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

Abstract

The preparation and characterization of new Ru­(II) polypyridyl-based chromophore–catalyst assemblies, [(4,4′-PO3H2-bpy)2Ru­(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)2Ru­(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 SnO2/TiO2 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 NaClO4. 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 O2 production of 74% measured over a 5 min illumination period.

Visible light-driven water oxidation with a ruthenium sensitizer and a cobalt-based catalyst connected with a polymeric platform

“…[2][3][4][5] Several Ru(II) based PS-WOC dyad assemblies have recently been coated on TiO 2 to build dyesensitized DSPECs with promising faradaic efficiencies for O 2 evolution. 6,7 The catalytic efficiency of dyad systems was investigated in a homogeneous system as well. In a study by Thummel et al, a Ru-Ru dyad assembly showed a TON of 134 under 6 h illumination, which is much higher than its analogous intermolecular system with a TON of 6.…”

A Noble‐Metal‐Free Heterogeneous Photosensitizer‐Relay Catalyst Triad That Catalyzes Water Oxidation under Visible Light

“…[2,3] Of these,d ye-sensitized photoelectrochemical cells (DS-PECs) utilize covalently coordinated chromophore-water oxidation catalyst (WOC) dyad assemblies [4][5][6] in an effort to mimic natural photosynthesis. [10][11][12][13][14][15][16][17][18][19] Although the use of robust heterogeneous assemblies such as oxides could be apromising solution to improve stability,the lack of complete control on the coordination of metal ions in oxide chemistry does not allow the preparation of oxidebased dyads. [7][8][9] Molecular ruthenium complexes (as photosensitizers and/or WOCs) remain the most widely used despite their high cost and easy decomposition under photocatalytic conditions.…”

Stabilized photoanodes for water oxidation by integration of organic dyes, water oxidation catalysts, and electron-transfer mediators

“…Photoelectrochemical Water Oxidation. Water oxidation was explored in core/shell nanoparticle SnO 2 /TiO 2 films with the core/shell structure assisting electron-hole separation at the SnO 2 /TiO 2 interface (25)(26)(27)(28)(29). Surface-loaded versions of related assemblies were investigated previously (30).…”