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Long M.,Shanghai JiaoTong University | Hu P.,Shanghai JiaoTong University | Wu H.,Identity Environmental Technology Shanghai Co. | Cai J.,Shanghai JiaoTong University | And 2 more authors.
Applied Catalysis B: Environmental | Year: 2016

Bismuth oxide based (BOB) materials display strong potentials in visible light photocatalytic applications, but are greatly restricted by the poor stability for organic degradation in aqueous solutions. Herein, a unique heterostructural photocatalyst, nonstoichiometric bismuth oxyiodide Bi2O3-xI2x(x=0.243) covered with iodine intercalated Bi2O2CO3, were developed through a treatment of Bi7O9I3 in urea solution and subsequent calcinations. The interesting formation chemistry of this heterostructure were revealed and their dramatically enhanced photoresponse properties were studied. The lower amount of iodine in Bi2O3-xI2x contributes a higher oxidation potential of photogenerated holes, while the presence of outlayer of iodine intercalated Bi2O2CO3 retards the transformation of inner bismuth oxyiodide. We anticipate this strategy can be generalized to tune iodine contents and to fabricate delicate BOB photocatalytic heterostructures with desirable performance for environmental applications. © 2015 Elsevier B.V.

Wu H.,Shanghai JiaoTong University | Wu H.,Identity Environmental Technology Shanghai Co. | Cai W.,Shanghai JiaoTong University | Cai W.,Identity Environmental Technology Shanghai Co. | And 8 more authors.
Environmental Science and Technology | Year: 2016

Here we demonstrate that sulfur dioxide (SO2) is efficiently captured via heterogeneous oxidation into sulfate on the surface of hydroxylated manganese dioxide (MnO2). Lab-scale activity tests in a fluidized bed reactor showed that the removal efficiency for a simulated flue gas containing 5000 mg·Nm-3 SO2 could reach nearly 100% with a GHSV (gas hourly space velocity) of 10000 h-1. The mechanism was investigated using a combination of experimental characterizations and theoretical calculations. It was found that formation of surface bound sulfate proceeds via association of SO2 with terminal hydroxyls. Both H2O and O2 are essential for the generation of reactive terminal hydroxyls, and the indirect role of O2 in heterogeneous SO2 oxidation at low temperature was also revealed. We propose that the high reactivity of terminal hydroxyls is attributed to the proper surface configuration of MnO2 to adsorb water with degenerate energies for associative and dissociative states, and maintain rapid proton dynamics. Viability analyses suggest that the desulfurization method that is based on such a direct oxidation reaction at the gas/solid interface represents a promising approach for SO2 capture. © 2016 American Chemical Society.

Long M.,Shanghai JiaoTong University | Hu P.,Shanghai JiaoTong University | Wu H.,Identity Environmental Technology Shanghai Co. | Chen Y.,Shanghai JiaoTong University | And 3 more authors.
Journal of Materials Chemistry A | Year: 2015

A series of bismuth oxyiodides were obtained by calcining the precursor compound (Bi7O9I3). Their compositions and electronic structures were analyzed by various physicochemical characterizations, slurry method measurements and theoretical calculations. Iodine vacancies appearing at elevated temperatures before the phase transition contribute to the increased photocatalytic activity, which can be attributed to the increase of band gaps, downward shifts of band potentials and the change of semiconductor behavior from p type to n type. The catalyst obtained at 400 °C displayed an excellent photocatalytic performance for phenol degradation, and it was characterized as a composite of two components with well-matched band potentials and good contact interfaces. Photogenerated holes were revealed as the main active species in the phenol degradation. This study could bring insights into the fabrication of novel highly efficient bismuth oxyiodide composites by simultaneously controlling the extent of phase transition and the amount of iodine vacancies. © 2015 The Royal Society of Chemistry.

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