Electrochemical impedance spectroscopy of dodecylsulphate doped polypyrrole films in the dark and under illumination

Abstract

Efeitos de morfologia, espessura, oxidação e iluminação dos filmes de polipirrol dopados com dodecilsulfato podem ser observados qualitativamente por EIS e consistem de variações de valores de resistências e capacitâncias de um circuito equivalente proposto, presentes nas interfaces e no interior do material. O circuito se ajusta bem para filmes sintetizados com densidade de carga de 190 mC cm -2 . Para filmes mais finos os valores calculados por espectroscopia de impedância eletroquímica (EIS) apresentam desvios provavelmente pela ausência de efeitos difusivos. A oxidação dos filmes causa uma diminuição geral da impedância em toda a faixa de freqüências medidas. Os efeitos de morfologia também são observados em todas as freqüências. Os efeitos de iluminação são reversíveis e aparecem, como esperado, apenas quando o polímero está na forma reduzida. A iluminação diminui a resistência interna e a capacitância de carga espacial e aumenta a resistência de transferência de carga e a capacitância de dupla camada.The morphology, thickness, oxidation and illumination effects in dodecylsulphate doped polypyrrole films can be qualitatively observed by EIS and consist in variations of interfacial and bulk resistances and capacitances of a proposed equivalent circuit. The circuit well with the measured spectra of films obtained with 190 mC cm -2 of synthesis charge density. For thinner films the calculated values observed by electrochemical impedance spectroscopy (EIS) deviate probably due to the absence of diffusion effects. The oxidation of the films diminishes the total impedance over the entire frequency range. The morphology effects are also observed in the entire spectra. The illumination effects are reversible and are observed as expected only in the reduced form of the polymer. The illumination reduces the internal resistance and the space-charge capacitance and increases the charge transfer resistance and the double layer capacitance.

Galvanostatic deposition of polypyrrole in the presence of tartaric acid for electrochemical supercapacitor

“…It was found that the R S and R ct values of PPy-TA-TX100 coating are smaller than those of PPy, and PPy-TA coatings for three electrodes as revealed in Table 2, which are primarily attributable to the improved wettability [24] and implies that the cation insertion/extraction process into/from PPy-TA-TX100 is more facile than in the case of the other coatings, respectively [38]. And PPy-TA-TX100 coating has the smallest internal resistance, probably because of bigger conjugation length similar to the study by Martini et al [46]. The W values gradually decrease for three electrodes when TA/T À and TX100 were inserted in the polymer in succession.…”

Electrochemical impedance spectroscopy of diluted solutions of Bisphenol A

“…A technique capable of measuring these small changes is the electrochemical impedance spectroscopy (EIS), always that a suitable equivalent circuit of the system is available. Many authors have found that small changes in the morphology, composition and reactivity of different electrodes can be quantified employing the impedance spectroscopy, characterizing in electrical terms some variables like ions migration, film formation, interactions between molecules and roughness of surfaces [23][24][25][26][27][28][29][30]. For example, Yan and Sadik developed a reproducible method that provides a generic approach for ds-DNA based sensor development and for the monitoring of DNA-analyte interactions.…”

Adsorption of sodium dodecyl sulfate on the bismuth (111), (001) and planes

“…7. In circuits, R el is the electrolyte resistance, C true and C ad are the double layer and adsorption capacitances, respectively; Z W is Warburglike diffusion impedance and R ad is the adsorption or partial charge transfer resistance [1][2][3][4][5][6]13,14,19,20,[22][23][24][25][26][27][29][30][31][32][33][34][35][36][37]. The value of C true (C true = (or/oE) C,l ) characterises the capacitance of the metaljelectrolyte interface at f !…”

“…It is important to know the kinetic behaviour of the SDS molecules at the geometrically flat chemically stable metal electrodes as this compound can be used as a doping agent in various electrically conducting polymer films (ECPF) [24][25][26][27]. Sometimes very complicated ac electrochemical impedance spectra (EIS) have been established for a ECPFj electrolyte interface [24][25][26][27][28], and the investigation of the SDS adsorption kinetics at geometrically flat metal electrodes is inevitable for better understanding of the extremely complicated processes occurring at the ECPFjelectrolyte interface.…”

“…Sometimes very complicated ac electrochemical impedance spectra (EIS) have been established for a ECPFj electrolyte interface [24][25][26][27][28], and the investigation of the SDS adsorption kinetics at geometrically flat metal electrodes is inevitable for better understanding of the extremely complicated processes occurring at the ECPFjelectrolyte interface.…”