PHOTOCATALYTIC REDUCTION OF NITRITE AND NITRATE IONS OVER OXIDE (ZNO,ZRO2 AND FE2O3) SEMICONDUCTORS

The photocatalytic reduction of nitrite and nit rate ions to ammonia h as been studied over ZnO, ZrO2, Fe2O3 and Fe3O4 oxide semiconductors. Many parameters such as the position of the conduction band edge of th e semiconductor, the metal-semiconductor junction, light absorption ca pacity elf the semiconductor, adsorption of the reagent species and pH of the medium used influence the yield of ammonia and hence one can n ot a priori predict the relative activity of these systems on the basi s of band edges alone. The resulting photoactivity is a balance of the above said factors some of which play contrasting roles.