Search Results (1,329)

The transformation of waste plastics into hydrogen and functional carbon (C) materials represents a promising pathway for achieving both resource recycling and the production of value-added products. Owing to their tunable physicochemical properties, plastic-derived carbons have attracted significant attention in electrochemical energy storage applications. Various C nanostructures, including graphene, porous C, hard C, and C nanotubes (CNTs), can be generated from discarded plastics through thermochemical processes. The electrochemical performance of these materials is closely governed by their structural characteristics, such as pore architecture, specific surface area, heteroatom doping, surface functionalities, and dimensional morphology. This review aims to provide a comprehensive and systematic overview of the conversion of waste plastics into functional C nanomaterials via thermochemical routes, particularly catalytic pyrolysis and carbonization. The resulting C nanostructures are systematically categorized based on their dimensional architectures (0D, 1D, 2D, and 3D) and comparatively analyzed in terms of their structural features and electrochemical performance. Emphasis is placed on the transformation of diverse plastic feedstocks into high-value C materials with tailored dimensional architectures, including graphene, CNTs, C nanospheres, C nanosheets, porous carbons, and their composites. Furthermore, recent progress and critical challenges in utilizing these materials for electrochemical energy storage systems, such as supercapacitors and rechargeable batteries (Li-ion, Na-ion, K-ion, Li-S, and Zn-air), are discussed. Distinct from previous reports, this review highlights the correlation between thermochemical processing strategies, resulting structural features, and electrochemical performance, providing new insights into the rational design of high-performance C materials. These findings are expected to facilitate the advancement of sustainable energy storage technologies while contributing to effective plastic waste valorization. Full article

Bio-based, biodegradable, and renewable polymers offer a promising alternative to traditional synthetic polymers derived from petroleum or other non-renewable resources. However, their use is limited by suboptimal properties and high costs. Incorporating sustainable reinforcements into the polymer matrix significantly improves biopolymer performance while preserving key properties, sustainability, and cost-effectiveness. Bio-based polymeric composites have emerged as a crucial category of biopolymers, playing a key role in advancing a sustainable, circular economy. This review provides an updated overview of bio-based polymer composites and nanocomposites, focusing on reinforcement strategies using natural nanofillers and engineered nanoparticles. We summarize key synthesis and processing methods, discuss structure–property relationships, and highlight recent advances in applications such as food packaging, biomedical devices, energy systems, environmental remediation, 3D printing, and supercapacitors. Polymer nanocomposites are versatile, with their performance depending on the type, size, and interactions between the fillers and the polymer matrix. Progress in metallic, ceramic, carbon-based, natural, and hybrid fillers has improved their properties. Using bio-based polymers and renewable fillers supports sustainability. Natural nanofillers derived from renewable sources and industrial byproducts offer a sustainable approach to developing high-performance, biodegradable nanocomposites. Smart nanocomposites can react to external stimuli by integrating specialized fillers that enhance their mechanical and mobility properties. Shape memory nanocomposites can be remotely activated—using heat, electricity, magnets, or light—enabling advanced applications. Finally, we address major challenges and outline future directions for scalable, circular-material solutions, drawing on perspectives from the circular economy and life cycle assessment (LCA). Full article

The rational design of electrode materials with tailored composition and architecture is crucial for advancing high-capability electrochemical energy storage systems. This study reports that gadolinium-modified NiFe₂O₄ nanosheet electrodes were effectively synthesized on nickel foam via a hydrothermal approach followed by thermal treatment. A series of compositions (NiFe, NiFe–Gd1, NiFe–Gd2, and NiFe–Gd3) were prepared to systematically examine the effect of Gd incorporation on structural features and electrochemical properties. X-ray diffraction (XRD) analysis confirmed the formation of the cubic spinel NiFe₂O₄ phase without detectable secondary phases, indicating that the crystal structure remains intact after Gd introduction. X-ray photoelectron spectroscopy (XPS) further verified the presence of Ni²⁺, Fe³⁺, and Gd³⁺ species within the lattice environment. Morphological analysis using field-emission scanning electron microscopy (FESEM) revealed a nanosheet-based architecture, where the optimized NiFe–Gd2 electrode exhibited a porous and interconnected nanosheet framework with abundant exposed edges. This structural configuration improves electrolyte penetration and facilitates efficient ion transport during charge storage processes. Electrochemical measurements demonstrated that the NiFe–Gd2 electrode delivers an areal capacitance of 5235 mF cm⁻² at 10 mA cm⁻², along with improved reaction kinetics and low internal resistance. An asymmetric supercapacitor assembled using NiFe–Gd2 as the positive electrode and activated carbon as the negative electrode operated stably within a 0–1.5 V potential window, achieving an energy density of 0.136 mWh cm⁻² and a power density of 3.14 mW cm⁻², while retaining 86.55% of its initial capacitance after 7000 cycles. These results highlight the potential of rare-earth engineering as a viable strategy for designing advanced spinel ferrite electrodes and pave the way for the development of high-performance, durable, and scalable supercapacitor systems for practical energy storage applications. Full article

