%0 Journal Article %A Hirakawa, Hiroaki %A Hashimoto, Masaki %A Shiraishi, Yasuhiro %A Hirai, Takayuki %D 2017 %T Selective Nitrate-to-Ammonia Transformation on Surface Defects of Titanium Dioxide Photocatalysts %U https://acs.figshare.com/articles/journal_contribution/Selective_Nitrate-to-Ammonia_Transformation_on_Surface_Defects_of_Titanium_Dioxide_Photocatalysts/4922909 %R 10.1021/acscatal.7b00611.s001 %2 https://ndownloader.figshare.com/files/8277227 %K to-NH 3 reduction %K Toxic nitrate anion %K NH 3 production %K to-NH 3 transformation %K Lewis acid sites %K N 2 %K HCOOH %K Lewis acid site %K Titanium Dioxide Photocatalysts Ammonia %K NH 3 %K UV %K Several photocatalytic systems %K NH 3 formation %K Selective Nitrate-to-Ammonia Transformation %K eight-electron reduction %K defect %K TiO 2 %X Ammonia (NH3) is an essential chemical in modern society, currently manufactured via the Haber–Bosch process with H2 and N2 under extremely high pressure (>200 bar) and high-temperature conditions (>673 K). Toxic nitrate anion (NO3) contained in wastewater is one potential nitrogen source. Selective NO3-to-NH3 transformation via eight-electron reduction, if promoted at atmospheric pressure and room temperature, may become a powerful recycling process for NH3 production. Several photocatalytic systems have been proposed, but many of them produce nitrogen gas (N2) via five-electron reduction of NO3. Here, we report that unmodified TiO2, when photoexcited by ultraviolet (UV) light (λ > 300 nm) with formic acid (HCOOH) as an electron donor, promotes selective NO3-to-NH3 reduction with 97% selectivity. Surface defects and Lewis acid sites of TiO2 behave as reduction sites for NO3. The surface defect selectively promotes eight-electron reduction (NH3 formation), while the Lewis acid site promotes nonselective reduction (N2 and NH3 formation). Therefore, the TiO2 with a large number of surface defects and a small number of Lewis acid sites produces NH3 with very high selectivity. %I ACS Publications