Graphene materials show great potential in the field of supercapacitors, but their tendency to agglomerate leads to a significant decrease in performance. Herein, manganese dioxide intercalated graphene oxide precursor was prepared using the modified Hummer method. During pyrolysis, manganese dioxide can not only act as a separator to prevent graphene aggregation but also undergo redox reactions with graphene to obtain oxygen-rich mesopore graphene (OMG). Benefiting from the mesoporous structure and abundant oxygen-containing functional groups, the OMG-600 electrode shows a specific capacitance of 248.67 F g− 1 at 0.5 A g− 1 and good electrochemical stability (92.25% capacitance retention after 10,000 cycles). Moreover, the assembled OMG-600//OMG-600 symmetric supercapacitor delivers an energy density of 17.69 Wh kg− 1 and superior electrochemical stabilization in 1 M Na2SO4 electrolyte.

Due to the severity of environmental degradation and depletion of natural energy resources, research on sustainable energy storage systems have become quite popular. Supercapacitor is one of the most innovative and promising type of energy storage devices. The effective performance of supercapacitor greatly depends on the electrode material. Therefore, new type of nanocomposite has been fabricated with βCD-stabilized CuO nanoparticles (CuO-βCD NPs) on Co-Al layered double hydroxide (Co-Al LDH) utilizing solvothermal process. The wet impregnation technique facilitates the formation of three distinct CuO-βCD/Co-Al LDH nanocomposites in the ratios of 1:1, 1:2, and 2:1 by promoting the growth of CuO-βCD on Co-Al LDH in corresponding compositions. Synthesized nanocomposites are characterized using a variety of spectroscopic techniques. The average pore size of 2:1 CuO-βCD/Co-Al LDH is 1.7 nm whereas the specific surface area and approximate pore volume of this nanocomposite are 38.306 m2 g− 1 and 0.043 cm3 g− 1, respectively. Electrochemical investigations like cyclic voltammetry (CV), galvanostatic charge–discharge (GCD), electrochemical impedance spectroscopic (EIS) measurements and along with cycle stability studies are performed to examine the electrochemical performance of synthesized nanocomposites. The 2:1 ratio has revealed improved specific capacitance (SC) of 1567 F g− 1 at 0.45 A g− 1 in 1 M potassium hydroxide medium in three electrode systems and maintains 76% of its original SC even after 5000 cycles. The improved electrochemical performance of 2:1 ratio reveals the appropriateness of this material as an effective electrode for supercapacitor application.

This research highlights the use of a WO3: CeO2@MXene/gC3N4 (MGWC) nanodisk as a versatile material. MGWC demonstrates efficient photocatalytic degradation of moxifloxacin (MOF) in water under sunlight and also shows great promise for high-performance supercapacitor applications. MGWC was synthesized using a modified hydrothermal method and thoroughly characterized using various techniques. The MGWC showed a band gap energy of 2.79 eV determined through UV–Vis DRS analysis and an average crystallite size of 39.6 nm calculated from XRD. A promising photocatalytic activity was observed for the degradation of MOF, outperforming other photocatalysts. Additionally, preliminary studies examined variations in catalyst concentration, pH, kinetics, electrolytes, scavengers, reusability, and TOC, contributing valuable insights. Under optimal conditions, the MOF achieved almost complete degradation, reaching about 99.7% within 180 min using the MGWC photocatalyst. Additionally, MGWC exhibits promising potential in supercapacitor applications. EIS and CV studies have been used to examine MGWC’s exceptional charge transfer properties. CV tests confirm the pseudocapacitive nature of MGWC electrodes. GCD studies of MGWC exhibit a high specific capacitance of 551 F/g at 1 A/g with incomparable capacitance retention of 98.1% over 10,000 cycles. This research not only aids in reducing emerging environmental pollutants but also sets the stage for sustainable energy solutions.

Electrochemical exfoliation of graphite to produce graphene flakes is receiving increased attention worldwide due to the simplicity and efficiency of the method. This study examines the effects of different exfoliation mediums, such as nitric acid, sulfuric acid, hydrochloric acid, and potassium hydroxide, on the characteristics of electrochemically exfoliated graphene flakes (EEGFs) and their performance in supercapacitor applications. The study demonstrates that the choice of exfoliation medium significantly impacts the electrochemical characteristics and energy storage capabilities of the resultant graphene flakes. Graphene exfoliated in hydrochloric acid exhibits superior performance, which is attributed to an optimal balance of high conductivity, low defect density, and accessible surface area. Nitric acid-exfoliated graphene, despite being defect rich, offers competitive performance due to increased active sites and enhanced ion accessibility. In contrast, graphene flakes exfoliated in potassium hydroxide present the lowest electrochemical performance and the highest defect density. These findings provide valuable insights into tailoring the properties of electrochemically exfoliated graphene for high-performance energy storage devices.

