Assembly, electrochemical characterisation and electrocatalytic ability of multilayer films based on [Fe(bpy)3]2+, and the Dawson heteropolyanion, [P2W18O62]6−

Successive adsorption onto a glassy carbon electrode of the Dawson heteropolyanion, [P2W18O62]6−, and the multiply charged cation [Fe(bpy)3]2+, resulted in the formation of stable multilayer assemblies on the electrode surface. Surface coverages were found to be typical of monolayer coverages for multilayer systems. Cyclic voltammetric studies of the assembly in aqueous 0.5 M NaHSO4, gave a range of redox couples associated with the Fe3+/2+ redox system, of the cationic [Fe(bpy)3]2+ moiety and the tungsten-oxo framework of the Dawson parent heteropolyanion, [P2W18O62]6−. It was possible to immobilise up to thirty monolayers, with the system exhibiting well-behaved redox behaviour. The stability of the assembly towards redox switching was investigated, with it being found to be extremely stable once the outer layer is anionic in nature. The immobilised film was also tested for electrocatalytic activity for the reduction of nitrite, hydrogen peroxide and bromate, and was shown to be an efficient electrocatalyst.