Nanostructured Visible-Light Photocatalysts for Water Purification

Titanium oxide (TiO,) photocatalysts have been widely studied for both solar energy conversion and environmental applications in the past several decades because of their high chemical stability, good photoactivity, relatively low cost, and nontoxicity. However, the photocatalytic capability of TiO, is limited to only ultraviolet light (wavelength, A,<400. nm), seriously limiting its solar efficiency. To overcome this limitation, both chemical and physical modification approaches were developed to extend the absorption band-edge of TiO, into visible-light region. These visible-light photocatalysts were further modified by nanoparticles of transition metal oxides and made into nanoparticles, nanoporous fibers, and nanoporous foams. The nanostructured photocatalysts showed very fast photocatalytic degradation rates in organics, bacteria, spores, and virus, and thus have great potential in water disinfection and removal of organic contaminants in water.