Recent advances in biocathode materials and configurations for reactor applications in microbial electrosynthesis of CO2.

Elevated atmospheric carbon dioxide (CO2) levels driven by urbanization and anthropogenic activities have accelerated global warming. CO2 upcycling using microbial electrosynthesis (MES) offers a unique opportunity to address this critical issue. The emerging field of MES is a sustainable approach toward transforming CO2 into resourceful chemicals because of the self-sustaining activity of electroactive bacteria (EAB). On the other hand, microbe-electrode interface engineering at the biocathode is critical for effective CO2 conversion. The applied potential at the biocathode supplies the necessary reducing energy to the EABs for CO2 conversion through various metabolic pathways. Various biocathode materials and configurations have been explored to enhance bioelectrochemical interactions, facilitate extracellular electron transfer in electroactive biofilms, accelerate biofilm formation, and improve CO2 conversion efficiency. This review summarizes the studies on biocathode development in MES systems, with a focus on improving the production rates, operational stability, scalability, and faradaic efficiency for electromicrobial CO2 conversion. A range of electrode materials and biocathode configurations is reviewed for their potential to enhance CO2 conversion in MES. The outlook and perspectives for future research on biocathode development toward the commercialization of MES systems for CO2 utilization are also highlighted.