Cu-exchanged chabazite
is the catalyst of choice for NO
x
abatement
in diesel vehicles aftertreatment systems
via ammonia-assisted selective catalytic reduction (NH
3
–SCR). Herein, we exploit
in situ
X-ray absorption
spectroscopy powered by wavelet transform analysis and machine learning-assisted
fitting to assess the impact of the zeolite composition on NH
3
-mobilized Cu-complexes formed during the reduction and oxidation
half-cycles in NH
3
–SCR at 200 °C. Comparatively
analyzing well-characterized Cu-CHA catalysts, we show that the Si/Al
ratio of the zeolite host affects the structure of mobile dicopper(II)
complexes formed during the oxidation of the [Cu
I
(NH
3
)
2
]
+
complexes by O
2
. Al-rich
zeolites promote a planar coordination motif with longer Cu–Cu
interatomic distances, while at higher Si/Al values, a bent motif
with shorter internuclear separations is also observed. This is paralleled
by a more efficient oxidation at a given volumetric Cu density at
lower Si/Al, beneficial for the NO
x
conversion
under NH
3
–SCR conditions at 200 °C.
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