Identification of electroactive sites in Prussian Yellow films

Abstract

Abstract.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

The role of NH 4 + cations on the electrochemistry of Prussian Blue studied by electrochemical, mass, and color impedance spectroscopy

“…On the contrary, the cathodic peak shows values around 0.5 mA cm 2 and 180 mV. The electrochemical reduction of PB to the ES under these experimental conditions can be described by the following simplified reaction scheme: increase of absorbance takes place during the oxidation to ES [14,37]. As it can be seen, the maximum positive and negative changes of absorbance close to 690 nm agree with the voltammetric peaks.…”

“…Initially, the structure of freshly prepared PB films has been described as a K + free structure and therefore, a direct PB oxidation to form PY films results in the structure breakdown of the films [11]. However, if freshly prepared PB films were previously cycled around the PB⇄ ES system by cyclic voltammetry, K + cations occupy key position in the inner structure of PB and then, the oxidation to the PY form can take place without destruction of the films [5,7,[12][13][14]. Once PB films are stabilized in acid KCl solutions by cyclic voltammetry, the voltammetric peaks of the PB⇄ ES system appear to be stable after hundred and even thousands of cycles [15].…”

“…Once PB films are stabilized in acid KCl solutions by cyclic voltammetry, the voltammetric peaks of the PB⇄ ES system appear to be stable after hundred and even thousands of cycles [15]. In recent papers [13,14], the stable PB structure has been described as 3 . The PB⇄ ES system has been studied by mass impedance spectroscopy and the role of potassium cations has been elucidated [9,16,17]:…”

“…As a consequence, PB⇄ PY system shows a low electrochemical response. Recently, a possible reaction scheme for the PB⇄ PY system has been proposed involving both cations and anions [14]:…”

Improving Electrochromic Cycle Life of Prussian Blue by Acid Addition to the Electrolyte

“…In addition, the peak current density of PB/PW is higher than that of PY/PB in the testing. On the one hand, the PB structure only contains 3Fe 2+ sites (involved in PB/PY) by each 4Fe 3+ (involved in PB/PW), so not all oxidized Fe 2+ may be balanced by cations [27]. On the other hand, the CV curves were measured in the potential cycled from −0.2 to 0.8 V. The redox reaction of PB/PY is not sufficient in this range.…”