Surface wetting gradient design plays a crucial role in enhancing liquid transportation in smart devices. However, achieving Janus wetting interfacial design to manage high-efficient ion transport paths remains a great challenge in textile electrodes. Herein, a porous polyvinyl alcohol (PVA) gel layer was constructed on one side of the composite electrode, while a polydimethylsiloxane (PDMS) solution was sprayed onto the opposite side of electrode to obtain an asymmetric Janus-wettability textile electrode. Furthermore, the design of asymmetric wettability gradient and multilevel structure has been facilitated to directional liquid self-drive and ion transmission in a Janus-wettability textile electrode. Compared with the charge transfer resistance (Rct) of pure PDMS superhydrophobic electrode (1.58 Ω), the Rct of Janus-wettability electrode was 1.31 Ω, which reveals that the porous PVA layer is beneficial to promoting a rapid electron transfer. For solid-state supercapacitors (FSCs) with Janus-wettability electrode, the Rct of Janus-FSCs (0.5 Ω) was reduced by 90% compared to the composite FSCs (4.6 Ω) without PDMS coating, confirming a faster ionic diffusion after the introduction of stable PDMS superhydrophobic surface for wettability gradient. Moreover, the Janus-wettability FSCs also achieved a specific energy density of 0.104 mWh cm− 2 at 1.2 mW cm− 2, and cycle stability (96.8% after 10,000 cycles). These insights demonstrate the effectiveness of interface coordination in textile electrodes for enhancing electrochemical performance.

Porous carbon derived from biomass represents pivotal electrode materials for electric double-layer capacitors (EDLCs). However, their applications are limited by the low pore utilization and low withstanding voltage (< 2.7 V), which largely hinder the energy density (Eg) of SCs. In this study, fulvic acid-derived porous carbons (FPs) were synthesized through the self-assembly and KOH activation strategy by employing fulvic acid (FA) as the precursor and cationic surfactant PDDA as the soft template. The electrostatic forces between FA and PDDA enable the structural orientation of FA, leading to the formation of stable layered liquid microcrystals. Besides, under the activation process, the decomposition of PDDA contributes to the interconnected pores in FPs. Thus, the obtained sample FP1 exhibits a high specific surface area (2593 m2 g− 1) and high mesopore ratio (48%). Moreover, low oxygen content and stable surface composition promote the withstanding voltage of FPs. In the TEABF4/ PC electrolyte, the sample FP1 is capable of a high voltage of 3.0 V, high-rate capability C10/0.05 of 76.3%, and high energy density of 39 Wh kg− 1.

Enhancing the energy storage capabilities of supercapacitors (SCs) while preserving their electrochemical performance is crucial for their widespread application. Our research focuses on developing Sb-modified tin oxide (ATO) nanoparticles via a scalable hydrothermal process, offering substantial potential in this domain. The tetragonal nanoparticle structure provides abundant active sites and a highly porous pathway, facilitating rapid and efficient energy storage. Additionally, tin's varied oxidation states significantly enhance redox capacitance. Electrochemical measurements demonstrate ATO's promise as an advanced SC electrode, achieving a peak specific capacitance of 332 F/g at 3 mA/cm2, with robust redox capacitance confirmed through kinetic analysis. Moreover, the ATO electrode exhibits exceptional capacitance retention over 2000 cycles. This study establishes ATO as a leading candidate for future energy storage applications, underscoring its pivotal role in advancing energy storage technologies.

Transition metal/porous carbon composite is good electrode candidate since porous carbon provides high surface porosity which promotes the access of electrolyte ions, and transition metal enables redox reactions to improve specific capacitance and energy density. In this study, iron/carbon nanofiber (CNF) composite electrodes were prepared by grafting ferrocenecarboxaldehyde to the CNFs which were fabricated by electrospinning and thermal treatment of polyacrylonitrile (PAN). The presence of iron on the CNF surface was confirmed by SEM/EDS, ICP-MS and XPS. Electrochemical performance was evaluated using a three-electrode cell with 1 M Na2SO4 as an electrolyte. Iron-grafted CNFs exhibited a high specific capacitance of 358 F g− 1 and an energy density of 49.7 Wh kg− 1 at 0.5 A g− 1, which is significantly higher than those for untreated CNFs (68 F g− 1 and 9.4 Wh kg− 1). This demonstrates that this iron/CNF composite is promising candidate for supercapacitor electrode with outstanding energy storage performance.

