Fe-Rich Biomass-Derived Hierarchically Porous Capacitive Electrodes as Electron Repeaters to Boost Power Generation in Microbial Electrochemical Systems.

Microbial electrochemical systems (MESs) present a promising approach for simultaneous water treatment and electricity generation. However, their performance is constrained by limited chemical-to-electrical energy conversion efficiency. Anode materials are central to this conversion process. Here, a self-supporting dual-precursor-derived carbon anode with excellent mechanical strength was developed by combining iron-rich biomass-derived heteroatom self-doping and pyrolytic pore formation with the intrinsic pore-forming ability and high carbon yield of phenolic resin. The resulting high-capacitance anode integrates hierarchically porous, heteroatom-doped carbon scaffolds with a mechanically robust matrix. The high capacitance generated by the synergistic effect of the porous architecture and endogenous Fe/N heteroatoms from the biomass precursor functions as both an electron repeaters and a capacitive buffer to support high biocurrent generation. Electrode materials derived from Enteromorpha sp. (E-MPR) exhibit a maximum capacitance of 1.67 ± 0.004 F cm-2 and supported a biomass loading of 1873.7 ± 74.1 μg cm-2, compared with 324.3 ± 12.1 μg cm-2 on carbon felt. The electroactive biofilm was dominated by Geobacter (81%). The functionally coupled electrode design optimizes the structure-performance relationships among the electrode material, the electroactive biofilm, and overall system efficiency. Consequently, a breakthrough in power and current densities was achieved, with values reaching 6138 ± 118 mW m-2 and 22 ± 1.2 A m-2, respectively. This work provides a notable enhancement in MES performance, suggesting that the high-performance anode is a promising candidate for engineering-scale applications of MES.