Graphitic Carbon Nitride: A Rising Star Electrode Material for Supercapacitors

The rising global energy demand requires the development of high-performance supercapacitors (SCs) that synergize high-power density with substantial energy density. The pursuit of such energy storage devices is fundamentally related to the innovation of advanced electrode materials. Two-dimensional graphitic carbon nitride (g-C₃N₄) has recently emerged as a compelling candidate, distinguished by its unique nitrogen-rich structure, tunable electronic properties, and facile synthesis. This review provides a comprehensive and critical investigation of g-C₃N₄-based materials for SCs. We systematically analyze the crystal structure, physicochemical properties, and synthesis methodologies of g-C₃N₄, correlating these characteristics with their electrochemical performance. For the first time, a detailed comparative analysis is presented, categorizing strategies into the engineering of pristine g-C₃N₄, heteroatom doping, and the construction of composites. We place particular emphasis on the superior performance of composites formed with conductive polymers, transition metal oxides/sulfides (TMOs/TMSs), graphene, MXenes, and other families, where synergistic effects enhance conductivity, stability, and charge storage capacity. Finally, we provide a critical outlook on the existing challenges and future possible directions, aiming to guide the rational design of next-generation g-C₃N₄-based electrode materials to unlock their full potential in SCs.