A Living Semiartificial Photoelectrocatalytic Biohybrid for Solar CO2 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.