Development of a Spectroelectrochemistry Assembly (SNIFTIRS) Based on a Commercial Spectrophotometer. Test with the Ferrocyanide/Ferricyanide Redox Couple

Abstract

The development of a spectroelectrochemistry assembly for substractively normalized interfacial FTIR spectroscopy (SNIFTIRS), based on the commercial spectrophotometer Unicam Research Series 1, is presented. The sample chamber has been modified to achieve a vertical orientation of the cell and a special support was constructed for the same purpose. The original path of the IR radiation has been modified by using two black anodized aluminium 30° wedges, both supporting a parabolic mirror. This allows the radiation to reach the working electrode forming 60° with the vertical. The cell holder allows vertical and horizontal displacement of the cell. The electrochemical cell was made of Pyrex glass and permits an easy manipulation even in the sample chamber of the spectrometer, making it unnecessary to open this chamber in the manipulation of either the solution or the electrodes. The working electrode was a polished polycrystalline gold electrode. A computer‐based potentiostat was also constructed. To control the system, a set of 16‐bits Visual‐Basic programs was developed allowing the synchronization between the spectra acquisition and the application of potentials. A variety of sequences of operation can be selected. The system was checked with the ferrocyanide/ferricyanide redox couple, concluding that the system here described is useful to make SNIFTIRS experiments, being versatile enough to design new operational sequences that help improve the knowledge of the electrode processes.

Spectroelectrochemical Examination of the Ferro-Ferricyanide Redox Reaction: Impacts of Electrode Thickness and Applied Potential

“…However, the resultant spectra obtained from the ferri-ferrocyanide system provided more peaks than expected compared to previous spectrochemical studies. [39][40][41][42][43] So, the focus of our study shifted to examine the cause of these inconsistencies to better understand this benchmark reaction. Though the ferri-ferrocyanide reaction remains one of the moststudied redox reactions, available spectrochemical data [41][42][43][44][45] inconsistently detects reaction intermediates to confirm its inner sphere pathway despite the overwhelming electrochemical evidence of it being inner sphere.…”

“…46 To our knowledge, all spectroelectrochemical studies of the ferro-ferricyanide reaction on platinum were carried out using the IRRAS method. [39][40][41][42][43] The only ATR-based study found for this system was spectrochemical with no applied potentials. 47 Some IRRAS-based SEC studies detected possible intermediates for the ferri-ferrocyanide reaction.…”

UV‐Visible Spectroelectrochemical Detection of Side‐Reactions in the Hexacyanoferrate(III)/(II) Electrode Process

“…Linear regression from points in Figure 3 estimated by applying Equation 3. Working conditions: K 4 Fe(CN ) 6 1.5 Â 10 À3 M; KNO 3 0.8 M; v 5 Â 10 À4 V s À1 ;` 30 mm; l 420 nm; 100 experimental points in each replicate.…”

“…From the resulting linear regression, a formal potential E 0' Nernst;810 0.200 AE 0.004 V and a number of electrons of 0.52AE 0.03 were obtained. The value of the formal potential and the number of electrons corresponds to the generation of one molecule of soluble Prussian Blue, KFe III Fe II (CN) 6 , from two molecules of starting hexacyanoferrate(II).…”

“…3D plot absorbance/potential (time)/wavelength for K4 Fe(CN)6 8 Â 10 À3 M in KNO 3 0.8 M. v 5 Â 10 À3 V s À1 ;` 80 mm.a) Absorption spectrum from 350 to 500 nm. b) Absorption spectrum from 550 to 850 nm.…”