PALLADIUM-SUBSTITUTED KEGGIN-TYPE POLYOXOTUNGSTATE CHEMICALLY-MODIFIED ELECTRODE AND ITS CATALYTIC ACTIVITY TOWARD HYDROGEN-PEROXIDE REDUCTION

Keggin type heteropolytungstate, in which one of the positions normall y occupied by a tungsten cation is occupied by a palladium cation inst ead, is used to prepare a chemically modified electrode (CME). The ele ctrochemical and electrocatalytic properties of such a CME are investi gated. The electron transfer between the palladium-substituted heterop olytungstate and the glassy carbon electrode is fast. The palladium-su bstituted heteropolyanion CME, with a surface apparent coverage about 1.94 x 10(-9) mol.cm(-2), is shown to be an excellent catalyst for the electrochemical reduction of hydrogen peroxide, while the perfect and lacunary heteropolyanions show no catalytic activity. The effect of s olution pH on the stability of the CME, as well as on the electrocatal ytic activity toward H2O2, was also investigated. The catalytic curren t increases linearly with increasing concentration of H2O2 up to 150mm ol.L-1, and the detection limit is 4.0 x 10(-6)mol.L-1. Due to its sen sitivity and durability, this CME could be used as analytical sensor f or detecting H2O2 in real samples.