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We report the electrochemical performance of wrinkled/washable graphene-based supercapacitors (SCs). Sustainable graphene electrodes were fabricated by printing graphene microplates on recycled plastics (taken from wasted chip-packets), which provided flexibility to the SCs. The devices made with only graphene electrodes had an energy-density/specific-capacitance of 8.8 Wh kg−1/99.1 F g−1. To enhance the electrochemical properties of the SCs, a mixture of La 0.2 Gd 1.8 Zr 2 O 7 (LGZ) and La 0.7 Sr 0.3 MnO 3 (LSM) perovskites (redox materials) were added on their electrodes. After this, the energy-density/capacitance was enhanced to 53.1 Wh kg−1/596.90 F g−1, that is, an improvement of 503/502%, respectively. Subsequently, the solid state SCs were completely rolled or wrinkled, in consequence, the capacitance decreased by 12.1 and 35.6%, respectively. Even more, the SCs were immersed in water or subjected to washing/drying cycles using a washing-machine and the capacitance barely decreased by ⁓14.2%. Additionally, the thickness of the SC electrodes was varied in the range of 65–400 μm and obtained the maximum capacitance for a thickness of 330 μm. Overall, we demonstrated that incorporating the LGZ/LSM perovskite on the SC electrodes provided extra redox centers, which incremented the capacitance of the devices. The SCs reported here are waterproof and wrinkled, thus, they could provide energy to wearable devices. [ABSTRACT FROM AUTHOR]

Zinc hybrid supercapacitors (Zn‐HSCs) hold immense potential toward the next‐generation energy storage systems, effectively spanning the divide between conventional lithium‐ion batteries (LIBs) and supercapacitors. Unfortunately, the energy density of most of Zn‐HSCs has not yet rivalled the levels observed in LIBs. The electrochemical performance of aqueous Zn‐HSCs can be enhanced through the chemical functionalization of graphene‐based cathode materials with thiol moieties as they will be highly suitable for favoring Zn2+ adsorption/desorption. Here, a single‐step reaction is employed to synthesize thiol‐functionalized reduced graphene oxide (rGOSH), incorporating both oxygen functional groups (OFGs) and thiol functionalities, as demonstrated by X‐ray photoelectron spectroscopy (XPS) studies. Electrochemical analysis reveals that rGOSH cathodes exhibit a specific capacitance (540 F g−1) and specific capacity (139 mAh g−1) at 0.1 A g−1 as well as long‐term stability, with over 92% capacitance retention after 10 000 cycles, outperforming chemically reduced graphene oxide (CrGO). Notably, rGOSH electrodes displayed an exceptional maximum energy density of 187.6 Wh kg−1 and power density of 48.6 kW kg−1. Overall, this study offers an unprecedented powerful strategy for the design and optimization of cathode materials, paving the way for efficient and sustainable energy storage solutions to meet the increasing demands of modern energy applications. [ABSTRACT FROM AUTHOR]

We develop a new type of heterostructure nanocomposite made of reduced graphene oxide-boron carbon nitride nanosheets (rGOBCN) by B–C covalent bonds. The rGO-BCN nanocomposite delivers a large specific surface and excellent electrochemical properties, and is then constructed into flexible fabric-based high-performance supercapacitor electrodes based on the microfluidic electrospinning technology. [ABSTRACT FROM AUTHOR]

Supercapacitors, thanks to their unique properties, are considered among the main future energy storage systems. However, problems such as low energy density relative to batteries, spontaneous discharge, and low cell voltage have limited their widespread use. In this regard, the development of active and efficient materials is known as a viable solution. Thus, in this study, a hybrid supercapacitor made of nickel oxide and graphene was investigated. Nickel oxide and graphene were synthesized by calcination of nickel hydroxide and electrochemical exfoliation of graphite, respectively. Nickel oxide–graphene composites were synthesized at three levels, including 10, 20 and 30%wt of graphene by a facile hydrothermal-calcination route. The samples were characterized by XRD, FE-SEM, elemental mapping and FTIR tests, and their electrochemical performance was evaluated by electrochemical measurements including CV and EIS tests. The result of the characterization tests confirmed the successful synthesis of nickel oxide, graphene and composites. The results of the electrochemical measurements also showed that the addition of graphene to nickel oxide improved the supercapacitive properties of pure nickel oxide. Improved performance of the composites was attributed to the less aggregation of graphene sheets and their greater conductivity. Based on the results of electrochemical tests, the optimum level of graphene addition was 20%wt and NiO@G20 supercapacitor in 2.0 M KOH medium and a scan rate of 5 mV s showed a specific capacitance of 915.40 F g , energy density of 31.78 Wh kg and power density of 2.29 kW kg . Also, NiO@G20 supercapacitor was able to maintain 96.7% of its initial capacitance after 5000 cycles, which shows its high cycle stability. The high and stable activity of NiO@G20 introduces it as a promising and high-performance material for supercapacitor. [ABSTRACT FROM AUTHOR]

An all-in-one self-sustained integrated system composed of a Si film solar cell, spray-printed a micro-supercapacitor and a gas sensor, exhibits excellent flexibility and durability. [Display omitted] Printable micro-supercapacitors (MSCs) with remarkable versatility, customizability, high power density and long cycling lifespan, are regarded as a promising class of miniaturized power source for wearable and portable microelectronics. Herein, we demonstrate a novel Fe-based zeolitic imidazolate framework (Fe-ZIF)/graphene (FZG) heterostructure with high specific surface area and outstanding electrical conductivity for planar MSCs (FZG-MSCs) worked in a high-voltage ionic liquid gel electrolyte via a spray-printed strategy. The fully printed FZG-MSCs deliver a high areal energy density of 9.5 μWh/cm2, extraordinary cyclability, and tailored voltage/capacitance output. Furthermore, using a fully printed FZG-MSC, we seamlessly integrate a monolithically planar all-flexible self-sustained sensor system with a mounted solar cell and a printable NH 3 gas sensor on the same side of single flexible substrate. The self-sustained sensor system exhibits high-sensitivity NH 3 detection with a good response of 18.3% at 20 ppm and linear sensibility exposed to 2–20 ppm. Such a fully integrated system can utilize the converted solar energy stored in the MSC, and offer efficient electricity to power microelectronics whenever needed. Therefore, this contribution of printable planar device and integrated system paves a new avenue for constructing flexible microelectronics. [ABSTRACT FROM AUTHOR]

We developeda facile method to construct flexible, freestanding three dimensional hierarchical electrodes that consist of graphene encapsulated one-dimensional conducting polyaniline (PANi)@MnO2 coaxial nanowires grown on electrospun carbon nanofibers (denoted as G-PANi@MnO2/ECNFs). A combination of XRD, SEM, and TEM techniques were used to characterize the structures of G‑PANi@MnO2/ECNFs. Electrochemical measurements confirmed that such nanostructured composites possessed higher electrochemical capacitance than that of each individual component due to synergistic effects. The G-PANi@MnO2/ECNFs electrode exhibited extremely high specific capacitance (1364.3 F/g at 0.3 A/g) and superior cycling stability (89.2% retention rate after 2000 cycles) in a 1 M Na2SO4 aqueous solution. The excellent electrochemical performance of such nanoscale architectured electrodes provides a new route to develop flexible, freestanding, and high-performance supercapacitors. [ABSTRACT FROM AUTHOR]

