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 rolebased 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 nitrogendoped 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 lowcost, 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.

Activated carbon in microbial fuel cell: a role based-perspective
    Abstract
    Highlights
    1 Introduction
    2 Activated carbon: fundamentals
        2.1 Sources and sustainability of activated carbon
        2.2 Types of activation for activated carbon
        2.3 Influence of activation parameters on activated carbon
        2.4 Characterization techniques for activated carbon
    3 Role of activated carbon in microbial fuel cells
        3.1 Activated carbon as anode material
            3.1.1 Composite and hybrid activated carbon anodes
            3.1.2 Modified and doped activated carbon anodes
            3.1.3 Biomass derived and sustainable activated carbon anodes
    3.2 Activated carbon as cathode catalyst
        3.2.1 Catalytic role and oxygen reduction kinetics
        3.2.2 Sustainable, biofilm-integrated and conductivity-enhanced cathodes
    3.3 Activated carbon in membrane separator
    4 Factors affecting AC based components in MFC
        4.1 Surface chemistry and functionalization
        4.2 Electrical conductivity
        4.3 Microstructure and pore connectivity
        4.4 Hydrophobic or hydrophilic balance
        4.5 Integration with other nanomaterials
        4.6 Doping and defect engineering
        4.7 Operational and environmental factors
    5 Conclusion and outlook
    References

• M. S. Gayathri(Department of Physics, Amrita Vishwa Vidyapeetham, Amritapuri, 690525 Kollam, India)
• Devu Bindhu(Department of Physics, Amrita Vishwa Vidyapeetham, Amritapuri, 690525 Kollam, India)
• Anju Ramachandran(Department of Physics, Amrita Vishwa Vidyapeetham, Amritapuri, 690525 Kollam, India)
• C. O. Sreekala(Department of Physics, Amrita Vishwa Vidyapeetham, Amritapuri, 690525 Kollam, India) Corresponding author
• I. Jinchu(Department of Physics, Govt. College Kottayam, Kottayam 686013, India)
• B. Neethu(Kerala State Council for Science Technology and Environment, Sasthra Bhavan, Pattom 695004, India)
• F.I. Ezema(African Center of Excellence, ACE-SPED, University of Nigeria, Nsukka 410001, Nigeria, Department of Physics and Astronomy, University of Nigeria, Nsukka 410001, Nigeria)