Graphene quantum dots and its modified application for energy storage and conversion

Supercapacitors are highly attractive energy storage devices that produce enormous quantity of energy and high-power density which can be useful to fulfil the ever increasing demand for energy worldwide. In this respect, a new type of carbonaceous material, known as graphene quantum dots (GQDs) have wide ranging applications in supercapacitor field given its exceptional physicochemical properties, high surface area and abundant edge sites for modification. GQDs are zero-dimensional (0D) carbon nanomaterial, derived from a two-dimensional (2D) graphene, by altering the 2D graphene sheets into 0D GQDs. These exhibit new properties due to quantum confinement and edge effect, which is almost similar to that found in graphene. These materials find numerous applications in the field of sensing, bioimaging, catalysis, supercapacitor, adsorption, and separation. In this paper, the doping and modification techniques of GQDs, including fabrication of energy storage devices as well as their significant applications in the field of supercapacitors and deficiency of GQDs as energy conversion material and issues around its storage capacity. We also present possible research avenues and opportunities, as well as highlight associated challenges.