α-Sulfur Crystals as a Visible-Light-Active Photocatalyst

We show that in contrast to conventional compound photocatalysts, alpha-sulfur crystals of cyclo-octasulfur (S-8) are a visible-light-active elemental photocatalyst. The alpha-S crystals were found to have the ability not only to generate center dot OH radicals but also to split water in a photoelectrochemical process under both UV-vis and visible-light irradiation. Although the absolute activity obtained was low because of the large particle size and poor hydrophilicity of the alpha-S crystals studied, there is great potential for increasing the activity with the assistance of known strategies such as surface modification, nanoscaling, doping, and coupling with other photocatalysts.