Boosting microbial electrosynthesis: Integrating gas diffusion cathodes with vapor-fed anode-membrane systems

Microbial electrosynthesis (MES) has emerged as a sustainable technology for the bioconversion of CO₂ into value-added organic compounds such as acetate. Despite its promise, the practical implementation of MES remains constrained by the limited solubility of CO₂ in aqueous media and pH imbalances arising from ion migration during long-term operation. To address these challenges, this study developed a novel three-chamber MES reactor configuration integrating a gas diffusion electrode (GDE) at the cathode and a vapor-fed anode-membrane assembly. Compared to the non-GDE configuration, the GDE phase achieved significantly higher current densities (up to 1.35-fold increase) and acetate production rates (1.8-fold increase), indicating improved electron utilization and substrate availability at the cathodic biofilm. Structural characterization confirmed that the hydrophobic gas diffusion layer effectively prevented electrolyte flooding, while the hydrophilic catalyst layer facilitated microbial attachment and electrochemical activity, with enhanced CO₂ delivery to biofilm. Microbial community analysis revealed that electroactive genera, including Malaciobacter, Trichlorobacter, and Oryzomicrobium, dominated the active biofilm, suggesting robust interspecies electron transfer and carbon flux toward acetate production. The use of the vapor-fed anode also contributed to pH stability throughout the experimental period, which was critical for sustaining microbial activity and reactor performance. Collectively, the results of this study demonstrated the combined effects of integrating GDE-based cathodes and vapor-fed anodes in MES systems, providing a strategic reactor design framework for improving gas–liquid mass transfer, electron delivery efficiency, and biocatalyst stability in CO₂ reduction processes.