Enhanced Visible-Light-Induced Photocatalytic Activity in M(III)Salophen-Decorated TiO2 Nanoparticles for Heterogeneous Degradation of Organic Dyes

Abstract

In this work, the construction of two heterojunction photocatalysts by coordinative anchoring of M(salophen)Cl complexes (M = Fe(III) and Mn(III)) to rutile TiO2 through a silica–aminopyridine linker (SAPy) promotes the visible-light-assisted photodegradation of organic dyes. The degradation efficiency of both cationic rhodamine B (RhB) and anionic methyl orange (MO) dyes by Fe– and Mn–TiO2-based catalysts in the presence of H2O2 under sunlight and low-wattage visible bulbs (12–18 W) is investigated. Anionic MO is more degradable than cationic RhB, and the Mn catalyst shows more activity than its Fe counterpart. Action spectra demonstrate the maximum apparent quantum efficiency (AQY) at 400–450 nm, confirming the visible-light-driven photocatalytic reaction. The enhanced photocatalytic activity might be attributed to the improved charge transfer in the heterojunction photocatalysts evidenced by photoluminescence (PL) and electrochemical impedance spectroscopy (EIS) analyses. A radical pathway for the photodegradation of dyes is postulated based on scavenging experiments and spectral data. This work provides new opportunities for constructing highly efficient catalysts for wastewater treatment.