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

Abstract

We report a facile immobilization of riboflavin (RF) over in situ synthesized CeO 2 −reduced graphene oxide (RGO) nanohybrid surface synthesized through a simple wetchemical approach for photocatalytic degradation of organic pollutants under visible light (λ ≥ 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 photocurrent measurements corroborate that the hybrid RF@CeO 2 − RGO significantly absorbs visible light and exhibits lower recombination of charge carriers in comparison to RF@CeO 2 . The catalyst, RF@CeO 2 −RGO, offers enhancement in photocatalytic rate, i.e., 2.8-fold increase for methyl orange (MO) and 3.5-fold for p-nitrotoluene (PNT) in comparison to RF@CeO 2 under visible light (2 h). This enhancement could be attributed to the synergistic effect among CeO 2 , 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 × 10 −2 and 2.00 × 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 (CeO 2 and CeO 2 −RGO hybrids) and its viability for the remediation of water pollutants.

Defect Engineering Enhances the Charge Separation of CeO2 Nanorods toward Photocatalytic Methyl Blue Oxidation

“…Active species such as superoxide radicals, hydroxyl radicals, and h + play an important role in advanced oxidation processes (AOPS) technology [ 52 ]. To understand which active species generated during the photocatalytic oxidation reaction, we performed active species trapping experiments and electron spin resonance (ESR) measurements [ 4 , 34 ].…”

Boosted Charge Transfer Efficacy of an All‐Solid‐State Z‐Scheme BiOI‐CD‐CdS Photocatalyst for Enhanced Degradation of 4‐Nitrophenol and Oxidation of Benzyl Alcohol under Visible Light**

“…The light intensity was estimated as 7.365 × 10 16 Einstein/s over potassium ferric oxalate actinometer, the detailed method of intensity calculation was described in our previous manuscript. [67] 20 mg of the photocatalyst was dispersed in a pyrex glass vessel containing 20 mL of the aqueous solution of 4-nitrophenol [20 ppm] and the solution was allowed to stir in dark for 1 h to achieve an adsorption-desorption equilibrium between catalyst and reactant. We have assigned the initial sample as a 0 min in dark reaction.…”

Recyclable Functionalized Material for Sensitive Detection and Exceptional Sorption of Hexavalent Chromium and Permanganate Ions with Biosensing Applications

“…Attempts have been made to derive these dual functions from a single material but are very rare 6−9 compared to either function of detection 10−16 or removal. 17−26 Various removal approaches include chemical precipitation, 27 electrochemical precipitation, 22 photocatalysis, 20,21 adsorption, 23,24 and ion-exchange separation. 17−19 Similarly, various sensing approaches include spectrophotometry, 28 atomic absorption spectroscopy, 29 ion chromatography, 30 electrochemical sensings, 31,32 and optical sensing.…”

“…The World Health Organization has fixed the maximum contaminant level of Cr­(VI) as 50 ppb and total manganese as 37 μM. , Therefore, concurrent detection and remediation of these anions from the aqueous streams are significant for environmental remediation but are still challenging. Attempts have been made to derive these dual functions from a single material but are very rare − compared to either function of detection − or removal. − Various removal approaches include chemical precipitation, electrochemical precipitation, photocatalysis, , adsorption, , and ion-exchange separation. − Similarly, various sensing approaches include spectrophotometry, atomic absorption spectroscopy, ion chromatography, electrochemical sensings, , and optical sensing. − …”

“…A thorough analysis of the cited literature reveals that the two main mechanisms that are predominant are either ion exchange, where a small counter anion is exchanged easily with the bulky oxoanions − or the redox chemistry, where these oxoanions oxidize the substrate and are reduced to a lower oxidation state − and subsequently precipitated. Therefore, the metal–organic frameworks (MOFs) bearing the anion exchange properties (cationic MOFs) are predominant in this area of research.…”