Nickel oxide nanoparticles (NiO NPs) are synthesized using olive leaf extract (OLE), which contains a range of polyphenols. These polyphenols serve as both reducing and capping agents, stabilizing the nanoparticles. Aqueous nickel acetate is employed as a precursor. Simultaneously, exfoliated graphene (EG) is obtained via electrochemical exfoliation of graphite in aqueous solutions. These materials were employed as electroactive components in supercapacitor applications. Characterization of NiO and EG involved thermogravimetric analysis (TGA), X-ray diffraction (XRD), Raman spectroscopy (RS), X-ray photoelectron spectroscopy (XPS), and scanning/transmission electron microscopy (SEM/TEM), alongside Brunauer−Emmett−Teller (BET) analysis, confirming the formation of crystalline NiO NPs with a cubic phase and Fm-3m space group. Micrographs revealed nanoscale dimensions for both NiO and EG with a substantial surface area, as verified by BET analysis. Symmetric (NiO/NiO, EG/EG) and asymmetric (NiO/EG) supercapacitors were fabricated using the doctor blade method. Electrode evaluation, employing field-emission scanning electron microscopy FESEM, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS), demonstrated promising morphological and electrochemical characteristics. At low scan rates, both symmetric and asymmetric supercapacitors exhibited a notable gravimetric capacitance (221, 111, and 162 F g–1 at 1 mV s–1). Additionally, they revealed higher power density (173, 137, and 161 W kg–1 at 10 mV s–1), showcasing pseudocapacitive and electric double-layer capacitor (EDLC) behavior for NiO NPs and EG, respectively. This research significantly contributes valuable insights by presenting a sustainable synthesis route for NiO NPs, developing high-performance supercapacitor electrodes, and achieving a comprehensive understanding of the electrochemical behavior of NiO NPs and EG. [ABSTRACT FROM AUTHOR]

In the last ten years, there has been a significant increase in supercapacitor research in energy storage systems. A supercapacitor is an electrochemical capacitor made up of two electrodes, a separator, and a solution of electrolyte. The supercapacitor is distinguished from capacitors and li-ion batteries by its high power density and long cycle counts. This situation provides a broad application area for supercapacitors derived from consumables (cameras, computer equipment, etc.) in the defense industry (laser guns). Furthermore, electric and hybrid vehicle technologies are being developed gradually. The use of supercapacitors in these vehicles improves battery performance. The working principles of supercapacitors are examined in depth in this study. Furthermore, current electrochemical performance measurements of electrodes (graphene, activated carbon, carbon nanotubes, metal oxides, and conductive polymers) formed in accordance with supercapacitor types were investigated. According to this article, the studies will contribute to the development of superior-performance supercapacitors and their applications. [ABSTRACT FROM AUTHOR]

The rise in universal population and accompanying demands have directed toward an exponential surge in the generation of polymeric waste. The estimate predicts that world‐wide plastic production will rise to ≈590 million metric tons by 2050, whereas 5000 million more tires will be routinely abandoned by 2030. Handling this waste and its detrimental consequences on the Earth's ecosystem and human health presents a significant challenge. Converting the wastes into carbon‐based functional materials viz. activated carbon, graphene, and nanotubes is considered the most scientific and adaptable method. Herein, this world provides an overview of the various sources of polymeric wastes, modes of build‐up, impact on the environment, and management approaches. Update on advances and novel modifications made in methodologies for converting diverse types of polymeric wastes into carbon nanomaterials over the last 5 years are given. A remarkable focus is made to comprehend the applications of polymeric waste‐derived carbon nanomaterials (PWDCNMs) in the CO2 capture, removal of heavy metal ions, supercapacitor‐based energy storage and water splitting with an emphasis on the correlation between PWDCNMs' properties and their performances. This review offers insights into emerging developments in the upcycling of polymeric wastes and their applications in environment and energy. [ABSTRACT FROM AUTHOR]

The primary goal for the development of energy-storage devices is to find affordable ways to increase their efficiency, activity, and stability. In this regard, transition metal oxide mainly MoO 3 enhances the electrochemical properties of the material due to various oxidation states. On the other hand, carbonaceous materials, such as reduced graphene oxide, provide a large surface area that increases the conductivity of nanomaterials. In this work, we have synthesized pristine and codoped MoO 3 material using the co-precipitation route. While the r-GO based composite was prepared by a simple sonication approach. The prepared composite material showed a higher specific capacitance of 987 F/g than the pristine and codoped material. The BAMO@r-GO discharges after 346 s which was the higher time of discharge than that of pure and codoped material. Moreover, the obtained results from EIS measurement confirmed that the composite material showed less resistance than all other synthesized materials. The synergistic effect between the r-GO and BAMO materials is the reason for the higher supercapacitor performances of BAMO@r-GO. Based on these results, the fabricated BAMO@r-GO material can be effectively utilized as an electrode material in electrochemically powered energy storage devices. [ABSTRACT FROM AUTHOR]

Carbon-based supercapacitors have been extensively explored by the virtue of their exceptional performance in terms of charge-storage capacity, electrical conductivity, and good stability. However, the rush to find potential approaches for increasing their specific capacitance and specific energy without adversely affecting the specific power is still exciting. Herein, we synthesized hierarchically structured carbon-based composites based on 2D MXene sheets with an interconnected conductive porous network of 1D graphene nanoribbons (GNRs). Synergistic effects arising due to the defect engineering of 2D MXene sheets with 1D GNRs led to high surface-area, effective ion-transport, and improved structural robustness of the composite electrodes, thereby enhancing the specific capacitance along with specific energy of device while preserving its specific power. The electrochemical studies revealed that the composites with 1 wt.% GNRs (GMX-B) outperformed when the composition of GNRs was varied from 0.5 to 1.5 wt. % in MXene (GMX-A, GMX-B, and GMX-C). In comparison to pristine MXene and pristine GNRs, GMX-B exhibited ∼2.54 and ∼2.74 folded higher capacitance of 238.96 F/g at 0.6 A/g current density, respectively, a higher capacitance retention of 72.16% for a scan rate from 10–140 mV/s as well as a good cyclic stability of 85.11% over 10 000 charge/discharge cycles. Furthermore, GMX-B electrode achieved a high specific energy of 4.066 Wh/Kg while maintaining a specific power of 210.640 W/Kg as compared to pristine MXene (1.597 Wh/Kg at 211.989 W/Kg) and pristine GNRs (1.482 Wh/Kg at 211.089 W/Kg). Thus, we anticipated that the use of hierarchically engineered 1D/2D carbon-based composites with considerable improvement in its interfacial properties holds great potential to achieve high-performing energy-storage devices. [ABSTRACT FROM AUTHOR]

Niobium tungsten oxide has become one the promising electrode materials for supercapacitors due to its high ion diffusion coefficient, multiple redox pairs and structural stability, however, extremely low inherent electrical conductivity limits its rate capability. The study reports the synthesis of a W3Nb14O44/biomass carbon (BC) composite by introducing serine and histidine-functionalized and boron-doped graphene quantum dots (SHB-GQDs). Here, ammonium tungstate and niobium oxalate combined with SHB-GQDs to form a water-soluble SHB-GQD-Nb/W complex, sucked into rambutan peel, freeze-dried and annealed. The introduction of SHB-GQD realizes the construction of the W3Nb14O44 nanocrystals with a (4 × 4)-sheer structure, more exposed high-index crystal faces and small size (22 ± 0.18nm), oxygen vacancies and graphene electron trap. The integration of these multiple structure engineering improves the inherent electronic conductivity and expands the safe voltage window (2.1 V) and leads to outstanding supercapacitor performance. The W3Nb14O44-SHB-GQD/BC electrode offers a high capacitance of 535 F g−1 at 1 A g−1 (312 mA h g−1), which is more than the theoretical capacity of W3Nb14O44 in lithium ion batteries (293.56 mA h g−1). The symmetrical supercapacitor exhibits a high capacitance of 457 F g−1 at 1 A g−1, an energy density of 70 W h Kg−1 at 525 W Kg−1 and 95.6% capacitance retention after 10 000-cycle at 10 A g−1. It shows a broad prospect for applications in wearable electronics. [ABSTRACT FROM AUTHOR]

