The role of lithium, perchlorate and water during electrochemical processes in poly(3,4-ethylenedioxythiophene) films in LiClO4 aqueous solutions

Overview and Recent Advances in Hyphenated Electrochemical Techniques for the Characterization of Electroactive Materials

“…That causes a fast decrease in the absolute value of the electrochromic efficiency since there is a part of the current that does not cause any absorbance change. Thus, the time derivative of the absorbance shows a zero baseline, but the current can show a non-zero (increasing or decreasing) baseline due to the electrocatalytic reaction [ 55 ].…”

“…Since electrochemical processes are heterogeneous processes, there is always a mass change on the electrode’s surface due to adsorption/desorption processes, electrodeposition, corrosion, charge balance during redox processes of adsorbed species, etc. This is why electrogravimetry has been used for the study of kinetics during electrodeposition processes [ 55 ], electrodissolution processes [ 10 , 15 , 39 ], the formation of passive layers on the metal electrode’s surface [ 15 ], adsorption/desorption of active substances during electrochemical processes [ 58 ], or for the study of charge transfer reaction in conducting polymers [ 5 , 43 ]. Changes in mass can be indirectly recorded during the experiment thanks to the quartz crystal microbalance.…”

“…Therefore, changes in mass due to the charge in balance associated with the oxidation process should also be considered for a correct interpretation. In this case, both the polymer chain growth and the polymer oxidation reaction contribute to the function [ 55 ]. If the charge balance takes place during the exchange of anions, mass increases more than expected for a single polymer chain growth; on the contrary, if the polymer exchanges cations during the oxidation process, a smaller mass change should be expected.…”

“…If this exchange of solvent takes place at a different rate, it will be detected in this transfer function as a different process in mass changes, but not in electric charge, and a loop will appear in the transfer function [ 43 ]. As an example, during the electrochemical characterization of PEDOT films by ac -electrogravimetry ( Figure 5 ), the value of this transfer function at different frequencies has allowed identifying the exchanged species during the charge compensation process in PEDOT films at different potentials [ 55 ]. At the higher frequencies (0.1 Hz–10 Hz), there is the exchange of since the mass proves larger than the cation, but at the lower frequencies, the slow electrochemical reduction in molecular causes a larger current but no mass change, and then, decreases.…”

“… Dependence of on the frequency during am ac -electrogravimetric study of PEDOT films in 0.1 M aqueous solution [ 55 ]. …”