Valorization of Petroleum coke into High-Quality Few-Layer Graphene through Liquid-Phase Exfoliation

<title>Abstract</title> <p> Low-value fuel-grade petroleum coke (pet coke), an abundant byproduct from petroleum refining operations, is traditionally used in low-value fuel and metallurgical applications owing to its high carbon content and ability to be used in the synthesis of advanced carbon materials. In this paper, we demonstrate a non-oxidation-based route for producing conductive few-layer graphene from pet coke through sequential isopropanol assisted pre-treatment, thermal desulfurization, and CO ₂ assisted liquid phase exfoliation. Unlike conventional graphene synthesis processes using high temperature chemical vapor deposition, oxidation reduction-based Hummer’s type methods, or exfoliation from expensive graphite sources, our approach enables the conversion of inexpensive pet coke into graphene nanosheets using a scalable solvent assisted route. The thermal activation promotes the degree of graphitization to 78% and purity of petcoke, while CO ₂ assisted exfoliation allows for the formation of wrinkled few layer graphene sheets with thicknesses ranging from 3–5 layers. Structural and electrical characterization confirm the improvement in graphene exfoliation to 93.5%, decrease in disorder, and efficient production of graphene nanoflakes. The graphene dispersions display stability up to six months and can be transformed into conductive films with a maximum electrical conductivity of 872 S m⁻¹ after thermal annealing. This work establishes pet coke as a promising low-cost carbon resource for sustainable graphene production and offers a practical route for transforming refinery waste into value-added materials for energy storage, conductive coatings, composites, and carbon-based technologies. </p>