Recent Progress in Polyaniline and its Composites for Supercapacitors

Reversible Quinoid-Diradical Inter-Conversion in Single-Molecule Junctions

A profound understanding of the reversible regulation mechanisms among multiple redox states of organic molecules is essential for further development of molecular switching devices. In this study, an oligo-aniline derived quinoidal molecular wire was designed and synthesized. The reversible inter-conversion processes between its initial (quinoid) and protonated (diradical) states were comprehensively investigated with optical measurements, and the EPR experiments confirmed the formation of radical species upon protonation. The single-molecule charge transport properties were then investigated using scanning tunneling microscopy break junction (STM-BJ) technique. It was found that the molecular wire O-ANI can serve as a reversible molecular switching process with ≈ 6.5-fold conductance variation through acid/base adjustments. Additionally, theoretical analyses elucidated the mechanism of the quinoid-diradical inter-conversion. The enhanced comprehension of the reversible quinoid-diradical inter-conversion at the single-molecule level provides new strategies for advancing the molecular switching materials and devices.

Synthesis of SnO₂/COF Green Nanomaterials for Effective Pesticide Decomposition and Promoting Tomato Plants Growth

In last few decades, the agriculture sector is facing various type of crops diseases originated by crop pests. Among various crops the tomato plant is greatly affected by many pests such as aphids and whiteflies, which are badly decreasing tomato plant yield and effecting its growth. In last few years, various type of pesticides such as Neonicotinoids and Pyrethroids are employed which are badly effecting eco-system and water bodies. In this research work, we prepared SnO2 nanosheets (SONS) by in-situ and green synthesis approach. Remarkably, SONS exhibit a larger surface area, tailored pore size, and higher catalytic performance than SnO2 nanoparticles (SONP). To further improve the efficiency of SONS, we coupled it with covalent organic farmwork nanosheets (COFNS) via the hydrothermal approach. The SONS@COFNS hybrid nanocatalysts exhibit improved carrier migration, enhanced porosity, multiple active sites, and exceptional light absorption capabilities. The as prepared green nanomaterials delivered improved activities for Neonicotinoids and Pyrethroids degradation. Remarkably, the most active sample 6COFNS/SONS showed the highest degradation efficiency (94 %), which is approximately 1.92 times higher than the degradation efficiency of pristine SONS (49 %). This work will ultimately contribute to developing green, ecofriendly nanomaterials for pesticides degradation and promoting tomato plants growth.

Enhancing the Adhesion of Polyaniline on Steel Substrates Without a Binding Agent: Evaluated by ASTM D 3359 Tape Test and Sodium Chloride (NaCl) Exposure

This study presents a method for enhancing the adhesion of chemically synthesized polyaniline on steel substrates without the need for a binding agent. Hydrochloric acid (HCl) was used in the synthesis of polyaniline. The experiment details the in situ chemical synthesis of polyaniline and its application as a coating on steel surfaces using an air spray technique. Pre-surface treatment, including cleaning and sanding, was performed on the steel substrates prior to coating. Following the application of the polyaniline coating, heat treatment was applied, where the coating was heated to 350 °F for 3 h after it was fully dried. The adhesion properties of the coating were evaluated using the ASTM D 3359 adhesive tape test, along with short- and long-term exposure to 3.5% sodium chloride (NaCl) solution. Additional analysis, including SEM, XPS, XRD, and coating thickness measurements, demonstrates the effectiveness of polyaniline in enhancing adhesion on steel substrates.

