Manipulating electron extraction efficiency in microbial electrochemical carbon fixation via single-atom engineering

Abstract

Microbial electrochemical carbon fixation can directly convert CO2 to renewable fuels, holding the promise of reducing greenhouse gas emissions. Whereas its further development is largely shadowed by the unclear correlation between the coordination environment and carbon-fixation biohybrids. Here, we report a single-atom engineering approach to control extracellular and interspecies charge exchange pathways for high electron efficiency via synergistic effects of Co-N4 coordination and microbiome biohybrids in the electro-methanogenesis system. Optimized carbon-fixation microbial community structures composed of electroactive methanogens and boosted extracellular polymeric substance-mediated charge exchange achieved a 21.49 times methane production rate of 568.7 mmol/m2/day (up to a maximum value of 1014 mmol/m2/day at −1.0 V vs. Ag/AgCl) and a 4.76 times faradic efficiency of 90.1% at −0.9 V vs. Ag/AgCl compared to control groups. Density functional theory calculations indicate that high Co-N/Co-C incorporation promotes the conversion of redox electron carriers for CO2 reduction, and Co-N/Co-C reduced the energy barrier of conductive substances and facilitated the electron storage at the bio/abiotic interface. The synergistic effect between Co-N4 structure and microbiome biohybrids facilitates an effective electron transfer, serving as reliable guiding principles for other microbial electrochemical systems to synthesize sustainable and value-added products.