Supercapacitor's demand for hybrid vehicles, portable electronic gadgets, and high‐power applications is increasing unexpectedly. However, supercapacitors′ inadequacies (i. e. inflated costs, poor energy density, erratic cycle life) need to be addressed by introducing novel composite materials and developing facile synthesis techniques which can give them high surface area and improved electrochemical stability. Moreover, hybrid supercapacitor electrodes based on ternary composites should be designed to broaden their application range and to deal with the challenges. The primary aim of this review is to explore the recent advances in the field of hybrid supercapacitors to address the challenges in this field. Specifically, we have focused on ternary nanocomposites comprising Graphene‐Conducting Polymers‐Metal Oxides (G‐CPs‐MOs) and Graphene‐Conducting Polymers‐Metal Sulfides (G‐CPs‐MSs). Our investigations centred around exploring various synthesis techniques, the surface morphology of composites and analysing the reported electrochemical evaluations of supercapacitor electrodes to highlight the potential prospects and challenges they present. [ABSTRACT FROM AUTHOR]

This review considers the literature on electrochemical supercapacitors operating at extreme temperatures from –80 to +220°C, which is very important for practice. The influence of the following methods and factors on the efficiency of the electrochemical supercapacitors at the extreme temperatures is considered: the using of ionic liquids as electrolytes; the using of modified gel electrolyte, a combined electrolyte, aqueous electrolytes with low freezing point; the using of acetonitrile as an electrolyte solvent; the using of clay as a solid electrolyte; application of solid-state electrochemical supercapacitors; application of electrodes with optimized porous structure; the using of graphene and pseudocapacitive electrodes; the using of solar cells; using of combined techniques to create supercapacitors for extreme temperatures. Undoubtedly, this review will be of great interest both for fundamental electrochemistry and for practice. [ABSTRACT FROM AUTHOR]

[Display omitted] To facilitate the transition of laboratory research to industrial applications, it is critical to establish a reliable protocol for the mass synthesis of high-quality graphene. Here, we present an efficient electrochemical intercalation-based exfoliation approach utilizing alternating current that allows for the production of sub-kilogram quantities of graphene. This strategy involves repeatedly intercalating foreign anions and cations into the interlayer gaps of dual-graphite electrodes, accelerating the graphite expansion process and maximizing the exfoliation efficiency of both electrodes while inhibiting excessive anodic oxidation. The exfoliation process leads to high-yield graphene nanosheets (92 %, primarily 1–3 layers) with minimal structural deterioration (I D /I G ratio of 0.05), high purity (2.1 at% oxygen), and outstanding electrical property (7.28 × 104 S m−1). Notably, our scaled-up manufacturing technique produces a record-breaking throughput of 135 g h−1, improving on the best-reported exfoliation efficiency with direct current by 35%. Furthermore, the as-made graphene demonstrates a large reversible capacity of 102 mF cm−2 for flexible supercapacitors, with robust cyclability with 99.5% after 10,000 cycles, excellent mechanical flexibility, and exceptional serial integration for adjustable voltage output. The efficient and scalable method presents a significant advancement in the large-scale manufacture of graphene, with potential for widespread industrial applications. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) 1H molybdenum disulfide (1H-MoS2) is hard to be directly used in energy storage devices due to its inert basal plane and unfavorable 2D stacking. This work demonstrated how the basal plane of 1H MoS2 nanocrystals (NCs) can be activated to offer doubled specific capacitance by simple surface S depletions. Building on the expanded graphene with three-dimensional (3D) structures, as-prepared NCs were chemically grafted on the graphene surface to deliver stable energy storage and high capacitance, which overcame above challenges of 1H-MoS2. Aside from the mostly focused metastable phase, this work confirmed that the stable 1H Mo–S material is also promising in energy storage applications. [ABSTRACT FROM AUTHOR]

Graphene electrodes were firstly printed on recycled single‐use‐packets. Later, the Ni50Mn35In15 (NMI) alloy or Ca2.9Nd0.1Co3.9Cu0.1O9, (CNCCO) misfit perovskite was deposited on the graphene electrodes to enhance their capacitive performance. Next, flexible supercapacitors (SCs) were assembled by using such electrodes. The SCs made with NMI and CNCCO powders were named as GNMI‐SC, and GCNCCO‐SC, respectively. Those ones produced capacitances/energy‐densities of 761.8 F g−1/152.6 Wh kg−1 and 207.7 F g−1/41.6 Wh kg−1, respectively. Subsequently, a mixture 1 : 1 of NMI and CNCCO powders was melted/coalesced at 1700 °C by using a plasma treatment in argon atmosphere and obtained in this way a NMI/CNCCO composite powder. The SC made with this last composite generated a capacitance/energy‐density of 1235.2 F g−1/247.3 Wh kg−1. Those last values are 62–500 % higher than these for the GNMI‐SC, and GCNCCO‐SC devices. Other benefits obtained after the introduction of the NMI/CNCCO powders into the SCs were: 1) the formation of additional Cu2+, Mn4+, Nd2+ and In3+ species, which enhanced the capacitance; 2) the capacitance retention was maintained above 93 % after 500 cycles of charge discharge; and 3) the lowest values of series and charge transfer resistances were obtained, which favored the ion diffusion/storage in the SC electrodes. [ABSTRACT FROM AUTHOR]

Recent progress concerning the development of counter electrode material (CE) from the dye-sensitized solar cells (DSSCs) and the electrode material (EM) within supercapacitors is reviewed. From composites based on carbon nanotubes (CNTs) and conducting polymers (CPs) to their biggest competitor, namely composites based on graphene or graphene derivate (GD) and CPs, there are many methods of synthesis that influence the morphology and the functionalization inside the composite, making them valuable candidates for EM both inside DSSCs and in supercapacitors devices. From the combination of CPs with carbon-based materials, such as CNT and graphene or GD, the perfect network is created, and so the charge transfer takes place faster and more easily. Inside composites, between the functional groups of the components, different functionalizations are formed, namely covalent or non-covalent, which further provide the so-called synergic effect. Inside CPs/CNTs, CNTs could play the role of template but could also be wrapped in a CP film due to π–π coupling enhancing the composite conductivity. Active in regenerating the redox couple I−/I3−, the weakly bound electrons play a key role inside CPs/GD composites. [ABSTRACT FROM AUTHOR]

