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/m(2)d) and coulombic efficiency (58 %) than the MES without catalyst (180 mM/m(2)d and 34 %). The excellent performance of MES with FexMnOy was attributed to the high Brunauer-Emmett-Teller (BET) surface area (around 278 m(2)/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 similar to 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.