One-step electrodeposition of a polypyrrole/NiO nanocomposite as a supercapacitor electrode

A Nanofibrous Polypyrrole Membrane with an Ultrahigh Areal Specific Capacitance and Improved Energy and Power Densities

For conductive polymers to be competitive with carbon-based electrode materials, it is critical to increase their surface area and electroactivity. In this work, a thick nanofibrous polypyrrole (PPy) membrane with communicating interfiber spaces was prepared through one-pot interfacial polymerization for the first time. The electrochemical properties and conductivity of the membrane were studied with cyclic voltammetry, electrochemical impedance spectroscopy, and a four-point probe. Its morphology, chemistry, and thermostability were evaluated by scanning electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and thermogravimetric analysis. The areal specific capacitances measured between 0.0 and 0.8 V at 1 mA/cm2 were 19179, 13264, 7238, and 4458 mF/cm2 for the membranes doped with docusate sodium (AOT), camphor-10-sulfonic acid (β) (CSA), Cl-, and poly(sodium 4-styrenesulfonate) (PSS), respectively. The capacity retentions after 1000 cycles were 83, 74, 67, and 61% for the AOT-, CSA-, PSS-, and Cl--doped membranes, respectively. The Coulombic efficiency was above 99% for all of the membranes. They showed energy densities of 1.7, 1.2, 0.7, and 0.4 mWh/cm2 and power densities of 0.61, 0.75, 0.66, and 0.62 mW/cm2 for the AOT-, CSA-, Cl--, and PSS-doped membranes, respectively. The ultrahigh areal specific capacitance of PPy-AOT is due to its nanofibrous structure. A mechanism has been proposed to explain how this structure is formed based on the role of AOT as the surfactant. This nanofibrous PPy membrane is easy to prepare and metal-free and offers a very high areal specific capacitance, making it an excellent candidate to construct electrodes in pseudosupercapacitors.

Polypyrrole and activated carbon enriched MnCo2O4 ternary composite as efficient electrode material for hybrid supercapacitors

The development of proficient electrode materials is one of the major tasks faced by modern techniques for energy storage. Integrating different materials with synergistic effects can be a valuable strategy for designing storage devices with high capacity and energy density. The spinel manganese cobaltite (MnCo2O4) is an outstanding candidate for supercapacitors owing to its remarkable pseudocapacitive behavior. However, it suffers from low electric conductivity and limited cyclic stability. To overcome its limitations, activated carbon with superior cyclic stability and polypyrrole with high electric conductivity can be incorporated in MnCo2O4. The synergistic effect of these components offers high capacitance, better conductivity, and superior cyclic performance to the ternary composite. Herein, the MnCo2O4/AC/PPY ternary composite has been synthesized by a facile approach. The optimized ternary composite (MAP-20) exhibited a wonderful capacitance of 945.77 F g-1 at five mV s-1 compared to pristine MnCo2O4 (254.98 F g-1). The real-time applicability of the optimized composite was tested with asymmetric device configuration. The asymmetric device with MAP-20 and MnO2/AC electrodes exhibited a wonderful Ed of 88.12 W h kg-1 (Pd ∼ 1.6 kW kg-1). The asymmetric device also exhibited excellent cyclic performance of 89.68% for 10 000 cycles. Further, the real-time applicability of the device was tested by illuminating a 39 red LED panel. Three asymmetric cells connected in series illuminated the panel for about 45 minutes. All these results suggest that the synergistic integration of various efficient electrode materials leads to enhanced electrochemical performance of supercapacitors.

MOF/graphene oxide based composites in smart supercapacitors: a comprehensive review on the electrochemical evaluation and material development for advanced energy storage devices

The surge in interest surrounding energy storage solutions, driven by the demand for electric vehicles and the global energy crisis, has spotlighted the effectiveness of carbon-based supercapacitors in meeting high-power requirements. Concurrently, metal-organic frameworks (MOFs) have gained attention as a template for their integration with graphene oxide (GO) in composite materials which have emerged as a promising avenue for developing high-power supercapacitors, elevating smart supercapacitor efficiency, cyclic stability, and durability, providing crucial insights for overcoming contemporary energy storage obstacles. The identified combination leverages the strengths of both materials, showcasing significant potential for advancing energy storage technologies in a sustainable and efficient manner. In this research, an in-depth review has been presented, in which properties, rationale and integration of MOF/GO composites have been critically examined. Various fabrication techniques have been thoroughly analyzed, emphasizing the specific attributes of MOFs, such as high surface area and modifiable porosity, in tandem with the conductive and stabilizing features of graphene oxide. Electrochemical characterizations and physicochemical mechanisms underlying MOF/GO composites have been examined, emphasizing their synergistic interaction, leading to superior electrical conductivity, mechanical robustness, and energy storage capacity. The article concludes by identifying future research directions, emphasizing sustainable production, material optimization, and integration strategies to address the persistent challenges in the field of energy storage. In essence, this research article aims to offer a concise and insightful resource for researchers engaged in overcoming the pressing energy storage issues of our time through the exploration of MOF/GO composites in smart supercapacitors.

