Facile Electrodeposition of NiCo2O4 Nanosheets on Porous Carbonized Wood for Wood-Derived Asymmetric Supercapacitors

A comprehensive review on preparation and functional application of the wood aerogel with natural cellulose framework

As the traditional aerogel has defects such as poor mechanical properties, complicated preparation process, high energy consumption and non-renewable, wood aerogel as a new generation of aerogel shows unique advantages. With a natural cellulose framework, wood aerogel is a novel nano-porous material exhibiting exceptional properties such as light weight, high porosity, large specific surface area, and low thermal conductivity. Furthermore, its adaptability to further functionalization enables versatile applications across diverse fields. Driven by the imperative for sustainable development, wood aerogel as a renewable and eco-friendly material, has garnered significant attention from researchers. This review introduces preparation methods of wood aerogel based on the top-down strategy and analyzes the factors influencing their key properties intending to obtain wood aerogels with desirable properties. Avenues for realizing its functionality are also explored, and research progress across various domains are surveyed, including oil-water separation, conductivity and energy storage, as well as photothermal conversion. Finally, potential challenges associated with wood aerogel exploitation and utilization are addressed, alongside discussions on future prospects and research directions. The results emphasize the broad research value and future prospects of wood aerogels, which are poised to drive high-value utilization of wood and foster the development of green multifunctional aerogels.

Ammonium Ion-Pre-Intercalated MnO2 on Carbon Cloth for High-Energy Density Asymmetric Supercapacitors

With the continuous development of green energy, society is increasingly demanding advanced energy storage devices. Manganese-based asymmetric supercapacitors (ASCs) can deliver high energy density while possessing high power density. However, the structural instability hampers the wider application of manganese dioxide in ASCs. A novel MnO2-based electrode material was designed in this study. We synthesized a MnO2/carbon cloth electrode, CC@NMO, with NH4+ ion pre-intercalation through a one-step hydrothermal method. The pre-intercalation of NH4+ stabilizes the MnO2 interlayer structure, expanding the electrode stable working potential window to 0-1.1 V and achieving a remarkable mass specific capacitance of 181.4 F g-1. Furthermore, the ASC device fabricated using the CC@NMO electrode and activated carbon electrode exhibits excellent electrochemical properties. The CC@NMO//AC achieves a high energy density of 63.49 Wh kg-1 and a power density of 949.8 W kg-1. Even after cycling 10,000 times at 10 A g-1, the device retains 81.2% of its capacitance. This work sheds new light on manganese dioxide-based asymmetric supercapacitors and represents a significant contribution for future research on them.

CoNiO2/Co3O4 Nanosheets on Boron Doped Diamond for Supercapacitor Electrodes

Developing novel supercapacitor electrodes with high energy density and good cycle stability has aroused great interest. Herein, the vertically aligned CoNiO2/Co3O4 nanosheet arrays anchored on boron doped diamond (BDD) films are designed and fabricated by a simple one-step electrodeposition method. The CoNiO2/Co3O4/BDD electrode possesses a large specific capacitance (214 mF cm-2) and a long-term capacitance retention (85.9% after 10,000 cycles), which is attributed to the unique two-dimensional nanosheet architecture, high conductivity of CoNiO2/Co3O4 and the wide potential window of diamond. Nanosheet materials with an ultrathin thickness can decrease the diffusion length of ions, increase the contact area with electrolyte, as well as improve active material utilization, which leads to an enhanced electrochemical performance. Additionally, CoNiO2/Co3O4/BDD is fabricated as the positive electrode with activated carbon as the negative electrode, this assembled asymmetric supercapacitor exhibits an energy density of 7.5 W h kg-1 at a power density of 330.5 W kg-1 and capacity retention rate of 97.4% after 10,000 cycles in 6 M KOH. This work would provide insights into the design of advanced electrode materials for high-performance supercapacitors.

Influence of Fe Doping on the Electrochemical Performance of a ZnO-Nanostructure-Based Electrode for Supercapacitors