Effect of Carbon Nanomaterials Incorporated Polymeric Membrane Separators for Energy Storage Devices

The rapid expansion of the global population and technological advancements have heightened the need for efficient energy conversion and electrochemical energy storage. Electrochemical energy systems like batteries and supercapacitors have seen notable developments to meet this demand. However, conventional polymeric membrane separators in these systems face challenges due to limited porosity and poor mechanical and thermal properties, reducing overall electrochemical performance. Researchers have incorporated nanoparticles into the polymer matrix to address these limitations and enhance separator properties. Carbon-based nanomaterials, in particular, have gained prominence due to their unique features, such as surface-dependent characteristics, size, porosity, morphology, and electrical conductivity. These properties make carbon-based nanomaterials advantageous in improving energy storage compared to conventional materials. Advanced carbon-doped polymeric membrane separators have emerged as a potential solution to the issues faced by conventional separators. Adding carbon nanoparticles, such as graphene-based materials and carbon nanotubes to the polymeric separators of batteries and supercapacitors has helped researchers solve problems and improve electrochemical performance. This review article provides a state-of-the-art overview of carbon-doped polymeric membrane separators, their properties, fabrication processes, and performance in lithium batteries, as well as supercapacitors. It emphasizes advantages of these novel separator materials and suggests future research directions in this field.

Emerging Issues and Opportunities of 2D Layered Transition Metal Dichalcogenide Architectures for Supercapacitors

Two-dimensional layered transition metal dichalcogenides (2D TMDs) have emerged as promising candidates for supercapacitor (SCs) owing to their tunable electronic properties, layered structures, and effective ion intercalation capabilities. Despite these advantages, challenges such as low electrical conductivity, the interlayer restacking, oxidation and structural collapse hinder their practical implementation. This review provides a comprehensive overview of recent advances in the development of 2D TMDs for SCs. We begin by outlining the charge storage mechanisms and design principles for SCs, followed by an in-depth discussion of the synthesis methods and the associated challenges in fabricating 2D TMD architectures. The subsequent sections explore their crystal structures and reaction mechanisms, illustrating their electrochemical potential in SCs. Furthermore, we highlight material modification strategies, including nanostructuring, defect engineering, phase control, and surface/interface modulation, which have been proposed to overcome existing challenges. Finally, we address critical issues and emerging opportunities for 2D TMDs to inspire the development of SC technologies.

Advances in Graphene-Transition Metal Selenides Hybrid Materials for High-Performance Supercapacitors: A Review

Supercapacitors have attracted significant attention as energy storage devices due to their high power density, rapid charge-discharge capability, and long cycle life. Their performance is primarily influenced by electrode materials, electrolytes, and operational voltage windows. Among these, the development of advanced electrode materials is crucial for enhancing energy density, specific capacitance, and cyclic stability. This review focuses on recent advancements in graphene-based hybrid materials, particularly their integration with transition metal selenides (TMSs) for supercapacitor applications. Combining graphene and its derivatives with TMSs, which possess multiple oxidation states and high theoretical capacitance, results in hybrids with superior electrochemical performance. Studies show that these materials achieve higher specific capacitance, energy density, and power density compared to graphene composites with carbides, nitrides, phosphides, and oxides. Key findings include synthesis strategies, structural modifications, and electrochemical properties of graphene-TMS hybrids. Notably, these hybrids have demonstrated specific capacitances exceeding 3105 F/g at 1 A/g, power densities up to 5597.77 W/kg, and energy densities reaching 126.3 Wh/kg, making them highly promising for next-generation supercapacitors. This review critically evaluates the current state-of-the-art, explores the synergistic effects between graphene and TMSs, such as improved charge transfer kinetics and structural stability, and identifies challenges and future directions in graphene-TMS hybrid supercapacitors.

