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

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.