Solvent effects on the electrochemical p-doping of PEDOT

Abstract

EQCM experiments were carried out on PEDOT films exposed to TEABF(4)/CH(3)CN and TEABF(4)/CH(2)Cl(2) under permselective conditions and subjected to cyclic voltammetry in the potential range corresponding to p-doping. Current and frequency responses were used to obtain time-resolved ion and solvent flux data as functions of potential. Normalization of these fluxes with potential scan rate distinguishes thermodynamically (ir)reversible elementary steps in the overall redox process. The specific mechanisms are different in the two solvents, although both show mechanistic switches at partial redox conversion during both p-doping and undoping. These different mechanistic signatures are characterized according to the solvent identity, by different patterns of deviation from scan rate normalization for the experimentally measured ion and solvent fluxes. Comparison of these ion and solvent fluxes demonstrates that the rates of solvent expulsion (during doping) and entry (during undoping) are key determinants of mechanism. In both switching directions there are changes between kinetically limiting and rapid solvent transfer that depend upon solvent identity, i.e. the mechanism depends substantially upon charge state, switching direction and solvent. These mechanistic pathways and shifts can be visualized by a scheme-of-cubes representation.

Electrochemical Behavior of PEDOT/Lignin in Ionic Liquid Electrolytes: Suitable Cathode/Electrolyte System for Sodium Batteries

“…[23] During the oxidation process of the polymer, anionsf rom the bulk are incorporated into the polymer,c ompensating the chargea long the polymericb ackbone. [24] In the case of big cations and small anions, the cation exchangei s unexpected. Thus, owing to the big size of pyrrolidinium cation (1.1 nm radius), [25] an anionic exchange will happen in the case of BMPyrTFSI and BMPyrFSII Ls;a st he TFSI À (0.8 nm radius) [25,26] anions are biggert han FSI À (0.3 nm radius) [26] (Table S1), they create more accessible sites duringt his exchange and as ar esult, the current increases in greater steps with TFSI À anion.I nt he case of ILs, the transport mechanism of the ion exchange also depends on the symmetry of the IL.…”

Effect of electrochemical control function on the internal structure and composition of electrodeposited polypyrrole films: A neutron reflectometry study

“…This necessarily involves the exchange with the bathing electrolyte of ions (here, "dopant") and thermodynamics also demands the exchange of solvent with the bathing electrolyte [50, 51]. While redox-driven changes in these mobile species populations have been monitored in numerous EQCM experiments[23,24,52,53], the absolute solvent populations in the two doping states are generally unknown. In this section we address this frequently posed, but rarely answered, question.…”

Charge Storage Properties of Nanostructured Poly (3,4–ethylenedioxythiophene) Electrodes Revealed by Advanced Electrogravimetry

“…The mixed transfer of cations and anions was previously seen for PEDOT films, in TBAPF 6 containing ACN electrolytes [47]. These processes depend on different parameters as the synthesis conditions of the ECPs, the nature of the dopant and the electrolyte ions [48,49,50]. Due to the impedance coupling in AC–EG, the kinetics of the interfacial transfer is also determined.…”