X-ray photoelectron spectroscopic studies of carbon fibre surfaces—II: The effect of electrochemical treatment

Abstract

Carbon fibres, electrochemically treated using sulphuric acid and ammonium bicarbonate electrolytes, were analysed by X-ray photoelectron spectroscopy. In each case it is observed that polarization of the fibres at successively higher positive potentials causes an increase in the total surface oxide concentration. In addition, the relative proportion of different surface species also varies as a function of fibre potential and can be correlated with the cyclic voltammetric results in the case of sulphuric acid. The O1s spectra can be described simply by two main component signals corresponding to C=O and C-O- type groups, where the former dominate at low potential and the latter dominate at higher potentials. Assignment of curve fitted peaks in the C1s region is not straightforward and cannot be simply correlated with the O1s spectra. Formation of C-N groups on the fibre surface in ammonium bicarbonate shows that the electrolyte can play an important role in the final surface structure. No such interaction was observed in the sulphuric acid case.