Conversions of complex compounds and quinone on surface-modified electrodes

• Published in: Journal of electroanalytical chemistry and interfacial electrochemistry 1987-03, Vol.219 (1), p.153-163
• Main Authors: Gudavičius, Arvydas V., Razumas, Valdemaras J., Kulys, Juozas J.
• Format: Article
• Language: English
• Subjects: Chemistry; Electrochemistry; Exact sciences and technology; General and physical chemistry; Kinetics and mechanism of reactions
• ISSN: 0022-0728
• DOI: 10.1016/0022-0728(87)85037-4

Electrochemical conversions of the redox pairs Fe(CN) 3− 6/Fe(CN) 4− 6, Fe(EDTA) −/Fe(EDTA) 2−, Co(phen) 3+ 3/Co(phen) 2+ 3 and quinone/hydroquinone on Au electrodes modified by polyethyleneimine and electropolymerized methyl or benzyl viologens were studied. Polymeric films with refractive indices of 1.338, 1.332, 1.337 and thicknesses of 175, 190.5, 173.7 nm were used. It was found that the surface modification of gold increases the potential of the outer Helmholtz plane by more than 20 mV. It increases the formal heterogeneous rate constant of Fe(CN) 3− 6/Fe(CN) 4− 6 redox conversions by more than 15 times as compared with a naked surface of Au. The electrode reactions of negatively charged complexes are limited by their transfer rate through the diffusion layer. Studies on the transport of Co(phen) 3+ 3 and quinone through the modifier's layer, conducted with a rotating disc electrode, indicate that the process can be described by the theory of “diffusion in a membrane” (pinhole free). The permeabilities of the polymeric films vary over the range 1.32 × 10 −3–6.99 × 10 −2 cm/s.