Abstract: Microbial electrochemical systems are a promising green and sustainable technology that can transform waste into electricity. Improving conversion efficiency and lowering system costs, particularly for electrodes, are the primary directions that promote practical application. Cellulose sponges made from wood pulp have been industrially mass-produced in various application scenarios due to their porosity and green sustainability. In this study, the three-dimensional (3D) porous cellulose sponges carbon (CSC) was obtained by directly carbonizing cellulose sponges at different temperatures (600, 700, 800, 900, 1000, and 1100 °C). It has been successfully used as a high-performance anode in microbial fuel cells (MFCs). The carbonization temperature significantly impacted the materials' specific surface area, conductivity, and capacitance. The greater the anode material's carbonization temperature, the lower the charge transfer resistance and the higher the maximum power density (CSC-1100, 4.1 ± 0.1 W m^-2). The CSC-700′s maximum power density (3.62 ± 0.11 W m^-2) was the highest power density reported to date among lignocellulose-based anodes with relatively low energy consumption. The pleated multilayer porous surface promotes microbial adhesion and can build thicker biofilms with the highest biomass of 2661 ± 117 μg cm^-2 (CSC-1100) and containing 86 % electrogenic bacteria (Geobacter). To investigate the effect of conducting polymers on the material's surface, we introduced polyaniline and polypyrrole. We found that the CSC-1000/PPy bioanodes produced a maximum power density (4.18 ± 0.05 W m^-2), slightly higher than of without polypyrrole-modified (CSC-1000, 3.99 ± 0.06 W m^-2), indicating that the CSCs anode surface had excellent electron transfer efficiency and could achieve the same amount of energy as the polypyrrole surface. This study introduced a promising method for fabricating high-performance anodes using low-cost, industrialized, and sustainable materials.

Key words: Polyaniline, Polypyrrol, Capacitance anode, Electrogenic biofilms, Extracellular electron transfer