Quantitative Kinetic Analysis of a PdAu3 Alloy Catalyst for Oxygen Electro-Reduction

The oxygen reduction reaction (ORR) mechanism for electrochemical production of hydrogen peroxide is investigated for an Au-Pd catalyst with 25 at% palladium. The sample was prepared by chemical reduction of a precursor solution on a carbon-based substrate. Rotating ring-disk electrode (RRDE) measurements were performed for electrochemical characterization exhibiting H2O2 current efficiencies of about 75-78% at low disk potentials. The focus of this article is on the mathematical evaluation of the experimental data using the analytical method from Damjanovic et al. [J. Chem. Phys. 45, 4057 (1966)] and a powerful numerical data fitting technique based on RRDE simulations in MATLAB, which is capable of investigating reaction mechanisms with different structures. The latter method is presented in detail and the electro-kinetic parameters of the ORR mechanism at the considered catalyst resulting from both methods are compared quantitatively. It is found that the oxygen reductions via the 2-electron and the 4-electron pathways occur in parallel, whereas the hydrogen peroxide reduction pathway is found apparently inactive.