Interfacial engineering, exfoliation and functionalisation of printable graphene inks for energy applications

Since its discovery more than a decade ago, graphene has enabled the dramatic improvement of modern energy devices by providing better means for charge storage and transfer. The implementation of graphene has brought in many previously unknown features to energy devices, from transparent batteries to flexible solar cells and hyper-long-life supercapacitors. However, due to the lack of scalable and cost-effective fabrication techniques, it is still a great challenge to bring these advanced graphene-based technologies from laboratories to practical applications. This thesis presents a promising and versatile platform for the production and patterning of aqueous graphene inks into functional energy devices based on the interfacial engineering approach (i.e., exfoliation-induced non-covalent functionalisation of graphene). Aqueous dispersions of pristine graphene are produced via liquid-phase exfoliation process, employing various types of electroactive materials as dispersing agents. These electroactive dispersants non-covalently functionalise the exfoliated graphene flakes and offer synergistic effects for stabilising graphene dispersions in aqueous medium (to formulate printable inks) and inducing intermolecular charge transfer (to improve its electrochemical properties). Dispersant-assisted and dispersant-free aqueous graphene inks have been successfully produced and printed into functional energy devices, including conductive circuits for flexible electronics, printed electrodes for supercapacitors, and electrocatalyst layers for fuel cells applications. The interfacial interaction between graphene and different amphiphilic electroactive dispersants is investigated using various advanced characterisation  techniques, wherefrom, a fundamental understanding of the surface interactions between graphene and amphiphilic molecules is developed for engineering of stable graphene dispersions in aqueous medium with printability. This work shows great promise of printable graphene inks to assist the journey of this wonder material from laboratories to practical applications. The knowledge derived from this thesis has been developed into significant inventive processes for industrial applications.