Electrogeneration and electrochemical properties of hybrid materials: polypyrrole doped with polyoxometalates PW12−xMoxO403− (x=0,3,6,12)

Hybrid materials such as polypyrrole doped with polyoxometalates PW12−xMoxO403− (x=0,3,6,12) were electrogenerated from organic solution. The effects of the Mo-substitution on the electrogeneration and electrochemical properties of the hybrid materials were studied by potential step and cyclic voltammetry. It was found that Mo-substituted polyoxometalates could stimulate the oxidation–polymerization of pyrrole. The oxidation–polymerization potential of pyrrole decreases as the Mo content increases, correlating the redox properties of the polyoxometalates. During the initial cathodic sweep, a great cathodic peak (altogether a blue cloud of material release) with a shoulder is shown by all the studied materials. A substantial loss of weight was always observed during this reduction process. Polyoxometalates and polypyrrole oligomers determined by FT-IR [J. Chem. Phys. B 104 (2000) 10528] and UV–VIS contributed to the weight loss giving rise to a partial electrochemically stimulated dissolution of the material. After this initial cycle, the consecutive voltammograms present two redox processes. Charges and current densities involved in those two cathodic processes show a linear variation, in opposite directions, at almost the same rate upon cycling. Those shifts of the cathodic processes are related to a continuous change of the counter-ion involved in the redox process from Li+ to ClO4−, altogether the subsequent release of polyoxometalate (that required the Li+ counter-ion) from the hybrid.