Sn promotes formate production to enhance microbial electrosynthesis of acetate via indirect electron transport

Microbial electrosynthesis (MES) is a carbon dioxide conversion technology in which a microbial catalyst obtains electrons through an electrode as a driving force to reduce CO₂ to multi-carbon organic matter. In this study, Sn-modified carbon felts were prepared by electrodeposition at different durations (30, 50, and 70 min). The presence of Sn provides formate as an electron donor for the MES system, which can accelerate the indirect electron transfer rate between microorganisms and electrodes, thus improving the yield of acetate. The result showed that the MES with Sn-modified cathode (70 min) obtained the highest acetate produce rate (0.32 g L⁻¹ d⁻¹) at − 1.3 V Ag/AgCl, which was about twice that of the control group and three times of the hydrogen evolution catalyst CoP. At the same time, scanning electron microscopy and microbial community analysis showed that the Sn catalyst was beneficial to the growth of biofilm on the cathode and increased the accumulation of Acetobacterium. This study provides a promising strategy for improving MES efficiency by enhancing formate-mediated electron transport rate.