Tremendous research has been done on seeking alternative sources of energy due to the very limited conventional fossil fuels. Hydrogen, as an environmentally friendly fuel, has become the most promising energy source and attracted a lot of attention. The challenge however lies in the efficient and economic production of hydrogen. Photocatalytic water-splitting using solar light is possibly the most ideal path.

For a photocatalyst to be applicable in the visible region, there are three considerations: 1) stability in water; 2) crystallinity, for reducing electron-hole recombination and 3) a band gap between 1.6 to 2.4 eV. Many transition metal oxides, such as TiO2 and NaTaO3, are known to be good photocatalysts, however, they are active only in the ultraviolet region. Our research attempts are focused on preparing crystalline alkali metal oxysulfides for their potential as visible region photocatalysts. The inclusion of sulfur in the structure will lead to more covalent interactions thus reducing the band gap. We are especially interested in the first row transition metals and Group III, IV and V main group metals because the oxides of these metals have shown promising photocatalytic activity. By obtaining structural information on these materials, we hope to build the structure/property relationship that may help better understanding of the photocatalytic water-splitting process. This presentation will highlight the basis of our research and the various approaches we have been exploring to prepare oxysulfides for the purpose of efficient visible-light driven water-splitting.