Membrane-Intercalating Conjugated Oligoelectrolytes Enhance Microbial CO2 Electroreduction by Promoting Transmembrane H2 Delivery.

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 (Jacetate) 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.