Albizia Procera-Derived Nitrogen-Doped Carbon: A Versatile Material for Energy Conversion, Storage, and Environmental Applications

This review explores the diverse applications of nitrogen-doped carbon derived from Albizia procera, known as white siris. Native to the Indian subcontinent and tropical Asia, this species thrives in varied conditions, contributing to sustainable development. The nitrogen-rich leaves of Albizia procera are an excellent source for synthesizing nitrogen-doped carbon, which possesses remarkable properties for advanced technologies. This material demonstrates significant potential in energy conversion and storage systems, such as supercapacitors and batteries, due to its high surface area, electrical conductivity, and chemical stability. Nitrogen doping introduces active sites that enhance charge storage, making it ideal for renewable energy applications. Additionally, this material shows promise in environmental processes like water splitting and carbon dioxide capture, where its porous structure and chemical functionality enable efficient adsorption and remediation. The review discusses synthesis methodologies, including pyrolysis and activation, to optimize its properties for energy and environmental uses. Nitrogen-doped carbon derived from Albizia procera may expand into catalytic applications, enhancing its role in sustainable technologies. This review underscores the importance of utilizing natural resources like Albizia procera to develop materials that drive both environmental sustainability and technological innovation.

MnO2 Nanoflowers Electrodeposited on Vertically Aligned CNTs as Binder-Free Electrodes for High-Rate Supercapacitors

Supercapacitors are gaining attention for their ability to deliver rapid energy discharge while maintaining a high energy storage capacity, effectively bridging the gap between capacitors and batteries. In this paper, we report the performance of a high-capacity, fast-charging, and reliable supercapacitor consisting of nanoflower-like manganese dioxide (MnO2) decorated on CVD-grown carbon nanotube (CNT) electrodes fabricated using a simple and efficient room-temperature electrodeposition method. The binder-free, self-supporting MnO2@CNT composite electrodes formed on a flexible carbon fabric demonstrated excellent electrochemical energy storage capabilities, as confirmed by cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) experiments. The MnO2 loading significantly affected the electrode's capacity, with the highest specific capacitance of 219 F g-1 achieved at low mass loading (3.37 mg cm-2) and the highest areal capacitance of 1.5 F cm-2 for high mass loading (15.6 mg cm-2). The rectangular curve observed in CV experiments at faster scan rates (5-50 mV s-1) and the triangular curve observed in the GCD experiment at high current densities (0.1 to 0.5 A g-1) demonstrate the high-rate capability of the MnO2@CNT electrode. The electrode also showed outstanding stability, retaining 88% of its initial capacity after 7000 cycles. Electrochemical impedance spectroscopy (EIS) measurement and corresponding analysis of the data indicated fast charge transfer kinetics and facile ion diffusion into the MnO2 electrode, which is attributed to the nanoflower-like structure of MnO2 formed on porous carbon nanotubes, leading to excellent rate performance. With these advancements, our MnO2@CNT supercapacitors have significant potential in electric vehicles, complementing batteries by enabling fast discharge for quick acceleration.

Enhanced electrochemical performance of a polyaniline-based supercapacitor by a bicontinuous microemulsion nanoreactor approach

Polyaniline (PANI)-based supercapacitors suffer from environmental and mechanical instabilities. In this work, a novel bicontinuous microemulsion approach was developed to fabricate a unique nanofibre structure of polyaniline and its 3D-crosslinked network using crosslinking chemistry, which improved both the mechanical and electrochemical performance of a PANI-based supercapacitor. The polyaniline nanofibers and its 3D-crosslinked networks produced by bicontinuous nanoreactors were investigated using experimental tools, such as SEM, FTIR, BET, TGA and DSC. Electrochemical evaluations for the above polyaniline nanofibers and its 3D-crosslinked materials was performed via cyclic voltammetry and galvanostatic charge-discharge measurements. The result of this study demonstrated that the PANI nanofiber exhibited the highest specific capacitance of 280.4 F g-1 at a current density of 1 A g-1, while both PANI-based supercapacitors made of nanofibers and 3D-crosslinked materials retained good cycling stability of 98% during continuous redox cycling.

