Component

BE (eV)

FWHM (eV)

Assignment

1

533.37 ± 0.05

2.51 ± 0.12

Surface oxygen bonded to carbon

2

531.36 ± 0.05

3.12 ± 0.07

Oxygen in short O-Fe bonds

3

529.61 ± 0.19

2.54 ± 0.20

Oxygen in long O-Fe bonds

4

528.32

2.48

Physi-sorbed oxygen