In-situ engineered KBiFe2O5/BiOBr Z-scheme heterojunction photocatalyst for the pharmaceutical pollutant degradation and nitrogen fixation

This study reports the rational design of a multifunctional Z-scheme heterojunction photocatalyst, KBiFe₂O₅/BiOBr (KBF-BB-I), synthesized via an in-situ hydrothermal method. Transmission electron microscopy confirmed the formation of an intimate heterojunction, with rod-like KBiFe₂O₅ uniformly anchored on plate-like BiOBr. Compared to the precipitation-derived counterpart (KBF-BB), the in-situ approach enhanced interfacial contact and band alignment, promoting efficient charge separation and interfacial transfer. Under visible light irradiation, KBF-BB-I exhibited outstanding photocatalytic activity, achieving 97 % degradation of tetracycline (TC) and 90 % of paracetamol (PCM) within 60 min, both individually and in binary mixtures. This is the first report on integration of KBiFe₂O₅ with BiOBr for pharmaceutical pollutant degradation and nitrogen fixation. The composite also demonstrated nitrogen fixation, producing 6 mmol L⁻¹g⁻¹ of ammonia after 240 min. Photoluminescence and Mott-Schottky analyses confirmed suppressed electron-hole recombination and favourable band alignment, supporting a direct Z-scheme mechanism. Radical trapping experiments verified the generation of key reactive oxygen species (^•O₂^–, ^•OH). The catalyst showed excellent stability and reusability. The enhanced performance arises from the synergistic effects of interfacial engineering, high surface area, and efficient charge migration, positioning KBF-BB-I as a promising photocatalyst for environmental remediation.