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A quantum mechanical theory is employed to describe heterogeneous ferrocene (Fc)/ferrocenium (Fc + ) electron transfer across Au(111)/[bmim][BF 4 ] and Au(111)/acetonitrile interfaces. Classical molecular dynamics simulations were performed to calculate the potential of mean force for Fc and Fc + and to estimate the solvent reorganization energy. The structure of the reaction layer and the solvent shell of Fc and Fc + as derived from molecular dynamics are thoroughly investigated. The molecular structure of ferrocene and ferrocenium species, as well as the reactant−electrode orbital overlap are addressed on the basis of a quantum chemical approach. The experimental dielectric spectra for both types of solvents are used for quantum corrections of the outer-sphere reorganization energy as well as for estimations of the effective frequency factor in the limit of strong and weak electronic coupling. The dependence of the electronic transmission coefficient on the electrode−reactant distance is calculated for several orientations of the ferrocenium cation relative to the electrode surface which was represented by a cluster. Emphasis is put on the molecular nature of the elementary act and its qualitatively interesting features for both interfaces. The electron transfer rate constants are calculated and discussed in the viewpoint of available experimental data.

The mechanism of the oxygen reduction reaction (ORR) on LaCoO(3) and La(0.8)Sr(0.2)MnO(3) perovskite oxides is studied in 1 M NaOH by using the rotating ring disc electrode (RRDE) method. By combining experimental studies with kinetic modeling, it was demonstrated that on perovskite, as well as on perovskite/carbon electrodes, the ORR follows a series pathway through the intermediate formation of hydrogen peroxide. The escape of this intermediate from the electrode strongly depends on: 1) The loading of perovskite; high loadings lead to an overall 4 e(-) oxygen reduction due to efficient hydrogen peroxide re-adsorption on the active sites and its further reduction. 2) The addition of carbon to the catalytic layer, which affects both the utilization of the perovskite surface and the production of hydrogen peroxide. 3) The type of oxide; La(0.8)Sr(0.2)MnO(3) displays higher (compared to LaCoO(3)) activity in the reduction of oxygen to hydrogen peroxide and in the reduction/oxidation of the latter.

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Hydrogen peroxide has been identified as a stable intermediate of the electrochemical oxygen reduction reaction on various electrodes including metal, metal oxide and carbon materials. In this article we study the hydrogen peroxide oxidation and reduction reactions in alkaline medium using a rotating disc electrode (RDE) method on oxides of the perovskite family (LaCoO3, LaMnO3 and La0.8Sr0.2MnO3) which are considered as promising electrocatalytic materials for the cathode of liquid and solid alkaline fuel cells. The experimental findings, such as the higher activity of Mn-compared to that of Co-perovskites, the shape of RDE curves, and the influence of the H2O2 concentration, are rationalized with the help of a microkinetic model.

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