Light-Driven Water Splitting by a Covalently Linked Ruthenium-Based Chromophore–Catalyst Assembly

The preparation and characterization of new Ru(II) polypyridyl-based chromophore–catalyst assemblies, [(4,4′-PO 3 H 2 -bpy) 2 Ru(4-Mebpy-4′-epic)Ru(bda)(pic)] 2+ ( 1, bpy = 2,2′-bipyridine; 4-Mebpy-4′-epic = 4-(4-methylbipyridin-4′-yl-ethyl)-pyridine; bda = 2,2′-bipyridine-6,6′-dicarboxylate; pic = 4-picoline), and [(bpy) 2 Ru(4-Mebpy-4′-epic)Ru(bda)(pic)] 2+ ( 1 ′) are described, as is the application of 1 in a dye-sensitized photoelectrosynthesis cell (DSPEC) for solar water splitting. On SnO 2 /TiO 2 core–shell electrodes in a DSPEC configuration with a Pt cathode, the chromophore–catalyst assembly undergoes light-driven water oxidation at pH 5.7 in a 0.1 M acetate buffer, 0.5 M in NaClO 4 . With illumination by a 100 mW cm –2 white light source, photocurrents of ∼0.85 mA cm –2 were observed after 30 s under a 0.1 V vs Ag/AgCl applied bias with a faradaic efficiency for O 2 production of 74% measured over a 5 min illumination period.