A Living Semiartificial Photoelectrocatalytic Biohybrid for Solar CO ₂ Fixation and Fermentation to Fatty Acids

To address the global climate and energy crisis, innovative strategies are urgently needed to transform CO2 into sustainable fuels and chemicals. We present a semiartificial biophotoelectrochemical (BPEC) platform, combining solar energy conversion with naturally evolved microbes to develop solutions for transforming CO2 and water into multicarbon products─without sacrificial additives or precious materials. This remains extremely challenging for fully artificial photocatalytic systems. Our system features a scalable and low-cost CuBi2O4 photocathode, stabilized by a thin MgO interlayer, in direct contact with the CO2-fixing bacterium Sporomusa ovata grown on the electrode surface. This interface enables direct electron uptake, eliminating the need for diffusible redox mediators or externally supplied H2─limitations commonly seen in bionic leaf systems. The BPEC operated stably for 140 h (5.5 days), a record duration for a Cu-based system, producing 673.2 ±  71.4 μM cm–2 acetate and 683 ± 55.2 μM cm–2 of ethanol with a Faradaic efficiency of 69% for C2 products. Subsequent addition of Clostridium kluyveri enabled biological chain elongation, producing 1.31  ±  0.2 μmol butyrate (C4) and 0.6  ±  0.1 μmol caproate (C6), with 0.72  ±  0.2 μmol H2 as a fermentation byproduct. To our knowledge, this represents the longest-chain solar-driven CO2-derived product reported to date, highlighting a critical advance in artificial photosynthesis. This approach demonstrates the power of pairing stable photoelectrochemical interfaces with microbial consortia to utilize CO2 as a feedstock for solar chemical production.