Fabrication of leaf extract mediated bismuth oxybromide/oxyiodide (BiOBrxI1-x) photocatalysts with tunable band gap and enhanced optical absorption for degradation of organic pollutants.

The use of Azadirachta indica (A.I.) leaf extract to synthesize green photocatalysts for efficient separation of photogenerated charges has been a promising way to enhance the photocatalytic activity. Herein, we report the synthesis of green bismuth oxybromide/oxyiodide composites (G-BiOBrxI1-x) using A.I. leaf extract with effective size control, high specific surface area, and porosity. The A.I. leaf extract also acted as an excellent sensitizer that boosted the optical window of the G-BiOBrxI1-x photocatalysts. The as-prepared G-BiOBrxI1-x photocatalysts possessed three-dimensional (3-D) nanoplates like structure with successive modulation of the band gaps from 2.28 eV to 1.98 eV by varying the bromine/iodine (Br/I) ratio. Furthermore, the photocatalytic activity of the G-BiOBrxI1-x samples was measured and compared with the bismuth oxybromide/oxyiodide composite (C-BiOBr0.5I0.5) synthesized via conventional hydrolysis route (without the leaf extract). The G-BiOBrxI1-x photocatalysts degraded higher percentage of methyl orange (MO) and amoxicillin (AMX) than C-BiOBr0.5I0.5 under visible light irradiation. The superior photocatalytic efficiency was attributed to the multiple heterojunctions developed between BiOBr, BiOI, and electron-accepting π-conjugated system offered by leaf extract constituents, thereby facilitating the charge transfer process and effective separation of photogenerated charges.