ZnO is a potential candidate for providing an economic and environmentally friendly substitute for energy storage materials. Therefore, in this work, Fe-doped ZnO nanostructures prepared using the microwave irradiation procedure were investigated for structural, morphological, magnetic, electronic structural, specific surface area and electrochemical properties to be used as electrodes for supercapacitors. The X-ray diffraction, high-resolution transmission electron microscopy images, and selective-area electron diffraction pattern indicated that the nanocrystalline structures of Fe-doped ZnO were found to possess a hexagonal wurtzite structure. The effect of Fe doping in the ZnO matrix was observed on the lattice parameters, which were found to increase with the dopant concentration. Rods and a nanosheet-like morphology were observed via FESEM images. The ferromagnetic nature of samples is associated with the presence of bound magnetic polarons. The enhancement of saturation magnetization was observed due to Fe doping up to 3% in correspondence with the increase in the number of bound magnetic polarons with an Fe content of up to 3%. This behavior is observed as a result of the change in the oxidation state from +2 to +3, which was a consequence of Fe doping ranging from 3% to 5%. The electrode performance of Fe-doped ZnO nanostructures was studied using electrochemical measurements. The cyclic voltammetry (CV) results inferred that the specific capacitance increased with Fe doping and displayed a high specific capacitance of 286 F·g-1 at 10 mV/s for 3% Fe-doped ZnO nanostructures and decreased beyond that. Furthermore, the stability of the Zn0.97Fe0.03O electrode, which was examined by performing 2000 cycles, showed excellent cyclic stability (85.0% of value retained up to 2000 cycles) with the highest specific capacitance of 276.4 F·g-1, signifying its appropriateness as an electrode for energy storage applications.

A Flexible Supercapacitor Based on Niobium Carbide MXene and Sodium Anthraquinone-2-Sulfonate Composite Electrode

MXene-based composites have been widely used in electric energy storage device. As a member of MXene, niobium carbide (Nb2C) is a good electrode candidate for energy storage because of its high specific surface area and electronic conductivity. However, a pure Nb2C MXene electrode exhibits limited supercapacitive performance due to its easy stacking. Herein, sodium anthraquinone-2-sulfonate (AQS) with high redox reactivity was employed as a tailor to enhance the accessibility of ions and electrolyte and enhance the capacitance performance of Nb2C MXene. The resulting Nb2C-AQS composite had three-dimensional porous layered structures. The supercapacitors (SCs) based on the Nb2C-AQS composite exhibited a considerably higher electrochemical capacitance (36.3 mF cm-2) than the pure Nb2C electrode (16.8 mF cm-2) at a scan rate of 20 mV s-1. The SCs also exhibited excellent flexibility as deduced from the almost unchanged capacitance values after being subjected to bending. A capacitance retention of 99.5% after 600 cycles was observed for the resulting SCs, indicating their good cycling stability. This work proposes a surface modification method for Nb2C MXene and facilitates the development of high-performance SCs.

Activated Carbon Derived from Waste Oil Shale Semi-Coke for Supercapacitor Application

As fossil fuels gradually deplete, oil shale, one of the world's largest energy resources, has attracted much attention. Oil shale semi-coke (OSS) is the main byproduct of oil shale pyrolysis, which is produced in large quantities and causes severe environmental pollution. Therefore, there is an urgent need to explore a method suitable for the sustainable and effective utilization of OSS. In this study, OSS was used to prepare activated carbon by microwave-assisted separation and chemical activation, which was then applied in the field of supercapacitors. Raman, XRD, FT-IR, TEM, and nitrogen adsorption-desorption were adopted to characterize activated carbon. The results showed that ACF activated with FeCl₃-ZnCl₂/carbon as a precursor has larger specific surface area, suitable pore size, and higher degree of graphitization compared with the materials prepared by other activation methods. The electrochemical properties of several active carbon materials were also evaluated by CV, GCD, and EIS measurements. The specific surface area of ACF is 1478 m² g^-1, when the current density is 1 A g^-1, the specific capacitance is 185.0 F g^-1. After 5000 cycles of testing, the capacitance retention rate was as high as 99.5%, which is expected to provide a new strategy of converting waste products to low-cost activated carbon materials for high-performance supercapacitors.

A 3D stacked corrugated pore structure composed of CoNiO2 and polyaniline within the tracheids of wood-derived carbon for high-performance asymmetric supercapacitors

A novel 3D stacked corrugated pore structure of polyaniline (PANI)/CoNiO₂@activated wood-derived carbon (AWC) has been successfully constructed to prepare high-performance electrode materials for supercapacitors. AWC functions as a supporting framework that provides ample attachment sites for the loaded active materials. The CoNiO₂ nanowire substrate, consisting of 3D stacked pores, not only serves as a template for subsequent PANI loading, but also acts as an effective buffer to mitigate the volume expansion of the PANI during ionic intercalation. The distinctive corrugated pore structure of PANI/CoNiO₂@AWC facilitates electrolyte contact and significantly enhances the electrode material properties. The PANI/CoNiO₂@AWC composite materials exhibit excellent performance (14.31F cm^-2 at 5 mA cm^-2) and superior capacitance retention (80% from 5 to 30 mA cm^-2), owing to the synergistic effect among their components. Finally, PANI/CoNiO₂@ AWC//reduced graphene oxide (rGO)@AWC asymmetric supercapacitor is assembled, which has a wide operating voltage (0 ∼ 1.8 V), high energy density (4.95 mWh cm^-3 at 26.44 mW cm^-3) and cycling stability (90.96% after 7000 cycles).

