High photocatalytic activity and selectivity for nitrogen in nitrate reduction on Ag/TiO2 catalyst with fine silver clusters

Ag/TiO2 catalyst with fine size and homogeneous dispersion of coated silver clusters was synthesized by a recently developed pH-controlled photocatalytic process and applied to the photocatalytic reduction of nitrate as an environmentally friendly and low-cost catalyst with formic acid as a hole scavenger. Compared with conventional preparation routes, the as-prepared Ag/TiO2 catalyst in this study shows better catalytic performance: a nitrate conversion of 98% and selectivity for nitrogen of ca. 100%, which can be achieved after 30 min of irradiation. The average activity was calculated to be ca. 24mmolNO3−gAg−1min−1, which is much higher than that of most of Pd–Cu-based nitrate hydrogenation systems in terms of metal usage, demonstrating its application potential. A similar photocatalytic efficiency and selectivity for nitrogen were also observed for nitrite photocatalytic reduction on this catalyst. The effects of Ag content, hole scavengers, concentration of formic acid, and other anions present in drinking water, such as SO42−, CO32−, and HCO3−, were systematically investigated.