Boosting Microbial CO 2 Electroreduction by the Biocompatible and Electroactive Bimetallic Fe–Mn Oxide Cathode for Acetate Production

The electroreduction of carbon dioxide (CO 2 ) to high-value organic chemicals by the microbial electrosynthesis (MES) system relies heavily on the electrochemical properties of the electrode materials. In this work, CO 2 reduction for acetate production was greatly boosted by decorating the carbon felt cathode using the Fe–Mn bimetallic oxides, using an enriched anaerobic mixed culture dominated by the homoacetogen Acetobacterium wieringae . In comparison with the unmodified carbon felt as the cathode in the MES reactor, modification with MnFe 2 O 4 increased the acetate production rate from 28 to 78 g/(m 2 ·d), higher than those with MnO at 59 g/(m 2 ·d) and Fe 2 O 3 at 62 g/(m 2 ·d), and the relative abundance of A. wieringae increased dramatically from 51 to 87% in the biofilm. This was probably due to the mediated electron uptake via the redox cycles of Mn(III)/(II) and Fe(III)/(II), improved specific surface area, and enhanced hydrophilicity of the cathode, benefiting from the synergistic effect of Fe and Mn ions. Overall, this study provides a facile and promising electrode modification strategy for MES with Fe–Mn bimetallic oxides for efficient CO 2 conversion and acetate production, bringing the world closer to achieving carbon neutrality.