The high value-added utilization of traditional coal resources is one of the important ways to achieve the strategic goals of carbon peaking and carbon neutrality. Simultaneously, coal-based carbon materials, noted for their cost-effectiveness, superior conductivity, and inherent stability, are emerging as promising candidates for next-generation capacitor technologies. This research presents a series of coal-derived porous carbon by pyrolysis using low rank lignite as raw material and KOH as activator, which are employed in symmetrical supercapacitors filled with liquid electrolytes. The physicochemical properties of the as-prepared electrode materials are characterized by means of scanning electron microscopy, X-ray diffraction, Raman spectroscopy, and their supercapacitive performance are evaluated through cyclic voltammetry and galvanostatic charge–discharge tests. The coal-based porous carbon electrode prepared at an activation temperature of 800 °C (KOH-800) exhibits a specific capacitance of 142.2 F g− 1 at a current density of 1 A g− 1, and retaining 80% of its capacitance (114.0 F g− 1) even at 10 A g− 1. The fabricated liquid supercapacitor displays a power density of 999.8 W kg− 1 and an energy density of 19.4 Wh kg− 1 at a current density of 1 A g− 1. Undergoing 10,000 cycles at 2 A g− 1, the supercapacitor maintains nearperfect capacitance retention and coulombic efficiency close to 100%, demonstrating its excellent durability and stability for supercapacitor applications.

Aqueous zinc–iodine batteries (AZIBs) are gaining attention for their ability to store and convert electrical energy. Nevertheless, their performance is hindered by the continual migration of polyiodides towards the zinc anodes, leading to undesirable side reactions, diminished coulombic efficiency, and compromised cycling stability. Traditional carbon materials have proven inadequate in resolving these challenges, mainly due to their limited iodine capacity and weak binding forces. Herein, we explore the use of porous carbon nanosheets (PCNSs) synthesized via the “Pharaoh’s Serpent” reaction as cathode electrodes in AZIBs without pre-load iodine. The PCNSs, characterized by their nanosheet structure and expansive specific surface area, not only facilitate a shorter diffusion path for rapid electrolyte infiltration but also provide numerous sites for ion adsorption and capacitive storage, markedly improving the efficacy of electrochemical reactions and ion migration rates. Utilizing the synthesized PCNSs as the cathode electrode in AZIBs, a specific capacity of 296 mAh g− 1 was achieved at 0.3 A g− 1. Even when the current density increased to 30 A g− 1, a specific capacity of 144 mAh g− 1 was still attained, with a capacity retention ratio of up to 48.6%, which is competitive with that of supercapacitors. In addition, the AZIBs demonstrated impressive cycling stability, retaining 103% of their capacity after 10,000 cycles, and a notable energy density of 266.4 Wh kg− 1 based on the cathode material. These findings significantly broaden the application of carbon materials in AZIBs research, emphasizing their potential in advancing AZIB technology.

Graphene aerogels have gained widespread recognition in recent years as electrode materials for supercapacitors, primarily attributed to their excellent stability and impressive specific capacitance. However, further enhancing their specific capacitance is a formidable task. One viable strategy to overcome this hurdle is to composite them with metal oxides. In doing so, the metal oxides boost the specific capacitance of graphene aerogels, while the latter addresses the stability issues inherent in metal oxides. This article reviews recent research on Ni, Co, and Mn oxide–graphene composite aerogels in supercapacitors, summarizing their preparation processes, performance and energy storage mechanism. While existing studies have demonstrated the feasibility of metal oxide–graphene composite aerogels as supercapacitor electrodes, several challenges remain, necessitating deeper exploration by researchers in this field.

Fiber supercapacitors have attracted significant interest as potential textile energy storage devices due to their remarkable flexibility and rapid charge/discharge capabilities. This study describes the fabrication of a composite fiber supercapacitor (FSC) electrode through a multi-shell architecture, featuring layers of carbon nanotube (CNT) conductive shells and MnO2 nanoparticle active shells. The number of layers was adjusted to assess their impact on FSC energy storage performance. Increasing the number of shells reduced electrode resistance and enhanced pseudocapacitive characteristics. Compared to the MnS@1 electrode, the MnS@5 electrode exhibited a high areal capacitance of 301.2 mF/cm2, a 411% increase, but showed a higher charge transfer resistance (RCT) of 701.6 Ω. This is attributed to reduced ion diffusion and charge transfer ability resulting from the thicker multi-shell configuration. These results indicate that fine-tuning the quantity of shells is crucial for achieving an optimal balance between energy storage efficiency and stability.

Supercapacitors, renowned for their high power density and rapid charge-discharge rates, are limited by their low energy density. This limitation has prompted the need for advanced electrode materials. The present study investigated reduced graphene oxide (rGO) in two distinct structures, as a film and as an aerogel, for use as supercapacitor electrodes. The rGO film, prepared by vacuum filtration and thermal reduction, exhibited a compact, lamellar structure, while the aerogel, synthesized through hydrothermal treatment, was a highly porous three-dimensional network. Electrochemical analyses demonstrated the aerogel’s superior performance, as shown by a specific capacitance of 121.2 F/g at 5 mV/s, with 94% capacitance retention after 10,000 cycles. These findings emphasize the importance of structural design in optimizing ion accessibility and charge transfer. They also demonstrate the potential of rGO aerogels for increasing the energy storage efficiency of advanced supercapacitor systems.

