Modulation of electrochemical hydrogen evolution rate by araliphatic thiol monolayers on gold

[Display omitted] ► Araliphatic SAM with extraordinary electrochemical stability. ► Enhancement of the hydrogen evolution after reductive SAM desorption. ► In situ real time sum frequency generation (SFG) spectroscopy. ► Relation between reductive SAM desorption and hydrogen evolution. Electroreduct...

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Bibliographic Details
Published in:Electrochimica acta 2013-02, Vol.90, p.17-26
Main Authors: Muglali, Mutlu I., Erbe, Andreas, Chen, Ying, Barth, Christoph, Koelsch, Patrick, Rohwerder, Michael
Format: Article
Language:English
Subjects:
Acoustic microscopes
Catalysis
Desorption
Electrodes
Gold
Hydrogen evolution
Modulation
Monolayers
Reductive SAM desorption
Spectroscopic ellipsometry
Spectroscopy
Sum frequency generation spectroscopy
Thiols
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Summary:[Display omitted] ► Araliphatic SAM with extraordinary electrochemical stability. ► Enhancement of the hydrogen evolution after reductive SAM desorption. ► In situ real time sum frequency generation (SFG) spectroscopy. ► Relation between reductive SAM desorption and hydrogen evolution. Electroreductive desorption of a highly ordered self-assembled monolayer (SAM) formed by the araliphatic thiol (4-(4-(4-pyridyl)phenyl)phenyl)methanethiol leads to a concurrent rapid hydrogen evolution reaction (HER). The desorption process and resulting interfacial structure were investigated by voltammetric techniques, in situ spectroscopic ellipsometry, and in situ vibrational sum-frequency-generation (SFG) spectroscopy. Voltammetric experiments on SAM-modified electrodes exhibit extraordinarily high peak currents, which differ between Au(111) and polycrystalline Au substrates. Association of reductive desorption with HER is shown to be the origin of the observed excess cathodic charges. The studied SAM preserves its two-dimensional order near Au surface throughout a fast voltammetric scan even when the vertex potential is set several hundred millivolt beyond the desorption potential. A model is developed for the explanation of the observed rapid HER involving ordering and pre-orientation of water present in the nanometer-sized reaction volume between desorbed SAM and the Au electrode, by the structurally extremely stable monolayer, leading to the observed catalysis of the HER.
ISSN:0013-4686
1873-3859
DOI:10.1016/j.electacta.2012.11.116