Monodisperse carbon microspheres derived from potato starch for asymmetric supercapacitors

Sustainable Approach to Fabricate High-Performance Symmetry Supercapacitor Electrodes from Natural Coconut-Shell-Derived Porous Activated Carbon with Nickel Oxide Nanocomposites

This paper reports high specific capacitance of an activated carbon nickel oxide nanocomposite (PCNiO) electrode that has been synthesized from natural coconut shell using carbonization and an activated PCNiO nanocomposite with the help of a hydrothermal process. The structural phase, chemical change, morphology, and pore structure of the PCNiO nanocomposite were investigated using a variety of techniques including X-ray diffraction (XRD), Fourier transform infrared (FTIR), Brunauer-Emmett-Teller (BET), thermo-gravimetric analysis (TGA), Raman spectroscopy, field emission scanning electron microscopy (FESEM), and high-resolution transmission electron microscopy (HRTEM) techniques. Among the prepared samples, PCNiO-150 displays the most significant characteristics that were used to create symmetric supercapacitors (SSCs). It had a specific capacitance (C sp) of 598.6 F/g at a scan rate of 10 mV/s. The Galvanostatic charging-discharging (GCD) curves showed a high specific capacitance (C sp) of 656.2 F/g at a current density (CD) of 1.5 A/g. Additionally, even after 5000 cycles, it had achieved long-term cycle stability with capacitance retention of 78.34% and Coulombic efficiency of 97.55%. Its highest energy density (ED) and power density (PD) were 44 Wh kg-1 and 562.5 W kg-1, respectively. Additionally, the fabricated SSC device is serially connected to turn on a commercial green LED for 30-40 s at the time of the experiment. This paper proposes a novel environmentally sustainable and easy-to-use carbon source as well as a cost-effective and technologically unique approach for carbon supercapacitors in environmental applications.

Biopolymers-Derived Materials for Supercapacitors: Recent Trends, Challenges, and Future Prospects

Supercapacitors may be able to store more energy while maintaining fast charging times; however, they need low-cost and sophisticated electrode materials. Developing innovative and effective carbon-based electrode materials from naturally occurring chemical components is thus critical for supercapacitor development. In this context, biopolymer-derived porous carbon electrode materials for energy storage applications have gained considerable momentum due to their wide accessibility, high porosity, cost-effectiveness, low weight, biodegradability, and environmental friendliness. Moreover, the carbon structures derived from biopolymeric materials possess unique compositional, morphological, and electrochemical properties. This review aims to emphasize (i) the comprehensive concepts of biopolymers and supercapacitors to approach smart carbon-based materials for supercapacitors, (ii) synthesis strategies for biopolymer derived nanostructured carbons, (iii) recent advancements in biopolymer derived nanostructured carbons for supercapacitors, and (iv) challenges and future prospects from the viewpoint of green chemistry-based energy storage. This study is likely to be useful to the scientific community interested in the design of low-cost, efficient, and green electrode materials for supercapacitors as well as various types of electrocatalysis for energy production.

Nitrogen, phosphorus co-doped hollow porous carbon microspheres as an oxidase-like electrochemical sensor for baicalin

The extraordinary properties and unique structure of porous carbon has rapidly turned into a new favorite in the development and application of high-performance electrocatalytic sensor. Nitrogen, phosphorus co-doped hollow porous...

An asymmetric supercapacitor based on controllable WO3 nanorod bundle and alfalfa-derived porous carbon

A novel asymmetric supercapacitor (ASC) is assembled on the basis of an inerratic hexagonal-like WO₃ nanorod bundle as a negative electrode and graphene-like alfalfa-derived porous activated carbon (APAC) as the positive electrode in 1 M H₂SO₄ aqueous electrolyte. The WO₃ nanostructures prepared at pH of 1.6, 1.8, 2.0, 2.5 and 3.0 display hexagonal disc-like, nanorod bundle, inerratic hexagonal-like, sphere-like, and needle-shaped nanorod morphology. WO₃-2.0, which was prepared at a pH of 2.0, exhibits high specific capacitance (415.3 F g⁻¹ at 0.5 A g⁻¹). APAC-2, which had the mass ratios of dried alfalfa and ZnCl₂ as 1 : 2, showed a 3D porous structure, large surface area (1576.3 m² g⁻¹), high specific capacitance (262.1 F g⁻¹ at 0.5 A g⁻¹), good cycling stability with 96% of initial specific capacitance after 5000 consecutive cycles. The ASC assembled with WO₃-2.0 and APAC-2 exhibits high energy density (27.3 W h kg⁻¹ at a power density of 403.1 W kg⁻¹), as well as good electrochemical stability (82.6% capacitance retention after 5000 cycles). Such outstanding electrochemical behavior implies that the electrode materials are promising for practical energy-storage systems.

A asymmetric supercapacitor is assembled on the basis of an inerratic hexagonal-like WO₃ nanorod bundle as a negative electrode and graphene-like alfalfa-derived porous activated carbon as the positive electrode in 1 M H₂SO₄ aqueous electrolyte.

