A development study for liquid- and vapor-fed anode zero-gap bioelectrolysis cells

Improving microbial electrosynthesis could be one solution for transitioning toward sustainable chemical production, offering a pathway to convert CO₂ into valuable commodities from renewable energy sources. Therefore, we further developed liquid- and vapor-fed anode zero-gap bioelectrochemical cells for electromethanogenesis, utilizing a membrane electrode assembly to enhance mass and ohmic transport. Focusing on CH₄ and H₂ production, we tested two ion-exchange membranes with the liquid-fed anode system and selected the best-performing ion-exchange membrane for the vapor-fed anode system. The liquid-fed anode system did not show considerable differences in volumetric CH₄ production rates compared to vapor-fed anode systems. However, the latter demonstrated advantages in reducing electrocatalyst degradation and maintaining stable cell voltages, resulting in the highest reported maximum CH₄ production efficiency of 48.7 L kWh^-1, thus far. The research underscores the need for further optimization to address performance losses and suggests potential for industrial applications of microbial electrosynthesis, highlighting the importance of catalyst protection.