Less defective, nitrogen-doped 3-dimensional graphene (N3DG) and defect-rich, nitrogen-doped 3-dimensional graphene (N3DG-D) were made by the thermal CVD (Chemical Vapor Deposition) process via varying the carbon precursors and synthesis temperature. These modified 3D graphene materials were compared with pristine 3-dimensional graphene (P3DG), which has fewer defects and no nitrogen in its structure. The different types of graphene obtained were characterized for morphological, structural, and compositional assessment through Scanning Electron Microscopy (SEM), Raman Spectroscopy, and X-ray Photoelectron Spectroscopy (XPS) techniques. Electrodes were fabricated, and electrochemical characterizations were conducted to evaluate the suitability of the three types of graphene for heavy metal sensing (lead) and Electric Double-Layer Capacitor (EDLC) applications. Initially, the various electrodes were treated with a mixture of 2.5 mM Ruhex (Ru (NH3)6Cl3 and 25 mM KCl to confirm that all the electrodes underwent a reversible and diffusion-controlled electrochemical process. Defect-rich graphene (N3DG-D) revealed the highest current density, followed by pristine (P3DG) and less-defect graphene (N3DG). Further, the three types of graphene were subjected to a sensing test by square wave anodic stripping voltammetry (SWASV) for lead detection. The obtained preliminary results showed that the N3DG material provided a great lead-sensing capability, detecting as little as 1 µM of lead in a water solution. The suitability of the electrodes to be employed in an Electric Double-Layer Capacitor (EDLC) was also comparatively assessed. Electrochemical characterization using 1 M sodium sulfate electrolyte was conducted through cyclic voltammetry and galvanostatic charge-discharge studies. The voltammogram and the galvanostatic charge-discharge (GCD) curves of the three types of graphene confirmed their suitability to be used as EDLC. The N3DG electrode proved superior with a gravimetric capacitance of 6.1 mF/g, followed by P3DG and N3DG, exhibiting 1.74 mF/g and 0.32 mF/g, respectively, at a current density of 2 A/g. [ABSTRACT FROM AUTHOR]

Supercapacitors have the characteristics of high power density, long cycle life, and fast charge and discharge rates, making them promising alternatives to traditional capacitors and batteries. The use of transition-metal compounds as electrode materials for supercapacitors has been a compelling research topic in recent years because their use can effectively enhance the electrical performance of supercapacitors. The current research on capacitor electrode materials can mainly be divided into the following three categories: carbon-based materials, metal oxides, and conductive polymers. Nickel hydroxide (Ni(OH)2) is a potential electrode material for use in supercapacitors. Depending on the preparation conditions, two crystal phases of nickel hydroxide, α and β, can be produced. When compared to α-NiOH, the structure of β-Ni(OH)2 does not experience ion intercalation. As a result, the carrier transmission rate of α-Ni(OH)2 is slower, and its specific capacitance value is smaller. Its carrier transport rate can be improved by adding conductive materials, such as graphene. β-Ni(OH)2 was chosen as an electrode material for a supercapacitor in this study. Homemade low-pressure chemical vapor deposition graphene (LPCVD-Graphene) conductive material was introduced to modify β-Ni(OH)2 in order to increase its carrier transport rate. The LPCVD method was used to grow high-quality graphene films on three-dimensional (3D) nickel foam substrates. Then, a hydrothermal synthesis method was used to grow β-Ni(OH)2 nanostructures on the 3D graphene/nickel foam substrate. In order to improve the electrical properties of the composite structure, a high-quality graphene layer was incorporated between the nickel hydroxide and the 3D nickel foam substrate. The effect of the conductive graphene layer on the growth of β-Ni(OH)2, as well as its electrical properties and electrochemical performance, was studied. When this β-Ni(OH)2/CVD-Graphene/3D-NF (nickel foam) material was used as the working electrodes of the supercapacitor under a current density of 1 A/g and 3 A/g, they exhibited a specific capacitance of 2015 F/g and 1218.9 F/g, respectively. This capacitance value is 2.62 times higher than that of the structure without modification with a graphene layer. The capacitance value remains at 99.2% even after 1000 consecutive charge and discharge cycles at a current density of 20 A/g. This value also improved compared to the structure without graphene layer modification (94.7%). [ABSTRACT FROM AUTHOR]

Energy storage systems (ESSs) are attracting increasing attention for the development of sustainable and renewable energy technologies owing to limited fossil fuels. Supercapacitors are gaining significant interest as energy storage devices owing to their high-power density and long-term cycle stability. The use of suitable electrode materials affects the performance of supercapacitors. In this study, we fabricated a carboxyl-doped graphene nanoplatelet (CGnP) via a mechanochemical reaction. Additionally, CGnP was activated by controlling parameters such as temperature, flow rate, and maintenance period and evaluated as an electrode material for supercapacitors. The effect of the specific surface area (SSA) and functional groups of the fabricated samples on the capacitance was confirmed by controlling the activation parameters. The activated CGnP with 300 mL/min of CO2 at 1173 K for 4 h exhibited a high SSA of 1300 m2/g. The activated CGnP (180 F/g), with a high SSA, showed an increased capacitance of 46% compared to pristine CGnP (123 F/g). Additionally, activated CGnP1100 demonstrated good wettability and exhibited excellent stability with a low capacitance decrease of 6.1%, even after 10,000 cycles. [ABSTRACT FROM AUTHOR]

One of the main problems faced by 2D materials used in supercapacitor applications when scaling up is restacking, such that their gravimetric capacitances become dramatically inferior to that of their monolayer forms. This study analyzes the Raman spectra of transferred layers of CVD-graphene revealing decoupling and rotational stacking of layers, with the potential of retention of intrinsic monolayer properties. Rotationally stacked layers have the potential to mitigate restacking and, thus, are capable of easing ion intercalation and boosting their performance in supercapacitor applications. In this pursuit, binder-free supercapacitors are fabricated out of chemical vapor deposited bilayer graphene, successively transferred to form rotationally stacked multilayers. Supercapacitors constructed with rotationally stacked four-layer graphene have an incredible specific gravimetric capacitance of 316.1 F g−1 at 1 mV s−1, with a corresponding energy density of 28.1 Wh kg−1 and ∼100% capacitance retention at 10 000 cycles. [ABSTRACT FROM AUTHOR]

Design and development of promising electrode materials for supercapacitors has been a vital topic of current research focus. Here, we report the supercapacitive performance of the strontium titanate–graphene quantum dot–polyaniline heterohybrid. The synthesis strategy involves a sequential sol–gel synthesis of strontium titanate, followed by hydrothermal aided interface formation with graphene quantum dots (GQD) and polyaniline (PANI) deposition by chemical oxidative polymerization. A high specific capacitance of 2134 F g−1 could be observed in 1 M H2SO4 electrolyte at a current density of 1 A g−1. The Ragone plot for the symmetric cell reveals an energy density of 16.2 W h kg−1 at a power density of 4533.7 W kg−1. The 97.7% retention of specific capacitance demonstrated at higher current densities ensures high rate capability. Further, the device demonstrated a capacitance retention of 80% at 10 A g−1 after 10000 galvanostatic charge–discharge cycles. Low interfacial charge transfer resistance as evidenced by impedance spectroscopy analysis and high performance could be attributed to the synergistic interaction at the interface. [ABSTRACT FROM AUTHOR]

Microsupercapacitors (µSCs) have received a lot of interest for their possible use in miniaturized electronics and in the field of the Internet of Things (IoT) to power distributed sensors. µSCs fill the gap between batteries and traditional capacitors, providing high power densities and acceptable energy densities to fulfill onboard power supply requirements, coupled with quick charge/discharge rates and extended lifetime. Charge balancing of µSCs is not a standard practice, although the optimization of electrodes can provide beneficial effects on the electrochemical performance and stability of the device. In this work, a charge‐balanced double‐layer µSC based on laser‐induced graphene (LIG) with [PYR14][TFSI] as an ionic liquid electrolyte is presented for the first time. The optimized device shows an improvement in terms of the increased lifetime of a factor of four and its energy efficiency is raised above 80%. [ABSTRACT FROM AUTHOR]

