Influence of aluminium distribution on the diffusion mechanisms and pairing of [Cu(NH<sub>3</sub>)<sub>2</sub>]<sup>+</sup> complexes in Cu-CHA.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 39799150.
- Also identified by DOI 10.1038/s41467-025-55859-1 and PMC identifier 11724864.
- Licence recorded as CC BY.
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Abstract
The performance of Cu-exchanged chabazite (Cu-CHA) for the ammonia-assisted selective catalytic reduction of NO<sub>x</sub> (NH<sub>3</sub>-SCR) depends critically on the presence of paired <math xmlns="http://www.w3.org/1998/Math/MathML"> <msup> <mrow><mrow><mo>[</mo> <mrow><mi>Cu</mi> <msub> <mrow><mrow><mo>(</mo> <mrow> <msub><mrow><mi>NH</mi></mrow> <mrow><mn>3</mn></mrow> </msub> </mrow> <mo>)</mo></mrow> </mrow> <mrow><mn>2</mn></mrow> </msub> </mrow> <mo>]</mo></mrow> </mrow> <mrow><mo>+</mo></mrow> </msup> </math> complexes. Here, a machine-learning force field augmented with long-range Coulomb interactions is developed to investigate the effect of Al-distribution and Cu-loading on the mobility and pairing of <math xmlns="http://www.w3.org/1998/Math/MathML"> <msup> <mrow><mrow><mo>[</mo> <mrow><mi>Cu</mi> <msub> <mrow><mrow><mo>(</mo> <mrow> <msub><mrow><mi>NH</mi></mrow> <mrow><mn>3</mn></mrow> </msub> </mrow> <mo>)</mo></mrow> </mrow> <mrow><mn>2</mn></mrow> </msub> </mrow> <mo>]</mo></mrow> </mrow> <mrow><mo>+</mo></mrow> </msup> </math> complexes. Performing unbiased and constrained molecular dynamics simulations, we obtain unique information inaccessible to first-principle calculations and experiments. The free energy barrier for <math xmlns="http://www.w3.org/1998/Math/MathML"> <msup> <mrow><mrow><mo>[</mo> <mrow><mi>Cu</mi> <msub> <mrow><mrow><mo>(</mo> <mrow> <msub><mrow><mi>NH</mi></mrow> <mrow><mn>3</mn></mrow> </msub> </mrow> <mo>)</mo></mrow> </mrow> <mrow><mn>2</mn></mrow> </msub> </mrow> <mo>]</mo></mrow> </mrow> <mrow><mo>+</mo></mrow> </msup> </math> diffusion between CHA-cages depends sensitively on both the local and distant Al-distribution. Importantly, certain Al-distributions and arrangements of neighboring <math xmlns="http://www.w3.org/1998/Math/MathML"> <msup> <mrow><mrow><mo>[</mo> <mrow><mi>Cu</mi> <msub> <mrow><mrow><mo>(</mo> <mrow> <msub><mrow><mi>NH</mi></mrow> <mrow><mn>3</mn></mrow> </msub> </mrow> <mo>)</mo></mrow> </mrow> <mrow><mn>2</mn></mrow> </msub> </mrow> <mo>]</mo></mrow> </mrow> <mrow><mo>+</mo></mrow> </msup> </math> and <math xmlns="http://www.w3.org/1998/Math/MathML"> <msup> <mrow> <msub><mrow><mi>NH</mi></mrow> <mrow><mn>4</mn></mrow> </msub> </mrow> <mrow><mo>+</mo></mrow> </msup> </math> cations make paired <math xmlns="http://www.w3.org/1998/Math/MathML"> <msup> <mrow><mrow><mo>[</mo> <mrow><mi>Cu</mi> <msub> <mrow><mrow><mo>(</mo> <mrow> <msub><mrow><mi>NH</mi></mrow> <mrow><mn>3</mn></mrow> </msub> </mrow> <mo>)</mo></mrow> </mrow> <mrow><mn>2</mn></mrow> </msub> </mrow> <mo>]</mo></mrow> </mrow> <mrow><mo>+</mo></mrow> </msup> </math> complexes exothermic with respect to separated configurations. Our results suggest that the NH<sub>3</sub>-SCR activity can be enhanced by increasing the Cu-loading and Al-content. The dynamic interplay between <math xmlns="http://www.w3.org/1998/Math/MathML"> <msup> <mrow><mrow><mo>[</mo> <mrow><mi>Cu</mi> <msub> <mrow><mrow><mo>(</mo> <mrow> <msub><mrow><mi>NH</mi></mrow> <mrow><mn>3</mn></mrow> </msub> </mrow> <mo>)</mo></mrow> </mrow> <mrow><mn>2</mn></mrow> </msub> </mrow> <mo>]</mo></mrow> </mrow> <mrow><mo>+</mo></mrow> </msup> </math> and <math xmlns="http://www.w3.org/1998/Math/MathML"> <msup> <mrow> <msub><mrow><mi>NH</mi></mrow> <mrow><mn>4</mn></mrow> </msub> </mrow> <mrow><mo>+</mo></mrow> </msup> </math> diffusion is crucial for the <math xmlns="http://www.w3.org/1998/Math/MathML"> <msup> <mrow><mrow><mo>[</mo> <mrow><mi>Cu</mi> <msub> <mrow><mrow><mo>(</mo> <mrow> <msub><mrow><mi>NH</mi></mrow> <mrow><mn>3</mn></mrow> </msub> </mrow> <mo>)</mo></mrow> </mrow> <mrow><mn>2</mn></mrow> </msub> </mrow> <mo>]</mo></mrow> </mrow> <mrow><mo>+</mo></mrow> </msup> </math> mobility and stresses the need to explore large systems including long-range Coulomb interactions when studying diffusion of charged species in zeolites.