The visible-light-driven photocatalytic activities of graphene-semiconductor catalysts have recently been demonstrated, however, the transfer pathway of photogenerated carriers especially where the role of graphene still remains controversial. Here we report graphene-SnO2 aerosol nanocomposites that exhibit more superior dye adsorption capacity and photocatalytic efficiency compared with pure SnO2 quantum dots, P25 TiO2, and pure graphene aerosol under the visible light. This study examines the origin of the visible-light-driven photocatalysis, which for the first time links to the synergistic effect of the cophotosensitization of the dye and graphene to SnO2. We hope this concept and corresponding mechanism of cophotosensitization could provide an original understanding for the photocatalytic reaction process at the level of carrier transfer pathway as well as a brand new approach to design novel and versatile graphene-based composites for solar energy conversion.
The ultrafine SnO 2 quantum dots (QDs) modified with poly(ethylene glycol methyl ether) (PEGME) (PEGME-SnO 2 QDs) were synthesized via hydrothermal method. X-ray diffraction and high-resolution transmission electron microscopy were employed to illustrate that the PEGME-SnO 2 QDs are uniform, monodispersed and about 4 nm in diameter. Then infrared spectrum and thermogravimetric analysis were used to prove that PEGME groups are bound tightly to SnO 2 surfaces. The as-synthesized PEGME-SnO 2 QDs excellently achieved photocatalytic degradation to Rhodamine B dye (RhB). The photon efficiency of the PEGME-SnO 2 QDs catalyst and corresponding RhB dye degradation rate constant could reach 0.0058% and 9.98 Â 10 À2 min À1 , respectively. This outstanding photocatalytic performance could be attributed to not only large surface-to-volume ratio and high crystallinity of the ultrafine and monodispersed QDs, but also good hydrophilicity and conductivity of the PEGME surface modifier.Remarkably, such PEGME-SnO 2 QDs with outstanding photocatalytic efficiency and stable recyclability are promising to be applied to environmental purification.
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