In Situ Synthesis of a Polyaniline/ Fe-Ni Codoped Co3O4 Composite for the Electrode Material of Supercapacitors with Improved Cyclic Stability

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.

Square-Facet Nanobar MOF-Derived Co3O4@Co/N-doped CNT Core-Shell-based Nanocomposites as Cathode Materials for High-Performance Supercapacitor Studies

The binary as well as ternary nanocomposites of the square-facet nanobar Co-MOF-derived Co₃O₄@Co/N-CNTs (N-CNTs: nitrogen-doped carbon nanotubes) with Ag NPs and rGO have been synthesized via an easy wet chemical route, and their supercapacitor behavior was then studied. At a controlled pH of the precursor solution, square-facet nanobars of Co-MOF were first synthesized by the solvothermal method and then pyrolyzed under a controlled nitrogen atmosphere to get a core-shell system of Co₃O₄@Co/N-CNTs. In the second step, different compositions of Co₃O₄@Co/N-CNT core-shell structures were formed by an ex-situ method with Ag NPs and rGO moieties. Among several bare, binary, and ternary compositions tested in 6 M aqueous KOH electrolyte, a ternary nanocomposite having a 7.0:1.5:1.5 stoichiometric ratio of Co₃O₄@Co/N-CNT, Ag NPs, and rGO, respectively, reported the highest specific capacitance (3393.8 F g^-1 at 5 mV s^-1). The optimized nanocomposite showed the energy density, power density, and Coulombic efficiency of 74.1 W h.kg^-1, 443.7 W.kg^-1, and 101.3%, respectively, with excellent electrochemical stability. After testing an asymmetrical supercapacitor with a Co₃O₄@Co/N-CNT/Ag NPs/rGO/nickel foam cathode and an activated carbon/nickel foam anode, it showed 4.9 W h.kg^-1 of energy density and 5000.0 W.kg^-1 of power density.

Nanoengineering of NiO/MnO2/GO Ternary Composite for Use in High-Energy Storage Asymmetric Supercapacitor and Oxygen Evolution Reaction (OER)

Designing multifunctional nanomaterials for high performing electrochemical energy conversion and storage devices has been very challenging. A number of strategies have been reported to introduce multifunctionality in electrode/catalyst materials including alloying, doping, nanostructuring, compositing, etc. Here, we report the fabrication of a reduced graphene oxide (rGO)-based ternary composite NiO/MnO₂/rGO (NMGO) having a range of active sites for enhanced electrochemical activity. The resultant sandwich structure consisted of a mesoporous backbone with NiO and MnO₂ nanoparticles encapsulated between successive rGO layers, having different active sites in the form of Ni-, Mn-, and C-based species. The modified structure exhibited high conductivity owing to the presence of rGO, excellent charge storage capacity of 402 F·g^-1 at a current density of 1 A·g^-1, and stability with a capacitance retention of ~93% after 14,000 cycles. Moreover, the NMGO//MWCNT asymmetric device, assembled with NMGO and multi-wall carbon nanotubes (MWCNTs) as positive and negative electrodes, respectively, exhibited good energy density (28 Wh·kg^-1), excellent power density (750 W·kg^-1), and capacitance retention (88%) after 6000 cycles. To evaluate the multifunctionality of the modified nanostructure, the NMGO was also tested for its oxygen evolution reaction (OER) activity. The NMGO delivered a current density of 10 mA·cm^-2 at the potential of 1.59 V versus RHE. These results clearly demonstrate high activity of the modified electrode with strong future potential.

Aluminum Doping Effects on Interface Depletion Width of Low Temperature Processed ZnO Electron Transport Layer-Based Perovskite Solar Cells

Rapid improvement in efficiency and stabilities of perovskite solar cells (PSCs) is an indication of its prime role for future energy demands. Various research has been carried out to improve efficiency including reducing the exciton recombination and enhancement of electron mobilities within cells by using electron transport material (ETM). In the present research, electrical, optical, and depletion width reduction properties of low temperature processed ZnO electron transport layer-based perovskite solar cells are studied. The ZnO thin films vary with the concentration of Al doping, and improvement of optical transmission percentage up to 80% for doped samples is confirmed by optical analysis. Reduction in electrical resistance for 1% Al concentration and maximum conductivity 11,697.41 (1/Ω-cm) among the prepared samples and carrier concentration 1.06×10²² cm⁻³ were corroborated by Hall effect measurements. Systematic impedance spectroscopy of perovskite devices with synthesized ETM is presented in the study, while the depletion width reduction is observed by Mott Schottky curves. IV measurements of the device and the interfacial charge transfer between the absorber layer of methylammonium lead iodide and ETM have also been elaborated on interface electronic characteristics.

Fabrication of Co3O4 nanoparticle-decorated porous activated carbon electrode for the electrochemical detection of 4-nitrophenol

Preparation of Co3O4@BVFC for the electrochemical detection of 4-NP.