Environmentally friendly preparation of exfoliated graphite

Abstract

Graphite intercalation compounds (GIC) have received global attention in the last decade because of the growing number of applications of these materials. Conventionally, bisulfate intercalated graphite is synthesized by chemical intercalation; which requires concentrated sulfuric acid (98%) and an oxidizing agent such as H2O2 and HNO3. In this study, bisulfate intercalated graphite was prepared by electrochemical intercalation using dilute sulfuric acid with the aim to reduce the sulfur content in the final product. The electrochemical intercalation method required sulfuric acid with half of the concentration of that required for chemical intercalation, and without the need for an oxidizing agent. Chinese natural large flake graphite was used as the raw material for the electrochemical process. The GIC was characterized by the exfoliation volume obtained by thermal shock at a temperature of 850°C. The effect of sulfuric acid concentration, electrochemical treatment time, particle size and temperature on the exfoliation volume was investigated. It was found that the exfoliation volume of the GIC-bisulfate, which is a function of degree of intercalation, can be controlled using the sulfuric acid concentration and treatment time. A sulfuric acid concentration of 50% and an electrochemical treatment time of 60min were found to produce a GIC with the maximum exfoliation volume for the range of conditions studied.