Sensing of heavy metal Pb2+ ions in water utilizing the photonic structure of highly controlled hexagonal TiON/TiO2 nanotubes

The detection of heavy metals in water, especially Pb2+ ions, is important due to their severe hazardous effects. To address this issue, a highly controlled hexagonal TiON/TiO2 heterostructure has been synthesized in this study. The fabrication process involved the utilization of atomic layer deposition and direct current sputtering techniques to deposit TiO2 and TiON layers onto a porous Al2O3 membrane used as a template. The resulting heterostructure exhibits a well-ordered hollow tube structure with a diameter of 345 nm and a length of 1.2 µm. The electrochemical sensing of Pb2+ ions in water is carried out using a cyclic voltammetry technique under both light and dark conditions. The concentration range for the Pb2+ ions ranges from 10-5 to 10-1 M. The sensitivity values obtained for the sensor are 1.0 × 10-6 in dark conditions and 1.0 × 10-4 in light conditions. The remarkable enhancement in sensitivity under light illumination can be attributed to the increased activity and electron transfer facilitated by the presence of light. The sensor demonstrates excellent reproducibility, highlighting its reliability and consistency. These findings suggest that the proposed sensor holds great promise for the detection of Pb2+ ions in water, thereby facilitating environmental monitoring, water quality assessment, and safety regulation across various industries. Furthermore, the eco-friendly and straightforward preparation techniques employed in its fabrication provide a significant advantage for practical and scalable implementation.

Self-supported polypyrrole flexible electrodes for electrochemical reduction of nitrite

The efficiency of an electrochemical oxidation/reduction process strongly depends on the working electrode's surface area to volume ratio. By making electrodes flexible and employing different configurations such as roll-to-roll membrane, the surface area to volume ratio can be enhanced, therefore improving the overall efficiency of electrochemical processes. Conductive polymers emerge as a new framework to enable alternative electrochemical water treatment cell configurations. Self-standing polypyrrole flexible electrodes were synthesized by electropolymerization and evaluated on the treatment of an oxyanion pollutant: nitrite. Mechanical characterization through stress-strain curves and bending tests demonstrated high electrode resilience that sustained over 1000 bending cycles without impacting mechanical integrity or electrocatalytic responses. The electrocatalytic response towards nitrite reduction was assessed under linear scan voltammetry (LSV) and removal performance evaluated under potentiostatic conditions reaching 79% abatement of initial concentrations of nitrite of 15 mg/L [NO2--N]. Self-standing flexible electrodes appear as a novel framework to enable modular compact water treatment unit designs that maximize the electrode area/volume ratio and substitute expensive platinum group metal (PGMs) electrocatalysts.

Ag2S-Ag2O-Ag/poly-2-aminobenzene-1-thiol Nanocomposite as a Promising Two-Electrode Symmetric Supercapacitor: Tested in Acidic and Basic Mediums

A Ag₂S-Ag₂O-Ag/poly-2-aminobenzene-1-thiol (P2ABT) nanocomposite was prepared using the photopolymerization reaction using AgNO₃ as an oxidant. The size of the nanocomposite was about 40 nm, in which the morphology was confirmed using TEM and SEM analyses. The functional groups of Ag₂S-Ag₂O-Ag/P2ABT were confirmed using FTIR; also, XRD confirmed the inorganic Ag₂S, Ag, and Ag₂O formation. This nanocomposite has great performance in supercapacitor applications, with it tested in acidic (1.0 M HCl) and basic mediums (1.0 M NaOH). This pseudo-capacitor has great performance that appeared through the charge time in an acid medium in comparison to the basic medium with values of 118 s and 103 s, correspondingly. The cyclic voltammetry (CV) analysis further confirmed the excellent performance of the supercapacitor material, as indicated by the large area under the cyclic curve. The specific capacitance (C_S) and energy density (E) values (at 0.3 A/g) were 92.5 and 44.4 F/g and 5.0 and 2.52 W·h·Kg^-1 in the acidic and basic mediums, correspondingly. The charge transfer was studied through a Nyquist plot, and the produced R_s values were 4.9 and 6.2 Ω, respectively. Building on these findings, our objective is to make a significant contribution to the progress of supercapacitor technology through a prototype design soon.

