Biohybrid CO2 electrolysis under external mode: using pure formic acid extracted from CO2 electroreduction for diverse microbial conversion

Abstract

The demand for converting CO2 into fuels or chemicals is on the rise to achieve a carbon-efficient circular economy. Biohybrid CO2 electrolysis shows potential for increasing production rates and diversifying product spectra by combining electrocatalysts and microbial catalysts. However, it is important to note that utilizing a shared catholyte for biohybrid CO2 electrolysis has not demonstrated significant performance improvements to date. In this study, we developed a biohybrid CO2 electrolysis system utilizing a solid electrolyte operating in an external mode. The produced formic acid was extracted and used as an intermediate for microbial conversion. Impressively, the solid-electrolyte CO2 electrolysers obtained a remarkable total Faraday efficiency of 81.4% for formic acid production. In-situ mechanism studies unveiled metallic tin as the probable real active site, prompting further exploration of strategies to boost the activity and stability of electrocatalysts. In the bioconversion step, we achieved a noteworthy 8-day duration for generating bioelectricity, nearly 100% electron recovery for biomethane production, and 90.8% for acetate generation. Additionally, when ethanol was co-fed, a C6 specificity of 41.1% was observed for the generation of medium-chain fatty acids (MCFAs). This study presents groundbreaking experimental data that demonstrates the numerous advantages of utilizing hybrid systems as advanced synthesis techniques.