A comparative study of the adsorption and oxidation of L-alanine and L-serine on Au(1 0 0), Au(1 1 1) and gold thin film electrodes in acid media

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Title: A comparative study of the adsorption and oxidation of L-alanine and L-serine on Au(1 0 0), Au(1 1 1) and gold thin film electrodes in acid media
Authors: Sandoval, Andrea P. | Orts Mateo, José M. | Rodes García, Antonio | Feliu, Juan M.
Research Group/s: Grupo de Espectroelectroquímica y Modelización (GEM) | Electroquímica de Superficies
Center, Department or Service: Universidad de Alicante. Departamento de Química Física | Universidad de Alicante. Instituto Universitario de Electroquímica
Keywords: l-Alanine | l-Serine | Gold electrodes | Infrared spectroscopy | DFT
Knowledge Area: Química Física
Issue Date: 1-Feb-2013
Publisher: Elsevier
Citation: Electrochimica Acta. 2013, 89: 72-83. doi:10.1016/j.electacta.2012.10.052
Abstract: The adsorption and oxidation of l-alanine and l-serine at Au(1 1 1) and Au(1 0 0) single crystal and evaporated thin-film electrodes with preferential (1 1 1) orientation was studied in perchloric acid solutions. For this purpose, cyclic voltammetry experiments were combined with external reflection infrared spectroscopy (gold single crystals) and surface-enhanced infrared reflection–absorption spectroscopy under attenuated total reflection conditions (ATR-SEIRAS) (gold thin films). In addition, theoretical harmonic vibrational frequencies, obtained from B3LYP/LANL2DZ, 6-31+G(d) calculations for the zwitterionic species adsorbed on Au clusters with (1 1 1) orientation, were used to interpret the experimental spectra. The optimized geometry obtained from DFT calculations for the corresponding zwitterion plus a water molecule, under the application of an external electric field of 0.01 a.u. corresponds to a bidentate asymmetrical bridge adsorption configuration. The absence of an adsorbate band for the asymmetric OCO stretching in the experimental infrared spectra confirms the bidentate bonding of the adsorbed zwitterion through the oxygen atoms of the carboxylate group irrespective of the crystallographic orientation of the electrode surface, the adsorbate coverage and the electrode potential. In addition to typical interfacial water bands associated to perchlorate anions, which are co-adsorbed in order to compensate the positive charge of the ammonium group, the ATR-SEIRA spectra also show bands around 2950 cm−1 that can be related to the formation of hydrogen bonds between interfacial water and the ammonium group of the adsorbed zwitterion. The voltammetric experiments have shown that, as in the case of platinum electrodes, l-serine oxidizes at lower potentials than l-alanine. Under these conditions, the in situ infrared experiments show the formation of carbon dioxide and adsorbed cyanide as oxidation products of l-serine. In the case of l-alanine, only carbon dioxide was detected.
Sponsor: Financial support from Ministerio de Ciencia e Innovación (projects CTQ2010-16271 and CTQ2009-13142, Fondos FEDER) and Generalitat Valenciana (Prometeo/2009/045, ACOMP/2011/200 and ACOMP/2012/137, Fondos FEDER) is gratefully acknowledged. A.P.S is endebted to the Generalitat Valenciana for the award of a Santiago Grisolía grant.
URI: http://hdl.handle.net/10045/39115
ISSN: 0013-4686 (Print) | 1873-3859 (Online)
DOI: 10.1016/j.electacta.2012.10.052
Language: eng
Type: info:eu-repo/semantics/article
Peer Review: si
Publisher version: http://dx.doi.org/10.1016/j.electacta.2012.10.052
Appears in Collections:INV - EQSUP - Artículos de Revistas
INV - GEM - Artículos de Revistas

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