Fig. 3. Quantification of Cu speciation during the in situ Cu K-edge XANES measurements from LCF, using the reference spectra shown in Fig. 2. Upper panels: R-factors of the linear combination fits. Lower panels: concentration profiles for the different Cu species during reduction in NH₃ + NO, the formation of the [Cu₂^II(NH₃)₄O₂]²⁺-complex, and exposure of the [Cu₂^II(NH₃)₄O₂]²⁺-complex to SO₂, for the low-Cu (left) and high-Cu (right) catalysts.