Investigations into the Electrochemical, Surface, and Electrocatalytic Properties of the Surface-Immobilized Polyoxometalate, TBA₃K[SiW₁₀O₃₆(PhPO)₂]

Surface anchoring of an organic functionalized POM, TBA₃K­[SiW₁₀O₃₆(PhPO)₂] was carried out by two methods, the layer-by-layer (LBL) assembly technique by employing a pentaerythritol-based ruthenium­(II) metallodendrimer as a cationic moiety and also by entrapping the POM in a conducting polypyrrole film. The redox behavior of the constructed films was studied by using cyclic voltammetry and electrochemical impedance spectroscopy. The surface morphologies of the constructed multilayers were examined by scanning electron microscopy and atomic force microscopy. X-ray photoelectron spectroscopy was conducted to confirm the elements present within the fabricated films. The multilayer assembly was also investigated for its catalytic efficiency towards the reduction of nitrite

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

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