Electrocatalytic oxidation of thiosulfate by metal hexacyanoferrate film modified electrodes

The electrocatalytic oxidation of S2O32- by metal (iron(II), indium(III), nickel(II), and cobalt(II)) hexacyanoferrate film from consecutive cyclic voltammetry was investigated. The ferric hexacyanoferrate film catalyzed the rapid oxidation of thiosulfate after oxidizing the film [Fe(II)-CN-Fe(II)] to [Fe(III)-CN-Fe(III)]. The indium(III) hexacyanoferrate film has a similar catalytic mechanism. While nickel(II) hexacyanoferrate and cobalt(II) hexacyanoferrate films exhibit a different reaction mechanism, at the working electrode a more positive potential than E(Pa) of the metal(II) hexacyanoferrate(II)/metal(II) hexacyanoferrate(III) redox couple must be applied. The electrocatalytic oxidation of S4O62- to SO42- by ferric hexacyanoferrate film proceeds at a very slow reaction rate. The electrocatalytic oxidation of S2O32- was also performed using two layers of different metal hexacyanoferrate film modified electrodes. The results resemble the one layer metal hexacyanoferrate film modified electrode. A bicatalyst electrocatalytic reaction was performed using the rotating ring-disk electrode method. The electrocatalytic reduction current of S4O62- through Fe(I)(2-TMPyP) appears when S4O62- is produced from the electrocatalytic oxidation of S2O32- by metal hexacyanoferrate film.