PCA illustrating the method of trapping a reaction intermediate: (a) TR XANES of reduction of showing the structural evolution during the reaction (the arrow indicates reaction direction); (b) the first five components from PCA calculation weighted by eigenvalues; (c) representative spectrum (in dots) superimposed with the linear combination of two components (solid line); the arrows point to the largest misfits; (d) residual plots resulted from a two-component fit [the arrow points to the time stamp of intermediate]; (e) representative spectrum (dots) superimposed with the linear combination of three components (solid); (f) residual plot resulted from a three-component fit.
TR mixing fractions of the start, the end, and the intermediate phase (when present) during the reduction of Cu-doped ceria at (a), and reoxidation of Cu-doped ceria at (b).
Cu -edge XANES and -weighted EXAFS (inset) data extracted by PCA for the reaction intermediate during the TR reduction of Cu-doped ceria at (a); Fourier transform magnitudes of the data (dots) and FEFF6 fit (solid) of the intermediate phase (b).
EXAFS results obtained by FEFF6 fitting analysis of the reaction phases during hydrogen reduction reaction of Cu/ceria system at . Given also are relevant quantities obtained here for the following references: CuO, , and Cu at room temperature.
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