Fig. 1: Structure and morphology of SC81-air sample.

a, d XRD Rietveld refinement patterns of SC81-pristine (a) and SC81-air sample (d). b, e XPS C 1 s spectra of SC81-pristine (b) and SC81-air sample (e). c, f XPS O 1 s spectra of SC81-pristine (c) and SC81-air sample (f). g SEM image of SC81-air. h EDS mapping of SC81-air particle. i Low-magnification TEM image of the SC81-air surface. j Low-dose HRTEM image of the surface impurity and corresponding FFT pattern.