Artificial Electron Mediator with Nanocubic Architecture Highly Promotes Microbial Electrosynthesis from Carbon Dioxide

Microbial electrosynthesis (MES) is an emerging strategy for converting electrical energy into chemical energy. Many efforts have been made toward the enhancement of cathode-microorganism interactions and electron transfer by modifying cathodic materials; however, high electrochemical activity and good biocompatibility have often not been available at the same time in previously reported materials. Here, we deliver a novel MES bioreactor by designing a well-defined Prussian blue nanocube-modified carbon felt (PBNC-CF) as an artificial electron mediator-decorated cathode for organic molecule production from a CO2 source. Because of the rapid electronic transition between Fe2+ to Fe3+ atoms in a unit cell, PBNCs significantly improve the electrochemical activity of the cathode by dramatically increasing the electron supply to electroautotrophic microorganisms. This modification also enhances the biocatalytic activity by regulating the composition of microbial community with the accumulation of acetogens such as Acetobacterium and the reduction of the electrontransferring bacterium, Arcobacter. Furthermore, the hydrophilicity and positive charge of PBNCs improve cathodic biocompatibility and are conducive to the growth of biofilms on the electrode surface and internal fibers. This strategy provides a new direction for MES electrode modification, showing that the development of an artificial electron mediator-based cathode is significantly important to improve MES efficiency.