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On the Redox Mechanism of Low‐Temperature NH 3 ‐SCR over Cu‐CHA: A Combined Experimental and Theoretical Study of the Reduction Half Cycle
Author(s) -
Hu Wenshuo,
Selleri Tommaso,
Gramigni Federica,
Fenes Endre,
Rout Kumar R.,
Liu Shaojun,
Nova Isabella,
Chen De,
Gao Xiang,
Tronconi Enrico
Publication year - 2021
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.202014926
Subject(s) - nox , chemistry , redox , catalysis , catalytic cycle , selective catalytic reduction , reaction mechanism , decomposition , ion , nitrite , density functional theory , photochemistry , inorganic chemistry , computational chemistry , organic chemistry , nitrate , combustion
Cu‐CHA is the state‐of‐the‐art catalyst for the Selective Catalytic Reduction (SCR) of NOx in vehicle applications. Although extensively studied, diverse mechanistic proposals still stand in terms of the nature of active Cu‐ions and reaction pathways in SCR working conditions. Herein we address the redox mechanism underlying Low‐Temperature (LT) SCR on Cu‐CHA by an integration of chemical‐trapping techniques, transient‐response methods, operando UV/Vis‐NIR spectroscopy with modelling tools based on transient kinetic analysis and density functional theory calculations. We show that the rates of the Reduction Half‐Cycle (RHC) of LT‐SCR display a quadratic dependence on Cu II , thus questioning mechanisms based on isolated Cu II ‐ions. We propose, instead, a Cu II ‐pair mediated LT‐RHC pathway, in which NO oxidative activation to mobile nitrite‐precursor intermediates accounts for Cu II reduction. These results highlight the role of dinuclear Cu complexes not only in the oxidation part of LT‐SCR, but also in the RHC reaction cascade.