An important challenge for materials researchers in the modern era is the fabrication of high-performance electrodes with novel designs and structures to enhance electrochemical sensing and energy storage performance. Recently, perovskite-structured bimetallic hydroxide materials, owing to their high conductivity, decent surface area, abundant redox activity, and good stability, have emerged as promising candidates for bifunctional electrochemical applications. In this study, we designed perovskite-type CuSn(OH)₆ microspheres via a facile coprecipitation method for nifedipine (NFD) sensing and supercapacitors (SCs). Various characterization techniques were employed to confirm the successful synthesis of CuSn(OH)₆. The uniform formation and distribution of CuSn(OH)₆ within the sphere structure provide rich reactive sites and enhance structural stability, thereby improving electrochemical activity. This architecture also induces a synergistic effect between Cu and Sn, which increases conductivity and accelerates redox kinetics. Consequently, the electrode modified with CuSn(OH)₆/GCE exhibited a wide linear concentration range of 0.4–303.3 µM and a low detection limit of 0.44 µM for NFD detection. This sensor further demonstrated superior analytical reliability, with selectivity of <5%, cycling stability of 84.79%, reproducibility of 3.3%, and recovery rates of 99.2–99.8% in the serum sample. Concurrently, the CuSn(OH)₆/NF showcased a high specific capacitance of 514 F g⁻¹ at 1 A g⁻¹, good longevity of 83.05% retention after 5000 cycles, and low charge transfer resistance of 6.56 Ω and solution resistance of 1.04 Ω, validating fast ion–electron transport. These results underscore that perovskite-based CuSn(OH)₆ is an efficient dual-functional electrocatalyst for sensitive electrochemical detection and high-performance SCs. Full article

The literature data on the solid-state and surface chemistry of cobalt and cobalt–aluminum oxide and hydroxide systems are reviewed. The actual and potential applications of these materials in the fields of catalysis, electrocatalysis, photocatalysis, adsorption and sensor technologies are reviewed. A comprehensive analysis of the peculiar redox and acid–base properties of these cobalt-based systems, both at the solid–gas and at the solid–water solution interface, is conducted. Evidence is provided for the exceptional versatility of these systems and on their relevant potential for optimal applications, in particular, in several catalytic total oxidation reactions, in N₂O catalytic decomposition, in ammonia catalytic oxidation to NO, as electrocatalysts in water splitting reactions, as active elements in supercapacitors, and as precursors of cobalt metal-based systems. It is underlined that these systems could successfully substitute more critical and expensive noble metal-based systems in several technological fields. Full article

Background: The growing demand for sustainable, high-performance energy storage systems has intensified interest in biomass-derived materials for supercapacitor applications. This study presents a green and scalable approach to fabricating novel electrodes and solid-state electrolytes using Phoenix dactylifera (Ajwa date) seed biomass and palm waste-derived activated carbon. Methods: KOH-activated carbon from date pits was employed to enhance surface area and redox activity. A double-network hydrogel electrolyte (DSHC) was synthesized by incorporating 0.5 g of date seed powder with sodium alginate and wheat starch (0.2 g each), followed by chemical crosslinking in 2 M H₂SO₄. Structural and physicochemical properties were analyzed using SEM, XRD, and FTIR, while electrochemical performance was evaluated through cyclic voltammetry and galvanostatic charge–discharge measurements. Results: SEM revealed a densely ordered porous network with regular cylindrical channels favorable for ion transport. XRD and FTIR confirmed amorphous carbon formation and effective molecular crosslinking. The hydrogel electrolyte exhibited a wide potential window of ~2 V and strong pseudocapacitive behavior, delivering a maximum specific capacitance of 179 F g⁻¹ at 5 mV s⁻¹ and a discharge capacitance of 159 F g⁻¹ at 0.2 A g⁻¹, with excellent stability over 5500 cycles. Conclusions: Agricultural waste-derived materials demonstrate strong potential as low-cost, eco-friendly, and mechanically robust components for flexible supercapacitors, suitable for sustainable energy storage and rapid-charging applications. Full article

