adjusted to the required value. A few micrometer thick electrolyte layer is
sandwiched between the optical window and a flat IR mirror [13, 20]. The cell is
placed on a rotating platform (k) allowing the setting of the required angle of
incidence of the incoming IR radiation. This configuration of the cell is suitable
for IRRAS with electrochemical control [13, 14, 20, 21].
The IR absorption spectra from molecules adsorbed on the electrode surface will
be obtained when parameters corresponding to the maximum of MSEFS can be
applied in in situ PM IRRAS experiments. These spectra are used to perform
potential-dependent qualitative (composition) and quantitative (orientation) analysis
of molecules in films adsorbed on the electrode surface [3, 5, 26, 28]. Before any in
situ spectroelectrochemical experiment will be performed, the thickness of the
electrolyte layer between the optical window and the IR mirror (electrode) has to
be determined.
The determination of the thickness of the electrolyte layer was developed by Li
[29]. The thickness of the electrolyte layer is determined by measuring the reflectivity spectra from the empty and next from filled with the electrolyte solution
spectroelectrochemical cell. The measured reflectivity spectrum is compared with
reflectivity spectra computed for a stratified system, representing the
spectroelectrochemical cell. In in situ experiments the stratified system composed
of CaF 2 optical window, D 2 O solvent and Au mirror and electrode is often used. For
this experimental condition the angle of incidence is set to φ i ¼ 53
, ensuring the
maximum value of MSEFS (Table 2.1). Figure 2.7 shows, calculated from Fresnel
equations, reflectivity spectra for CaF 2 |D 2 O|Au stratified system at φ i ¼ 53
for
4000
3000
2000
0.0
0.2
0.4
0.6
0.8
1.0
Reflectivity
Wavenumber / cm
-1
1 µm
2 µm
3 µm
4 µm
5 µm
6 µm
7 µm
8 µm
9 µm
10 µm
Reflectivity cell
5.2 µm
5.4 µm
5.6 µm
Fig. 2.7 Reflectivity vs wavenumber plots calculated using Fresnel equations for stratified system
composed of CaF 2 |D 2 O|Au for electrolyte thicknesses varying from 1 to 10 μm and measured
reflectivity in the corresponding spectroelectrochemical cell (red line)
2.2 Application of IRRAS to the Electrochemical Interface
19
sandwiched between the optical window and a flat IR mirror [13, 20]. The cell is
placed on a rotating platform (k) allowing the setting of the required angle of
incidence of the incoming IR radiation. This configuration of the cell is suitable
for IRRAS with electrochemical control [13, 14, 20, 21].
The IR absorption spectra from molecules adsorbed on the electrode surface will
be obtained when parameters corresponding to the maximum of MSEFS can be
applied in in situ PM IRRAS experiments. These spectra are used to perform
potential-dependent qualitative (composition) and quantitative (orientation) analysis
of molecules in films adsorbed on the electrode surface [3, 5, 26, 28]. Before any in
situ spectroelectrochemical experiment will be performed, the thickness of the
electrolyte layer between the optical window and the IR mirror (electrode) has to
be determined.
The determination of the thickness of the electrolyte layer was developed by Li
[29]. The thickness of the electrolyte layer is determined by measuring the reflectivity spectra from the empty and next from filled with the electrolyte solution
spectroelectrochemical cell. The measured reflectivity spectrum is compared with
reflectivity spectra computed for a stratified system, representing the
spectroelectrochemical cell. In in situ experiments the stratified system composed
of CaF 2 optical window, D 2 O solvent and Au mirror and electrode is often used. For
this experimental condition the angle of incidence is set to φ i ¼ 53
, ensuring the
maximum value of MSEFS (Table 2.1). Figure 2.7 shows, calculated from Fresnel
equations, reflectivity spectra for CaF 2 |D 2 O|Au stratified system at φ i ¼ 53
for
4000
3000
2000
0.0
0.2
0.4
0.6
0.8
1.0
Reflectivity
Wavenumber / cm
-1
1 µm
2 µm
3 µm
4 µm
5 µm
6 µm
7 µm
8 µm
9 µm
10 µm
Reflectivity cell
5.2 µm
5.4 µm
5.6 µm
Fig. 2.7 Reflectivity vs wavenumber plots calculated using Fresnel equations for stratified system
composed of CaF 2 |D 2 O|Au for electrolyte thicknesses varying from 1 to 10 μm and measured
reflectivity in the corresponding spectroelectrochemical cell (red line)
2.2 Application of IRRAS to the Electrochemical Interface
19