HOPG AS A HOST FOR REDOX REACTIONS WITH FECL4- IN WATER MEDIUM

An ionic graphite intercalation compound (GIG) with FeCl4- was prepare d electrochemically under controlled charge from an FeCl3/HCl solution using highly oriented pyrolytic graphite (HOPG) and a graphitized pol yimide him as hosts. From the X-ray diffraction (XRD) 001 lines, the s tage of the GIC was determined and the unstable properties of the samp les were examined. Gradual transformation of stage-s GIC to stage-(s 1) GIC confirmed their instability after exposure to air or pumping u nder vaccum at 120 degrees C. Thermogravimetry analysis of the samples and IR spectra of the gas evolving during GIC drying allowed the quan titative estimation of the co-intercalated species (H2O, HCl) and, hen ce, the formula of the second-stage GIC was established to be C20-36+F eCl4-, 1.5H(2)O, 0.5HCl. Electrochemical reduction of the second-stage FeCl4--GIC to higher stages and/or Fe-0 particles dispersed on exfoli ated graphite was performed in aprotic solution. The influence of co-i ntercalated molecules on the reduction behaviour of FeCl4--GIC is disc ussed.