Growing interest in sustainable, high-performance energy storage has driven extensive studies on advanced electrode materials for supercapacitor applications. In this study, a FeNiCo metal–organic framework/multiwalled carbon nanotube (MOF–MWCNT) composite was synthesized and employed as a modifying layer on a carbon felt electrode (CFE) via a drop-casting method. The electrochemical performance of the composite electrode was systematically evaluated in 1 M H₂SO₄ electrolyte. Structural and electrochemical studies demonstrate that the combined effect of the conductive CFE substrate, the electric double-layer capacitance of MWCNTs, and the pseudocapacitive properties of the trimetallic FeNiCo MOF markedly enhances the charge storage performance. Cyclic voltammetry and galvanostatic charge–discharge measurements demonstrate a maximum specific capacitance of approximately 180 F g⁻¹. The electrode delivers an energy density of 73.20 Wh kg⁻¹ at a power density of 3796.17 W kg⁻¹, demonstrating a favorable balance between energy and power performance. In addition, high coulombic efficiency confirms excellent charge–discharge reversibility. Notably, 71% of the initial capacitance is retained after 900 cycles in 1 M H₂SO₄, indicating stable electrochemical behavior even under strongly acidic conditions. These findings emphasize the promise of the FeNiCo MOF–MWCNT/CFE composite as a durable electrode design for next-generation supercapacitor devices. Full article

The last years have seen the increasing development of innovative railway pantographs based on smart materials and equipped with monitoring features based on wireless sensor nodes. In this scenario, one of the most important challenges is the power supply of pantograph sensors. Energy harvesting systems have been proposed for powering monitoring sensors in a variety of applications, including railway pantographs. These systems convert ambient energy sources into electrical energy. The use of energy harvesting systems coupled with storage devices, such as rechargeable batteries or supercapacitors, can be a very promising solution for making the sensors self-powered, thus avoiding the drawbacks associated with supplying from the main grid or disposable batteries. In this paper, the operating principles of the main technologies used for energy harvesting in railway pantographs are described in detail, together with some examples of laboratory prototypes and commercial devices. The proposed analysis focuses on the perspectives and challenges of various energy harvesting technologies and can help select the most suitable technology for the development of innovative sensorized pantographs. Full article

In this study, a novel layered WO₃@Co₃O₄ composite electrode was synthesized via a controlled electrodeposition method employing different surfactants to finely tune its nanostructure. The incorporation of polyacrylic acid (PAA) surfactant yielded an optimized P-W@Co electrode with a hierarchical porous morphology and reduced crystallite size, markedly enhancing electroactive site exposure and electron transport. Structural analyses confirmed the amorphous nature of WO₃ and crystalline spinel Co₃O₄ phases forming an integrated composite architecture. Electrochemical characterizations in a three-electrode system revealed that the P-W@Co electrode exhibited superior pseudocapacitive behavior, with an areal capacitance of 11.70 F/cm² at 20 mA/cm² and excellent rate capability, retaining 80% capacitance at 40 mA/cm². Kinetic studies demonstrated enhanced diffusion-controlled charge storage attributed to improved ion accessibility and charge transfer kinetics. To evaluate practical feasibility, asymmetric supercapacitor devices incorporating P-W@Co as the positive electrode coupled with activated carbon as the negative electrode were fabricated. This device showcased a widened operational voltage (1.5 V), outstanding areal capacitance (211 mF/cm²), and energy density (0.066 mWh/cm²). Importantly, the device exhibited exceptional cycling stability, retaining 81.8% capacitance after 7000 cycles. This work signifies a major advancement in surfactant-mediated design of WO₃@Co₃O₄ layered electrodes for scalable, high-performance supercapacitor applications, combining structural stability, enhanced conductivity, and multifaceted charge storage mechanisms. Full article

