(560ba) H+ Conductivity and O2 Impermeability of Ultrathin Oxide Layers with Built-in SiO2 Separation Membrane for Scalable Artificial Photosynthesis

Replacing fossil fuels with renewable resources to meet the global need requires a technology that is scalable to the unprecedented level of several terawatts. Natural photosynthesis is the sole existing technology that produces energy dense chemicals on the terawatt scale (> 100 TW). Its key design feature is the closed cycle of H₂O oxidation and formation of the primary reduction products on the shortest possible length scale, nanoscale, while separating the incompatible redox environments by an ultrathin membrane. This offers the advantage of minimizing efficiency-degrading mass transport processes and unwanted side reactions.

To incorporate the key feature into artificial photosystems, we assembled ultrathin (2 nm), pinhole-free, molecular wires-embedded SiO₂ membrane on planar and nanotube constructs. This membrane system spatially separates the H2O oxidation CO₂ reduction, but enables (photo-)electrochemical communication between the incompatible redox reactions by transmitting protons and electrons in a precisely controlled manner, while preventing O₂ diffusion causing unwanted reverse reactions. This unique mass-transfer behavior on planar and nanotube configurations was systematically studied via cyclic voltammetry, electrochemical impedance spectroscopy, and visible light-sensitized short circuit current experiments. The embedded molecular wires’ integrity before and after the mass (proton) transfer process was confirmed by time-resolved optical spectroscopy and grazing angle ATR-FT-IR or IRRAS characterization.