Fig. 2. Atomic-scale structure evolution of SCO during water vapor oxidation.

(A to C) HAADF-STEM images of BM-SCO, IP-SCO, and PL-SCO, respectively, with corresponding FFT patterns (insets). Scale bars, 2 nm. (D to F) Lattice parameter measurements from the yellow dashed boxes in (A) to (C), showing progressive changes in out-of-plane and in-plane lattice distances. (G) Out-of-plane Sr-Sr interatomic distance maps revealing the reduction in layer spacing across the vacancy-containing sublayers as oxidation proceeds. (H and I) EELS spectra of the O-K and Co-L edges, demonstrating increased prepeak intensity of O-K (pink shaded) and positive shift in Co valence states as oxidation proceeds.