Reduction of nitrate to ammonia using photocatalytically accumulated electrons on titanium(IV) oxide in a time-separated redox reaction

Abstract

• Reduction of NO 3 − to ammonia NH 3 was performed by a time-separated redox reaction. • The reaction uses a two-step reaction under the control of photoexcitation an electron acceptor. • Eight-electron reduction of NO 3 − to NH 3 was performed by accumulated electrons in a TiO 2 suspension. • The use of a rutile sample with a large number of defective sites is a key factor for the reaction. Reduction of nitrate (NO 3 − ) to ammonia (NH 3 ) was performed by a time-separated redox reaction using photocatalytically accumulated electrons in a titanium(IV) oxide (TiO 2 ) suspension. The time-separated redox reaction uses a two-step reaction under the control of photoexcitation and an electron acceptor: (1) accumulation of electrons in TiO 2 powder under photoexcitation and (2) reduction of added NO 3 − by accumulated electrons in the dark. Color change of TiO 2 depending on the degree of electron accumulation was observed during the reaction, and 8-electron reduction of NO 3 − to NH 3 was performed by accumulated electrons. The results of the time-separated redox reaction using 10 kinds of commercial TiO 2 powder indicate that the use of a rutile sample with a large number of trivalent titanium species is a key factor for NH 3 production.