On the electrochemical exfoliation of graphene materials via cation intercalation

Abstract

The controlled electrochemical intercalation of tetraalkylammonium species has been studied as a potential high purity, high yield, and scalable fabrication method toward graphene materials. In order to avoid any induced surface oxidation or chemical functionalization, necessary for the production of pristine and high quality graphene materials, cationic intercalation was favoured over anionic intercalation, which has hitherto dominated the literature regarding both chemical and electrochemical solution-phase graphene production routes.The mechanism of the exfoliation process operates via the formation of graphite intercalation compounds, formed amid the interplanar graphene galleries during electrochemical cathodic load of a graphite electrode. The intercalation compounds are stabilised by the neighbouring graphene sheets, even during exposure to relatively large cathodic potentials. Crucially, the intercalation mechanism depends on the presence of an intercalating electrolyte to function, and although the exfoliated products have been shown to be relatively free of oxygenated functional groups, large flakes fall prey to spontaneous re-aggregation when in the presence of electrolyte; it is believed the materials exhibit a slight degree of surface charge and any resulting electrostatically-driven stability is sufficiently masked by the supporting electrolyte.The route as a whole is presented over several investigative stages, probing the intercalation, cathode expansion and subsequent exfoliation processes of the graphite source in divisions, with the aid of both electrochemical and spectroscopic analysis techniques as well as a comprehensive characterisation of the produced exfoliated graphene materials.

Date of Award	1 Aug 2014
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Robert Dryfe (Supervisor)