The nickel-derived metal–organic framework (MOF), Ni-BTB, synthesized from 4,4′,4″-benzene-1,3,5-tribenzoic acid (H₃BTB), was investigated as a multifunctional platform for enhanced energy applications including production and storage. In catalytic hydrogen generation by NaBH₄ hydrolysis, Ni-BTB attained a hydrogen generation rate (HGR) of 4640 mL H₂/g•min with 1 mg of catalyst, with an activation energy of 76.44 kJ/mol. Under optimized reaction conditions (60 °C, 20 mg catalyst, and 1 g NaBH₄), the HGR increased to 9542 mL H₂/g•min, while exhibiting high recyclability throughout four successive cycles. As a supercapacitor electrode, Ni-BTB achieved a specific capacitance of 156 F/g at 1 A/g and showed remarkable cycling stability, maintaining its capacitance after 10,000 charge–discharge cycles. Furthermore, Ni-BTB exhibited exceptional electrocatalytic activity for oxygen evolution reaction (OER), requiring only 106 mV overpotential to achieve 10 mA/cm², offering a time-of-flight (TOF) of 0.0585 s⁻¹ and demonstrating significant operational longevity of at least 12 h. These findings underscore Ni-BTB as a durable, reusable, and adaptable material for hydrogen production, energy storage, and electrocatalytic applications. Full article

In this study, the structural and electrochemical performance of Nb₂CT_x MXene-based composite electrodes modified with activated carbon (AC) derived from food waste was systematically investigated for supercapacitor applications. Three composites with Nb₂CT_x:AC mass ratios of 90:10 (MXAC1), 80:20 (MXAC2), and 70:30 (MXAC3) were prepared and comparatively evaluated. SEM/EDS, XRD, HR-TEM, XPS, and BET analyses revealed that, in the MXAC2 composite, activated carbon was homogeneously distributed between the MXene layers, effectively suppressing restacking and promoting the formation of a hierarchical micro/mesoporous structure. XPS results confirmed the preservation of the Nb–C framework and the enrichment of surface functional groups (–O, –OH, and –F). BET analysis demonstrated that MXAC2 possesses an optimized pore architecture that facilitates efficient ion diffusion. Electrochemical measurements revealed that the MXAC2 electrode exhibited the highest specific capacitance at all scan rates and current densities. At 5 mV·s⁻¹, MXAC2 achieved a specific capacitance of 651.84 F·g⁻¹ and maintained a substantial capacitance even at a high current density of 4 A·g⁻¹. EIS analysis confirmed the very low charge transfer resistance (0.023 Ω) and enhanced capacitive behavior for MXAC2. Additionally, MXAC2 has high cycle stability, demonstrating 82.15% capacitive retention and 92.45% coulombic efficiency after 10000 cycles. These results indicate that food waste-derived AC-optimized Nb₂CT_x MXene composite materials are a strong candidate for sustainable and high-performance supercapacitor electrodes. Full article

To enhance the electrochemical performance of NiMn layered double hydroxides (LDH), this study explores the Ce-doped NiMn-LDH (CeNiMn-LDH) as a cathode material for supercapacitors. In the CeNiMn-LDH structure, partial substitution of Ni/Mn ions by Ce increases the number of active sites, facilitates electron transfer, and improves current density, leading to a significant enhancement in the electrochemical properties compared with NiMn-LDH. Experimental results show that the 0.3CeNiMn-LDH electrode delivers excellent electrochemical performance, achieving a specific capacitance of 1928.16 F/g at a current density of 1 A/g. Furthermore, an assembled CeNiMn-LDH//AC asymmetric supercapacitor exhibits an energy density of 36.36 Wh/kg and a power density of 850 W/kg at 1 A/g. Therefore, the strategy of employing CeNiMn-LDH offers an effective technical approach for improving the electrochemical performance of supercapacitor cathode materials, demonstrating considerable potential for practical applications. Full article

