Effect of Anions on the Kinetics of Tris(1,10-phenanthroline)-cobalt(II)/(III) Redox-Electrode Reaction on a Platinum (111) Single Crystal Electrode

Abstract

The redox-electrode reaction of Co(II)(phen)3/Co(III)(phen)3 (phen = 1,10-phenanthroline) in potassium halide solutions was kinetically studied on a Pt(111) single crystal electrode. The formal rate constants were found to depend on the anions and to decrease in the order: F->Cl->Br-. It was found that modification of the electrode surface with a monolayer of thiocyanate ion accelerates the heterogeneous electron-transfer reaction, whereas the reaction was retarded by the modification with iodide. These findings are discussed based on the adsorption of anions.