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Evaluation of the electrocatalytic properties of pure and modified manganese oxides for the oxygen reduction reaction in alkaline solutions


The combination of low cost with an excellent electrocatalytic activity of manganese oxides for the oxygen reduction reaction in alkaline solutions is the main reason for the huge amount of studies on this subject aimed at elucidating the reaction mechanism on such catalysts, a pathway for the improvement of the catalytic properties of these materials. Based on such studies, a general reaction mechanism is proposed where the electron transfer from the catalyst surface, MnOOH, to the oxygen molecule proceeds by a mediation process generating water or hydrogen peroxide as final products. It is also well established that the electrocatalic activity of these materials is highly dependent on the initial crystallographic structure of the manganese dioxide used as the catalyst.Meanwhile, MnOOH is effectively the catalyst of this reaction and for this reason the influence of the manganese dioxide crystallographic structure on the catalytic performance is relative. Thus, it is more convenient to associate the catalytic activity with the oxyhydroxy structure instead of the manganese dioxide structure, an aspect which demands more scientific investigation. Other important aspects which have not been widely studied are the manganese oxide structure stabilization avoiding the production of the non-electroactive hausmannite oxide (Mn3O4) and possible strategies for the improvement of the performance towards ORR. Such strategies may include the addition of modifiers. The effect of these modifiers on activity and stability of the catalysts towards ORR, as well as the study of MnOOH structure produced from different MnO2 crystallographic structures are the main objectives of this project. (AU)

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(References retrieved automatically from Web of Science and SciELO through information on FAPESP grants and their corresponding numbers as mentioned in the publications by the authors)
VALIM, R. B.; SANTOS, M. C.; LANZA, M. R. V.; MACHADO, S. A. S.; LIMA, F. H. B.; CALEGARO, M. L.. Oxygen reduction reaction catalyzed by epsilon-MnO2: Influence of the crystalline structure on the reaction mechanism. Electrochimica Acta, v. 85, p. 423-431, . (11/02158-5)
VILAS BOAS, N.; BATISTA SOUZA JUNIOR, J.; CARLOS VARANDA, L.; ANTONIO SPINOLA MACHADO, S.; LUIZ CALEGARO, M.. Bismuth and cerium doped cryptomelane-type manganese dioxide nanorods as bifunctional catalysts for rechargeable alkaline metal-air batteries. APPLIED CATALYSIS B-ENVIRONMENTAL, v. 258, . (11/02158-5)

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