Graphene and its derivatives have garnered significant attention as catalysts without the presence of metal. This chapter focuses on elucidating the active sites that contribute to the catalytic activity in these systems. The presence of various chemical functional groups and defects on graphene sheets has been identified as catalysts for reactions, encompassing oxygenated functional groups, edge effects, carbon vacancies/holes, and the incorporation of dopants. Furthermore, beyond discrete active functional mortise, the collective properties of graphene-based materials enable catalytic activity through substrate and reagent adsorption and subsequent activation via charge transfer. The chapter includes an introductory section that provides a summary of the general methodologies employed to support the structure of functional moieties. Furthermore, the chapter concludes by offering insights into future advancements anticipated in this field.