This study focuses on the synthesis and characterization of supercapacitor materials derived from pyrolyzed natural compounds. Four compounds were investigated: methylcellulose with lysine (ML), methylcellulose with lysine-graphene composite (MLG), algae (A), and algae-graphene composite (AG). The pyrolysis process was utilized to convert these natural compounds into carbon-based materials suitable for supercapacitor applications. The properties of the resulting materials were analyzed extensively to evaluate their potential as supercapacitor electrodes. The electrochemical performance, including specific capacitance, cyclic stability, and rate capability was measured using various characterization techniques. The effects of incorporating graphene into the lysine-methylcellulose and algae matrices were also studied to explore the enhancements in supercapacitor performance. In both cases, the addition of graphene resulted in a positive effect. Among all the materials investigated, the algae-graphene composite exhibited the most favorable properties, demonstrating a specific capacitance of 192 F g−1 after 10,000 galvanostatic charge–discharge cycles at a current of 5 A g−1 in K2SO4 electrolyte. This exceptional performance underscores the potential of the algae-graphene composite as a highly efficient and durable electrode material for supercapacitor applications. [ABSTRACT FROM AUTHOR]

Ionogel electrolytes are critical to electrochemical devices owing to mechanical and electrical properties. Here, graphene-enhanced double-network ionogel electrolytes have been developed with superior properties for energy storage and strain sensing. The uniformly dispersed graphene nanosheets enhance mechanical properties of double-network ionogels and then, provide fluent channels for ion transport. The electrolytes display high ionic conductivity of 0.186 mS cm−1, tensile modulus of 3.64 MPa, and breaking elongation of 217%. The as-prepared electrochemical devices give a high energy capacity of 213 F g−1 at current density of 2 A g−1, and excellent cycling stability beyond 30,000 charge–discharge cycles. In addition, the devices with piezoionic effect present superior sensing properties and have been utilized for real-time monitoring of breath status, which is very important to detection of breath-related disease. [ABSTRACT FROM AUTHOR]

As an organic pseudocapacitive active material, 2, 3‐Dichloro‐1, 4‐naphthoquinone (DNQ) was used in supercapacitors. Graphene with unique structures and high electrical conductivity acts as substrate. DNQ non‐covalently modified graphene composite material (DNQ@rGO) was synthesized through the simple solvothermal synthesis. The redox reaction between naphthol and naphthoquinone occurs on reduced graphene oxide(rGO), which forms an ideal pseudocapacitance without destroying its sp2 network. The optimal DNQ@rGO electrode material obtained the specific capacitance of 361.2 Fg−1 at 5 mV s−1 in 1 mol L−1 H2SO4 and exhibited excellent rate capability (capacitance retention of 87.5 % at 100 mV s−1) in the three‐electrode system. We also prepared holey layered oxygen‐rich graphene hydrogels (HLGH) material, whose electrochemical performance is superior to traditional three‐dimensional (3D) graphene hydrogels (GH). Finally, two asymmetric supercapacitors (ASCs) were assembled by using the DNQ@rGO (positive electrode), the HLGH and GH (negative electrode). The results show that the ASC with HLGH as negative electrode achieved the high energy and power densities due to the perfect matching of capacitance and kinetics between the positive and negative electrodes. The specific capacitance was almost no loss after 4700 cycles, showing the excellent stability. [ABSTRACT FROM AUTHOR]

The field of supercapacitors consistently focuses on research and challenges to improve energy efficiency, capacitance, flexibility, and stability. Low-cost laser-induced graphene (LIG) offers a promising alternative to commercially available graphene for next-generation wearable and portable devices, thanks to its remarkable specific surface area, excellent mechanical flexibility, and exceptional electrical properties. We report on the development of LIG-based flexible supercapacitors with optimized geometries, which demonstrate high capacitance and energy density while maintaining flexibility and stability. Three-dimensional porous graphene films were synthesized, and devices with optimized parameters were fabricated and tested. One type of device utilized LIG, while two other types were fabricated on LIG by coating multi-walled carbon nanotubes (MWCNT) at varying concentrations. Characterization techniques, including scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD), Raman spectroscopy, and voltammetry, were employed to analyze the fabricated devices. AFM analysis revealed a surface roughness of 2.03 µm for LIG due to laser treatment. SEM images displayed compact, dense, and porous surface morphology. XRD analysis confirmed the presence of graphene and graphene oxide, which was further supported by energy-dispersive X-ray spectroscopy (EDX) data. Raman spectroscopy indicated that the fabricated samples exhibited distinct D and G bands at 1362 cm–1 and 1579 cm–1, respectively. Cyclic voltammetry (CV) results showed that LIG's capacitance, power density, and energy density were 6.09 mF cm–2, 0.199 mW cm–2, and 3.38 µWh cm–2, respectively, at a current density of 0.2 mA cm–2. The LIG-MWCNT coated electrode exhibited a higher energy density of 6.05 µWh cm–2 and an areal-specific capacitance of 51.975 mF cm–2 compared to the LIG-based devices. The fabricated device has potential applications in smart electronics, nanorobotics, microelectromechanical systems (MEMS), and wearable and portable electronics. [ABSTRACT FROM AUTHOR]

[Display omitted] • An azure C/ N -doped graphene aerogel (AC/NGA) is prepared via a hydrothermal method. • AC molecules graft onto NGA by strong non-covalent π-π conjugation. • AC/NGA shows enhanced electrochemical performance under pH-universal conditions. • The AC/NGA//AC/NGA symmetric supercapacitor exhibits high efficiency performance in a full pH range. Current aqueous supercapacitors (SCs) possess the relative low energy density, and there is therefore widespread interest in cost-effective fabrication of capacitive materials with promoted specific capacitance and/or broadened voltage window. Here, a redox-active azure C-decorated N -doped graphene aerogel (AC − NGA) is fabricated using a simple hydrothermal self-assembly method through strong noncovalent π-π interaction. AC − NGA highlights an excellent charge storage performance (a high 591F g−1 gravimetric capacitance under a current density of 1.0 A g-1 and ultrahigh voltage window of 2.3 V) under pH-universal conditions. The capacitive contribution of charge storage is 91.7%, exceeding or comparable to those of the best pseudocapacitors known. Furthermore, a symmetric AC − NGA//AC − NGA device realizes high energy and power densities (15.2 – 60.2 Wh kg−1 at 650 – 23,000 W kg−1) and excellent cycling stability in acidic, neutral, and basic aqueous solutions. This work offers a cost-effective strategy to combine redox dye molecules with heteroatom-doped graphene aerogel for building green efficient pH-universal aqueous supercapacitors. [ABSTRACT FROM AUTHOR]

