“…The high-resolution spectrum of Cu 2p (Figure c) shows a peak of Cu 2p 3/2 near 934 eV, which is decomposed into two peaks at 934.1 and 932.2 eV, corresponding to Cu 2+ and Cu 0 /Cu + , respectively. − The ratio of the peaks of Cu + /Cu 0 and Cu 2+ has been calculated and shown in Table S2. Similarly, in the Auger spectrum of Cu LMM (Figure d), peaks at 913.1, 917.1, and 920.8 eV correspond to Cu + , Cu 2+ , and Cu 0 , respectively. , The doublet separation between the 2p 3/2 and 2p 1/2 signals approaches 15.5 eV (Figure b), which agrees with the standard spectra of elemental cobalt, suggesting the existence of Co 3+ or Co 2+ species . The satellite peak at 789.6 eV corresponds to Co 2+ , and the peaks at 785.2 and 780.5 eV correspond to the binding energies of Co 2+ and Co 3+ , respectively, indicating that cobalt exists mainly in the form of oxides. − …”