Ultrahigh Purity Graphite Electrode by Core Level and Valence Band XPS

Abstract

Both core level and valence band XPS spectra were obtained from an ultrahigh purity (UHP) graphite electrode surface. This UHP graphite had a very low oxygen content and an extremely low nitrogen content on its surface. It had a very graphitic structure in both the surface and the bulk as evidenced by XPS and XRD studies. [See Y. Xie and P. M. A. Sherwood, Appl. Spectrosc. 43, 1153 (1989); Chem. Mater. 1, 427 (1989); 2, 293 (1990); Appl. Spectrosc. 44, 797 (1990); Chem. Mater. 3, 164 (1991); Appl. Spectrosc. 44, 1621 (1990); 45, 1158 (1991); Y. Xie, T. Wang, O. Franklin, and P. M. A. Sherwood, ibid. 46, 645 (1992).] Our previously reported work [Y. Xie and P. M. A. Sherwood, Chem. Mater. 1, 427 (1989); 2, 293 (1990); Appl. Spectrosc. 44, 797 (1990); Chem. Mater. 3, 164 (1991); Appl. Spectrosc. 44, 1621 (1990); 45, 1158 (1991); Y. Xie, T. Wang, O. Franklin, and P. M. A. Sherwood, 46, 645 (1992)] showed that XPS valence band spectra were more sensitive to the surface chemical environment than core level spectra, and could be well interpreted by X–α calculations with model compounds. In this work, the valence band spectrum shows that there were two different types of oxygen species on the UHP graphite surface. In separate data records published in Surface Science Spectra, however [see Y. Xie, T. Wang, M. A. Rooke, and P. M. A. Sherwood, Surf. Sci. Spectra 2, 192 (1992)], the valence band spectra showed that only one of the two different oxygen species could be seen on the highly oriented pyrolytic graphite (HOPG) surface, and the other of the two different oxygen species could be seen on the Du Pont E-120 high modulus pitch-based carbon fiber surface. No nitrogen was detected on either the HOPG or the E-120 carbon fiber surface.