| Summary: | 碩士 === 國立成功大學 === 化學工程學系碩博士班 === 98 === A graphite oxide (GO) semiconductor photocatalyst with an apparent bandgap of 2.4–4.3 eV is synthesized by a modified Hummers’ procedure. The as-synthesized GO photocatalyst has an interlayer spacing of 0.42nm because of its moderate oxidation level. Under irradiation with UV or visible light, this GO photocatalyst steadily catalyzes H2 generation from a 20 vol % aqueous methanol solution and pure water. As the GO sheets extensively disperse in water, a cocatalyst is not required for H2 generation over the GO photocatalyst.
During photocatalytic reaction, the GO loses some oxygen functional groups, leading to bandgap reduction and increased conductivity. This structural variation does not affect the stable H2 generation over the GO. The encouraging results presented in this study demonstrate the potential of graphitic materials as a medium for water splitting under solar illumination.
On the other hand, GO photocatalyst can catalyze O2 generation from an aqueous NaIO3 solution in different concentration. In addition, we use p-type GO and n-tpye TiO2 as photocatalysts and the conduction band and valence band of both catalysts are bending during Hg-lamp irradiation. The electrons on the conduction band of TiO2 cannot transit to the conduction band of GO and accumulate on p-n junction to reduce GO, and then form composites. The GO/TiO2 composites can catalyze O2 generation from a pure water.
GO/TiO2 composites can catalyze O2 generation with the presence of sacrificial reagents as electron donor and electron acceptor, respectively. However, GO and TiO2 are difficult to form composites in basic solution so that it cannot catalyze O2 generation from water spilitting. But GO and GO/TiO2 are conduced to product H2 in basic solution. Therefore, the reduction by GO or charge transfer between the GO-TiO2 linkage is the limiting step.
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