Fabrication of Ru/WO3-W2N/N-doped carbon sheets for hydrogen evolution reaction

Recent experimental analysis indicates WO₃-based nanostructures exhibit poor hydrogen evolution reactivity, particularly in alkaline medium, arising from the low electron transfer rate. It is imperative to tune the composition and structure of WO₃ to boost the cleavage of H-OH bond. Here, we construct Ru/WO₃-W₂N/N-doped carbon sheets (Ru/WO₃-W₂N/NC) using m-WO₃ nanosheets as precursors with the aid of RuCl₃, Tris (hydroxymethyl) aminomethane, and dopamine. Structural investigation reveals the formation of N-doped carbon sheets, Ru nanoparticles, and WO₃-W₂N. As a result, hydrogen evolution reactivity is greatly improved on Ru/WO₃-W₂N/N-doped carbon sheets with 64 mV at 10 mA/cm² in 1 mol/L (M) KOH, outperforming most of WO₃-based electrocatalysts in previous literatures. Meanwhile, it facilitates the generation of H₂ in 0.5 M H₂SO₄ with the excellent activity of 110 mV at 10 mA/cm². Our work provides an efficient strategy to tailor the electronic structure of WO₃ to catalyze acidic and alkaline hydrogen evolution reaction.

Fabrication of highly efficient Rh-doped cobalt-nickel-layered double hydroxide/MXene-based electrocatalyst with rich oxygen vacancies for hydrogen evolution

The development of nonprecious metal catalysts for producing hydrogen from economical alkaline water electrolysis that is both stable and efficient is crucial but remains challenging. In this study, Rh-doped cobalt-nickel-layered double hydroxide (CoNi LDH) nanosheet arrays with abundant oxygen vacancies (Ov) in-situ grown on Ti₃C₂T_x MXene nanosheets (Rh-CoNi LDH/MXene) were successfully fabricated. The synthesized Rh-CoNi LDH/MXene exhibited excellent long-term stability and a low overpotential of 74.6 ± 0.4 mV at -10 mA cm^-2 for hydrogen evolution reaction (HER) owing to its optimized electronic structure. Experimental results and density functional theory calculations revealed that the incorporation of Rh dopant and Ov into CoNi LDH and the coupling interface between Rh-CoNi LDH and MXene optimized the hydrogen adsorption energy, which accelerated the hydrogen evolution kinetics, thereby accelerating the overall alkaline HER process. This work presents a promising strategy for designing and synthesizing highly efficient electrocatalysts for electrochemical energy conversion devices.

Highly Porous Carbon Aerogels for High-Performance Supercapacitor Electrodes

In recent years, porous carbon materials with high specific surface area and porosity have been developed to meet the commercial demands of supercapacitor applications. Carbon aerogels (CAs) with three-dimensional porous networks are promising materials for electrochemical energy storage applications. Physical activation using gaseous reagents provides controllable and eco-friendly processes due to homogeneous gas phase reaction and removal of unnecessary residue, whereas chemical activation produced wastes. In this work, we have prepared porous CAs activated by gaseous carbon dioxide, with efficient collisions between the carbon surface and the activating agent. Prepared CAs display botryoidal shapes resulting from aggregation of spherical carbon particles, whereas activated CAs (ACAs) display hollow space and irregular particles from activation reactions. ACAs have high specific surface areas (2503 m² g^-1) and large total pore volumes (1.604 cm³ g^-1), which are key factors for achieving a high electrical double-layer capacitance. The present ACAs achieved a specific gravimetric capacitance of up to 89.1 F g^-1 at a current density of 1 A g^-1, along with a high capacitance retention of 93.2% after 3000 cycles.

