TaON and Ta3N5 as new visible light driven photocatalysts

TaON and Ta3N5, Ta5+-based (oxy)nitrides, were studied as visible light driven photocatalysts. Under visible light irradiation (lambda greater than or equal to 420 nm), the (oxy)nitrides oxidize water to O-2 and reduce H+ to H-2 in the presence of sacrificial reagents (Ag+ and methanol). TaON oxidizes water into O-2 efficiently, with a maximum quantum yield of 10%. The photocatalytic reactions proceed via the bandgap transitions (E-g, TaON: 2.5 eV, Ta3N5: 2.1 eV) without any noticeable degradation of the catalysts. The small energy gaps of TaON and Ta3N5 are ascribed to the valence band structures consisting of N 2p orbitals. (C) 2002 Elsevier Science B.V. All rights reserved.