Fabrication of Core–Shell Nanotube Array for Artificial Photosynthesis Featuring an Ultrathin Composite Separation Membrane

Macroscale arrays of cobalt oxide–silica core–shell nanotubes with high aspect ratio and ultrathin walls of less than 20 nm have been fabricated. The silica shells feature embedded oligo -para(phenylenevinylene) molecules for charge transport across the insulating silica layer, which is tightly controlled by their electronic properties. The assembly is based on the use of a sacrificial Si nanorod array template combined with atomic layer deposition, covalent anchoring of organic wire molecules, and dry cryo-etching. High-resolution TEM imaging of samples prepared by microtome affords structural details of single core–shell nanotubes. The integrity of silica-embedded organic wire molecules exposed to atomic layer deposition, thermal treatment, and harsh etching procedures is demonstrated by grazing angle ATR FT-IR, FT-Raman, and XPS spectroscopy. The inorganic oxide-based core–shell nanotubes with ultrathin gas-impermeable, proton-conducting silica shells functionalized by molecular wires enable complete nanoscale photosynthetic units for CO 2 reduction by H 2 O under membrane separation. Arrays of massive numbers of such core–shell nanotube units afford a design that extends the separation of the incompatible H 2 O oxidation and CO 2 reduction catalysis environments across the continuum of length scales from nanometers to centimeters.