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.

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.

Photocatalysis is a promising process for decomposing harmful organic pollutants in water. In this study, solar/photocatalytic degradation of two model azo dyes, i.e., methylene blue (MB) and methyl red (MR), in water usinga nanostructured chitosan-modified nickel magnetite (CS-NM) bio-composite was investigated. The CS-NM bio-composite was synthesized through a co-precipitation method and characterized by Fourier transform infrared (FTIR), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), thermogravimetry (TGA), and UV-Vis spectroscopy. FTIR analysis showed the uniform incorporation and conjugation of nickel magnetite (NM) into the chitosan (CS) polymer matrix. SEM showed that the average particle size was 0.5 μm. The TGA results revealed the good thermal stability of the prepared bio-composite at 300 °C. The point of zero charge was calculated as 7.5. The effect of water quality and process parameters, such as concentration of dyes, catalyst dose, solution pH, and temperatures, was investigated, for application purposes. The solar/CS-NM photocatalysis resulted in 99 and 96% degradation of individual MB and MR (C₀ = 50 ppm), respectively, in 90 min. The degradation of MB and MR by solar/CS-NM photocatalysis followed pseudo-first-order kinetics, with observed rate constants (k) of 0.077 and 0.072 min⁻¹, respectively. The CS-NM photocatalyst showed high recyclability, represented by only a 4–6% loss in the photocatalytic efficiency, after four cycles. The results showed that solar/CS-NM photocatalysis is an efficient technique for degrading recalcitrant organic pollutants, such as azo dyes, in water environments.

The removal of water pollutants by photocatalysis is a promising technique, mainly due to its environmentally friendly and sustainable nature. In this study, the degradation of a recalcitrant organic pollutant, malachite green (MG), was investigated in water by a microstructured silver oxide photocatalyst. The silver oxide (Ag₂O) microparticles (MPs) were synthesized by a low-cost, green method, mediated by green tea leaves extract. The surface, morphological and optical properties of the synthesized Ag₂O MPs were determined by scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis, X-ray diffraction (XRD) analysis, Fourier transform infrared (FTIR) spectroscopy, and ultraviolet-visible (UV-visible) spectrophotometry. The synthesized Ag₂O MPs showed good photoactivity, represented by 83% degradation of malachite green (MG) ([C]₀ = 0.4 mM, Ag₂O loading = 0.1 g L⁻¹) at neutral pH, in 3 h. Persulfate ions (PS) showed a strong synergistic effect on the efficiency of solar/Ag₂O photocatalysis, represented by complete MG removal in 15 min, in the presence of 1.6 mM PS. The results revealed that solar/Ag₂O, particularly solar/Ag₂O/PS photocatalysis is a promising method for the elimination of toxic organic pollutants, such as malachite green, from the water environment.

The present study is aimed at the synthesis and exploring the efficiency of a novel activated carbon incorporated polyindole (AC@PIN) composite for adsorptive removal of Malachite Green (MG) dye from aqueous solution. An AC@PIN hybrid material was prepared by in situ chemical oxidative polymerization. The physico-chemical characteristics of the AC@PIN composite were assessed using Fourier-transform infrared spectrometer, X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, ultraviolet visible spectroscopy, and determination of point of zero charge (pH_PZC). A series of adsorption studies was conducted to evaluate the influence of operational parameters such as pH, contact time, initial dye concentration, AC@PIN dosage, and temperature on dye adsorption behavior of developed composite. A maximum dye removal percentage (97.3%) was achieved at the pH = 10, AC@PIN dosage = 6.0 mg, initial dye concentration 150 mg L⁻¹, and temperature = 20 °C. The kinetic studies demonstrated that the adsorption of MG on AC@PIN followed pseudo-second-order model (R² ≥ 0.99). Meanwhile, Langmuir isotherm model was founded to be the best isotherm model to describe the adsorption process. Finally, the recyclability test revealed that the composite exhibits good recycle efficiency and is stable after 5 cycles. The obtained results suggest that AC@PIN composite could be a potential candidate for the removal of MG from wastewater.

In this study, amine-functionalized MWCNTs (f-MWCNTs) have been investigated as potential material for the removal of Mordant black dye 11 (MBD 11). To evaluate the optimal condition and adsorption capability of the adsorbents (f-MWCNTs), the effect of temperature, pH, adsorbent dosage, and contact time on adsorption rate are examined. The study shows a stronger interaction between the dye and f-MWCNTs. The highest removal efficiency is observed in acidic medium (pH 2) with an initial dye concentration of 50 mg L⁻¹, where 99% of the dye is adsorbed from the medium in 40 min using 0.05 g of f-MWCNTs. Adsorption isotherm and kinetic studies reveal that adsorption occurs by the Langmuir adsorption model and pseudo-second-order adsorption kinetics. According to the thermodynamic parameters, the adsorption exhibits endothermic and spontaneous behavior. Graphical Abstract