Graphene-based solar cells and supercapacitors integrated into photosupercapacitors represent a pioneering advancement. These devices leverage the exceptional properties of graphene, such as high conductivity and large surface area, to enhance both solar energy conversion and energy storage. The integration of these technologies into photosupercapacitors creates a multifunctional device capable of harnessing solar energy and storing it efficiently. This innovative approach holds promise for sustainable and versatile energy solutions, marking a significant step towards developing efficient and compact energy storage systems. This integration addresses the intermittent nature of solar power generation by providing a continuous and reliable power supply through energy storage. Supercapacitors are one such energy device with a high-power density and excellent specific capacitance which is integrated will a dye-sensitized solar cell (DSSC) comprising a single system of photosupercapacitor. A novel electrode material of NiO/CuO/Co3O4/rGO was synthesized which serves as the Pt-free counter electrode of DSSC and working or storage electrode of supercapacitor later was used as the intermediate electrode and storage electrode of a photosupercapacitor. The integrated photosupercapacitor device had a photovoltage of 0.81 V with arealspecific capacitance, energy and power density of 190.12 mF cm− 2, 17.325 μW h cm− 2 and 0.162 mW cm− 2, respectively. The device self-discharged in 385 s with an overall conversion efficiency of 2.17%, resulting in a self-charged energy device.

Energy storage is one of the leading problems being faced globally, due to the population explosion in recent times. The conventional energy sources that are available are on the verge of extinction, hence researchers are keen on developing a storage system that will face the upcoming energy needs. Supercapacitors, also known as ultracapacitors or electrochemical capacitors, are advanced energy storage devices characterised by high power density and rapid charge–discharge cycles. Unlike traditional batteries, supercapacitors store energy through electrostatic separation, offering quick energy release and prolonged operational life. They hold exceptional performance in various applications, from portable electronics to electric vehicles, where their ability to deliver bursts of energy efficiently complements or replaces conventional energy storage solutions. Ongoing research focuses on enhancing energy density and overall efficiency, positioning supercapacitors as pivotal components in the evolving landscape of energy storage technologies. A novel electrode material of NiO/CuO/Co3O4/rGO was synthesized which when used as a supercapacitor, the highest value of CS is 873.14 F/g which is achieved for a current density of 1 A/g under with an energy density of 190 Wh/kg and the highest power density of 2.5 kW/kg along with 87.3% retention after 5000 GCD cycles under 1 M KOH.

Porous carbon nanofiber (CNF) electrodes for supercapacitors were prepared by using polyacrylonitrile (PAN) and cucurbituril (CB), which is a macrocyclic compound comprising glycoluril units containing hollow cores. Mixture of PAN and CB in dimethyl sulfoxide was electrospun, and thermally treated to produce CNF electrodes. Their thermal stability, surface morphology, carbon microstructures, and surface porosity were investigated. Electrochemical properties were measured using three-electrode with synthesized CNFs without further treatment as a working electrode and 1 M Na2SO4 as an electrolyte. CNFs derived from PAN and CB exhibited a high specific capacitance of 183.5 F g− 1 and an energy density of 25.4 Wh kg− 1 at 0.5 A g− 1 with stable cyclic stability during 1000 cycles, which is significantly higher than those for CNFs derived from PAN only. This demonstrated that the introduction of CB successfully improved the energy storage performance of CNF electrodes.

Large-area porous carbon is easily produced for supercapacitors from polyvinylidene chloride (PVDC) and polyvinylidene fluoride (PVDF) precursors, composed of carbon backbone and attached heteroatoms. The released heteroatoms during pyrolysis leave the porous carbon. This study explored the activation of both precursors using chemical agents (ZnO, Mg(OH)2, and KOH) to develop carbon with multiple micropores and mesopores. The activation process and relevant precursors were studied to implement synthesized porous carbon as an electrode in supercapacitors. During the activation of PVDC-resin, ZnO served both as templates and activating agents, while Mg(OH)2 served only as a template, and KOH served as an activating agent. For activation of PVDF, ZnO acted as a template and activating agent, whereas Mg(OH)2 and KOH impeded activation owing to side reactions. Therefore, with the above chemical agents, PVDC-resin was converted to carbon with a higher surface area than PVDF. The porous carbon produced using PVDC-resin with KOH had the highest specific capacitance of 137 F g− 1 and rate performance of 79% at 50 mV s− 1 (vs. 5 mV s− 1) owing to the successful creation of micropores and mesopores. This study identifies optimal conditions for synthesizing porous carbon using polymer precursors and chemical agents for supercapacitors.