Construction of Z-scheme Titanium-MOF/plasmonic silver nanoparticle/NiFe layered double hydroxide photocatalysts with enhanced dye and antibiotic degradation activity under visible light

Abstract

Z-scheme hetero-structured photocatalysts show outstanding photocatalytic activity in many reactions. In this work, a series of novel Z-scheme photocatalysts were fabricated via the photo-reduction of plasmonic sliver nanoparticles on the surface of NH2-MIL-125 (Ti)/NiFe layered double hydroxide (Ti-MOF/NiFeLDH) hybrids. The obtained Ti-MOF/Ag/NiFeLDH composites showed excellent photocatalytic performance under visible light, with the Ag nanoparticles facilitating charge transfer across Ti-MOF/NiFeLDH heterojunctions, thus boosting the photocatalytic activity. At an optimized Ag loading, 95% of Rhodamine B (RhB) degradation was achieved within 50 min and 92% Levofloxacin (LVX) degradation within 70 min. The degradation intermediates of LVX were analyzed by LC-MS and the decomposition pathways were proposed. Further, the Z-scheme Ti-MOF/Ag/NiFeLDH photocatalyst demonstrated outstanding reusability and stability in recycling tests (removal efficiencies of 92% for RhB and 90% for LVX after 5 successive test cycles). Trapping experiments revealed that superoxide radicals (•O2−) and hydroxyl radicals (•OH) were two main reactive species formed under visible light, with valence holes (h+) playing a minor role. Results allowed the mechanisms for antibiotic (i.e. LVX) and dye degradation over Ti-MOF/Ag/NiFeLDH to be proposed. This study introduces a new strategy, the combination of MOFs, LDHs and plasmonic Ag nanoparticles, for fabrication of high-performance Z-scheme photocatalysts for the removal of water pollutants.