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

Abstract

The role of the ammonium cation on the reversible electrochemistry of Prussian Blue thin films was analyzed through in situ combination of three different impedance techniques. Electrochemical impedance spectroscopy provides information on the electron transfer. Mass impedance spectroscopy allows the exchange of free water, ammonium and proton ions to be elucidated. Color impedance spectroscopy provides the kinetics of electrochromic changes of Prussian Blue structure (main backbone structure, ferrocyanide vacancies and trapped structures). The simultaneous measurement of the three impedances gives detailed information on the mechanism of the whole process, specifically one faster and two slower, which have been identified during the electrochemical reactions of Prussian Blue films in NH 4 Cl acidic solutions.

Charge coloration dynamics of electrochromic amorphous tungsten oxide studied by simultaneous electrochemical and color impedance measurements

“…This is usually referred to as color impedance spectroscopy 8 (CIS) and was first introduced for inspecting the kinetics of adsorption processes at the electrolyte-electrode interface. 9 Thereafter, it has been employed in the study of diverse systems, such as polyaniline, [10][11][12] nickel oxide, 13 polypyrrole, 8,[14][15][16] tungsten oxide, [17][18][19][20][21][22][23][24] hemin and nile blue A, 25 cytochrome c proteins, [26][27][28][29][30] Alexa 488 fluorochromes, 31 Prussian blue, [32][33][34][35] poly (3,4-ethylenedioxythiophene) and poly(3,4-ethylenedioxythiophene methanol), 36 niobium oxide, 22 pyridine-capped CdSe nanocrystals, 37 and graphite. 38 Here, CIS is circumscribed to optical impedance measurements-performed over a range of modulating frequenciesthat probe the dispersion of the relevant complex impedance quantities.…”

Kinetics of Surface Chemical Reactions from a Digital Video

“…Mostly, a physical magnitude related with the chemical reaction advance is measured to be converted into number of mols reacting or produced. Mass changes due to the adsorption/desorption of different substances, − concentration of different chemicals near the surface, , reflectance or absorbance changes, − electrical current passing through an electrode, , the use of molecular beams for kinetic measurements, ion mass spectrometry, or following the structural changes with scanning electron microscopy are some of these possibilities.…”

Specific carbon/iodide interactions in electrochemical capacitors monitored by EQCM technique

“…15 It is well known that in situ techniques, despite being powerful tools, display some technical limitations, such as the need for operation in a three-electrode setup; however, with some efforts, these results might be successfully translated to full-device performance. [16][17][18][19][20] In this context, the adsorption/ desorption of ions monitored by an electrochemical quartz crystal microbalance (EQCM) for a single electrode appears to be advantageous [21][22][23][24] and has already been applied to monitor capacitive [24][25][26][27][28][29] and faradaic charge storage processes. 30 Though, it is widely accepted that for highly porous activated carbon (AC) materials, the ion adsorption process is complex and could encounter several barriers preventing the full material capacity or capacitance from being exploited.…”