<p>Activated carbon (AC) has become a key material in microbial fuel cell technology (MFC), thanks to its high surface area, tunable porosity, structure-dependent electrical conductivity and sustainable origin. This review intends to present a role-based perspective on the functions of AC in the major MFC components including the anode, cathode and proton exchange membrane (PEM). The effects of the precursor, activation method and processing parameters on the physicochemical and electrochemical properties of AC are critically analysed. In anodes, AC enhances microbial adhesion and extracellular electron transfer through oxygenated surface groups and hierarchical porosity. As a cathode catalyst, metal- and nitrogen-doped AC promotes efficient oxygen reduction reactions comparable to Pt-based systems, while drastically lowering costs. In PEMs, AC-based composites improve proton transport, water retention and mechanical integrity, offering low-cost, renewable alternatives to Nafion. The review also highlights how factors such as surface functionality, conductivity and pore structure govern electrochemical performance. Finally, emerging strategies like biomass activation, heteroatom doping, nanohybrid design and AI-driven optimization are identified as pathways toward scalable, high-performance and circular-economy-based MFC systems.</p> Graphical abstract <p></p>