Journal of Energy Bioscience 2024, Vol.15, No.4, 233-242 http://bioscipublisher.com/index.php/jeb 236 biofilm formation. For example, a study reported that nitrogen-doped CNTs (NCNTs) on carbon felt (CF) significantly improved the power density and chemical oxygen demand (COD) removal in MFCs (Wang et al., 2022). Additionally, the combination of CNTs with other materials, such as polypyrrole, has shown to further enhance the performance. A vertical CNT/polypyrrole composite anode achieved a maximum power density of 1 876.62 mW·m², which was approximately 2.63 times higher than unmodified carbon fiber brush anodes (Zhao et al., 2019). 4.3 Conductive polymers (polyaniline, polypyrrole) Conductive polymers like polyaniline (PANI) and polypyrrole (PPy) have been used to modify electrode materials to improve their conductivity and biocompatibility. These polymers provide a conducive environment for microbial growth and electron transfer. For instance, a cellulose-derived graphene/polyaniline (GO-PANI) nanocomposite anode demonstrated a significant improvement in electron transfer rate and current density in benthic MFCs (Yaqoob et al., 2020b). Similarly, a polypyrrole-carboxymethyl cellulose-titanium nitride/carbon brush (PPy-CMC-TiN/CB) hydrogel anode showed a maximum power density of 14.11 W·m³, which was 4.72 times larger than that of a blank carbon brush anode (Wang et al., 2020). 4.4 Metal-organic frameworks (MOFs) Metal-organic frameworks (MOFs) are a class of materials that have shown potential in enhancing the performance of MFC electrodes due to their high surface area and tunable porosity. A study demonstrated that a Ni-catecholate-based MOF grown on NiCoAl-layered double hydroxide/multi-wall carbon nanotubes (Ni-CAT/NiCoAl-LDH/MWCNTs) significantly improved the power generation efficiency and cycle stability of the electrode (Chen et al., 2021b). Another research highlighted the use of zeolitic imidazolate framework-67 (ZIF-67) combined with electrospinning polyacrylonitrile to create a carbon nanofiber composite cathode, which achieved a maximum power density of 1.191 W·m² (Jiang et al., 2021). 4.5 Nanostructured materials Nanostructured materials, including hierarchical nanostructures and composites, have been explored to enhance the performance of MFC electrodes. These materials offer a high surface area and improved electron transfer properties. For example, a hierarchically porous nitrogen-doped CNTs/reduced graphene oxide (N-CNTs/rGO) composite anode achieved a maximum power density of 1 137 mW·m², which was significantly higher than that of non-doped composites (Wu et al., 2018). Additionally, a 3D hierarchical Co8FeS8-FeCo2O4/N-CNTs@CF anode showed a power density of 3.04 W·m², demonstrating the effectiveness of hierarchical nanostructures in improving MFC performance (Wang et al., 2022). By leveraging these advanced electrode materials, significant improvements in the efficiency and stability of microbial fuel cells can be achieved, paving the way for their practical applications in energy generation and environmental remediation. 5 Strategies for Improving Electrode Performance 5.1 Surface modification techniques 5.1.1 Physical modifications (nano-patterning, 3D structures) Physical modifications such as nano-patterning and the creation of 3D structures can significantly enhance the performance of microbial fuel cell (MFC) electrodes. For instance, the development of hierarchical nanostructures like Co8FeS8-FeCo2O4/N-CNTs on carbon felt has been shown to improve wettability, specific areal capacitance, and diffusion coefficient, while reducing charge transfer resistance. This results in a substantial increase in power density and COD removal efficiency (Wang et al., 2022). Similarly, the use of stainless steel cloth modified with carbon nanoparticles has demonstrated a 2.3-fold increase in maximum power density, attributed to the increased electrochemically-active surface area and enhanced electron transfer (Wu et al., 2020). 5.1.2 Chemical modifications (functionalization, doping) Chemical modifications, including functionalization and doping, are effective strategies for improving electrode performance. For example, the incorporation of covalent organic frameworks (COFs) on carbon felt has led to
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