Fig. 2: Identification of the reconstructed CeO_2-x/CoO_1-x/Co dual-interfaces after WGS reaction.

a HAADF-STEM images; (b) magnified STEM image; (c) elemental mappings (Co, Ce, and O) for the selected area of 1Ce9CoO_x catalyst after light-off WGS reaction test. d–f XPS spectra of fresh and used 1Ce9CoO_x: (d) Co 2p, (e) Ce 3d and (f) O 1s spectra. The XPS spectra for the spent catalyst were collected after light-off WGS reaction (2%CO/10%H₂O/Ar, 180–320 °C). g in situ Raman spectra collected under WGS reaction condition at 250 °C. h HRTEM image of spent 1Ce9CoO_x catalyst, where the interfacial region is illustrated by dotted line. i the corresponding FFT image of selected region A in Fig. 2h. j Schematic illustration of the phase transformation within the 1Ce9CoO_x catalyst during the WGS reaction.