄O₅Br₂ heterojunctions is mostly attributed to the similarities in their lattice structures and crystal growth conditions. As a result, the direct Z-scheme BiOBr/Bi₄O₅Br₂ heterojunction exhibits a high NH₃ yield of 66.87 μmol g^-1 h^-1 without using sacrificing reagents, surpassing that of the pristine BiOBr and Bi₄O₅Br₂ by approximately 3.3 and 5.6 times, respectively. This study provides an achievable approach to construct direct Z-scheme heterojunction systems for implementing high-performance N₂ fixation under mild conditions.