Biomass-derived O, N-codoped hierarchically porous carbon prepared by black fungus and Hericium erinaceus for high performance supercapacitor

Biomass-derived carbon materials have been widely researched due to their advantages such as low cost, environmental friendliness, readily available raw materials. Black fungus and Hericium erinaceus contain many kinds of amino acids. In this paper, unique O, N-codoped black fungus-derived activated carbons (FAC X ), and Hericium erinaceus-derived activated carbons (HAC X ) were prepared by KOH chemical activation under different temperatures without adding additional reagents containing nitrogen and oxygen functional groups, respectively. As electrode materials of symmetric supercapacitors, FAC2 and HAC2 calcined at 800 °C exhibited the highest specific capacitance of 209.3 F g-1 and 238.6 F g-1 at 1.0 A g-1 in the two-electrode configuration with 6.0 M KOH as the electrolyte, respectively. The X-ray photoelectron spectroscopy confirmed that the as-synthesized FAC X and HAC X contained small amounts of nitrogen and oxygen elements. Moreover, heteroatom-doped FAC2 and HAC2 electrode materials shown excellent rate performance (84.1% and 75.0% capacitance retention at 20 A g-1, respectively). By comparison, the oxygen-rich hierarchical porous carbon (HAC2) shows higher specific capacitance and energy density and longer cycling performance. Nevertheless, carbon-rich hierarchical porous carbon (FAC2) indicates excellent rate performance. Biomass-derived heteroatom self-doped porous carbons are expected to become ideal active materials for high performance supercapacitor.

Carbon-Based Composite Phase Change Materials for Thermal Energy Storage, Transfer, and Conversion

Phase change materials (PCMs) can alleviate concerns over energy to some extent by reversibly storing a tremendous amount of renewable and sustainable thermal energy. However, the low thermal conductivity, low electrical conductivity, and weak photoabsorption of pure PCMs hinder their wider applicability and development. To overcome these deficiencies and improve the utilization efficiency of thermal energy, versatile carbon materials have been increasingly considered as supporting materials to construct shape-stabilized composite PCMs. Despite some carbon-based composite PCMs reviews regarding thermal conductivity enhancement, a comprehensive review of carbon-based composite PCMs does not exist. Herein, a systematic overview of recent carbon-based composite PCMs for thermal storage, transfer, conversion (solar-to-thermal, electro-to-thermal and magnetic-to-thermal), and advanced multifunctional applications, including novel metal organic framework (MOF)-derived carbon materials are provided. The current challenges and future opportunities are also highlighted. The authors hope this review can provide in-depth insights and serve as a useful guide for the targeted design of high-performance carbon-based composite PCMs.

Biomass-Derived Porous Carbon Materials for Supercapacitor

The fast consumption of fossil energy accompanied by the ever-worsening environment urge the development of a clean and novel energy storage system. As one of the most promising candidates, the supercapacitor owns unique advantages, and numerous electrodes materials have been exploited. Hence, biomass-derived porous carbon materials (BDPCs), at low cost, abundant and sustainable, with adjustable dimension, superb electrical conductivity, satisfactory specific surface area (SSA) and superior electrochemical stability have been attracting intense attention and highly trusted to be a capable candidate for supercapacitors. This review will highlight the recent lab-scale methods for preparing BDPCs, and analyze their effects on BDPCs' microstructure, electrical conductivity, chemical composition and electrochemical properties. Future research trends in this field also will be provided.

Hierarchical Porous Carbon Microfibers Derived from Tamarind Seed Coat for High-Energy Supercapacitor Application

The overwhelming interest in supercapacitors has led to the search for various carbonaceous materials, leading to hierarchical porous carbons. Herein, we report a natural biomass (tamarind seed)-based hierarchical porous carbon without any template and activated by a facile scheme. The tamarind seed coat-based hierarchical porous carbon possessed a unique configuration, making the material exhibit superior supercapacitor properties. A single carbon fiber hosting a distinctive micro- and mesoporous structure formed a connecting thread between the pores. This unique structure enabled high surface area and high capacitance. The highest surface area obtained by this method was 1702 m² g^-1, whereas the capacitance was 157 F g^-1 in 6 M KOH. Further, an ionic liquid-based electrolyte revealed 78 F g^-1 at a current density of 0.5 A g^-1. Outstanding capacity retentions of 96 and 93% were obtained over 1000 cycles at a current density of 2 A g^-1 for aqueous (6 M KOH) and ionic liquid (1-butyl 3-methyl imidazoliumbistrifluorosulfonylimide) electrolytes, respectively. The high charge-storage ability of the porous carbon microfibers (PCMFs) can be ascribed to the coexistence of micro- and mesopores. The power characteristics and the cyclic stability of PCMF materials were appealing in both electrolytes. The synthesis process described is amenable for large-scale applications with less complexity.

