Efficient light-driven CO₂ conversion to ethanol using a CQDs/InP@bacteria biohybrid system

Bacteria can convert CO₂ into acetate and ethanol via the Wood-Ljungdahl pathway with H₂ as an electron donor, providing a green route for renewable energy production. However, the low solubility of H₂ in water limits conversion efficiency. Although in semi-artificial biohybrid systems such as InP-based systems, photogenerated electrons can replace H₂ as an alternative driving force, rapid electron-hole recombination limits carbon fixation efficiency. In this work, CQDs were introduced to construct a CQDs/InP composite to facilitate carrier separation and interfacial electron transfer, forming a CQDs/InP@bacteria biohybrid system. Compared with pure InP, CQDs/InP showed a 78.3% reduction in interfacial charge transfer resistance and a 1.95-fold increase in photocurrent. Metabolomic analysis further revealed that key intermediates involved in intracellular respiration and ATP synthesis, such as succinic acid and fructose 1,6-bisphosphate, were downregulated by 23% and 21.35%, respectively, indicating that the input of external electrons enabled the biohybrid system to effectively reduce the bacterial dependence on intracellular catabolic energy production. Consequently, the CQDs/InP@bacteria biohybrid system under 450 nm blue light achieved acetate and ethanol production of 0.70 and 0.24 g·L^-1, respectively, representing increases of 114.46% and 126.98% over the pure bacterial system, with an apparent quantum yield of 1.76%, indicating improved light-to-chemical energy conversion efficiency. This work effectively enhances interfacial electron transfer in InP-based systems and promotes light-driven CO₂ fixation and chemical production in non-photosynthetic bacteria, providing a pathway for constructing efficient semi-artificial photosynthetic microbial CO₂ conversion systems.