Riboflavin-Immobilized CeO2-RGO Nanohybrid as a Potential Photoredox Catalyst for Enhanced Removal of Organic Pollutants under Visible Light

摘要

We report a facile immobilization of riboflavin (RF) over in situ synthesized CeO2-reduced graphene oxide (RGO) nanohybrid surface synthesized through a simple wet-chemical approach for photocatalytic degradation of organic pollutants under visible light (lambda >= 420 nm). The hybrid containing 3% w/w RGO shows an excellent photocatalytic activity under visible light. The UV-visible diffuse reflectance spectra, photoluminescence (PL) analysis, and transient photo current measurements corroborate that the hybrid RF@CeO2-RGO significantly absorbs visible light and exhibits lower recombination of charge carriers in comparison to RF@CeO2. The catalyst, RF@CeO2-RGO, offers enhancement in photo catalytic rate, i.e., 2.8-fold increase for methyl orange (MO) and 3.5-fold for p-nitrotoluene (PNT) in comparison to RF@CeO2 under visible light (2 h). This enhancement could be attributed to the synergistic effect among CeO2, RF (broadens visible light absorption region), and RGO (an electron-shuttling agent), which lead to an efficient separation of charge carriers. Consequently, the hybrid photocatalyst shows higher rate constant values, 2.31 x 10(-2) and 2.00 x 10(-2) min(-1) for PNT and MO dye, respectively. The catalytic studies were monitored using UV-vis spectroscopy, high-performance liquid chromatography-photodiode array (HPLC-PDA), and gas chromatography-mass spectrometry (GC-MS) techniques. From the radical trapping experiments, the involvement of both superoxide and hydroxyl radicals was inferred. The present study provides more insights into the photochemical activity of metal-free sensitizer, RF, on metal oxide/hybrids (CeO2 and CeO2-RGO hybrids) and its viability for the remediation of water pollutants.