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Advanced nanostructured photocatalysts based on reduced graphene oxide–TiO2 composites for degradation of diphenhydramine pharmaceutical and methyl orange dye

Paper ID Volume ID Publish Year Pages File Format Full-Text
46143 46430 2012 16 PDF Available
Title
Advanced nanostructured photocatalysts based on reduced graphene oxide–TiO2 composites for degradation of diphenhydramine pharmaceutical and methyl orange dye
Abstract

Reduced graphene oxide–TiO2 composites (GOT) were prepared by liquid phase deposition followed by post-thermal reduction at different temperatures. The composite materials were systematically evaluated as photocatalysts for the degradation of an important pharmaceutical water pollutant, diphenhydramine (DP), and an azo-dye, methyl orange (MO), under both near-UV/Vis and visible light irradiation as a function of the graphene oxide (GO) content. A marked compositional dependence of the photocatalytic activity was evidenced for DP and MO pollutants degradation and mineralization under both UV/Vis and visible light. Especially under visible light, optimum photocatalytic performance was obtained for the composites treated at 200 °C comprising 3.3–4.0 wt.% GO, exceeding that of the benchmark P25 (Evonik) catalyst. According to scanning electron microscopy, Raman spectroscopy, and porosimetry analysis data, this was attributed to the optimal assembly and interfacial coupling between the reduced GO sheets and TiO2 nanoparticles. Almost total degradation and significant mineralization of DP and MO pollutants (in less than 60 min) was achieved under near-UV/Vis irradiation for the optimum GOT composites. However, higher GO content and calcination temperatures (350 °C) led to detrimental effects due to the GO excess and the disruption of the GO–TiO2 binding. Photocatalytic experiments employing sacrificial hole and radical scavenging agents revealed that photogenerated holes are the primary active species in DP degradation for both bare TiO2 and GOT under UV/Vis irradiation, while an enhanced contribution of radical mediated DP oxidation was evidenced under visible light. These results combined with the distinct quenching of the GO photoluminescence under visible and NIR laser excitation, indicate that reduced GO acts either as electron acceptor or electron donor (sensitizer) of TiO2 under UV and visible light, respectively. Fine-tuning of the reduced GO–TiO2 interface is concluded as a very promising route to alleviate electron–hole recombination and circumvent the inherently poor light harvesting ability of TiO2 in the visible range.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights▸ GOT photocatalytic activity exceeded that of P25, especially under visible light. ▸ Optimization of the GO–TiO2 interface is crucial for the photocatalytic efficiency. ▸ Photogenerated holes were identified as the main reactive species. ▸ GO may operate as a visible light sensitizer of TiO2. ▸ Enhanced contribution of radical mediated oxidation evidenced under visible light.

Keywords
Reduced graphene oxide; Titanium dioxide; Heterogeneous photocatalysis; Scavengers for holes and radicals; Photoluminescence quenching; Raman spectroscopy
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Advanced nanostructured photocatalysts based on reduced graphene oxide–TiO2 composites for degradation of diphenhydramine pharmaceutical and methyl orange dye
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Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis B: Environmental - Volumes 123–124, 23 July 2012, Pages 241–256
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Catalysis
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us