Stabilization of a molecular water oxidation catalyst on a dye−sensitized photoanode by a pyridyl anchor

• Understanding and controlling the properties of water-splitting assemblies in dye-sensitized photoelectrosynthesis cells is a key to the exploitation of their properties. We demonstrate here that, following surface loading of a [Ru(bpy)3]2+ (bpy = 2,2′-bipyridine) chromophore on nanoparticle electrodes, addition of the molecular catalysts, Ru(bda)(L)2 (bda = 2,2′-bipyridine-6,6′-dicarboxylate) with phosphonate or pyridyl sites for water oxidation, gives surfaces with a 5:1 chromophore to catalyst ratio. Addition of the surface-bound phosphonate derivatives with L = 4-pyridyl phosphonic acid or diethyl 3-(pyridin-4-yloxy)decyl-phosphonic acid, leads to well-defined surfaces but, following oxidation to Ru(III), they undergo facile, on-surface dimerization to give surface-bound, oxo-bridged dimers. The dimers have a diminished reactivity toward water oxidation compared to related monomers in solution. By contrast, immobilization of the Ru-bda catalyst on TiO2 with the 4,4′-dipyridyl anchoring ligand can maintain the monomeric structure of catalyst and gives relatively stable photoanodes with photocurrents that reach to 1.7 mA cm−2 with an optimized, applied bias photon-to-current efficiency of 1.5%.

Subject headings

NATURVETENSKAP  -- Kemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences (hsv//eng)

Keyword

dye

phosphonic acid derivative

water

catalyst

chemical composition

electrode

hydrolysis

immobilization

ligand

molecular analysis

nanoparticle

photochemistry

Article

chromatophore

cyclic voltammetry

dimerization

electron transport

gas chromatography

impedance spectroscopy

oxidation

Publication and Content Type

ref (subject category)

art (subject category)