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Surface Immobilization of a Tetra-Ruthenium Substituted Polyoxometalate Water Oxidation Catalyst Through the Employment of Conducting Polypyrrole and the Layer-by-Layer (LBL) Technique

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posted on 11.06.2014, 00:00 by Nargis Anwar, Andrea Sartorel, Mustansara Yaqub, Kevin Wearen, Fathima Laffir, Gordon Armstrong, Calum Dickinson, Marcella Bonchio, Timothy McCormac
A tetra Ru-substituted polyoxometalate Na10[{Ru4O4(OH)2(H2O)4}­(γ-SiW10O36)2] (Ru4POM) has been successfully immobilised onto glassy carbon electrodes and indium tin oxide (ITO) coated glass slides through the employment of a conducting polypyrrole matrix and the layer-by-layer (LBL) technique. The resulting Ru4POM doped polypyrrole films showed stable redox behavior associated with the Ru centres within the Ru4POM, whereas, the POM’s tungsten-oxo redox centres were not accessible. The films showed pH dependent redox behavior within the pH range 2–5 whilst exhibiting excellent stability towards redox cycling. The layer-by-layer assembly was constructed onto poly­(diallyldimethylammonium chloride) (PDDA) modified carbon electrodes by alternate depositions of Ru4POM and a Ru­(II) metallodendrimer. The resulting Ru4POM assemblies showed stable redox behavior for the redox processes associated with Ru4POM in the pH range 2–5. The charge transfer resistance of the LBL films was calculated through AC-Impedance. Surface characterization of both the polymer and LBL Ru4POM films was carried out using atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). Initial investigations into the ability of the Ru4POM LBL films to electrocatalytically oxidise water at pH 7 have also been conducted.

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