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 normally occupied by a tungsten cation is occupied by a palladium cation instead, is used to prepare a chemically modified electrode (CME). The electrochemical and electrocatalytic properties of such a CME are investigated. The electron transfer between the palladium-substituted heteropolytungstate and the glassy carbon electrode is fast. The palladium-substituted 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 solution pH on the stability of the CME, as well as on the electrocatalytic activity toward H2O2, was also investigated. The catalytic current increases linearly with increasing concentration of H2O2 up to 150mmol.L-1, and the detection limit is 4.0 x 10(-6)mol.L-1. Due to its sensitivity and durability, this CME could be used as analytical sensor for detecting H2O2 in real samples.