A study on electronic states and intercalation behaviors of heteroatom-substituted carbon materials

Abstract

Electronic states of heteroatom-substituted carbon materials, such as boron/carbon (B/C) and boron/carbon/nitrogen (B/C/N) materials, have been studied experimentally through the X-ray absorption near-edge structures (XANES) together with the DV-Xα molecular orbital calculations. XANES study indicated that lowest unoccupied molecular orbital (LUMO) energies of B/C/N and B/C materials were lower than that of graphite. In these cases, B had a role of lowering the LUMO energies of B/C/N and B/C materials. Calcium (Ca) was intercalated into B/C materials to form intercalation compounds showing a first stage as well as a second stage structures through vapor phase reaction of Ca with the B/C materials solids, while Ca could not be easily intercalated into graphite through the same method. This is probably due to that the LUMO energies of B/C materials were lower than that of graphite and intercalated Ca having large ionization potential. The author concluded that there is a relation between the electronic structures and the donor-type intercalation behaviors of B/C and B/C/N materials.