Steven H. Bergens
University of Alberta, Canada
Title: Molecular Brick Building Sets for Chromophores and Catalysts for Solar-Powered Water Splitting and CO2 Reduction
Biography
Biography: Steven H. Bergens
Abstract
Dye-sensitized photoelectrochemical cells often utilize molecular dyes and catalysts bonded to semiconductors to absorb sunlight, split water, and reduce carbon dioxide in order to store solar engery in hydrocarbon form.1 We have developed molecular bricks that bond by covalent or electrostatic interactions. We will report on the use of these bricks to construct several systems to study visible light photoelectrochemical oxidations and reductions under acidic, neutral, and basic conditions. For example, we grafted 1,10-phenanthroline by a covalent bond at C5 to a variety of semiconductors and glassy carbon electrodes using diazonium chemistry.2,3 We then used this electrode-ligand brick to build a number of grafted [Ru(phensurface)(aromatic diamine)2]2+ chromophores by displacement of MeCN from the corresponding [Ru(MeCN)2(aromatic diamine)2]2+ precursors. Further, incorporation of one 1,10-phenanthroline-5,6-dione ligand into the Ru(MeCN)2 precursor allows for subsequent modifications of the chromophore after it is grafted to the electrode surface. Specifically, condensation reactions between the dione group in the grafted chromophore, and diamines in solution allowed for systematic tuning of the efficiency and wavelength range of the photoelectrode. As well, electrostatic self-assembly between the cationic Ru-chromophore surfaces and anionic, hydrous oxide Ir-Ni nanoparticle catalysts prepared test photoanodes for water splitting. Similar building reactions were used to covalently attach Mn- and Re-based CO2 reduction electrocatalysts to electrode surfaces.