Collaboration of two-star nanomaterials: The applications of nanocellulose-based metal organic frameworks composites

Nanocellulose, as the star nanomaterial in carbohydrate polymers, has excellent mechanical properties, biodegradability, and easy chemical modification. However, further practical applications of nanocellulose are limited by their inadequate functionalization. Metal-organic frameworks (MOFs), as the star nanomaterial in functional polymers, have a large surface area, high porosity, and adjustable structure. The collaboration of nanocellulose and MOFs is a desirable strategy to make composites especially interesting for multifunctional and multi-field applications. What sparks will be produced by the collaboration of two-star nanomaterials? In this review article, we highlight an up-to-date overview of nanocellulose-based MOFs composites. The sewage treatment, gas separation, energy storage, and biomedical applications are mainly summarized. Finally, the challenges and research trends of nanocellulose-based MOFs composites are prospected. We hope this review may provide a valuable reference for the development and applications of carbohydrate polymer composites soon.

Valorization of Banana Peel Using Carbonization: Potential Use in the Sustainable Manufacturing of Flexible Supercapacitors

Sustainable and environmentally friendly activated carbon from biomass materials is proposed to produce supercapacitors from banana peels and has the potential to replace the non-sustainable and hazardous process from either graphite or/and fossil fuels. In order to determine the potential of using banana peel for supercapacitor application, raw banana peel, a bio-waste, was activated both mechanically and chemically to observe the real differences. The sample was activated at 700 °C and chemically activated using KOH. Characterization of activated banana peel was performed using FTIR, DLS, TGA and XRD analytical equipment. FTIR analysis revised the presence of hydroxyl, carbonyl and aromatic compounds on a banana peel cellulose-based carbon. The TGA results proved that 700 °C could be sufficient to totally carbonize banana peel. DLS clearly showed a strong difference between the carbonized and KOH-activated material in particle size distribution. Meanwhile, surface area analysis using BET displayed an increase from 553.862 m²/g to 565.024 m²/g BET in surface area (SBET) when carbon was activated using KOH with a nitrogen isotherm at 77.350 K. Specific capacitance was increased from 0.3997 Fg^-1 to 0.821 Fg^-1, suggesting more than a 100% increase in the specific capacity due to KOH activation, as proved by the cyclic voltammetry (CV) curve. The X-ray diffraction results revealed the patterns of activated carbon. The findings demonstrated the feasibility of using banana peel waste as a low-cost and sustainable material for the preparation of flexible supercapacitor batteries.

Biodegradable Polymers in Triboelectric Nanogenerators

Triboelectric nanogenerators (TENGs) have attracted much attention because they not only efficiently harvest energy from the surrounding environment and living organisms but also serve as multifunctional sensors toward the detection of various chemical and physical stimuli. In particular, biodegradable TENG (BD-TENG) represents an emerging type of self-powered device that can be degraded, either in physiological environments as an implantable power source without the necessity of second surgery for device retrieval, or in the ambient environment to minimize associated environmental pollution. Such TENGs or TNEG-based self-powered devices can find important applications in many scenarios, such as tissue regeneration, drug release, pacemakers, etc. In this review, the recent progress of TENGs developed on the basis of biodegradable polymers is comprehensively summarized. Material strategies and fabrication schemes of biodegradable and self-powered devices are thoroughly introduced according to the classification of plant-degradable polymer, animal-degradable polymer, and synthetic degradable polymer. Finally, current problems, challenges, and potential opportunities for the future development of BD-TENGs are discussed. We hope this work may provide new insights for modulating the design of BD-TNEGs that can be beneficial for both environmental protection and healthcare.

Electrochemical and Electrical Performances of High Energy Storage Polyaniline Electrode with Supercapattery Behavior

Polyaniline (PANI), due to its highly reversible electrochemistry with superior energy storage and delivery characteristics, is considered as an electrode material in batteries, capacitors, and hybrid systems. We used a facile electrochemical synthesis for the formation of the PANI electrode using galvanostatic polymerization of aniline on the graphite electrode at the current density of 2.0 mA cm^-2 from the aqueous electrolyte containing 0.25 mol dm^-3 aniline and 1.0 mol dm^-3 H₂SO₄. Electrochemical and electrical characterization suggested excellent energy storage features of the PANI electrode in a three-electrode system with specific energy up to 53 Wh kg^-1 and specific power up to 7600 W kg^-1. After 2000 successive charge/discharge cycles at 9.5 Ag^-1, the PANI electrode retained 95% of the initial capacity, with practically unaltered Coulombic efficiency of nearly 98%, providing a good base for future studies and practical applications.

