Facile synthesis of g-C3N4/Bi4O5Br2 S-scheme heterojunction composite with enhanced photocatalytic performance in nitrogen fixation and contaminant degradation

Abstract

g-C₃N₄/Bi₄O₅Br₂ S-scheme heterojunctions were synthesized via a facile solvothermal route. Two-dimensional (2D) Bi₄O₅Br₂ nanostructures with dominantly exposed (10 − 1) facets were distributed on 2D g-C₃N₄ nanosheets, forming an inorganic/organic heterojunction interface. The S-scheme heterojunction effectively enhanced charge carrier separation and transfer while retaining the maximum redox potential of the semiconductors, significantly improving photocatalytic nitrogen fixation and contaminant degradation. For instance, BCN6 achieved an NH₃ production rate (R_N) of 151.9 μmol h⁻¹ g⁻¹, which is approximately 2.8 and 3.4 times higher than pure Bi₄O₅Br₂ and g-C₃N₄, respectively, using high-purity nitrogen under simulated visible light. The reaction conditions for nitrogen fixation and contaminant degradation were systematically investigated. Notably, BCN6 reached an R_N value of 110.3 μmol h⁻¹ g⁻¹ with air as the nitrogen source under outdoor sunlight, demonstrating its practical potential. Similar results were observed in the degradation experiments of salicylic acid (SA) and Rhodamine B (RhB). Furthermore, the g-C₃N₄/Bi₄O₅Br₂ photocatalysts exhibited excellent stability. This study provides a simple and effective strategy for constructing Bi-based inorganic/organic heterojunctions for enhanced photocatalytic activity.