Well-defined graphene/polyaniline flake composites for high performance supercapacitors

Recent Progress in Polyaniline and its Composites for Supercapacitors

Polyaniline (PANI) has piqued the interest of nanotechnology researchers due to its potential as an electrode material for supercapacitors. Despite its ease of synthesis and ability to be doped with a wide range of materials, PANI's poor mechanical properties have limited its use in practical applications. To address this issue, researchers investigated using PANI composites with materials with highly specific surface areas, active sites, porous architectures, and high conductivity. The resulting composite materials have improved energy storage performance, making them promising electrode materials for supercapacitors. Here, we provide an overview of recent developments in PANI-based supercapacitors, focusing on using electrochemically active carbon and redox-active materials as composites. We discuss challenges and opportunities of synthesizing PANI-based composites for supercapacitor applications. Furthermore, we provide theoretical insights into the electrical properties of PANI composites and their potential as active electrode materials. The need for this review stems from the growing interest in PANI-based composites to improve supercapacitor performance. By examining recent progress in this field, we provide a comprehensive overview of the current state-of-the-art and potential of PANI-based composites for supercapacitor applications. This review adds value by highlighting challenges and opportunities associated with synthesizing and utilizing PANI-based composites, thereby guiding future research directions.

A High-Energy Asymmetric Supercapacitor Based on Tomato-Leaf-Derived Hierarchical Porous Activated Carbon and Electrochemically Deposited Polyaniline Electrodes for Battery-Free Heart-Pulse-Rate Monitoring

A simple and scalable method to fabricate a novel high-energy asymmetric supercapacitor using tomato-leaf-derived hierarchical porous activated carbon (TAC) and electrochemically deposited polyaniline (PANI) for a battery-free heart-pulse-rate monitor is reported. In this study, TAC is prepared by simple pyrolysis, exhibiting nanosheet-type morphology and a high specific surface area of ≈1440 m2 g-1 , and PANI is electrochemically deposited onto carbon cloth. The TAC- and PANI- based asymmetric supercapacitor demonstrates an electrochemical performance superior to that of symmetric supercapacitors, delivering a high specific capacitance of 248 mF cm-2 at a current density of 1.0 mA cm-2 . The developed asymmetric supercapacitor shows a high energy density of 270 µWh cm-2 at a power density of 1400 µW cm-2 , as well as an excellent cyclic stability of ≈95% capacitance retention after 10 000 charging-discharging cycles while maintaining ≈98% Coulombic efficiency. Impressively, the series-connected asymmetric supercapacitors can operate a battery-free heart-pulse-rate monitor extremely efficiently upon solar-panel charging under regular laboratory illumination.

Architecturally Robust Graphene-Encapsulated MXene Ti2CT x@Polyaniline Composite for High-Performance Pouch-Type Asymmetric Supercapacitor

A harmonized three-component composite system which preserves the characteristics of individual components is of interest in the field of energy storage. Here, we present a graphene-encapsulated MXene Ti₂CT _x@polyaniline composite (GMP) material realized in a systematically stable configuration with different ternary nanomaterials for supercapacitor electrodes. Due to the different ζ-potentials in a high-pH solution, chemically converted graphene (negatively charged) is thoroughly unfolded to allow full encapsulation, but the MXene Ti₂CT _x@polyaniline composite with a low positive ζ-potential is easily attracted toward a counter-charged substance. The obtained GMP electrode exhibits improved cycling stability and better electrochemical performance owing to the use of mechanically robust and chemically inert graphene and the densely intercalated conductive polyaniline between the multilayer MXenes. The GMP electrode has a high gravimetric capacitance of 635 F g^-1 (volumetric capacitance of 1143 F cm^-3) at a current density of 1 A g^-1 with excellent cycling stability of 97.54% after 10 000 cycles. Furthermore, the asymmetric pouch-type supercapacitor assembled using the GMP as a positive electrode and graphene as a negative electrode yields a high energy density of 42.3 Wh kg^-1 at a power density of 950 W kg^-1 and remarkable cycling stability (94.25% after 10 000 cycles at 10 A g^-1).

Twist fibrous structure of CS–SnO2–PANI ternary hybrid composite for electrochemical capacitance performance

In this study, a twisted fibrous CS–SnO₂–PANI ternary hybrid composite structure was synthesized via a two step method; the CS–SnO₂ hybrid composite was prepared by a simple chemical precipitation method and the resulting CS–SnO₂ suspension was coated with PANI by in situ chemical oxidative polymerization of aniline monomer in acidic medium using ammonium persulphate as the oxidant.

Synthesis and spectroscopic analysis of polydiphenylamine via oxidation with bentonite clay in the solid state

In this study, solids of polydiphenylamine (PDPA) synthesized mechanochemically by reaction with bentonite (PDPAOB) were studied using Raman spectroscopy. It was possible to identify the chemical species in the PDPA-bentonite compound. The spectra obtained were compared to the spectra of PDPA prepared chemically by oxidation of DPA with K2S2O8 in the solid state, and PDPA produced electrochemically, with the aim of studying the characteristic frequencies of the aromatic segments (DPB), radical cation (DPB(+)) and dication (DPB(2+)) of N,N-diphenylbenzidine (DPB) in the polymer structure of the PDPA. To analyze the segments present, the band characteristic of CC asymmetric stretching of the aromatic ring in the Raman spectra was deconvoluted because of the widening of the band and shifts observed by irradiation at wavelengths of 532 and 785 nm. This procedure showed that there are three distinct contributions in the spectra which facilitate the monitoring of changes in the contributions of the segments in the materials doped with HCl (PDPAOBD) and de-doped with NH4OH, (PDPAOBR).

Polyaniline nanofibers–graphene oxide nanoplatelets composite thin film electrodes for electrochemical capacitors

A facile electrochemical method was applied to synthesize graphene oxide nanoplatelets and polyaniline nanofiber composite thin film electrodes for supercapacitors.

Graphene-wrapped polyaniline hollow spheres as novel hybrid electrode materials for supercapacitor applications

Polyaniline hollow spheres (PANI-HS)@electrochemical reduced graphene oxide (ERGO) hybrids with core-shell structures have been fabricated via a solution-based coassembly process. The hollow nanostructured designing for the PANI-HS greatly enlarges the specific surface area, providing high electroactive regions and short diffusion lengths for both charge and ion transport. The wrapping of ERGO sheets on the PANI-HS can offer highly conductive pathways by bridging individual PANI-HS together, thus facilitating the rate and cycling performance of supercapacitors. The specific capacitance of PANI-HS36@ERGO hybrids can reach 614 F g(-1) at a current density of 1 A g(-1). Furthermore, the capacitance of the PANI-HS36@ERGO hybrids maintains 90% after 500 charging/discharging cycles at a current density of 1 A g(-1), indicating a good cycling stability. The greatly enhanced electrochemical performance can be ascribed to the synergic effects of the two components of PANI-HS and ERGO, suggesting that the PANI-HS@ERGO hybrids as novel electrode materials may have potential applications in high-performance energy storage devices.