Semi-Embedding Zn-Co3O4 Derived from Hybrid ZIFs into Wood-Derived Carbon for High-Performance Supercapacitors

Transition metal oxides (TMOs) can provide high theoretical capacitance due to the change of multiple valence states of transition metals. However, their intrinsic drawbacks, including poor electrical conductivity, lower energy density, and huge volume expansion, will result in the pulverization of electrode materials and restricted electrochemical kinetics, thus leading to poor rate capability and rapid capacity fading. Composite electrodes based on transition metal oxides and carbon-based materials are considered to be promising candidates for overcoming these limitations. Herein, we reported a preparation method of hybrid ZIFs derived Zn-doped Co3O4/carbon (Zn-Co3O4/C-230) particles semi-embedded in wood-derived carbon skeleton for integrated electrodes. A large specific surface area, excellent conductivity, and electrochemical stability provide a larger electrochemical activity and potential window for the electrode. Prepared Zn-Co3O4@CW-230 electrode (0.6 mm thick) displays ultrahigh area specific capacitances of 7.83 and 6.46 F cm-2 at the current densities of 5 and 30 mA cm-2, respectively. Moreover, a symmetric supercapacitor assembled by two identical Zn-Co3O4@CW-230 electrodes delivers a superior area-specific capacitance of 2.61 F cm-2 at the current densities of 5 mA cm-2 and great energy densities of 0.36 mWh cm-2 (6.0 mWh cm-3) at 2.5 mW cm-2, while maintaining 97.3% of initial capacitance over 10,000 cycles. It notably outperforms those of most carbon-based metal oxides, endowing the Zn-Co3O4@CW-230 with extensive prospects for practical application.

Preparation, Application and Enhancement Dyeing Properties of ZnO Nanoparticles in Silk Fabrics Dyed with Natural Dyes

In this study, ZnO nanoparticles were prepared by a hydrothermal method with varying the reaction times, material ratios and reaction temperatures. The samples were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray Diffraction (XRD) and Fourier infrared spectroscopy (FTIR). It was shown that the material ratio significantly affected the structure and morphology of the synthesized ZnO nanoparticles, and then the uneven nano-octahedral structure, uniform nano-octahedral structure, nano-tubular structure, and nano-sheet structure could be obtained successively. The synthesized ZnO nanoparticles as mordant were used for the dyeing of silk fabrics with different natural dyes (tea polyphenols and hematoxylin). Moreover, they could improve the dyeing properties and fastness (wash and light) on silk fabrics to a certain extent.

Recent Advanced Supercapacitor: A Review of Storage Mechanisms, Electrode Materials, Modification, and Perspectives

In recent years, the development of energy storage devices has received much attention due to the increasing demand for renewable energy. Supercapacitors (SCs) have attracted considerable attention among various energy storage devices due to their high specific capacity, high power density, long cycle life, economic efficiency, environmental friendliness, high safety, and fast charge/discharge rates. SCs are devices that can store large amounts of electrical energy and release it quickly, making them ideal for use in a wide range of applications. They are often used in conjunction with batteries to provide a power boost when needed and can also be used as a standalone power source. They can be used in various potential applications, such as portable equipment, smart electronic systems, electric vehicles, and grid energy storage systems. There are a variety of materials that have been studied for use as SC electrodes, each with its advantages and limitations. The electrode material must have a high surface area to volume ratio to enable high energy storage densities. Additionally, the electrode material must be highly conductive to enable efficient charge transfer. Over the past several years, several novel materials have been developed which can be used to improve the capacitance of the SCs. This article reviews three types of SCs: electrochemical double-layer capacitors (EDLCs), pseudocapacitors, and hybrid supercapacitors, their respective development, energy storage mechanisms, and the latest research progress in material preparation and modification. In addition, it proposes potentially feasible solutions to the problems encountered during the development of supercapacitors and looks forward to the future development direction of SCs.

Source of Nanocellulose and Its Application in Nanocomposite Packaging Material: A Review

Food packaging nowadays is not only essential to preserve food from being contaminated and damaged, but also to comply with science develop and technology advances. New functional packaging materials with degradable features will become a hot spot in the future. By far, plastic is the most common packaging material, but plastic waste has caused immeasurable damage to the environment. Cellulose known as a kind of material with large output, wide range sources, and biodegradable features has gotten more and more attention. Cellulose-based materials possess better degradability compared with traditional packaging materials. With such advantages above, cellulose was gradually introduced into packaging field. It is vital to make packaging materials achieve protection, storage, transportation, market, and other functions in the circulation process. In addition, it satisfied the practical value such as convenient sale and environmental protection, reduced cost and maximized sales profit. This review introduces the cellulose resource and its application in composite packaging materials, antibacterial active packaging materials, and intelligent packaging materials. Subsequently, sustainable packaging and its improvement for packaging applications were introduced. Finally, the future challenges and possible solution were provided for future development of cellulose-based composite packaging materials.