Theoretical
Study on Electroreduction of <i>p</i>‑Nitrothiophenol
on Silver and Gold Electrode Surfaces
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Abstract
The electroreduction
of <i>p</i>-nitrothiophenol (PNTP)
on gold and silver electrodes has been investigated by means of density
functional theory. A combination of thermodynamic calculations and
surface Raman/IR spectral simulations has allowed us to reveal the
reaction mechanism and reaction products of electroreduction of PNTP
on metal electrodes. First, thermodynamic calculations were carried
out to calculate the standard electrode potentials of PNTP and its
possible intermediates. The potential energy curves of PNTP reduction
as a function of the applied potential are obtained on the basis of
the calculated standard electrode potentials of the elementary electrochemical
reactions. Second, surface vibrational spectral simulation was performed
to provide theoretical assignments of reaction products for the in
situ Raman/IR experimental studies of electroreduction of PNTP. The
most interesting finding in the reaction product identified by IR
spectroscopy is PATP; however, Raman spectroscopy shows that the main
product is <i>p</i>,<i>p</i>′-dimercaptoazobenzene
(DMAB). The difference between IR and Raman measurements arises from
the fact that the incident laser used in Raman measurement can induce
the formation of DMAB by photoreduction of PNTP or photo-oxidation
of PATP. Finally, the reaction mechanism of electroreduction of PNTP
was compared with its photoreduction mechanism