A high-performance asymmetric supercapacitor based on vanadyl phosphate/carbon nanocomposites and polypyrrole-derived carbon nanowires

A novel asymmetric supercapacitor device in an aqueous electrolyte is fabricated using a vanadyl phosphate/carbon nanocomposite as the positive electrode and a polypyrrole-derived carbon nanowire as the negative electrode. The vanadyl phosphate/carbon nanocomposites are synthesized by a simple two-step approach in which layered VOPO₄·2H₂O is first intercalated by dodecylamine and then annealed at high temperature, leading to the in situ carbonization of the intercalated dodecylamine. It is found that the sample in which the incorporated carbon with a high degree of graphitization exhibits a high specific capacitance of 469 F g^-1 at a current density of 1 A g^-1 and excellent rate performance (retained 77% capacitance at 10 A g^-1). A polypyrrole-derived carbon nanowire is synthesized by the direct carbonization of nanowire-shaped polypyrrole, revealing a rough surface of nanowire-like frameworks and good electrochemical behavior. Taking advantage of both positive and negative materials, the assembled asymmetric supercapacitor device exhibits a high energy density of 30.6 W h kg^-1 at a high power density of 813 W kg^-1 in a wide voltage region of 0-1.6 V, as well as a good electrochemical stability (84.3% capacitance retention after 5000 cycles). The present work can shed light on the fabrication of novel asymmetric supercapacitors with high-performance.

High-Performance Flexible Supercapacitors obtained via Recycled Jute: Bio-Waste to Energy Storage Approach

In search of affordable, flexible, lightweight, efficient and stable supercapacitors, metal oxides have been shown to provide high charge storage capacity but with poor cyclic stability due to structural damage occurring during the redox process. Here, we develop an efficient flexible supercapacitor obtained by carbonizing abundantly available and recyclable jute. The active material was synthesized from jute by a facile hydrothermal method and its electrochemical performance was further enhanced by chemical activation. Specific capacitance of 408 F/g at 1 mV/s using CV and 185 F/g at 500 mA/g using charge-discharge measurements with excellent flexibility (~100% retention in charge storage capacity on bending) were observed. The cyclic stability test confirmed no loss in the charge storage capacity of the electrode even after 5,000 charge-discharge measurements. In addition, a supercapacitor device fabricated using this carbonized jute showed promising specific capacitance of about 51 F/g, and improvement of over 60% in the charge storage capacity on increasing temperature from 5 to 75 °C. Based on these results, we propose that recycled jute should be considered for fabrication of high-performance flexible energy storage devices at extremely low cost.

High Per formance and Flexible Supercapacitors based on Carbonized Bamboo Fibers for Wide Temperature Applications

High performance carbonized bamboo fibers were synthesized for a wide range of temperature dependent energy storage applications. The structural and electrochemical properties of the carbonized bamboo fibers were studied for flexible supercapacitor applications. The galvanostatic charge-discharge studies on carbonized fibers exhibited specific capacity of ~510F/g at 0.4 A/g with energy density of 54 Wh/kg. Interestingly, the carbonized bamboo fibers displayed excellent charge storage stability without any appreciable degradation in charge storage capacity over 5,000 charge-discharge cycles. The symmetrical supercapacitor device fabricated using these carbonized bamboo fibers exhibited an areal capacitance of ~1.55 F/cm(2) at room temperature. In addition to high charge storage capacity and cyclic stability, the device showed excellent flexibility without any degradation to charge storage capacity on bending the electrode. The performance of the supercapacitor device exhibited ~65% improvement at 70 °C compare to that at 10 °C. Our studies suggest that carbonized bamboo fibers are promising candidates for stable, high performance and flexible supercapacitor devices.

Spectroscopic tracking of mechanochemical reactivity and modification of a hydrothermal char

A glucose hydrothermal char (HTC) was synthesized and ball milled to break chemical bonds, generate defects, and form new chemical structures.

Highly energetic flexible all-solid-state asymmetric supercapacitor with Fe2O3 and CuO thin films

Figure shows (A) XRD pattern of Fe₂O₃ thin film, (B and C) FE-SEM images of Fe₂O₃ thin film, (D) XRD pattern of CuO thin film and (E and F) FE-SEM images of CuO thin film.

Preparation and thermal properties of shape-stabilized composite phase change materials based on polyethylene glycol and porous carbon prepared from potato

A shape-stabilized composite phase change material comprising PEG and porous carbon was prepared by absorbing PEG into porous carbon.

Nitrogen-doped heterostructure carbon functionalized by electroactive organic molecules for asymmetric supercapacitors with high energy density

The organic molecules (TCBQ, AQ) with multi-electron redox center are selected to modify nitrogen-doped heterostructure carbon (NHC) by noncovalent interaction and the electrode materials show good performances and potential self-matching behaviors.

One-step molten salt carbonization (MSC) of firwood biomass for capacitive carbon

Capacitive carbon is prepared via the molten salt carbonization of firwood biomass, and the size of the feedstock does matter.

Electrochemical performances of CoFe2O4 nanoparticles and a rGO based asymmetric supercapacitor

CoFe₂O₄ nanoparticles were prepared using a polyethylene glycol (PEG) assisted solution combustion method.