Electrochemical exfoliation of graphite to graphene

Electrochemical exfoliation of graphite has emerged as an efficient, scalable, and low-cost approach to synthesise graphene. Despite its great technological prospect, cathodic exfoliation has mainly been performed based on organic solvents, and it is desirable in establishing a new protocol to use environmentally friendly aqueous electrolyte. In this thesis, a new aqueous based cathodic electrochemical exfoliation approach for producing high quality low defect graphene has been developed. The approach has been examined for simultaneous anodic and cathodic graphite exfoliation and extended to various sources of graphite materials. A novel conductive polymer composite derived from polyurethane polymer and cathodically exfoliated graphene has been synthesised. The aqueous-based electrochemical cathodic exfoliation of graphite to graphene was found to work in alkali metal salts as simple as KCl. Other cations such as Li+, Na+ Rb+ and Cs+ were also found to facilitate the exfoliation. Successful exfoliation requires application of a sufficiently high voltage, and a high salt concentration in facilitating cation intercalation, and promoting hydrogen evolution to exfoliate the graphene. The cathodic exfoliation of graphite foil using KCl aqueous electrolyte exhibits a low defect density (ID/IG of 0.06, a C/O ratio of 57.8) and high graphite exfoliation yields (> 80%). The highly conductive exfoliated graphene has served as an excellent support material for electrocatalytic reactions.