Photocatalytic reduction of nitrate ions over tantalate photocatalysts

Abstract

Tantalate photocatalysts reduced nitrate ions to nitrite ions, dinitrogen, and ammonia under UV irradiation even without co-catalysts or reducing reagents such as organic compounds. The photocatalytic activities of tantalate photocatalysts were larger than those of TiO₂ photocatalysts. The selectivity for the photocatalytic reduction of nitrate ions was affected by the addition of co-catalysts. In particular, the efficiencies of dinitrogen and ammonia formation increased by one to two orders of magnitude when a Ni co-catalyst was loaded. The selectivity was also affected by the amount of loaded Ni and the loading method. 44% and 39% of nitrate ions in an aqueous KNO₃ solution (0.010 mol L⁻¹, 400 mL) were reduced to dinitrogen and ammonia, respectively, over the Ni(1 wt.%)/KTaO₃ photocatalyst after 25 h irradiation.