Chapter 4
In Situ PM IRRAS Studies of Redox-Active
Molecular Films Adsorbed on Electrode
Surfaces
Determination of potential-dependent changes in the composition and structure of
redox-active molecules involved in electrochemical reactions is one of the most
important research objects in electrochemistry. Reduction and oxidation reactions
take place on the electrode surface indicating that a redox-active substrate, at least
during the redox reaction, is in direct contact with the electrode surface. As described
in Chap. 3, in situ PM IRRAS is an excellent structure analyzing method for the
studies of potential-dependent changes in redox-inactive molecular films adsorbed
on metallic electrode surfaces. Below, the applicability of PM IRRAS for studies of
redox-active species present on electrode surfaces is described.
4.1 In Situ PM IRRAS of Redox-Active Species Adsorbed
on Metallic Electrode Surfaces
Golden was the first who introduced PM IRRAS to the electrochemical experiments
[1]. In this pioneering study, the adsorption and oxidation of carbon monoxide on a
platinum electrode in the acidic solution was studied. The adsorption of CO on the
platinum surface gives a strong ν(CO) mode. Figure 4.1 shows the PM IRRA spectra
in the ν(CO) mode region at potentials corresponding to the adsorption and oxidation
of CO on the Pt electrode. The wavenumber of the absorption maximum and
intensity of the ν(CO) mode depend on the potential applied to the Pt electrode. In
the potential range 0.0 < E < 0.5 versus NHE (NHE: normal hydrogen electrode) the
ν(CO) mode is strong. It corresponds to CO adsorbed on the Pt electrode surface. A
further positive potential shift leads to a fast decrease in the intensity of the
ν(CO) mode. At E > 0.7 V the intensity of the ν(CO) mode decreases to zero, due
to the oxidation reaction of CO to CO 2 .
© Springer Nature Switzerland AG 2020
I. Brand, Application of Polarization Modulation Infrared Reflection Absorption
Spectroscopy in Electrochemistry, Monographs in Electrochemistry,
https://doi.org/10.1007/978-3-030-42164-9_4
97
In Situ PM IRRAS Studies of Redox-Active
Molecular Films Adsorbed on Electrode
Surfaces
Determination of potential-dependent changes in the composition and structure of
redox-active molecules involved in electrochemical reactions is one of the most
important research objects in electrochemistry. Reduction and oxidation reactions
take place on the electrode surface indicating that a redox-active substrate, at least
during the redox reaction, is in direct contact with the electrode surface. As described
in Chap. 3, in situ PM IRRAS is an excellent structure analyzing method for the
studies of potential-dependent changes in redox-inactive molecular films adsorbed
on metallic electrode surfaces. Below, the applicability of PM IRRAS for studies of
redox-active species present on electrode surfaces is described.
4.1 In Situ PM IRRAS of Redox-Active Species Adsorbed
on Metallic Electrode Surfaces
Golden was the first who introduced PM IRRAS to the electrochemical experiments
[1]. In this pioneering study, the adsorption and oxidation of carbon monoxide on a
platinum electrode in the acidic solution was studied. The adsorption of CO on the
platinum surface gives a strong ν(CO) mode. Figure 4.1 shows the PM IRRA spectra
in the ν(CO) mode region at potentials corresponding to the adsorption and oxidation
of CO on the Pt electrode. The wavenumber of the absorption maximum and
intensity of the ν(CO) mode depend on the potential applied to the Pt electrode. In
the potential range 0.0 < E < 0.5 versus NHE (NHE: normal hydrogen electrode) the
ν(CO) mode is strong. It corresponds to CO adsorbed on the Pt electrode surface. A
further positive potential shift leads to a fast decrease in the intensity of the
ν(CO) mode. At E > 0.7 V the intensity of the ν(CO) mode decreases to zero, due
to the oxidation reaction of CO to CO 2 .
© Springer Nature Switzerland AG 2020
I. Brand, Application of Polarization Modulation Infrared Reflection Absorption
Spectroscopy in Electrochemistry, Monographs in Electrochemistry,
https://doi.org/10.1007/978-3-030-42164-9_4
97