Selective removal of nitrate via the synergistic effect of oxygen vacancies and plasmon-induced hot carriers.

• A solid lithiothermic reduction method is used to produce oxygen vacancies in P25. • Plasmonic metals of Ag and Cu nanoparticles are deposited onto the reduced P25. • Synergistic effect of oxygen vacancies and plasmon-induced hot carriers. • High NO 3 − removal efficiency of 93% and N 2 selectivity of 68% yielded without HCOOH. Photoreduction has been proven effective to remove NO 3 − from water, as NO 3 − has severely damaged water quality over decades. However, the typical photoreduction of NO 3 − usually requires sufficient hole scavengers (mostly formic acid) to produce strong reducing carboxyl radical (CO 2 −) species for the elementary conversion of NO 3 −. The excessive employment of hole scavengers increases the cost of water treatment, and further results in secondary chemical pollution. Here, a novel hole-scavenger-free efficient NO 3 − photoreduction route is developed by using a novel oxygen-deficient photocatalyst (R-P25@Ag/Cu nanoparticles). Graded oxygen vacancies are introduced into P25 nanocrystals via lithiothermic reduction approach, significantly promoting the photocatalytic capability. Subsequently, bimetal (Ag and Cu) nanoparticles are stepwise anchored onto the reduced P25 particles to improve the separation of the photogenerated carriers from the reduced P25 particles; more importantly, the plasmonic nanoparticles trigger the initial elementary step of NO 3 − reduction to NO 3 2− [E0(NO 3 −/ NO 3 2−) = −0.89 V versus SHE] with plasmon-induced hot carriers. Consequently, the optimized R-P25@Ag/Cu catalyst shows an outstanding NO 3 − removal performance with a high removal efficiency of 93% and a N 2 selectivity of 68% (mercury lamp, 180 min) by a synergistic effect without hole scavengers. [ABSTRACT FROM AUTHOR]