Wide spectral degradation of Norfloxacin by Ag@BiPO4/BiOBr/BiFeO3 nano-assembly: Elucidating the photocatalytic mechanism under different light sources.

Metallic Ag deposited BiPO4/BiOBr/BiFeO3 ternary nano-hetero-structures were rationally designed and synthesized by a simple precipitation-wet impregnation-photo deposition method. The plasmonic junction possesses an excellent wide spectrum photo-response and makes best use of BiPO4 which is otherwise a poor photocatalyst. Ag@BiPO4/BiOBr/BiFeO3 showed superior photocatalytic activity for degradation of norfloxacin (NFN) under visible, ultra-violet, near-infra-red and natural solar light. Especially catalyst APBF-3 (0.3 wt% Ag@BiPO4/BiOBr/BiFeO3) shows 98.1% degradation of NFN (20 mg/L) in 90 min under visible light and 99.1% in less than 45 min under UV exposure. Free radical scavenging experiments and electron spin resonance (ESR) results has been used for explanation of charge transfer, photocatalytic mechanism and role of radicals for binary, ternary and Ag deposited ternary junctions for UV and visible exposure. Metallic Ag in addition to its surface plasmon resonance helps in protection of high conduction band and valence band in the three semiconductors. A dual Z-scheme mechanism has been predicted by comparing with possibilities of double charge and vectorial charge transfer.