438296 Hierarchical Inorganic Assemblies for the Photocatalytic Reduction of CO2 by H2O

Monday, November 9, 2015: 9:30 AM
155D (Salt Palace Convention Center)
Heinz Frei, Lawrence Berkeley National Laboratory, Berkeley, CA

The multi-electron processes of CO2 reduction and H2O oxidation, which constitute the essential reactions of sunlight to fuel conversion require efficient coupling of light absorber and catalyst. Using all-inorganic heterobinuclear units such as ZrOCo(II) anchored on high surface area silica, we have developed photodeposition methods for the directional assembly of nanometer sized catalysts for H2O oxidation or CO2 reduction with proper coupling to the binuclear light absorber. Copper oxide nanoclusters were assembled adjacent to the Zr acceptor sites of the heterobinuclear unit, and light driven reduction of CO2 upon excitation of the ZrOCo unit demonstrated. Illumination of the ZrOCo chromophore coupled to an Ir oxide nanocatalyst for H2O oxidation  allow us to reduce CO2 by taking the electrons from water, thereby closing the photocatalytic cycle. Time resolved FT-IR spectroscopy provides detailed mechanistic insight into the multi-electron reactions on the metal oxide catalyst surface under reaction conditions. To achieve CO2 photoreduction by H2O under product separation, Co3O4-SiO2 core-shell nanotubes were developed in which the inner surface acts as efficient water oxidation catalyst while the nanoscale silica layer with embedded molecular wires serves as a proton conducting, gas impermeable separation membrane with tight control of electron transport. Using nanofabrication based on sacrificial Si nanowire array methods, macroscale arrays of Co oxide-silica nanotubes are being developed for accomplishing the complete photocatalytic cycle in a macroscale assembly.

Extended Abstract: File Not Uploaded