| RESEARCH |
Photocatalyst is driven by visible light A new sulfide photocatalyst induces water to generate hydrogen in the presence of visible light. Many photocatalysts split water when irradiated with ultraviolet light, but that leaves a large portion of light unused. Akihiko Kudo and coworkers at Tokyo University of Science showed that a solid solution of zinc sulfide, copper indium sulfide, and silver indium sulfide is a highly active photocatalyst when loaded with ruthenium [Angew. Chem. Int. Ed., published online May 6, http://dx.doi.org/10.1002/anie.200500314]. The chemists dispersed the ZnS-CuInS2-AgInS2 photocatalyst powder in an aqueous solution containing potassium sulfite and sodium sulfide and then loaded the ruthenium cocatalyst in situ by photodeposition. When the mixture is irradiated by visible light, the sulfite and sulfide ions act as sacrificial reagents that donate electrons to hydrogen ions, which then form hydrogen gas. They also showed that the ZnS-CuInS2-AgInS2 solid solution absorbs light over a wider wavelength range than do ZnS-AgInS2 or ZnS-CuInS2 solid solutions. These solid solutions could find practical use in photocatalytic hydrogen production if quantum yields and activities can be further improved, they suggest. One of the potential environmental benefits of these systems is the use of unwanted by-products, such as hydrogen sulfide and sulfur dioxide emitted from chemical factories and power plants, as sources of sulfide and sulfite, they add. |
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