A MATHEMATICAL-MODEL FOR ANODIC OXYGEN-TRANSFER REACTIONS AT BI(V)-DOPED PBO2-FILM ELECTRODES

An approximate model is developed to describe the voltammetric respons e for anodic O-transfer reactions at Bi(V)-doped PbO2-film electrodes (Bi-PbO2). Because the Bi(V) sites were found earlier to function for preadsorption of reactant in the anodic O-transfer reactions of cystei ne, the model developed here includes reactant adsorption at Bi(V) sit es in the Bi-PbO2 surface. The validity of the model is demonstrated o n the basis of the voltammetric response obtained for DMSO in 1.0 M HC lO4. Good agreement is obtained between predicted and observed values of half-wave potential (E-1/2) as a function of the relative density o f Bi(V) sites (rho = Gamma(Bi(V))/Gamma(Pb(IV))) in Bi-PbO2 film elect rodes configured as rotated disks. For low site densities (0.11 less t han or equal to rho less than or equal to 0.4), E-1/2 is a linear func tion of ln(rho/(1 + rho)(2)); however, for high site densities (0.4 le ss than or equal to rho less than or equal to 0.84), E-1/2 is a linear function of ln(1/(1 + rho)). Agreement is also demonstrated for E-1/2 as a function of variations in the rotational velocity of these elect rodes. The agreement of the proposed model with experimental data is c oncluded to be evidence for the importance of reactant adsorption in a nodic O-transfer reactions at Bi(V) sites in these Bi-PbO2 electrodes. (C) 1998 Elsevier Science S.A. All rights reserved.