Identification of electroactive sites in Prussian Yellow films

Prussian Blue films were electrogenerated on the surface of the transparent ITO electrodes. The electrochemical oxidation to the Prussian Yellow form was investigated by means of in situ voltammetry and vis-NIR spectroscopic techniques. Changes of the whole spectra between 400 and 950 nm were analyzed and three characteristic wavelengths were selected to in situ follow the electrochemical changes of the films. Voltammetric peaks and absorbance derivative curves at these three wavelengths were deconvoluted and were interpreted such as the overlapping of different electrochemical processes. The correlation between these overlapped processes has allowed proposing three different electrochemical processes for the interpretation of the whole electrochemical response. One of these processes corresponds to the oxidation of Fe-low spin(2+) - CN - Fe-high spin(3+) units where the electrical charge is balanced by the exchange of low neighbor potassium cations. The second one is associated to the oxidation of Fe-low spin(2+) - CN - Fe-high spin(3+) trapped sites and the third one also to the oxidation of Fe-low spin(2+) - CN - Fe-high spin(3+) units but in this last case, the absence of neighbor potassium cations causes that the electrical charge balance takes place by the exchange of some anions such as the chloride. These processes have been identified on the basis of previous results and on the interesting information provided by the coupling voltammetry and absorbance derivative curves at these characteristic wavelengths. (C) 2013 Elsevier Ltd. All rights reserved.