Controllable fabrication of hierarchical porous anode for exoelectrogens internal colonization in microbial...

Efficient interfacial energy conversion and rapid charge transfer are crucial for application-oriented microbial electrochemical systems (MES) and depend on affordable high-performance anodes. Herein, hierarchically porous 3D anodes with controlled millimeter-scale macropores (1-2 mm) were fabricated via carbonization of phenolic foam embedded with expanded polystyrene (EPS) sacrificial templates. Optimizing EPS loading (4 wt%) and pore-sizes yielded anode L-4M, exhibiting appropriate hydrophilicity (contact angle: 60.0 ± 0.7°) and enhanced electrochemically active surface area (ECSA: 61 cm²) attributed to surface oxygen-containing groups and multiscale porosity. The L-4M achieved a remarkable maximum power density of 3800 ± 80 mW m^-2, 2.1-fold higher than carbon-cloth anodes. Engineered macropores facilitated unprecedented microbial colonization depth (≥ 2.5 mm) and biomass density (1300 ± 36 μg cm^-2) predominated by Geobacter sp. (75 % relative abundance). This millimeter-scale pore engineering strategy enhanced bio-accessible surface area, substrate diffusion, and electroactive biofilm development, offering a scalable approach for high-current-density MES.