Electro-biochemical profiles of the boosted CO2-to-acetate conversion in microbial electrosynthesis using FeS-Hydrochar modified cathodes.

To mitigate CO2 emissions, microbial electrosynthesis (MES) with rationally designed cathodes offers a promising route for value-added chemical production. Herein, an FeS-loaded algae-derived hydrochar (FeSHC) biocathode was developed by coupling redox-active FeS with a conductive and biocompatible hydrochar matrix rich in surface functional groups. This structural design enabled homogeneous FeS anchoring, enhanced interfacial electron transfer, and improved microbe-electrode interactions. Consequently, the FeSHC biocathode achieved an acetate concentration of 1212.52 mg·L-1, representing a 76.98 % increase compared to the Control. The performance enhancement was associated with increased electrochemical activity, redox capacity, extracellular polymeric substances (EPS) production, and intracellular electron transport. Moreover, the relative abundance of Acetobacterium increased from 1.43 % to 10.45 %, further promoting CO2-to-acetate conversion. This study demonstrates a synergistic FeS-hydrochar cathode design strategy for efficient and sustainable CO2 fixation in MES systems.