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The electrochemical behavior of Prussian Blue (PB) deposited onto a transparent electrode is specially attractive to students beginning their laboratory experiences in Electrochemistry. The color changes observed during the cyclic voltammetry facilitate the qualitative introduction of such important electrochemical topics as the dependence of composition (ratio of oxidized to reduced state) on the electrode with the applied potential (Nernst equation). The experiment also introduces the student to the measurement of electrochemical magnitudes (peak potential, peak current, half-peak width) for the voltammogram. The knowledge of an electrochemical technique as important as the cyclic voltametry is also of interest to students, due to its application in several fields such as corrosion, electroanalysis, heterogeneous catalysis, characterization of materials, or electrochemical kinetics.
The electrogeneration of Prussian Blue, potentiostatically or galvanostatically, makes possible the correlation between the charge transferred during the electrogeneration and the amount deposited on the electrode (Faraday's law). The aims of this laboratory experience are:
1) to deposit Prussian Blue films onto transparent ITO (indium-tin oxide) electrodes galvanostatically;
2) to initiate students into the measurement of electrochemical magnitudes from voltammograms, taking as example the voltammetric waves of PB on ITO and their variation with the thickness; and
3) to observe the electrochromic effect.
The experiment is easy to set up and the result can be interpreted by students with no difficulty.
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