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Mechanistic understanding of Cu-CHA catalyst as sensor for direct NH 3-SCR monitoring : the role of Cu mobility

Title data

Chen, Peirong ; Rizzotto, Valentina ; Khetan, Abhishek ; Xie, Kunpeng ; Moos, Ralf ; Pitsch, Heinz ; Ye, Daiqi ; Simon, Ulrich:
Mechanistic understanding of Cu-CHA catalyst as sensor for direct NH 3-SCR monitoring : the role of Cu mobility.
In: ACS Applied Materials & Interfaces. Vol. 11 (2019) Issue 8 . - pp. 8097-8105.
ISSN 1944-8252
DOI: https://doi.org/10.1021/acsami.8b22104

Abstract in another language

The concept to utilize a catalyst directly as a sensor is fundamentally and technically attractive for a number of catalytic applications, in particular, for the catalytic abatement of automotive emission. Here, we explore the potential of microporous copper-exchanged chabazite (Cu-CHA, including Cu-SSZ-13 and Cu-SAPO-34) zeolite catalysts, which are used commercially in the selective catalytic reduction of automotive nitrogen oxide emission by NH3 (NH3-SCR), as impedance sensor elements to monitor directly the NH3-SCR process. The NH3-SCR sensing behavior of commercial Cu-SSZ-13 and Cu-SAPO-34 catalysts at typical reaction temperatures (i.e., 200 and 350 °C) was evaluated according to the change of ionic conductivity and was mechanistically investigated by complex impedance-based in situ modulus spectroscopy. Short-range (local) movement of Cu ions within the zeolite structure was found to determine largely the NH3-SCR sensing behavior of both catalysts. Formation of NH3-solvated, highly mobile CuI species showed a predominant influence on the ionic conductivity of both catalysts and, consequently, hindered NH3-SCR sensing at 200 °C. Density functional theory calculations over a model Cu-SAPO-34 system revealed that CuII reduction to CuI by coadsorbed NH3 and NO weakened significantly the coordination of the Cu site to the CHA framework, enabling high mobility of CuI species that influences substantially the NH3-SCR sensing. The in situ spectroscopic and theoretical investigations not only unveil the mechanisms of Cu-CHA catalyst as sensor elements for direct NH3-SCR monitoring but also allow us to get insights into the speciation of active Cu sites in NH3-SCR under different reaction conditions with varied temperatures and gas compositions.

Further data

Item Type: Article in a journal
Refereed: Yes
Institutions of the University: Faculties > Faculty of Engineering Science
Faculties > Faculty of Engineering Science > Chair Functional Materials > Chair Functional Materials - Univ.-Prof. Dr.-Ing. Ralf Moos
Profile Fields > Advanced Fields > Advanced Materials
Research Institutions > Research Centres > Bayreuth Center for Material Science and Engineering - BayMAT
Research Institutions > Research Units > BERC - Bayreuth Engine Research Center
Result of work at the UBT: Yes
DDC Subjects: 600 Technology, medicine, applied sciences > 620 Engineering
Date Deposited: 18 Mar 2019 07:24
Last Modified: 18 Mar 2019 07:24
URI: https://eref.uni-bayreuth.de/id/eprint/47988