Recent advances in abiotic and biotic cathodes for microbial energy generation systems

The increasing global demand for low-carbon energy and circular wastewater management has intensified interest in bioelectrochemical systems (BESs), particularly microbial fuel cells (MFCs). In MFCs, microorganisms generate electricity by oxidizing substrates at the anode surface area, while the cathode governs the terminal electron-accepting reaction and can function either with abiotic catalysts or biologically driven biocathodes. This review synthesizes recent advances in abiotic (noble, non-noble, nanocarbon, and photocatalytic) and biotic (enzymatic, microbial, and algal) cathodes for microbial energy generation systems. Comparative assessments demonstrate that biocathodes can outperform abiotic cathodes in terms of multifunctionality, enabling simultaneous power production, pollutant removal, and CO2 valorization. Meanwhile, non-noble Fe-N-C and Co-N-C catalysts deliver high oxygen reduction reaction (ORR) activity at a low cost. Hybrid cathode concepts, material circularity, solar-driven ORR, and Electro-Fenton pathways further expand performance envelopes toward scalable BESs. Critical barriers include durability, pH stability, electron transfer limitations, and eco-efficient manufacturing. Strategic integration of sustainable catalysts, hybrid designs, and system-level intensification is required to position MFC cathodes as viable contributors to renewable energy portfolios and net-zero wastewater treatment.