Electroreduction kinetics and mechanism of palladium(II) glycinate chloride complexes on rotating palladium disk electrode

摘要

The electroreduction kinetics of Pd(Hgly)_2Cl_2 on rotating palladium disk electrode was studied by means of cyclic voltammetry. The double layer range of the palladium charging curve showed a single wave with the diffusion limited current I _d, which yielded the diffusion coefficient of Pd(Hgly)_2Cl_2 complex D = 6 × 10 ~(-6) cm~2/s. The plotted direct and reverse voltammetric curves were linearized in coordinates E, log[I/(I _d - I)]. The slope of this line gave b _k factor evidencing the slow electrochemical step. When [Cl~-] decreased from 1 to 0.2 M, E _(1/2) potential shifted to positive values. This was accounted for by reversible cleavage of Cl~- ion from Pd(Hgly)_2Cl_2 complexes before the irreversible electrochemical step. The pulse galvanostatic experiment resulted in the double electrical layer capacity and roughness factors f of electrolytic palladium deposits. The calculated values of f from 60 to 310 were attributed to adsorption of glycine particles on the electrodeposited palladium surface, which promotes to increasing number of palladium microcrystal growing centers.