Vanadium oxide has become a promising electrode material for supercapacitors because of its multiple states, but the low electrical conductivity and poor cycling stability restrict its wide application in high-performance supercapacitors. This study reports the synthesis of a V2O5/biomass carbon nanocomposite using serine- and histidine-functionalized and boron-doped graphene quantum dots (S/H-GQD-B). NH4VO3 reacted with S/H-GQD-B to form a stable V-S/H-GQD-B complex, which was absorbed into cotton, vacuum-dried and annealed to produce V2O5-S/H-GQD-B/BC. The introduction of S/H-GQD-B and cotton to aid the construction of small V2O5 nanocrystals (25 ± 1.2 nm), oxygen vacancies and graphene electron traps. The integration of these structural engineering features significantly improved the inherent electronic conductivity, expanded the safe voltage window (1.7 V) and enhanced the discharge capacity. The specific capacitance of the V2O5-S/H-GQD-B/BC electrode reached 552.94 F g−1 at 1 A g−1 and 291.48 F g−1 at 50 A g−1. The symmetrical supercapacitor exhibited high capacitance (435.53 F g−1 at 1 A g−1), high rate behavior (205.88 F g−1 at 50 A g−1), energy density (43.7 W h Kg−1 at 425 W Kg−1), and cycling stability (98.9% capacitance retention after 10 000 cycles at 10 A g−1). The study also paves an avenue for the synthesis of metal nanomaterials with outstanding electrochemical behavior for energy storage, catalysis and sensing applications. [ABSTRACT FROM AUTHOR]

In light of the rapid development of intelligence and miniaturization in electronics, the growing demand for sustainable energy sources gives rise to a plethora of environmental/mechanical energy harvesters. However, the fluctuating nature of these generated energies frequently presents a challenge to their immediate usability. Although electrolytic capacitors can smooth fluctuating energy, lacking miniaturization and flexibility constrain their potential applications. Conversely, electrochemical capacitors (ECs), particularly fiber‐shaped electrochemical capacitors (FSECs), can offer superior flexibility. Nevertheless, the inherent trade‐off between ion transport and charge storage in fibrous electrodes poses a significant obstacle to their filtering capability. Here, a hierarchically 3D fibrous electrode that effectively balances ion transport and charge storage through its unhindered primary framework and intertwined secondary frameworks is presented. The resulting FSEC exhibits an exceptional specific areal capacitance of 1.37 mF cm−2 with a phase angle of −82° at 120 Hz, surpassing that of fiber‐shaped filter capacitors and most non‐fibrous filter ECs previously reported. Additionally, the FSEC displays excellent flexibility and high‐frequency response, rendering it well‐suited for filtering arbitrary ripple voltage and compatible with environmental/mechanical energy harvesters. These results demonstrate a promising approach for designing fibrous high‐frequency response electrodes and a foundation for portable environmental energy harvesting devices. [ABSTRACT FROM AUTHOR]

Supercapacitors (SCs) have drawn much attention owing to their unique superiorities. The selection of electrode materials is significantly crucial as it influences SC performance. Defects such as low specific capacitance and poor rate performance need to be settled urgently to achieve enhanced SC performance. Here, we have developed an effective and facile strategy to prepare a binder-free nitrogen-doped graphene hydrogel (NDGH) as an electrode material. The electrochemical performance of NDGH was measured in three different electrolytes (2 M KOH, 1 M Na2SO4 and 1 M H2SO4), and it showed superior performance in 2 M KOH. NDGH had an outstanding specific capacitance of 224.1 F g−1 at 1 A g−1 and retained 80.7% of the capacitance at 10 A g−1. Meanwhile, NDGH possessed good cycling stability, with 93% capacitance retention after 6000 cycles. The contributions of surface-controlled and diffusion-controlled processes to NDGH capacitance were analyzed in different electrolytes. Compared with 1 M Na2SO4 (52%) and 1 M H2SO4 (13%), superior surface-controlled contribution was observed in the 2 M KOH (73%) electrolyte at 10 mV s−1. The symmetric supercapacitor (SSC) consisting of NDGH delivered an energy density of 14.3 W h kg−1 at a power density of 582.8 W kg−1 in the KOH electrolyte. These excellent electrochemical performance parameters could be achieved due to the synergistic effect of the multistage pore structure, nitrogen doping and binder-free hydrogel, which allow abundant electrochemical reactions to take place at the interface between the electrode materials and the electrolyte. This strategy may be further broadened to prominently enhance the specific capacitance and rate performance of graphene oxide. [ABSTRACT FROM AUTHOR]

The blending of waste tin tailings with graphene derived from waste rice husks in the production of high-specific capacitance supercapacitors was developed in this work. Alkaline treatment method was used to develop graphene from rice husks. The doping casting method was used to produce 0, 10, 20, and 30 wt% graphene with constant 20 wt% tin tailings. Cyclic voltammetry (CV), electrochemical impedance spectroscopy, scanning electron microscopy, and X-ray diffractogram (XRD) were used to analyze the composite electrode material. The specific capacitance rises with an increase in the dopant graphene of up to 30% with a specific capacitance of 379.58 at a 5 mV/s scanning rate. The high specific capacitances obtained are within the standard for flexible supercapacitors. It was established that waste tin tailings and graphene derived from waste rice husks could be used in the production of low-cost supercapacitors. [ABSTRACT FROM AUTHOR]

[Display omitted] A facile and expandable methodology was successfully developed to fabricate laser-induced graphene from novel pristine aminated polyethersulfone (amPES) membranes. The as-prepared materials were applied as flexible electrodes for microsupercapacitors. The doping of amPES membranes with various weight percentages of carbon black (CB) microparticles was then performed to improve their energy storage performance. The lasing process allowed the formation of sulfur- and nitrogen-codoped graphene electrodes. The effect of electrolyte on the electrochemical performance of as-prepared electrodes was investigated and the specific capacitance was significantly enhanced in 0.5 M HClO 4. Remarkably, the highest areal capacitance of 47.3 mF·cm−2 was achieved at a current density of 0.25 mA·cm−2. This capacitance is approximately 12.3 times higher than the average value for commonly used polyimide membranes. Furthermore, the energy and power densities were as high as 9.46 µWh·cm−2 and 0.3 mW·cm−2 at 0.25 mA·cm−2, respectively. The galvanostatic charge–discharge experiments confirmed the excellent performance and stability of amPES membranes during 5,000 cycles, where more than 100% of capacitance retention was achieved and the coulombic efficiency was improved up to 96.67%. Consequently, the fabricated CB-doped PES membranes offer several advantages including low carbon fingerprint, cost-effectiveness, high electrochemical performance and potential applications in wearable electronic systems. [ABSTRACT FROM AUTHOR]

Graphene nanostructures (GNSs) are among the most promising materials for producing supercapacitors. However, GNSs are still not used in creating supercapacitors due to the impossibility of obtaining large volumes of high-quality material at an acceptable cost. In our previous works, we have shown the possibility of synthesizing large volumes of few-layer graphene (FLG, the number of layers is not more than five) from cyclic biopolymers under conditions of self-propagating high-temperature synthesis (SHS). Using the SHS process makes it possible to synthesize large volumes of FLG without Stone–Wales defects. This work is devoted to the study of the possibility of using FLG synthesized under the conditions of the SHS process in the creation of supercapacitors. It was found that the synthesized FLG makes it possible to obtain better results than using classical materials, namely activated carbon (AC). It was found that the sample based on FLG had a higher specific capacitance of 65 F × g−1 compared to the sample from AC, the specific capacitance of which was 35 F × g−1; for a speed of 5 mV × s−1, these values were170 and 64 F × g−1, respectively. The drop in capacitance over 1000 cycles was 4%, indicating a sufficiently high FLG stability, allowing us to consider FLG as a prospective material for use in supercapacitors. [ABSTRACT FROM AUTHOR]