Flexible supercapacitors have attracted significant attention as promising power sources for portable and wearable electronic devices. However, achieving simultaneous high power density, energy density and long-term cyclic stability in a simple device configuration remains a critical challenge. Herein, we report an all-solid-state flexible planar supercapacitor based on hierarchically structured cellulose nanofiber-carbon nanotube@manganese dioxide (CNF-CNT@MnO₂) composite aerogels. The electrode architecture is rationally designed by first dispersing CNTs within a hydrophilic CNF scaffold to form a conductive three-dimensional network, followed by in situ oxidative polymerization of MnO₂ onto the CNF-CNT fibrous skeleton. The hydrophilic CNFs network ensures thorough electrolyte penetration, the interconnected CNTs facilitate rapid electron transport, and the uniformly coated MnO₂ layer provides substantial pseudocapacitance. The aerogel electrode with a low density of 14.6 mg cm⁻³ and a high specific surface area of 214.4 m² g⁻¹ delivers a specific capacitance of 273.0 F g⁻¹ at 0.4 A g⁻¹. The assembled planar supercapacitor, incorporating gel electrolyte and a flexible hydrogel substrate, achieves an impressive areal capacitance of 885.0 mF cm⁻² at 2 mA cm⁻², energy density of 122.9 μWh cm⁻² and corresponding power density of 1000.0 μW cm⁻². The device exhibits excellent electrochemical stability, retaining 83.3% capacitance after 2500 charge–discharge cycles, and outstanding mechanical flexibility, with 96.3% capacitance retention after 200 repeated bending cycles. Furthermore, multiple devices can be connected in series or parallel to proportionally increase output voltage or current, meeting the practical power requirements of electronic applications. This work offers a viable pathway toward high-performance, durable energy storage solutions for next-generation wearable electronics. Full article

Hydrogels have attracted significant interest in multifunctional applications. Among them, self-healing hydrogel stands out for its ability to autonomously repair damage through reversible interactions, yet achieving both rapid self-healing and superior mechanical strength remains challenging. In this study, we report the fabrication of a dual cross-linked hydrogel (PAA-Alg-B) prepared via free radical polymerization of acrylic acid and alginic acid, employing N,N′-methylenebisacrylamide, or vinyl-modified nanocellulose as primary cross-linker, with Fe³⁺ or borax serving as an additional dynamic cross-linker. The resulting borax based hydrogel (PAA-Alg-B) exhibits remarkable fast self-healing efficiency enabled by reversible borate ester bonds and hydrogen bonding. It demonstrates tunable mechanical strength with toughness of 137 kJ/m³ and elongation at break up to 1117%, alongside exceptional swelling capacity (448 g/g). The adsorption studies reveal high removal efficiencies for heavy metals, with maximum capacities of 87.57 mg/g (Cr³⁺), 114.02 mg/g (Ni²⁺), and 99.42 mg/g (Cu²⁺), governed by chemisorption kinetics. The PAA-Alg-B can also be used as a promising solid-state electrolyte and separator for flexible supercapacitors. Protonic modulation via H₂SO₄ soaking significantly enhances ionic conductivity, electrochemical performance, and cycling stability. These findings highlight the potential of natural polymer-based, mechanically robust, self-healing hydrogels for sustainable wastewater treatment and advanced energy storage applications. Full article

In this work, a polypyrrole–tungsten disulfide (PPy–WS₂) nanocomposite was synthesized through oxidative polymerization and evaluated as an electrode material for supercapacitors. Structural and morphological analyses confirmed the successful integration of WS₂ within the PPy matrix. Electrochemical testing revealed a high specific capacitance of 816 F g⁻¹ at a scan rate of 1 mVs⁻¹, together with excellent cycling durability. To further assess device-level performance, an asymmetric supercapacitor was assembled using the PPy–WS₂ nanocomposite as the positive electrode, activated carbon as the negative electrode, and a PVA/KOH gel electrolyte. The device achieved an energy density of 41.6 Wh kg⁻¹ and a power density of 1500 W kg⁻¹, while maintaining 105% of its capacitance after 2500 charge–discharge cycles. The prototype was also able to power a light-emitting diode, highlighting its practical potential. These findings demonstrate that the synergistic coupling between polypyrrole and tungsten disulfide substantially improves electrochemical behaviour, positioning the PPy–WS₂ nanocomposite as a promising candidate for advanced energy storage applications. Full article