Efficient Separation of Electron鈥揌ole Pairs in Graphene Quantum Dots by TiO2 Heterojunctions for Dye Degradation

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• 作者：Dengyu Pan ; Jinkai Jiao ; Zhen Li ; Yanting Guo ; Chuanqi Feng ; Yuan Liu ; Liang Wang ; Minghong Wu
• 刊名：ACS Sustainable Chemistry & Engineering
• 出版年：2015
• 出版时间：October 5, 2015
• 年：2015
• 卷：3
• 期：10
• 页码：2405-2413
• 全文大小：604K
• ISSN：2168-0485

文摘

Water-soluble, single-crystalline, and amine-functionalized graphene quantum dots (GQDs) with absorption edge at 鈭?90 nm were synthesized by a molecular fusion method, and stably deposited onto anatase TiO₂ nanoparticles under hydrothermal conditions. The effective incorporation of the GQDs extends the light absorption of the TiO₂ nanoparticles from UV to a wide visible region. Moreover, amine-functionalized GQD鈥揟iO₂ heterojunctions can absorb more O₂ than pure TiO₂, which can generate more 路O₂ species for MO degradation. Accordingly, the heterojunctions exhibit much higher photocatalytic performance for degrading methyl orange (MO) under visible-light irradiation than TiO₂ alone. At optimum GQD content (1.0 wt %), an apparent MO decomposition rate constant is 15 times higher than that of TiO₂ alone, and photocurrent intensity in response to visible-light excitation increases by 9 times. Compared with conventional sensitization by toxic, photounstable quantum dots such as CdSe QDs, the sensitization by environmentally friendly GQDs shows higher visible-light photocatalytic activity and higher cycling stability. Monodispersed QD-based heterojunctions can effectively inhibit the fast recombination of electron鈥揾ole pairs of GQDs with a large exciton binding energy. The photogenerated electron transfer, energy-band-matching mechanism of GQD/TiO₂, and possible MO decomposition pathways under visible-light irradiation are proposed.