No abstract

Polybenzopyrrole (Pbp) is an emerging candidate for electrochemical energy conversion and storage. There is a need to develop synthesis strategies for this class of polymers that can help improve its overall properties and make it as suitable for energy storage applications as other well-studied polymers in this substance class, such as polyaniline and polypyrrole. In this study, by synthesizing Pbp in surfactant-supported acidic medium, we were able to show that the physicochemical and electrochemical properties of Pbp-based electrodes are strongly influenced by the respective polymerization conditions. Through appropriate optimization of various reaction parameters, a significant enhancement of the thermal stability (up to 549.9 °C) and the electrochemical properties could be achieved. A maximum specific capacitance of 166.0 ± 2.0 F g−1 with an excellent cycle stability of 87% after 5000 cycles at a current density of 1 A g−1 was achieved. In addition, a particularly high-power density of 2.75 kW kg−1 was obtained for this polybenzopyrrole, having a gravimetric energy density of 17 Wh kg−1. The results show that polybenzopyrroles are suitable candidates to compete with other conducting polymers as electrode materials for next-generation Faradaic supercapacitors. In addition, the results of the current study can also be easily applied to other systems and used for adaptations or new syntheses of advanced hybrid/composite Pbp-based electrode materials.

A polybenzopyrrole@nickel oxide (Pbp@NiO) nanocomposite was synthesized by an oxidative chemical one-pot method and tested as an active material for hybrid electrodes in an electrochemical supercapattery device. The as-prepared composite material exhibits a desirable 3D cross-linked nanostructured morphology and a synergistic effect between the polymer and metal oxide, which improved both physical properties and electrochemical performance. The unprocessed material was characterized by X-ray diffraction, FTIR and UV–Vis spectroscopy, scanning electron microscopy/energy disperse X-ray analysis, and thermogravimetry. The nanocomposite material was deposited without a binder on gold current collectors and investigated for electrochemical behavior and performance in a symmetrical two- and three-electrode cell setup. A high specific capacity of up to 105 C g−1 was obtained for the Pbp@NiO-based electrodes with a gravimetric energy density of 17.5 Wh kg−1, a power density of 1,925 W kg‑1, and excellent stability over 10,000 cycles.

Conducting polymers integrated with metal oxides create opportunities for hybrid capacitive electrodes. In this work, we report a one-pot oxidative polymerization for the synthesis of integrated conductive polyindole/nickel oxide (PIn/NiO), polyindole/zinc oxide (PIn/ZnO), and polyindole/nickel oxide/zinc oxide (PNZ). The polymers were analyzed thoroughly for their composition and physical as well as chemical properties by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), ultraviolet–visible spectroscopy (UV–Vis), and thermogravimetric analysis (TGA). The PIn and its composites were processed into electrodes, and their use in symmetrical supercapacitors in two- and three-electrode setups was evaluated by cyclic voltammetry (CV), galvanostatic discharge (GCD), and electrochemical impedance spectroscopy (EIS). The best electrochemical charge storage capability was found for the ternary PNZ composite. The high performance directly correlates with its uniformly shaped nanofibrous structure and high crystallinity. For instance, the symmetrical supercapacitor fabricated with PNZ hybrid electrodes shows a high specific capacitance of 310.9 F g−1 at 0.5 A g−1 with an energy density of 42.1 Wh kg−1, a power density of 13.2 kW kg−1, and a good cycling stability of 78.5% after 5000 cycles. This report presents new electrode materials for advanced supercapacitor technology based on these results.

Oxidation of the iodide ion is an important facet of the solar cells such as perovskite solar cells and dye-sensitized solar cells. The rate of reaction undoubtedly depends upon several factors. Such parameters include reaction media, electrolyte, and the nature of solvents, and electrolyte. If these factors are optimized then the rate of the reaction can be controlled and could be used to get the maximum benefit out of it such as economically and industrially cost-effective uses of the reaction and globally environmentally benign. We studied the kinetics of the oxidation of the iodide ion in the binary solvent system that consisted of 10% (v/v) tertiary butyl alcohol and water. The transition metal complex such as dicyanobis(phenanthroline)iron(III) oxidizes the iodide ion spontaneously without any external triggering with a fast rate at 293 ± 1 K. The reaction was probed under the pseudo-first-order condition with an excess concentration of the iodide ion over dicyanobis(phenanthroline)iron(III) at 0.06 M ionic strength. The reaction was observed independent of the concentration of dicyanobis(phenanthroline)iron(III), that is, the zero order and third order with respect to the iodide ion in the selected solvent system. An overall third-order was observed for the redox reaction. The value of the multiplication product of the molar absorptivity (ɛ), path length of the cuvette (b), and overall rate constant (k) was deduced to be 1.59 × 10 6 M −3 s −1. The observed zero-order rate constant of the reaction was increased by the fractional (1.5) power of the concentration of protons in the excess concentration of acid 1 mM to 0.1 M. The multiplication product of ɛ⋅b to the fractional order rate constant (k′) was found 0.773 M −1.5 s −1 that confirms protonation of triiodide in acidic-10% (v/v) tertiary butyl alcohol-water. The effect of ionic strength showed a similar impact in different compositions of solvents such as 5, 10, and 20% (v/v) tertiary butyl alcoholwater. The observed zero-order rate constant was decreased upon increasing the ionic strength in each medium consisting of the binary solvent system.