|Quantum efficiency of the photocatalyst plotted as a function of wavelength of the incident light.|
Researchers from Tokyo University and Nagaoka University of Technology have developed a new photocatalyst that more efficiently splits water to produce hydrogen under visible light. The researchers reported their findings in the 16 March 2006 issue of Nature.
The newly developed catalyst is a solid solution of gallium nitride and zinc oxide with a mixture of rhodium and chromium oxide nanoparticles on its surface.
The modified catalyst delivered overall quantum efficiency of about 2.5% at 420–440 nm wavelength—about an order of magnitude higher than the previously reported activity of photocatalytic water-splitting using visible light.
(Light at λ = 420 nm is violet—the beginning of the visible spectrum.)
The researchers suggest that by improving the hydrogen-evolution site on the system, the quantum efficiency could be much increased. A trial with silver nitrate as the sacrificial electron acceptor yielded an efficiency of 51% at the same 420–440 nm—20 times higher.
Its composition could also be modified to extend the absorption edge to longer wavelengths. For now, our results demonstrate the feasibility of using photocatalysts and solar energy to produce hydrogen from water.
Photocatalyst releasing hydrogen from water”; Kazuhiko Maeda, Kentaro Teramura, Daling Lu, Tsuyoshi Takata, Nobuo Saito, Yasunobu Inoue and Kazunari Domen; Nature 440, 295 (16 March 2006) | doi:10.1038/440295a