Selective CO2 Electroreduction to Formate on Polypyrrole-Modified Oxygen Vacancy-Rich Bi2 O3 Nanosheet Precatalysts by Local Microenvironment Modulation

Challenges remain in the development of highly efficient catalysts for selective electrochemical transformation of carbon dioxide (CO₂ ) to high-valued hydrocarbons. In this study, oxygen vacancy-rich Bi₂ O₃ nanosheets coated with polypyrrole (Bi₂ O₃ @PPy NSs) are designed and synthesized, as precatalysts for selective electrocatalytic CO₂ reduction to formate. Systematic material characterization demonstrated that Bi₂ O₃ @PPy precatalyst can evolve intoBi₂ O₂ CO₃ @PPy nanosheets with rich oxygen vacancies (Bi₂ O₂ CO₃ @PPy NSs) via electrolyte-mediated conversion and function as the real active catalyst for CO₂ reduction reaction electrocatalysis. Coating catalyst with a PPy shell can modulate the interfacial microenvironment of active sites, which work in coordination with rich oxygen vacancies in Bi₂ O₂ CO₃ and efficiently mediate directional selective CO₂ reduction toward formate formation. With the fine-tuning of interfacial microenvironment, the optimized Bi₂ O₃ @PPy-2 NSs derived Bi₂ O₂ CO₃ @PPy-2 NSs exhibit a maximum Faradaic efficiency of 95.8% at -0.8 V (versus. reversible hydrogen electrode) for formate production. This work might shed some light on designing advanced catalysts toward selective electrocatalytic CO₂ reduction through local microenvironment engineering.

Fabrication of Flexible Supercapacitor Electrode Materials by Chemical Oxidation of Iron-Based Amorphous Ribbons

A flexible electrode constructed from Fe-based amorphous ribbons decorated with nanostructured iron oxides, representing the novelty of this research, was successfully achieved in one-step via a chemical oxidation method, using a low concentration of NaOH solution. The growth of metal oxides on a conductive substrate, which forms some metal/oxide structure, has been demonstrated to be an efficient method for increasing the charge transfer efficiency. Through the control and variation of synthetic parameters, different structures and morphologies of iron oxide were obtained, including hexagonal structures with a hollow ball shape and rhombohedral structures with rhombus-like shapes. Structural and morphological characterization methods such as X-ray diffraction and SEM morphology were used on the as-synthesized composite materials. The supercapacitor properties of the as-developed amorphous ribbons decorated with Fe₂O₃ nanoparticles were investigated by cyclic voltammetry, galvanostatic charge discharge, and electrochemical impedance spectroscopy. The flexible supercapacitor negative electrode demonstrates a specific capacitance of 5.96 F g^-1 for the 0.2 M NaOH treated sample and 8.94 Fg^-1 for the 0.4 M NaOH treated sample. The 0.2 M treated negative electrodes deliver 0.48 Wh/kg at a power density of 20.11 W/kg, and the 0.4 M treated electrode delivers 0.61 Wh/kg at a power density of 20.85 W/kg. The above results show that these flexible electrodes are adequate for integration in supercapacitor devices, for example, as negative electrodes.

Supercapacitor based on polymeric binary composite of polythiophene and single-walled carbon nanotubes

The aim of this work is to fabricate supercapacitor electrode based on poly (3-hexyl-thiophene-2, 5-diyl) (P3HT) and single-walled carbon nanotubes (SWCNTs) nanocomposites with different ratios onto a graphite sheet as a substrate with a wide voltage window in nonaqueous electrolyte. Structural, morphological and electrochemical properties of the prepared nanocomposites of P3HT/SWCNTs were studied and discussed. The electrochemical properties included cyclic voltammetry (CV), galvanostatic charging-discharging (GCD), and electrochemical impedance spectroscopy (EIS) were investigated. The obtained results indicated that P3HT/SWCNTs nanocomposite possesses higher specific capacitance than that present in its individual component. The high electrochemical performance of the nanocomposite was due to formation of microporous structure which facilitates ions diffusion and electrolyte penetration in these pores. The morphological micrographs of the purified SWCNTs had buckypaper structure while the photomicrographs of P3HT/SWCNTs showed that SWCNTs appear behind and front of the P3HT nanospheres. The specific capacitance of 50% SWCNTs at 0.5 Ag⁻¹ was found to be 245.8 Fg⁻¹ compared with that of pure P3HT of 160.5 Fg⁻¹.