1. 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
-
Hu W, Selleri T, Gramigni F, Fenes E, Rout KR, Liu S, Nova I, Chen, Gao X, and Tronconi E
- Abstract
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 CuII -ions. We propose, instead, a CuII -pair mediated LT-RHC pathway, in which NO oxidative activation to mobile nitrite-precursor intermediates accounts for CuII 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., (© 2021 Wiley-VCH GmbH.)- Published
- 2021
- Full Text
- View/download PDF