ON THE ELECTROCHEMICAL PROPERTIES OF THE PD + HG SYSTEM

Intermetallic compounds of Pd with Hg were produced by simultaneous electrodeposition of palladium and mercury on platinum and carbon paste electrodes. Chronopotentiometric and linear potential scan voltammetric oxidation of such deposits revealed that oxidation of the individual compounds formed (PdHg, Pd2Hg5 and PdHg4) occurs in separate steps or peaks. It was proved that the whole deposit, not just its surface layers, is oxidized. Kinetic limitations were observed at higher current densities and scan rates. Oxidation of PdHg4 and Pd2Hg5 was found to proceed with the formation of PdHg as an intermediate. The Gibbs energies, enthalpies and entropies of formation of PdHg, Pd2Hg5 and PdHg4 were calculated from their deposition potentials determined at different temperatures.