Electrochemical Behaviour of Isopoly- and Heteropolyoxomolybdates Formed During Anodic Oxidation of Molybdenum in Seawater
Justyna Jońca, Carole Barus, William Giraud, Danièle Thouron, Véronique Garçon, Maurice Comtat
Int. J. Electrochem. Sci., 7 (2012) 7325 - 7348.
The electrochemical behaviour of isopoly- and heteropolyoxomolybdates formed during anodic oxidation of molybdenum in seawater at constant current intensity was investigated in this work. The results supported by spectrophotometry clearly indicate the formation of mixed valence molybdates (V/VI) during this process. The electrochemical behaviour of isopolyoxomolybdates shows a typical quasi-reversible mass-transport limited system coupled with an adsorption of reduced species and under some kinetic limitations. For heteropolyoxomolybdates a reversible mass-transport limited system coupled with an homogeneous chemical reaction was found. The coupled reaction, probably protonation, prevents a rapid heterogeneous electron transfer for heteropolyoxomolybdate complex. The phenomenon is more noticeable for the phosphomolybdate complex since the protonation step has a greater influence on the registered voltammograms. The presented results have a great importance in research areas where molybdate chemistry is used in detection of silicate and phosphate, namely in seawater.