Simple and fast self-polymerization of benzidine using anodic exfloated graphene oxide nanosheet

Nowadays, researchers are looking for green synthesis methods of polymers that solve the disadvantages of polymerization with different initiators and traditional methods. In this work, the self-polymerization process of benzidine by anodic exfloated graphene oxide Nanosheet electrode (AEGO Nsh) is reported for the first time in the world. The self-polymerization of benzidine onto AEGO Nsh electrode was done by an easy and simple method by anodizing the graphite sheet followed by immersing the AEGO Nsh electrode inside the benzidine monomer dissolved in organic and inorganic acid media. The surface morphology of the self-polymerized benzidine (SPB) onto the AEGO Nsh (SPB/AEGO Nsh) electrode was investigated by phone camera and scanning electron microscope (FE-SEM) imaging. The chemical characterization of the SPB/AEGO Nsh electrode was verified through XPS and ATR-IR analysis. Additionally, the self-polymerization of benzidine onto AEGO Nsh electrodes was confirmed by electrochemical tests using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) techniques. The results from these investigations unequivocally confirm the self-polymerization of benzidine onto the AEGO Nsh electrode.

Optimizing Electrodeposition of Polyaniline on Various Woven Steel Mesh Sizes for Enhanced Supercapacitor Performance

The development of efficient supercapacitors hinges on the innovation of superior electrodes, which are pivotal in augmenting their energy storage capabilities. Supercapacitors, recognized for their high-power density and extended cycle life, play a crucial role as sustainable solutions in addressing energy storage challenges. A fundamental aspect of supercapacitor functionality involves the electrode material, which works in concert with other key components such as the current collector, separator, and electrolyte. This study focuses on evaluating the impact of the current collector material on the performance of symmetric supercapacitors. We investigated the electropolymerization of polyaniline on woven steel mesh current collectors of varying mesh sizes, ranging from 20 to 200 mesh per inch, using assorted deposition conditions. The electrochemically modified woven steel meshes were utilized to construct symmetric supercapacitors. The electrochemical performance of the assembled supercapacitors, configured in a two-electrode system, was investigated using a variety of electrochemical techniques to better understand the kinetics of electrolyte ion migration. Notably, the 20-mesh size, characterized by the fewest pores per inch, demonstrated superior performance with an optimum capacitance of 4730 mF/cm2, an energy density of 317.8 μWh/cm2, and a power density of 400 μW/cm2 at a current density of 1 mA/cm2.

Conducting Polymer-Based Gel Materials: Synthesis, Morphology, Thermal Properties, and Applications in Supercapacitors

Despite the numerous ongoing research studies in the area of conducting polymer-based electrode materials for supercapacitors, the implementation has been inadequate for commercialization. Further understanding is required for the design and synthesis of suitable materials like conducting polymer-based gels as electrode materials for supercapacitor applications. Among the polymers, conductive polymer gels (CPGs) have generated great curiosity for their use as supercapacitors, owing to their attractive qualities like integrated 3D porous nanostructures, softness features, very good conductivity, greater pseudo capacitance, and environmental friendliness. In this review, we describe the current progress on the synthesis of CPGs for supercapacitor applications along with their morphological behaviors and thermal properties. We clearly explain the synthesis approaches and related phenomena, including electrochemical approaches for supercapacitors, especially their potential applications as supercapacitors based on these materials. Focus is also given to the recent advances of CPG-based electrodes for supercapacitors, and the electrochemical performances of CP-based promising composites with CNT, graphene oxides, and metal oxides is discussed. This review may provide an extensive reference for forthcoming insights into CPG-based supercapacitors for large-scale applications.

Synthesis of NiMn2O4/PANI nanosized composite with increased specific capacitance for energy storage applications

