The electrocatalytic influence of underpotential lead adsorbates on the reduction of oxygen at glassy carbon electrodes in acid solution

Abstract

The electrochemical reduction of oxygen and hydrogen peroxide has been investigated on a glassy carbon rotating disk electrode in 0.5 M HClO 4 at various concentrations of Pb 2+. An overall 2-electron reduction of O 2 to H 2O 2 is found on glassy carbon which, in the presence of Pb 2+, is positively catalyzed. The electrocatalytic effect can be correlated to an underpotential deposition (UPD) of lead at a limited number of active sites on the glassy carbon surface. The hydrogen peroxide reduction is nearly completely inhibited by the UPD of lead. The observed concentration dependence with respect to Pb 2+ is in accordance with the Nernstian behaviour of the UPD process.