Electrochemical intercalation in the graphite–H 2SO 4–R(RCH 3COOH, H 3PO 4) system

Abstract

The anodic oxidation of highly oriented pyrolitic graphite (HOPG) in the mixture H 2SO 4–R (RCH 3COOH, H 3PO 4) with concentration of H 2SO 4 in the range 0–100 wt% was investigated in this research work. Galvanostatic oxidation of graphite in H 2SO 4–R solution allows one to obtain stages 1–5 graphite intercalation compounds (GICs). The presence of R in the electrolyte solutions significantly expands the concentration limit for intercalation down to 1 wt% of H 2SO 4. The co-intercalated stages 1 and 2 H 2SO 4–CH 3COOH–GICs with d i=7.94 Å were obtained in 60–80 wt% of H 2SO 4 solution. The stages 1–3 co-intercalated H 2SO 4–H 3PO 4–GICs with d i=8.08–8.20 Å were synthesized for the first time. It was shown that the form of galvanostatic curve E( Q) is determinated by the content of strong intercalate H 2SO 4. It was established that the potential of intercalation E int of the stages 1–3 co-intercalated GICs and the quantity of electricity ( Q) are higher than E int and Q for the formation of binary GICs (graphite hydrogensulfate). The enhancement of the potential barrier for intercalation gives the evidence of the co-intercalation of H 2SO 4 with CH 3COOH or H 3PO 4 in graphite matrix. The mechanism of co-intercalation of graphite was proposed.