Efficient microbial electrosynthesis through the barrier and shearing effect of fillers

Abstract Microbial electrosynthesis (MES) is an electrochemical reduction technology that converts carbon dioxide (CO2) efficiently into chemicals by electrically driving microorganisms attached to electrodes. However, due to the limited solubility of CO2 and hydrogen (H2), low mass transfer efficiency affects the performance of MES. In this study, fillers were introduced into the MES system and combined with a vertical or horizontal cathode. Through the barrier and shearing effect of fillers, it realized the reduction of bubbles volume, the increase of gas residence time and the optimization of mass transfer rate, thereby providing a sufficient substrate supply for the biocatalyst. The results showed that MES with horizontal cathode and 4 series of fillers generated the highest acetate production rate (0.18 gL−1 day−1), which was 1.6 times that of the control group. Furthermore, the acetate concentration reached 5.28 ± 0.2 g L−1 within 30 days. Scanning electron microscope and microbial community analyses showed that the filler was beneficial to the growth of biofilm on cathodes and fillers, and improved the enrichment of Acetobacterium. The presence of fillers significantly enhanced the performance of MES and demonstrated the potential as a new and simple strategy for the MES reactor improvement.