Carbon-based electrodes for photo-bio-electrocatalytic microbial fuel and electrolysis cells: advances and perspectives.

The growing demand for sustainable energy and effective wastewater treatment has propelled the advancement of bio-electrochemical systems (BESs), particularly microbial fuel cells (MFCs) and microbial electrolysis cells (MECs). These systems integrate bioelectricity generation with organic and inorganic pollutant degradation, offering a sustainable solution for environmental remediation. However, challenges such as high overpotential, reliance on noble metal electrodes, and inconsistent performance have necessitated innovative improvements. The incorporation of photocatalysis into BESs has led to the development of photo-bio-electrochemical systems (PBESs), including photo-microbial fuel cells (PMFCs) and photo-microbial electrolysis cells (PMECs), which leverage optical energy to enhance efficiency. Carbon-based electrode materials, owing to their high porosity, conductivity, and biocompatibility, have emerged as ideal candidates for improving PBES performance. Advanced carbon nanostructures, such as graphene, carbon nanotubes, and metal-graphitic carbon nitride composites, have demonstrated superior photocatalytic properties, promoting enhanced charge separation, CO₂ reduction, hydrogen production, and wastewater treatment. PBES integrating light-activated semiconductor materials with BESs, further amplify pollutant degradation and energy conversion efficiency. Despite significant progress, optimizing electrode materials and improving charge transport remain key challenges for scalable and cost-effective deployment. This review highlights the latest advancements in carbon-based electrodes for PBESs, detailing their mechanisms, photocatalytic properties, and future prospects in sustainable energy production and environmental remediation. By addressing existing material limitations and exploring novel photocatalytic enhancements, this work aims to contribute to the development of next-generation PBESs, fostering circular economy practices and carbon-neutral energy solutions.