Membrane-Intercalating Conjugated Oligoelectrolytes Enhance Microbial CO₂ Electroreduction by Promoting Transmembrane...

Transmembrane H₂ delivery is a key yet long-overlooked factor governing the efficiency of microbial CO₂ electroreduction. In this work, we demonstrate that membrane-intercalating conjugated oligoelectrolytes (MICOEs) can accelerate microbial CO₂ electroreduction by promoting transmembrane H₂ transport. We designed a series of MICOE molecules with a naturally derived backbone and tunable side chain lengths, and systematically studied their bacterial association and electrochemical impact using acetogen Sporomusa ovata (S. ovata) as a model platform. At an appropriate loading concentration, the MICOE with intermediate side chain length enables efficient microbial CO₂ electroreduction, achieving a peak CO₂-to-acetate partial current density (J_acetate) of 1.15 mA cm^-2 and an acetate titer of 1.64 ± 0.21 g L^-1 within 5 days, which substantially outperforms the MICOEs with shorter or longer side chains, as well as untreated microbes. Mechanistic studies combining a vesicle-encapsulated fluorescent H₂ probe, Laurdan assays, and molecular dynamics (MD) simulations confirmed that the optimized MICOE specifically promotes transmembrane H₂ transport, an effect attributed to its optimal terminal charge distance, which enables appropriate membrane perturbation and thereby higher H₂ permeability. Our results establish MICOEs as an effective yet tunable strategy to enhance microbial CO₂ electroreduction and, by extension, other H₂-mediated whole-cell bioprocesses.