Recycling waste sources into nanocomposites of graphene materials: Overview from an energy- focused perspective

In line with the global recognition of waste-to-wealth concept aiming for circular economy, scientific articles are published in greatly increasing number on the eco-friendly and sustainable utilization of carbon nanocomposites. However, control on the structure and properties of waste-derived carbon nanomaterials still requires substantial future research. In this review, recycling materials into nanocomposites containing graphene are narrated by overviewing all the 120 publications currently available in the literature including their pioneering study in 2012 and their recent developments until 2022, focusing on energy-related aspects of functional graphene-based nanocomposites. Interestingly, almost all currently available sources report on composites in which graphene is a high value-added filler or matrix, and only the other phase originates from wastes. Flexibility of process parameters of pyrolysis methods enables the synthesis of biomass-derived graphene composites for virtually any kind of industrial applications. Biomass often acts both as carbon and SiO2 source, while only a few percentages of graphene material induce significant changes in their physicochemical properties. Utilization of wastes for energetic composites increases abruptly due to their outstanding price-to-value ratio and reusability. Future perspectives and current green chemistry or human health related challenges are also discussed to pave ways for new developments using unexplored waste sources.