Electrolytic Reduction of Dichromate Ion at a Mercury Cathode

Abstract

Electrolytic reduction of HCO3- at Hg was conducted in aqueous solutions of NaHCO3 (0.5-1.0 mol 9 kg-~)-Na~CO3 (0.025-0.1 mol. kg-') mixtures. HCOO- is formed as the product; this agrees with the results obtained in the cathodic reduc- tion of CO~. The following reaction mechanism is proposed: The dissociation of HCO3- takes place in the electrolyte solution and forms CO~, which diffuses through the reaction layer and is cathodically reduced at the electrode. The diffusion equa- tion and Tafel equation for the electrode kinetics are combined and mathematically treated. The partial current of HCOO- formation, ic, is related to the electrode potential and the concentration of the components in the solution. The analysis shows that the experimental data obey the relationship derived in accordance with the model. The rate constant of HCO~- dissociation is compared with literature values. Carbon