Anion intercalation into highly oriented pyrolytic graphite studied by electrochemical atomic force microscopy

Knowledge of the dimensional changes occurring during electrochemical proce sses is fundamental for understanding of the electrochemical intercalation/ insertion mechanism and for evaluation of potential application in electroc hemical devices. We studied a highly oriented pyrolitic graphite (HOPG) ele ctrode in perchloric acid, as a model to elucidate the mechanism of electro chemical anion intercalation in graphite. The aim of the work is the local and time dependent investigation of dimensional changes of the host materia l during electrochemical intercalation processes on the nanometer scale. We used atomic force microscopy (AFM), combined with cyclic voltammetry, as t he in situ tool of analysis during intercalation and deintercalation of per chlorate anions. According to the AFM measurements, the HOPG interlayer spa cing increases by 32% in agreement with the formation of stage IV of graphi te intercalation compounds, when perchlorate anions intercalate. In additio n, the local aspect of the process has been demonstrated by revealing coexi sting regions with different kinetics for intercalation and deintercalation processes. (C) 1999 Elsevier Science S.A. All rights reserved.