Polyaniline (PANI) stands out as a highly promising conducting polymer with potential for advanced utilization in high-performance pseudocapacitors. Therefore, there exists a pressing need to bolster the structural durability of PANI, achievable by developing composite materials that can enhance its viability for supercapacitor applications. In this particular study, a pioneering approach was undertaken to produce a novel NiMn2O4/PANI supercapacitor electrode material. A comprehensive array of analytical techniques was employed to ascertain the structural configuration, morphology, oxidation states of elements, composition, and surface characteristics of the electrode material. The electrochemical evaluation of the NiMn2O4/PANI composite shows a specific capacitance (Cs) of 1530 ± 2 F g-1 at 1 A g-1. Significantly, the composite material displays an outstanding 93.61% retention of its capacity after an extensive 10 000 cycles, signifying remarkable cycling stability, while the 2-electrode configuration reveals a Cs value of 764 F g-1 at 5 mV s-1 and 826 F g-1 at 1 A g-1 with a smaller charge transfer resistance (Rct) value of 0.67 Ω. Chronoamperometric tests showed excellent stability of the fabricated material up to 50 h. This significant advancement bears immense promise for its potential implementation in high-efficiency energy storage systems and heralds a new phase in the development of supercapacitor technology with improved stability and performance metrics.

Advanced High-Energy All-Solid-State Hybrid Supercapacitor with Nickel-Cobalt-Layered Double Hydroxide Nanoflowers Supported on Jute Stick-Derived Activated Carbon Nanosheets

Developing efficient, lightweight, and durable all-solid-state supercapacitors is crucial for future energy storage systems. The study focuses on optimizing electrode materials to achieve high capacitance and stability. This study introduces a novel two-step pyrolysis process to synthesize activated carbon nanosheets from jute sticks (JAC), resulting in an optimized JAC-2 material with a high yield (≈24%) and specific surface area (≈2600 m2 g-1). Furthermore, an innovative in situ synthesis approach is employed to synthesize hybrid nanocomposites (NiCoLDH-1@JAC-2) by integrating JAC nanosheets with nickel-cobalt-layered double hydroxide nanoflowers (NiCoLDH). These nanocomposites serve as positive electrode materials and JAC-2 as the negative electrode material in all-solid-state asymmetric hybrid supercapacitors (HSCs), exhibiting remarkable performance metrics. The HSCs achieve a specific capacitance of 750 F g-1, a specific capacity of 209 mAh g-1 (at 0.5 A g-1), and an energy density of 100 Wh kg-1 (at 250 W kg-1) using PVA/KOH solid electrolyte, while maintaining outstanding cyclic stability. Importantly, a density functional theory framework is utilized to validate the experimental findings, underscoring the potential of this novel approach for enhancing HSC performance and enabling the large-scale production of transition metal-based layered double hydroxides.

Enhancing supercapacitor performance of Ni-Co-Mn metal-organic frameworks by compositing it with polyaniline and reduced graphene oxide

Metal-organic frameworks (MOFs) are one of the most sought-after materials in the domain of supercapacitors and can be tailored to accommodate diverse compositions, making them amenable to facile functionalization. However, their intrinsic specific capacitance as well as energy density is minimal, which hinders their usage for advanced energy storage applications. Therefore, herein, we have prepared six electrodes, i.e., Ni-Co-Mn MOFs, polyaniline (PANI), and reduced graphene oxide (rGO) along with their novel nanocomposites, i.e., C1, C2, and C3, comprising MOFs : PANI : rGO in a mass ratio of 100 : 1 : 0.5, 100 : 1 : 1, and 100 : 1 : 10, respectively. The polyaniline conducting polymer and rGO enabled efficient electron transport, enhanced charge storage processes, substantial surface area facilitating higher loading of active materials, promoting electrochemical reactions, and ultimately enhanced nanocomposite system performance. As a result, scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques confirmed the successful synthesis and revealed distinct morphological features of the materials. Following electrochemical testing, it was observed that composition C2 exhibited the highest performance, demonstrating a groundbreaking specific capacitance of 1007 F g-1 at 1 A g-1. The device showed a good energy density of 25.11 W h kg-1 and a power density of 860 W kg-1. Remarkably, the device demonstrated a capacity retention of 115% after 1500 cycles, which is a clear indication of the wettability factor, according to the literature. The power law indicated b-values in a range of 0.58-0.64, verifying the hybrid-type behavior of supercapacitors.