Fig. 1. (a) In situ XANES of Cu-CHA catalysts with different compositions (different samples are denoted with (Cu/Al; Si/Al) labels) during dehydration under He flow from 25 °C to 400 °C, heating rate 5 °C min–1. (b) Comparison between XANES spectra of He-activated Cu-CHA samples with different compositions, collected at 400 °C. The inset shows a magnification of the weak pre-edge peak mostly deriving from the dipole-forbidden 1s → 3d transition in Cu(ii) sites. (c, d) Magnitude (c) and imaginary parts (d) of the k 2-weighted, phase uncorrected, Fourier transformed EXAFS spectra (k-range 2.4–12.4 Å–1) of He-activated Cu-CHA samples with different compositions, collected at 400 °C. Colour code for all of the panels: dashed thick lines: hydrated sample at 25 °C; solid thick lines: dehydrated sample at 400 °C; grey thin lines: intermediate spectra.
