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Wang C.,Nanjing University | Guo Y.,Nanjing University | Yang Y.,Nanjing University | Chu S.,Nanjing University | And 5 more authors.
ACS Applied Materials and Interfaces | Year: 2014

Sulfur-doped polyimide (SPI) photocatalysts were synthesized for the first time via an in situ thermal copolymerization method using sublimed sulfur (S4) as a dopant. Sulfur doping not only extended the absorption range of polyimide (PI) for visible light but also enhanced the oxidation ability of the photoinduced hole. The doped sulfur substitutes for the lattice nitrogen in triazine rings of PI to form the S-C bond and changes the distribution of negative charge in the two-dimensional plane of PI. The enhanced photocatalytic activity of SPI in the degradation of methyl orange is ascribed to the strong oxidation ability of the photoinduced hole of SPI and an effective suppression to the recombination of electrons and holes. © 2014 American Chemical Society.

Ma C.,National Renewable Energy Laboratory | Ma C.,Qinghai UniversityQinghai | Ma C.,Jiangsu Key Laboratory for Nanotechnology | Zhou J.,National Renewable Energy Laboratory | And 7 more authors.
Solar Energy Materials and Solar Cells | Year: 2016

A series of MoO3/PI composite photocatalysts were prepared via a facile in situ solid-thermal approach. Characterization results revealed that the growth of MoO3 nanoflakes epitaxial (010) face on the surface of PI and introduction of Mo did not change the skeleton structure but enhance the crystallinity of polyimide. The stronger interaction between MoO3 and substrate PI leads to the formation of Mo-N band and Mo5+ species. The measurements for the optical and electronic properties of MoO3/PI composites confirmed that MoO3 nanoflakes on the surface PI not only induce the absorption of visible light but also suppressed the radiative recombination of charge carriers, which endows the excellent photocatalytic activity of MoO3/PI samples in hydrogen evolution from a CH3OH-H2O solution 9:1 by volume) under solar energy driven. The enhancement of MoO3 nanoflake for the photocatalytic performance of PI is even more effective than that of Pt at the same loading amount. This work provides a promising choice to substitute noble metal as the cocatalyst on polymer photocatalyst and take a step forward effective utilization of renewable energy. © 2016 Elsevier B.V. All rights reserved.

Zhou J.,National Renewable Energy Laboratory | Liu L.,Jiangsu Key Laboratory for Nanotechnology | Wang Y.,National Renewable Energy Laboratory | Wang Y.,Jiangsu Key Laboratory for Nanotechnology | And 3 more authors.
Journal of Porous Materials | Year: 2015

A series of Fe-doped SH/TiO2 mesoporous photocatalysts have been firstly prepared by one-pot method using P123 as structure-directing agent. This bifunctionalized mesoporous TiO2 possesses perfect anatase crystal structure and high surface area. The surface area of Fe-doped SH/TiO2 mesoporous material is 4 times higher than that of P25. Based on the EPR results, it was found that trivalent Fe ions exist at low spin state and substitutes a part of Ti4+ ions into TiO2 lattice. Fe-dropping in TiO2 extends the adsorption band side of the resulting material to about 600 nm. Much high photocatalytic activity in the degradation of phenanthrene was obtained on the bifunctionalized mesoporous TiO2 under visible light irradiation (λ > 420 nm), which is 6 times higher than that of pristine mesoporous TiO2. The enhancement in the photocatalytic activity of bifunctionalized TiO2 is ascribed to the extended absorption to visible light and strong interaction between SH-groups and PHE molecules. © 2014, Springer Science+Business Media New York.

Chu S.,National Renewable Energy Laboratory | Wang C.,National Renewable Energy Laboratory | Yang Y.,National Renewable Energy Laboratory | Wang Y.,National Renewable Energy Laboratory | And 3 more authors.
RSC Advances | Year: 2014

In this study, a series of conjugated polyimide (PI) photocatalysts were prepared via a facile thermal condensation of melamine and various aromatic dianhydride monomers. The samples were characterized by Fourier transform infrared spectroscopy, elemental analysis, X-ray powder diffraction and UV-vis diffuse reflectance spectroscopy. All samples showed a well-developed polyimide structure and strong visible-light absorption. The electronic band structures of PI were simulated by density functional theory calculations. Photocatalytic results showed that the PI with a best coplanar conformation in the backbone and strongest photooxidative capability exhibited the highest activity for methyl orange (MO) degradation. In addition, it displayed an excellent stability during four cycles of photocatalytic testing. Photocatalytic mechanism study indicated that photogenerated holes rather than electrons play a crucial role on the photodegradation of MO. Moreover, the participation of reactive oxygen species such as OH., O2 .- and 1O2 was examined by adding corresponding scavengers. However, only 1O2 was identified as the active species involved in the MO degradation. This work represents the great potential of metal-free PI photocatalyst as sustainable, efficient and low-cost material for environmental remediation and solar energy conversion. © The Royal Society of Chemistry 2014.

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