(a)
(b)
(c)
(d)
(e)
(f)
Figure 9: XPS spectra of various graphene based materials: (a) C 1s of GO (before heat treatment); (b) C 1s of GO (after heat treatment); (c) C 1s of rGO (before heat treatment); (d) C 1s of rGO (after heat treatment); (e) C 1s of Ti@rGO-01; (f) Ti 2p of Ti@rGO-01.