Low temperature in situ fabrication of NiFeO/tetragonal-BiVO/BiMoO ternary heterostructure: A conjugated step-scheme multijunction photocatalyst with synergistic charge migration for antibiotic photodegradation and H generation.

Rational design of novel conjugated step-scheme (S-scheme) multijunction heterostructure with synergistic charge channelization, superior light harvesting efficiency and strong redox ability is a pioneering approach to mimic natural photosynthesis process. Herein, a mild cetyltrimethyl ammoniumbromide (CTAB) assisted one pot reflux synthesis route is designed for in situ integration of metal organic framework (MOF)-derived NiFeO with tetragonal-BiVO (t-BiVO) and γ-BiMoO to prepare NiFeO/t-BiVO/BiMoO (NFO/BVO/BMO) ternary composites. Morphologically, fine dispersion of NiFeO (NFO) quantum dots over γ-BiMoO (BMO) and t-BiVO (BVO) nanoplates yielded three types of microscopic heterojunctions among BMO-BVO, BVO-NFO and BMO-NFO phases. The ternary composites displayed important physicochemical attributes including high surface area, strong optical absorption, superior charge mobility and higher excited state lifetime which accounted for its improved photocatalytic activity towards ciprofloxacin degradation (>99% in 90 min) and H evolution (1.11 mmolhg, photon conversion efficiency 18.5%). Kinetics study revealed 12-55 fold higher ciprofloxacin photodegradation activity and 31-41 times higher H evolution rate for the ternary composite in comparison to the pure semiconductors. A conjugated S-scheme charge transfer mechanism has been deduced from comprehensive band position analysis and radical trapping study to explain the enhanced photocatalytic activity. This work for the first time demonstrated the rational construction of conjugated S-scheme heterostructures with potential application in water remediation and green H production.