Properties improvement of poly(o-methoxyaniline) based supercapacitors: experimental and theoretical behaviour study of self-doping effect

Abstract

ABSTRACT:Conducting polymers (CP) are very versatile materials with important properties due to their unique structure, including redox behaviour upon electrochemical polarization. Supercapacitors are among the devices in which CP show a promising performance due to their large specific capacitance. However, the major drawback of these materials is their low durability, which is an inbuilt process caused by ion intercalation, a side effect of the redox process. A viable strategy to increase CP stability is, therefore, the inhibition of the ion intercalation/de-intercalation process. Several strategies have been proposed to minimize this effect, among them self-doping. Self-doping makes the redox process mass-transport independent, decreasing the response time and increasing durability. With this purpose, this work have described the synthesis of layer-by-layer films (LBL) of poly(omethoxyaniline)/poly(3-thiopheneacetic acid) (POMA/PTAA) and contributes to understand how the redox process leads to premature aging, and how self-doping minimizes this problem. The main techniques of characterisation used were electrochemical impedance spectroscopy (EIS) experiments and density functional theory (DFT) calculations. EIS provides important information about the electrochemical behaviour, while DFT calculations allowed to characterize, at the molecular level, the changes in the material structure. The association of both techniques helped to understand how self-doping improves the POMA properties. DFT calculations showed that in the layer-by-layer (LBL) films, the twisting of the polymer chain due to the oxidation is 12% less while the chain shortening is 5% compared with films prepared POMA by casting. The EIS data showed the effect of these molecular changes in the structure; the swelling of the LBL films is 50% less than cast ones. These observations are important because the PTAA layer acts beyond a chargecompensator, working as a backbone structure that mechanically stabilize the POMA layer, leading to an increase in the durability, and improving the electrochemical properties.

Supercapacitors: Electrical Characteristics, Modeling, Applications, and Future Trends

“…As a result, the authors determined a strategy to design the best mesoporous material for SCs with regard to energy and power density. The authors of [129] use a transmission line model combined with electrochemical impedance spectroscopy experiments and density functional theory to understand how redox reactions lead to the premature ageing of conducting polymers. In this way, they are able to propose new methods to increase the durability of these SCs and to improve their electrochemical properties.…”

Conducting Polymers in the Fields of Energy, Environmental Remediation, and Chemical–Chiral Sensors

“…In these composites, interfacial interactions and synergistic or complementary effects are present, and therefore special models have been developed to explain their conductivity . Self-ionized conjugated polymers (also called self-doped or self-compensated CPs) combine electronic charge transport through the conjugated polymer backbones with polyelectrolyte properties arising from structurally incorporated ionic moieties. − Even though this class of CPs has been known for a long time, ,, recent work has demonstrated the great potential of self-compensated polymers in technological challenges like tuning of electrode work functions to produce ohmic contacts, preparation of air-stable, water-soluble conductive materials for organic electronics, increasing stability or efficiency in organic − and perovskite solar cells, and enhancing the performance of supercapacitors, and other organic electronic devices …”

Ag(e)ing and Degradation of Supercapacitors: Causes, Mechanisms, Models and Countermeasures

“…Layer-by-layer films of poly( o -methoxyaniline) and poly(3-thiophene acetic acid) have been examined as supercapacitor electrode material [ 114 ]. Films casted only with the formed material showed lower stability and faster degradation, attributed to counterion ingress/egress (see also [ 115 ]). The frequently deplored degradation of PANI was mostly attributed to swelling/shrinking during cycling [ 67 ], as well as to structural degradation on a molecular level [ 116 ], which has also been observed with composites employing this ICP, e.g., in particular at elevated temperatures with PANI/MnFe 2 O 4 [ 117 ].…”