%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