Smart Materials & Structures

Since the ground-breaking article in Science in October 2004 describing the occurrence, isolation and potential signifi cance of graphene, there has been a huge interest in developing industrially scalable methods of manufacture from bottom-up and top-down routes. One such top-down route developed for the mass manufacture of graphene involves electrochemical exfoliation. Th is can be conducted in anodic (oxidative) and cathodic (reductive) regimens, with the latter more suitable for production of higher quality (containing fewer defects) graphene, but hindered by lower effi ciency and yield. This makes the selection of an appropriate electrolyte particularly important. Previous work has shown that graphene prepared by electrochemical exfoliation can be simultaneously functionalized with groups tailored to improve solubility in aqueous systems. In this case, functionalization signifi cantly enhances the specifi c capacitance of the material when used as an electrode in super capacitors.Th is presentation details the expansion of this work in two ways.Firstly, it shows the relative characteristics of diff erent types of electrolyte and suggests a mechanism for the performance in each case. Secondly, it details the use of the preferred electrolyte with appropriate additional reagents in the exfoliation of graphite and simultaneous functionalization of the product graphene with metal nanostructures, specifi cally various morphologies of gold and cobalt.Th e metal-functionalized graphene sheets show high catalytic activity and stability when used as electrocatalysts for hydrogen evolution reactions. Other uses of these materials are found in fl exible electronics, in biosensing and in biomedicine. Th e methods demonstrated can be readily extended to functionalize graphene with other metal salts or mixtures of metal salts, further expanding the applicability. Functionalization of graphene with metal nanostructures, gold (top) and cobalt (bottom). Th e inset pictures show the color change of the electrolyte as electrolysis time increases.