In this study, we synthesized a bayberry-like Ni–Co–Mn ternary hydroxide with a secondary nanoneedle structure using a modified and cost-effective hydrothermal process assisted by the surfactant cetyltrimethylammonium bromide (CTAB). The incorporation of CTAB and graphene in the preparation process significantly enhances the electrochemical performance of NiCoMn–OH. The achieved results are truly impressive, with a high specific capacity of 1450 ​F ​g−1 and an outstanding capacity retention of 52.57% over 5000 cycles. The superior performance could be attributed to the specific bayberry-like microstructure with high effective specific surface area, which allowed for facile and rapid transport of ions and electrons. Moreover, the synergistic effect of CTAB and graphene proved to be crucial in stabilizing the Co2+ and Mn2+ ions within the ternary hydroxide structure. We developed a hybrid capacitor using a NiCoMn–OH-CTAB/Graphene composite electrode and an active electrode, which delivered a superior energy density of 50.79 ​Wh kg−1 at a power density of 400 ​W ​kg−1 and a cycling stability of 60.37% after 10000 cycles. These results indicate that the NiCoMn–OH-CTAB/Graphene composite electrode has great potential as an electrode material for energy storage devices. • Ni–Co–Mn ternary hydroxide is prepared by CTAB-Assisted cost-effective method. • CTAB and graphene significantly improve the electrochemical performance of NiCoMn–OH. • A high specific capacity of 1450 ​F g-1 and 52.57% capacity retention for 5000 cycles are achieved. • The bayberry-like microstructure enables fast ion and electron transport. • The synergistic effect of CTAB and G stabilizes Co2+ and Mn2+ ions in ternary hydroxide. [ABSTRACT FROM AUTHOR]

This work demonstrates a facile and efficient methodology to synthesize a composite material of zeolitic imidazolate frameworks (ZIFs) and laser-induced graphene (LIG). This ZIF-67 loaded LIG composite (ZIF-67/LIG) has been adequately characterized for its morphology and structure, and its electrochemical performance has been specifically examined. As supercapacitors (SCs) electrode material, the ZIF-67/LIG composite exhibits superb electrochemical performance, owing to the inherent high porosity, abundant active sites, large specific surface area of ZIF-67, and the excellent conductive three-dimensional hierarchical porous network structure provided by LIG. In three-electrode system, ZIF-67/LIG composite electrode displays outstanding areal specific capacitance (C A) of 135.6 mF cm−2 at a current density of 1 mA cm−2 with 1 M Na2SO4 aqueous electrolyte, which is far greater than that of pristine LIG (7.7 mF cm−2). Furthermore, the ZIF-67/LIG composite has been fabricated into an all-solid-state planar micro-supercapacitor (MSC). This ZIF-67/LIG MSC exhibits an impressive C A of 38.1 mF cm−2 at a current density of 0.20 mA cm−2, a good cycling stability of 80.3% capacitance retention after 3000 cycles, and a high energy density of 5.29 μ Wh cm−2 at a power density of 0.1 mW cm−2. All electrochemical results clearly manifest that as-prepared ZIF-67/LIG composite can be a candidate in energy storage field with exciting possibilities. [ABSTRACT FROM AUTHOR]

Carbon‐based nanomaterials, including graphene, fullerenes, and carbon nanotubes, are attracting significant attention as promising materials for next‐generation energy storage and conversion applications. They possess unique physicochemical properties, such as structural stability and flexibility, high porosity, and tunable physicochemical features, which render them well suited in these hot research fields. Technological advances at atomic and electronic levels are crucial for developing more efficient and durable devices. This comprehensive review provides a state‐of‐the‐art overview of these advanced carbon‐based nanomaterials for various energy storage and conversion applications, focusing on supercapacitors, lithium as well as sodium‐ion batteries, and hydrogen evolution reactions. Particular emphasis is placed on the strategies employed to enhance performance through nonmetallic elemental doping of N, B, S, and P in either individual doping or codoping, as well as structural modifications such as the creation of defect sites, edge functionalization, and inter‐layer distance manipulation, aiming to provide the general guidelines for designing these devices by the above approaches to achieve optimal performance. Furthermore, this review delves into the challenges and future prospects for the advancement of carbon‐based electrodes in energy storage and conversion. [ABSTRACT FROM AUTHOR]

The electrochemical performance of flexible carbon-nanotube (CN) based supercapacitors (SCs) is reported in this research. A mixture of Boron nitride (BN), graphene (G) and lithium titanate (Li 2 TiO 3 , LiTi) was added on the SC electrodes to enhance their capacitance/energy-density. SC devices were fabricated with the names of CN-SC, CN/BNG-SC and CN/BNG + LiTi-SC and generated a capacitance/energy density of 329.7 F g−1/7.3 Wh kg−1, 890.2 F g−1/35.2 Wh kg−1 and 1662.6 F g−1/124.2 Wh kg−1, respectively. From those last values, we realize that adding BN, G and LiTi (CN/BNG + LiTi-SC), enhanced the capacitance and the energy density by ~ 4 and ≈ 16 times, respectively. Interestingly, the output voltage of the SCs also increased from 0.1 to 0.4 V after adding these three compounds to their electrodes. The SC electrodes were analyzed by UV–vis absorbance, Raman and XPS and found the presence of defects (oxygen vacancies) and Ti3+/Ti4+ species, which worked as redox centers for the charge storage. Moreover, the best CN/BNG + LiTi-SC device was subjected to 500 bending/charging-discharging cycles and maintained a capacitance of 86–97% despite the mechanical deformations. Finally, we demonstrated that the incorporation of the BN and LiTi materials on the SC electrodes produced a widening of the operating voltage window from 1.2 to 2.2 V, which is of particular interest to increase the lifetime of portable energy sources. [ABSTRACT FROM AUTHOR]

Three-dimensional graphene (3DG)/metal–organic framework (MOF)-based composites have attracted more and more attention in the field of energy due to their unique hierarchical porous structure and properties. The combination of graphene with MOFs can not only effectively overcome the limitations of poor electrical conductivity and low stability of MOFs, but also prevent the aggregation and reaccumulation between graphene sheets. Moreover, 3DG/MOF composites can also be used as multifunctional precursors with adjustable structures and composition of derivatives, thus expanding their applications in the field of electrochemistry. This feature article elaborates the latest synthesis methods of 3DG/MOF composites and their derivatives, along with their applications in batteries, supercapacitors (SCs) and electrocatalysis. In addition, the current challenges and future prospects of 3DG/MOF-based composites are discussed. [ABSTRACT FROM AUTHOR]

We present a facile low-cost method to produce nitrogen-doped holey graphene (N-HGE) and its application to supercapacitors. A composite of N-HGE and activated carbon (AC) was used as the electrode active material in organic-electrolyte supercapacitors, and the performances were evaluated. Melamine was mixed into graphite oxide (GO) as the N source, and an ultra-rapid heating method was used to create numerous holes during the reduction process of GO. X-ray photoelectron spectra confirmed the successful doping with 2.9–4.5 at.% of nitrogen on all samples. Scanning electron micrographs and Raman spectra revealed that a higher heating rate resulted in more holes and defects on the reduced graphene sheets. An extra annealing step at 1000 °C for 1 h was carried out to further eliminate residual oxygen functional groups, which are undesirable in the organic electrolyte system. Compared to the low-heating-rate counterpart (N-GE-15), N-HGE boosted the specific capacity of the supercapacitor by 42 and 22% at current densities of 0.5 and 20 A/g, respectively. The effects of annealing time (0.5, 1, and 2 h) at 1000 °C were also studied. Longer annealing time resulted in higher capacitance values at all current densities due to the minimized oxygen content. Volumetric specific capacitances of 49 and 24 F/cm3 were achieved at current densities of 0.5 and 20 A/g, respectively. For the high-power-density operation at 31,000 W/kg (or 10,000 W/L), an energy density as high as 11 Wh/kg (or 3.5 Wh/L) was achieved. The results indicated that N-HGE not only improved the conductivity of the composite supercapacitors but also accelerated ion transport by way of shortened diffusion paths through the numerous holes all over the graphene sheets. [ABSTRACT FROM AUTHOR]

