Passivating reactions at a microdisk electrode as a model of passivation at a microparticle: theory and experiment

We have described the use of a microelectrode to simulate a passivating reaction taking place at a micro or nanoparticle. Reaction at the microelectrode is considered to lead to either diffusion of the product back into solution or the formation of a surface-bound species. A kinetic parameter describes the balance between the two processes. Linear sweep voltammograms were simulated for the first and second scan under different values of the kinetic parameter. These simulations were used to derive an empirical equation relating the change in peak height to the passivation kinetics. The equation was used to examine the oxidation of NADH, phenol and ascorbic acid at a Pt microelectrode, and the oxidation of phenol at alloy microelectrodes of different Pt:Rh content.