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

Abstract

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.