Graphene derivatives formation from waste asphaltenes for use as electroactive materials in supercapacitors

Converting waste asphaltene into graphene derivatives offers a sustainable solution for managing waste by-product by creating valuable materials. This study proposes an approach that utilizes acid treatments for transforming asphaltene into graphene derivatives. Such transformation occurs by removing the alkyl side chains from asphaltene by mild oxidation. The treatment also promotes the oxidation of carbon atoms at the boundaries of aromatic sheets, which further propagated the graphite lamellar sheet for further oxidation. The diffusion-controlled oxidation forms various oxygen functional groups on the basal planes and the sheet edges, resulting in notable increases in the interlayer distances between the aromatic sheets and remarkable reductions in their number per stack due to chemical exfoliation. The transformation of asphaltene into graphene derivatives was verified by measuring their structural parameters using SEM, XRD and Raman analyses, while the formation of oxygen functional groups was confirmed by the FTIR analysis. The electrochemical performance of the graphene derivatives was evaluated, and the measured capacitance revealed supercapacitance behavior. The measured capacitances were further analyzed by Trasatti method to differentiate between electrical double-layer capacitance and pseudocapacitance. The results indicated a significant pseudocapacitive contribution, which is advantageous for applications requiring high energy storage capabilities.