Tailoring interfacial microbiome and charge dynamics via a rationally designed atomic-nanoparticle bridge for bio-electrochemical CO2-fixation

Bio-electrochemical CO2 fixation represents a promising strategy for CO2-to-chemical conversion, yet it suffers from a low CO2-reducing rate. Limited microorganism attachment and unfavorable charge extraction at the bioinorganic interface are the key determinants that inhibit the reaction kinetics. Herein, we report a judiciously created atomic-nanoparticle bridge composed of cobalt (Co) single atoms covering Co nanoparticles (Co-SA@Co-NP) to concurrently promote the enrichment of the performing microbe and bio-interfacial charge extraction for CO2 conversion to methane. Finite element analysis (FEA) points to the increased electronegativity and more closely distributed electric intensity of the electrode surface with the introduction of Co nanoparticles underneath, whereby the close-packed biohybrids with enriched performing microbes are developed and assisted by electrostatic forces. The modified surface electronic structure of Co-SA@Co-NP further strengthens the interactions of Co–N4 and C=O in extracellular humic acid-mediated charge exchange and reduces the activation energy of the intermediator, enabling a high-speed charge transfer channel from the electrode to the microbes. Taken together, an extremely high methane production rate of up to ∼2512 mmol m−2 per day (FE = ∼94.1%, V = −1.1 V vs. Ag/AgCl) is delivered with the Co-SA@Co-NP bridge-derived biohybrid, which is 70 times that derived with Co-SA only (∼35.47 mmol m−2 per day). As such, the rationally designed atomic-nanoparticle bridge affords the effective tailoring of microbiome and charge dynamics via interfacial electronic structure engineering, thereby providing a unique platform for developing high-performance bio-electrochemical CO2-fixation systems.