Microbe-electrode interactions on biocathodes are facilitated through tip-enhanced electric fields during CO₂-fed microbial electrosynthesis

Microbial electrosynthesis is advantageous in producing value-added C₁₊ molecules from CO₂, complementing electrocatalysis that is efficient in producing C₁ molecules such as carbon monoxide and formate. However, a full understanding of microbe-electrode interactions at the biocathode is lacking, leading to suboptimal electron transfer efficiency. The interfacial electron transfer and biofilm formation on a constructed 3D cobalt-nickel-bimetallic-sulfide-coated carbon felt (CoNi-CF) biocathode were explored. Honeycomb-like metallic nanocrystals on CoNi-CF provide ample active sites for efficient electron transfer to microbes. Nanometer-sized tips on biocathodes intensify local electric fields, enabling efficient charge transfer and HCO₃⁻/CO₂ bio-electroreduction. Density functional theory analysis shows the catalysts effectively bind hydrogen atoms, crucial for facilitating interfacial charge transfer in biological metabolisms. The overall faradic efficiency of acetate and ethanol reaches 90.8% due to the constructed biocathode. This study advances understanding of abiotic-biotic electron transfer mechanisms, offering potential for efficient microbial electrosynthesis of chemicals from CO₂.