Acetonitrile Adsorption on Pt Single-Crystal Electrodes and Its Effect on Oxygen Reduction Reaction in Acidic and Alkaline Aqueous Solutions

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Title: Acetonitrile Adsorption on Pt Single-Crystal Electrodes and Its Effect on Oxygen Reduction Reaction in Acidic and Alkaline Aqueous Solutions
Authors: Briega-Martos, Valentín | Figueiredo, Marta C. | Orts Mateo, José M. | Rodes, Antonio | Koper, Marc T.M. | Herrero, Enrique | Feliu, Juan M.
Research Group/s: Electroquímica de Superficies | Grupo de Espectroelectroquímica y Modelización (GEM)
Center, Department or Service: Universidad de Alicante. Departamento de Química Física | Universidad de Alicante. Instituto Universitario de Electroquímica
Keywords: Acetonitrile adsorption | Pt single-crystal electrodes | Oxygen reduction reaction | Acidic and alkaline aqueous solutions
Knowledge Area: Química Física
Issue Date: 1-Jan-2019
Publisher: American Chemical Society
Citation: The Journal of Physical Chemistry C. 2019, 123(4): 2300-2313. doi:10.1021/acs.jpcc.8b10690
Abstract: The adsorption and reactivity of acetonitrile (CH3CN) have been studied on Pt(111) and Pt(100) electrodes in 0.1 M HClO4 and 0.1 M NaOH solutions with CH3CN concentrations ranging from 10–3 to 1 M. Cyclic voltammetry results show that these processes are structure sensitive and that the hydrogen adsorption/desorption region is partially blocked on Pt(111) in acidic solutions while the inhibition is almost complete on Pt(100) in both acidic and alkaline media. However, for Pt(111), hydrogen adsorption is practically unaltered in the 0.1 M NaOH electrolyte. In situ infrared measurements and density functional theory calculations suggest that rehybridized adsorbed acetonitrile reacts with adsorbed hydroxyl species at high potentials forming a hydroxylated adsorbed species. The latter is bonded to the Pt surface by electrodonation and can be reduced to an intermediate in which the double C–N bond is tilted with respect to the metal surface. Lastly, oxygen reduction reaction (ORR) has been investigated by using the hanging meniscus rotating disk electrode configuration. Limiting current densities decrease more drastically for Pt(100) than for Pt(111) as acetonitrile concentration is increased because of the higher acetonitrile coverage for the former one. The onset potential for ORR is shifted to less positive values in acidic media because of a blocking effect of acetonitrile. In alkaline media, the onset potential for Pt(111) is slightly more positive for low concentrations of acetonitrile because oxide formation, which hinders oxygen reduction for the more positive potentials, is inhibited due to the presence of adsorbed acetonitrile species at low coverages.
Sponsor: This work has been financially supported by MCINN-FEDER (Spain) through project CTQ2016-76221-P. V.B.-M. thankfully acknowledges MINECO, the award of a predoctoral grant (BES-2014-068176, project CTQ2013-44803-P) and a student stay grant (EEBB-I-16-11656).
ISSN: 1932-7447 (Print) | 1932-7455 (Online)
DOI: 10.1021/acs.jpcc.8b10690
Language: eng
Type: info:eu-repo/semantics/article
Rights: © 2019 American Chemical Society
Peer Review: si
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Appears in Collections:INV - GEM - Artículos de Revistas
INV - EQSUP - Artículos de Revistas

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