Kinetics and mechanism of the cobalt(II) electroreduction on a dropping mercury electrode in oxalate solutions with varying concentration of the supporting electrolyte

The kinetics and mechanism of electroreduction of oxalate complexes of coba lt(II) are studied by de polarography with allowance made for the structure of the electrical double layer (EDL). Our earlier conclusion that aquacomp lexes Co2+, formed from complexes CoC2O4 as a result of a reversible chemic al reaction, take part in the slow single-electron outer-sphere electrochem ical stage is confirmed. It is shown that the Co2+ ions undergoing reductio n essentially affect the EDL structure due to their charge being higher tha n that of the supporting electrolyte cations (Na+) and in view of the proce ss occurrence at high negative charges of the electrode surface. The equati ons that allow one to introduce pertinent corrections for the effect of the EDL structure on the electroreduction kinetics are validated.