KINETICS AND MECHANISM PERTAINING TO ELECTROREDUCTION OF AMMONIA COMPLEXES OF PALLADIUM(II) AT THE MERCURY-ELECTRODE

Kinetics of electroreduction of ammonia complexes of palladium(II) at the dropping mercury electrode are studied in solutions containing 0.0 1-0.5 M NaF, 0.01-1.0 M NaClO4, and approximately 0.01-1.0 M NH3 at so lution pH about 10.5-11.5. It is found that the limiting current is co ntrolled by diffusion, and the electroreduction rate of the complexes depends on neither the concentration of ammonia molecules nor solution pH. Rate constants of the slow electrochemical stage are calculated o n the basis of irreversible polarographic waves. The constants are sho wn to obey the Frumkin equation, which accounts for the influence exer ted by the electrical double layer structure on the rate of the electr ochemical stage. It is concluded that ammonia complexes of Pd(II) take part in the single-electron electrochemical stage and position themse lves in the outer Helmholtz plane.