INTERCALATION OF RHODIUM FLUORIDE INTO GRAPHITE - REACTION-MECHANISM IN ANHYDROUS HF AND PHYSICAL CHARACTERIZATION

The intercalation process of rhodium fluoride into graphite has been investigated using anhydrous liquid HF. Evidence of a two-step mechanism has been given by XRD. A cointercalation of HF2- and of rhodium fluorospecies is confirmed by both XRD and XPS. The final stage depends on the type of pristine graphite: a stage-2 compound of average composition C28RhF3.3 (HF2) 1.3 and I(c) = 11.25 angstrom is obtained from HOPG, whereas stage-1 compounds wih I(c) = 7.87 angstrom are formed with natural flaky samples. During the dissolution and intercalation processes, pentavalent rhodium is reduced to diamagnetic trivalent species. An excellent agreement is achieved between the experimental EXAFS spectrum of rhodium fluoride-GIC and calculations based on a regular octahedral environment of rhodium (with 6 Rh-F at 1.99 angstrom), similar to that of RhF3.