Journal
ENVIRONMENTAL SCIENCE & TECHNOLOGY
Volume 56, Issue 6, Pages 3710-3718Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acs.est.1c07739
Keywords
nitrogen oxides; selective catalytic reduction; V2O5/TiO2 catalysts; operando spectroscopy; DFT calculations
Categories
Funding
- National Key R&D Program of China [2017YFC0211101]
- National Natural Science Foundation of China [21906171, 21673277, 21637005, 22006158]
- Strategic Priority Research Program of the Chinese Academy of Sciences [XDA23010200]
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The reactivity of Bronsted acid sites on V2O5/TiO2 catalysts plays a crucial role in NH3-SCR reaction, while the reactivity of Lewis acid sites is overestimated. Abundant V-OH Bronsted acid sites govern the overall NOx reduction rate in realistic exhaust containing water vapor.
Selective catalytic reduction of NOx by ammonia (NH3-SCR) on V2O5/TiO2 catalysts is a widely used commercial technology in power plants and diesel vehicles due to its high elimination efficiency for NOx removal. However, the mechanistic aspects of the NH3-SCR reaction, especially the active sites on the V2O5/TiO2 catalysts, are still a puzzle. Herein, using combined operando spectroscopy and density functional theory calculations, we found that the reactivity of the Lewis acid site was significantly overestimated due to its conversion to the Bronsted acid site. Such interconversion makes it challenging to measure the intrinsic reactivity of different acid sites accurately. In contrast, the abundant V-OH Bronsted acid sites govern the overall NOx reduction rate in realistic exhaust containing water vapor. Moreover, the vanadia species cycle between V5+=O and V4+-OH during NOx reduction, and the re-oxidation of V4+ species to form V5+ is the rate-determining step.
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