Formic Acid Electrooxidation on Noble-Metal Electrodes: Role and Mechanistic Implications of pH, Surface Structure, and Anion Adsorption

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Title: Formic Acid Electrooxidation on Noble-Metal Electrodes: Role and Mechanistic Implications of pH, Surface Structure, and Anion Adsorption
Authors: Brimaud, Sylvain | Solla-Gullón, José | Weber, Isabella | Feliu, Juan M. | Behm, R. Jürgen
Research Group/s: Electroquímica de Superficies | Electroquímica Aplicada y Electrocatálisis
Center, Department or Service: Universidad de Alicante. Departamento de Química Física | Universidad de Alicante. Instituto Universitario de Electroquímica
Keywords: Formic acid oxidation | Gold | Ph effect | Platinum | Reaction mechanism
Knowledge Area: Química Física
Issue Date: 11-Jun-2014
Publisher: Wiley-VCH Verlag GmbH & Co. KGaA
Citation: ChemElectroChem. 2014, 1(6): 1075-1083. doi:10.1002/celc.201400011
Abstract: The influence of the electrolyte pH on formic acid (HCOOH) electrooxidation is investigated on both polycrystalline Pt and Au electrodes and on single-crystalline Au electrodes in perchloric and sulfuric acid-based electrolytes. On Au electrodes, the potentiodynamic oxidation currents are found to depend, in a nonlinear way, on the electrolyte pH in a bell-shaped relation, with a maximum of the catalytic activity at the pKa of HCOOH. On polycrystalline Pt electrodes, this feature is not observed; the catalytic activity increases steadily with increasing pH up to a pH value of approximately 5, which is followed by a plateau until pH 10, in contrast with recent observations [J. Joo, T. Uchida, A. Cuesta, M. T. M. Koper, M. Osawa, J. Amer. Chem. Soc.­ 2013, 135, 9991–9994]. In addition, for Au surfaces, the reaction is only weakly influenced by the electrode surface structure, whereas for Pt, structural effects are known to be considerable. Anion effects, in contrast, are much stronger for the reaction on Au electrodes compared to Pt electrodes. Also, it is shown that Pt-group-metal-free Au electrodes do not oxidize molecular hydrogen under reaction conditions. The results are discussed in relation to findings in previous mechanistic studies. Most importantly, the activity on both electrodes is closely correlated with the concentration of HCOO−, and for Au correlates with both HCOO− and HCOOH concentrations. Based on these results, a number of mechanistic proposals put forward in earlier studies must be discarded, and examples for mechanisms compatible with these results are discussed.
Sponsor: This work was supported by the Ministerio de Economía y Competitividad (MINECO) (Spain) (project EUI2009–04176) and by the Deutsche Forschungsgemeinschaft (BE 1201/17–1).
ISSN: 2196-0216
DOI: 10.1002/celc.201400011
Language: eng
Type: info:eu-repo/semantics/article
Rights: © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Peer Review: si
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