It is no secret that graphene, a two-dimensional single-layered carbon atom crystal lattice, has drawn tremendous attention due to its distinct electronic, surface, mechanical, and optoelectronic properties. Graphene also has opened up new possibilities for future systems and devices due to its distinct structure and characteristics which has increased its demand in a variety of applications. However, scaling up graphene production is still a difficult, daunting, and challenging task. Although there is a vast body of literature reported on the synthesis of graphene through conventional and eco-friendly methods, viable processes for mass graphene production are still lacking. This review focuses on the variety of unwanted waste materials, such as biowastes, coal, and industrial wastes, for producing graphene and its potential derivatives. Among the synthetic routes, the main emphasis relies on microwave-assisted production of graphene derivatives. In addition, a detailed analysis of the characterization of graphene-based materials is presented. This paper also highlights the current advances and applications through the recycling of waste-derived graphene materials using microwave-assisted technology. In the end, it would alleviate the current challenges and forecast the specific direction of waste-derived graphene future prospects and developments. [ABSTRACT FROM AUTHOR]

Due to the fact that graphene possesses high conductivity, large specific surface area and ex- cellent mechanical properties, it has excellent application prospects in the field of supercapacitors. However, when it's directly used as the active electrode materials of supercapacitors, pure graphene face the problem of relatively low specific capacitance. In this paper, 3D porous nanocomposites com- posed of 2D graphene nanosheets, which was modified by OD molybdenum dioxide (MoO2) nanodots, were synthesized by one-step hydrothermal method. And the electrochemical properties of this kind of 0D-2D-3D multi-scale composites were studied as the active electrode materials of supercapacitors. The results showed that the specific capacitance was as high as 499 F/g at 2 mV/s, displaying excellent ca- pacity performance. [ABSTRACT FROM AUTHOR]

The controlled chemical functionalization of graphene oxide (GO) represents a powerful strategy to finely tune its physical and chemical properties toward applications in energy storage. Herein, an unprecedented approach for the GO modification with thioamide‐based polymers featuring numerous heteroatoms (S,N,O) is reported, which is instrumental for achieving superior electrochemical performance in symmetric supercapacitors. While the electrochemical investigations in aqueous electrolytes reveal specific capacitance of 221 F g−1 at 1 A g−1, the use of organic media allows the specific capacitance to be boosted up to 340 F g−1. Additionally, the increase of operating window yields energy densities as high as 94.4 Wh kg−1, thereby exceeding state‐of‐the‐art performances of GO‐based supercapacitors. Furthermore, the symmetric devices exhibit great robustness in both aqueous and organic electrolytes as evidenced by an excellent stability after 5000 working cycles (>98% in H2SO4 and >90% in TEABF4/ACN). [ABSTRACT FROM AUTHOR]

Nitrogen-doped Bernal graphene has several advantages, including improved electrical conductivity, enhanced stability and better compatibility with electrolytes. This article presents the synthesis of few-layer pristine graphene and nitrogen-doped Bernal graphene (CVDNG) through the Low-pressure chemical vapor deposition approach and its application for flexible supercapacitors. A novel hot lamination-assisted approach is employed to transfer the graphene on the desired substrates, enabling the reusability of copper. Raman mapping is utilized to analyze the characteristic bands and statistical distribution of Bernal stacking in CVDNG. The doping in graphene is confirmed through the X-ray photoelectron spectroscopy suggesting the content of pyrrolic-N (73.38%), pyridinic-N (20.28%) and graphitic-N (6.38%) in the CVDNG. Cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy are performed by sandwiching the polyvinyl alcohol-sodium perchlorate based hydrogel membrane between two symmetrical supercapacitor electrodes. CVDNG symmetrical supercapacitor device delivers an enhanced areal capacitance of 26.75 mF cm−2 with a high energy density of 2.14 mWh cm−2 with a power density of 72 mW cm−2 at 0.05 mA cm−2. The device shows excellent flexibility by retaining 91.1% of its capacitance at extreme bending (180° angle) conditions and excellent specific capacitance retention (90.6%) after 10,000 charge-discharge cycles. [Display omitted] • Nitrogen-doped Bernal graphene through the LPCVD approach for flexible supercapacitors. • A novel PMMA free approach to transfer the graphene, enabling the reusability of copper. • NaClO 4 -PVA based quasi-solid-state hydrogel membrane electrolyte. • The device shows excellent flexibility by retaining 91.1% of its capacitance at extreme bending (180° angle) conditions. • Excellent specific capacitance retention (90.6%) after 10,000 charge-discharge cycles. [ABSTRACT FROM AUTHOR]

The rapid development of intelligent technology puts forward higher requirements for portable and flexible energy storage devices. In this paper, nitrogen and oxygen co-doped graphene quantum dots were used as electrode material of flexible planar micro-supercapacitors (PMSCs) and the electrode/gap width was 6 μm/2 μm. Electrochemical performance of the flexible devices was investigated at different bending angles with scan rates of 0.01 V/s to 10000 V/s. When bending 75°, the area capacitance and the energy density were 2.61 μF cm−2 and 0.36 nWh cm−2 at the scan rate of 0.01 V/s, and the power density was 173.66 μW cm−2 at the scan rate of 10000 V/s. When bending 0°, the area capacitance and energy density were the same as that when bending 75°, and the power density was 198.36 μw cm−2. The output current of the two flexible devices was 200 μA when bending 75° and 250 μA when bending 0°. The capacitance retention was 87.5% when bending 75° and 90.4% when bending 0° at the scan rate of 500 V/s after 10000 cycles. The results indicated that the bending has little effect on the electrochemical performance of the flexible PMSCs. [ABSTRACT FROM AUTHOR]

A novel ternary network organo-hydrogel electrolyte is developed to improve the environmental adaptability of flexible supercapacitors. The ternary network electrolyte is composed of graphene/boric acid/polyvinyl alcohol matrix and methyl sulfoxide/water/H 2 SO 4 mixture. A flexible supercapacitor with a sandwich structure is further assembled with the electrolyte and two polyaniline fiber/carbon cloth electrodes. The supercapacitor exhibits a high capacitance retention rate (90%) after 5 cutting/self-healing cycles. Furthermore, supercapacitors have high specific capacitance and capacitance retention on a wide temperature range of −65 °C–65 °C. The specific capacitance of supercapacitor is about 237.8 F/g and 152 F/g at 65 °C and −65 °C, in which the corresponding capacitance retention of supercapacitor is about 110.5% and 70.7%, respectively. The work provides an effective strategy to design and prepare flexible electrolyte with broad temperature adaptability, good self-healing ability and good mechanical flexibility for flexible energy storage devices. • A novel ternary network organo-hydrogel electrolyte is developed. • The ternary network possesses broad temperature adaptability and self-healing ability. • A self-healing and wide temperature tolerant flexible supercapacitor are developed. [ABSTRACT FROM AUTHOR]