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Effect of pH and temperature on carbon-supported manganese oxide oxygen reduction electrocatalysts

Lookup NU author(s): Dr Ivan Roche, Emeritus Professor Keith Scott


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Manganese oxides nanoparticles were chemically deposited on a high area (ca. 300 m(2) g(-1)) carbon black substrate to act as electrocatalysts for oxygen reduction. The morphology and chemistry of the carbon-supported MnOx nanoparticles was characterised by Transmission Electron Microscopy). X-ray Diffraction, and chemical analysis. The oxygen reduction reaction (ORR) catalytic activity was studied in the 7-10 pH range using a rotating disk electrode (RDE). High activity towards oxygen reduction and very good stability in neutral and slightly basic solution were obtained. At low current densities, at 25 degrees C, MnOx/C displayed a reaction order with respect to OH- ions of - 0.5 and Tafel slopes of - 0 153 and - 0.167 V dec(-1) at pH 7 and 10 respectively; showing that the ORR mechanism on MnOx/C is unchanged in the 7-10 pH range. From the data, we propose that the first electrochemical step of the 4-electron ORR mechanism, in the 7-10 pH range. is the quasi equilibrium proton insertion process in MnO2 yielding MnOOH (insoluble in neutral or slightly basic solution) The ORR activity of the MnOx/C materials increased with increasing temperatures from 5 to 40 degrees C. The 2-electron pathway of oxygen reduction, yielding hydrogen peroxides as intermediates, may however be favoured over the 4-electron O-2 reduction at higher temperatures. (C) 2009 Elsevier B.V. All rights reserved.

Publication metadata

Author(s): Roche I, Scott K

Publication type: Article

Publication status: Published

Journal: Journal of Electroanalytical Chemistry

Year: 2010

Volume: 638

Issue: 2

Pages: 280-286

ISSN (print): 1572-6657

ISSN (electronic): 1873-2569

Publisher: Elsevier SA


DOI: 10.1016/j.jelechem.2009.10.030


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Funder referenceFunder name
MTKD-CT-2004-517215European Union