Abstract
Low-temperature standard NH3-SCR over copper-exchanged zeolite catalysts occurs on NH3-solvated Cu-ion active sites in a quasi-homogeneous manner. As key kinetically relevant reaction steps, the reaction intermediate CuII(NH3)4 ion hydrolyzes to CuII(OH)(NH3)3 ion to gain redox activity. The CuII(OH)(NH3)3 ion also transfers between neighboring zeolite cages to form highly reactive reaction intermediates. Via operando electron paramagnetic resonance spectroscopy and SCR kinetic measurements and density functional theory calculations, we demonstrate here that such kinetically relevant steps become energetically more difficult with lower support Brønsted acid strength and density. Consequently, Cu/LTA displays lower Cu atomic efficiency than Cu/CHA and Cu/AEI, which can also be rationalized by considering differences in their support topology. By carrying out hydrothermal aging to eliminate support Brønsted acid sites, both CuII(NH3)4 ion hydrolysis and CuII(OH)(NH3)3 ion migration are hindered, leading to a marked decrease in Cu atomic efficiency for all catalysts.
| Original language | English |
|---|---|
| Article number | 2633 |
| Journal | Nature Communications |
| Volume | 14 |
| Issue number | 1 |
| DOIs | |
| State | Published - Dec 2023 |
Funding
The authors from Pacific Northwest National Laboratory (PNNL) gratefully acknowledge the US Department of Energy (DOE), Energy Efficiency and Renewable Energy, Vehicle Technologies Office for the support of this work. Part of the research described in this paper was performed in the Environmental Molecular Sciences Laboratory (EMSL), a national scientific user facility sponsored by the DOE’s Office of Biological and Environmental Research and located at PNNL. PNNL is operated for the US DOE by Battelle. The work at POSTECH was supported by the National Creative Research Initiative Program (2021R1A3A3088711, to S.B.H.) through the National Research Foundation of Korea. The authors from Pacific Northwest National Laboratory (PNNL) gratefully acknowledge the US Department of Energy (DOE), Energy Efficiency and Renewable Energy, Vehicle Technologies Office for the support of this work. Part of the research described in this paper was performed in the Environmental Molecular Sciences Laboratory (EMSL), a national scientific user facility sponsored by the DOE’s Office of Biological and Environmental Research and located at PNNL. PNNL is operated for the US DOE by Battelle. The work at POSTECH was supported by the National Creative Research Initiative Program (2021R1A3A3088711, to S.B.H.) through the National Research Foundation of Korea.