Highly Porous FexMnOy Microsphere as an Efficient Cathode Catalyst for Microbial Electrosynthesis of Volatile Fatty Acids from CO2

Microbial electrosynthesis (MES) can efficiently convert CO2 into valuable chemicals. A biocathode, which plays central role in MES process, is expected to have very high surface area and catalytic activity to derive the cathodic reaction flawlessly. In this study, a highly porous bimetallic FexMnOy (x=1, 2 and y=3, 4) microsphere was synthesized and applied as cathode catalyst in a single chamber MES. MES having FexMnOy exhibited higher net acetate production rate (204 mM/m2d) and coulombic efficiency (58 %) than the MES without catalyst (180 mM/m2d and 34 %). The excellent performance of MES with FexMnOy was attributed to the high Brunauer‐Emmett‐Teller (BET) surface area (around 278 m2/g) with rough surface and efficient electron transfer from cathode to microorganism promoted by FexMnOy complex. The cathode with FexMnOy reduced charge transfer resistance by ∼70 % and enhanced the exchange current density by 7.2‐times compared to plain cathode. This study suggests that FexMnOy can be used as the highly efficient and low‐cost catalyst on cathode of scaled up MESs.