Formation of iron chloride-graphite intercalation compounds in propylene carbonate by electrolysis

Abstract

Formation of graphite intercalation compounds (GICs) of iron chloride in propylene carbonate PC by electrolysis was studied. Three types of structure with different interplanar distance, d 1, were observed. The single phase of the new type having the d 1-value of 1.03 nm (named β-type) was synthesized in dilute solution of less than 1 M. The γ-type GICs with a d 1value of 1.18 nm, which was quite close to the so-called “type II” compounds synthesized by Soneda et al. in chloroform solution of FeCl 3, were formed at the medium-range of concentration from 1 to 4 m. The single phase of α-type GICs with a devalue of 0.95 nm which was very similar to the binary compounds, were obtained in solution more than 4 m. The influences of FeCl 3 concentration and reaction time on the formation of each type were investigated. The existence of co-intercalated PC solvents was suggested by the results of thermogravimetry. Mossbauer spectroscopy and energy dispersed spectroscopy showed that the intercalated species of iron chloride existed mainly as FeCl 4 − ions in β-type GICs, and FeCl 6 octahedrons in α-type. Based on these observations, the crystallographic structure in the intercalate layer of the new type GIC β-type) was discussed.