Electrochemical behavior and assembly of tetranuclear Dawson-derived sandwich compound [Cd4(H2O)2(As2W15O56)2]16− on 4-aminobenzoic acid modified glassy carbon electrode Original Research Article

The transition metal-substituted heteropolyoxoanion, Cd4(H2O)2(As2W15O56)212− (As4W30Cd4), is one of the trivacant Dawson derivatives. Its redox electrochemistry has been studied in acid buffer solutions using cyclic voltammetry. It exhibited three steps of four-electron redox waves attributed to redox processes of the tungsten-oxo framework. Through layer-by-layer assembly, the compound was first successfully immobilized on a 4-aminobenzoic acid modified glassy carbon electrode surface by alternate deposition with a quaternized poly(4-vinylpyridine) partially complexed with [Os(bpy)2Cl]2+/+ (denoted as QPVP-Os). Thus, prepared multilayer films have been characterized by cyclic voltammetry (CV), X-ray photoelectron spectroscopy (XPS) and UV–vis spectroscopy (UV–vis). The electrocatalytic activities of the multilayer films containing As4W30Cd4 have been investigated on the reduction of three substrates of important analytical interests, NO2−, BrO3− and IO3−. And with the increase of the number of As4W30Cd4 layers, the catalytic current towards the reduction of BrO3− was enhanced and the catalytic potential shifted positively.