Researchers at Japan’s National Institute for Materials Science (NIMS) have discovered a new photocatalyst, Sn3O4, which facilitates the production of hydrogen fuel from water, using sunlight as an energy source. A paper on their work is published in the ACS journal Applied Materials & Interfaces.
|Electron microscope imagery of Sn3O4 catalyst. The synthesized material is a collection of micro-sized (one millionth of a meter) flaky crystals. Source: NIMS. Click to enlarge.|
Many water-splitting photocatalysts, such as titanium dioxide (TiO2), can decompose water and produce hydrogen fuel when absorbing ultraviolet light. However, due to their inability to absorb visible light, which accounts for more than half of solar energy, their practical use in the conversion of solar energy is limited.
While the development of new photocatalysts that can split water by absorbing visible light has been worked on globally, there are cost- and environment-related issues because many of the available photocatalysts contain expensive rare metals, such as tantalum, or high concentrations of lead, which is very toxic.
Led by Hideki Abe and Naoto Umezawa, researchers at Japan’s National Institute for Materials Science (NIMS) recently discovered a novel photocatalyst by integrating both theoretical and experimental sciences.
The NIMS team searched for oxides containing divalent tin ions (Sn2+) based on the theoretical prediction that such substances may have an electronic structure conducive to water-splitting photocatalytic reactions under the presence of visible light. As a result, they found a tin oxide, Sn3O4 (Sn2+2Sn4+O4), that is made up of divalent tin ions (Sn2+) and tetravalent tin ions (Sn4+).
Their experiment revealed that this substance facilitates a water-splitting reaction leading to the generation of hydrogen when exposed to visible light which does not activate TiO2.
Since tin oxides are relatively non-toxic, inexpensive and abundant, they are widely used as transparent conductive materials.
Sn3O4 has great potential as an abundant, cheap, and environmentally benign solar-energy conversion catalyst.—Manikandan et al.
Maidhily Manikandan, Toyokazu Tanabe, Peng Li, Shigenori Ueda, Gubbala V. Ramesh, Rajesh Kodiyath, Junjie Wang, Toru Hara, Arivuoli Dakshanamoorthy, Shinsuke Ishihara, Katsuhiko Ariga, Jinhua Ye, Naoto Umezawa, and Hideki Abe (2014) “Photocatalytic Water Splitting under Visible Light by Mixed-Valence Sn3O4,” ACS Applied Materials & Interfaces 6 (6), 3790-3793 doi: 10.1021/am500157u