fig5

Figure 5. in-situ STEM images of Co-doped SF1.5M before and after reduction, after re-oxidation. (A) SEM images of a redox cycle at 800 °C; the R in the image is for reduction, and the O in the picture stands for oxidation; (B) photographs of a typical region in H₂ provided at 800 °C; and (C) images of a typical area in O₂ given at 600 °C, after that aggrandizing from 600 to 800 °C at rate of 5 °C·s^-1 and remaining at 800 °C. Reproduced with permission^[120], Copyright 2020, Wiley-VCH. STEM: Scanning transmission electron microscopy; SEM: scanning electron microscope.