Close-Packed Nanowire-Bacteria Hybrids for Efficient Solar-Driven CO2 Fixation

Microbial electro- and photo-electrochemical CO2 fixation, in which CO2-reducing microorganisms are directly interfaced with a cathode material, represent promising approaches for sustainable fuel production. Although considerable efforts have been invested to optimize microorganism species and electrode materials, the microorganism-cathode interface has not been systematically studied. Here, investigation of the interface allowed us to optimize the CO2-reducing rate of silicon nanowire/Sporomusa ovata system. Tuning the bulk electrolyte pH and increasing its buffering capacity supported the formation of a close-packed nanowire-bacteria cathode. Consequently, the resulting close-packed biohybrid achieved a CO2-reducing current density of ∼0.65 mA cm−2. When coupled with a photovoltaic device, our system enabled solar-to-acetate production with ∼3.6% efficiency over 7 days.