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Ni (Nickel) doped zeolitic-imidazolate framework (ZIF-67) has been prepared in presence of reduced graphene oxide (rGO) to realize a ZIF-67/rGO composite. The doping level of Ni and the ratio of rGO (wt%) in the composite have been optimized to attain desirable redox activity and electrical conductivity. A partial incorporation of redox active Ni ions to substitute Co (cobalt) ions in ZIF-67 has resulted in better electrochemical characteristics by inducing additional pseudocapacitance. A finalized composite with 33% Ni and 20% of rGO (i.e, Ni 33 /ZIF-67/rGO 20) has been used as a supercapacitor electrode material to achieve a high specific capacitance of 304 F/g at a current density of 1 A/g in the presence of 1 M H 2 SO 4 as an aqueous electrolyte. The above electrode has also been tested for an all-solid-state symmetric supercapacitor in the presence of a polymer gel electrolyte (PVA/1 M H 2 SO 4). This device delivered high values of power and energy densities, i.e., 1 kW/kg and 21.5 Wh/kg, respectively. The device also exhibited an excellent cyclic stability. About 87% of capacitance could be retained even after 4500 charge-discharge cycles. The device has shown superior results for a working potential window of 0–2 V. The practical usefulness of the device has been demonstrated by preparing a symmetrical supercapacitor, which could energize a white LED for 8 min upon a charging of only 40 s. Image 1 • High surface area and conductive composite of Ni doped ZIF-67/rGO is synthesized. • The as synthesized composite is studied for 2V symmetrical supercapacitor device. • Supercapacitor displays long cycle life of 87% after 4500 charge-discharge cycles. • High values of energy (21.5 W h/kg) and power (1 kW/kg) densities are obtained. [ABSTRACT FROM AUTHOR]

The selection of appropriate electrode materials and electrolytes in addition to optimization of their combinations is a key to improve the performance of supercapacitors. Among the new electrode materials, metal‐organic frameworks (MOFs) based electrodes are attracting attention in energy storage devices, including supercapacitors and batteries. In recent years, the redox additive electrolytes have been projected as efficient options over simple aqueous electrolytes. The present work reports the synthesis of a layered MOF, i. e. manganese‐1,4‐ benzene dicarboxylate (Mn‐BDC) and explores its utility as a supercapacitor electrode in the presence of an optimized redox additive electrolyte (0.2 M K3[Fe(CN)6] in 1 M Na2SO4 (0.2 M KFCN)). As demonstrated for the first time in this study, the combined use of the porous Mn‐BDC electrode and KFCN electrolyte has provided a synergistic enhancement in the supercapacitor performance. The present Mn‐BDC/KFCN combination has delivered a high specific capacitance of 1590 F/g at a current density of 3 A/g. Furthermore, the Mn‐BDC electrode could retain around 82% of its initial specific capacitance even after 3000 continuous charge‐discharge cycles. In view of its encouraging electrochemical performance parameters, the proposed system can be touted as an efficient supercapacitor assembly. Manganese‐1,4‐benzene dicarboxylate (Mn‐BDC) is a layered MOF synthesized using one‐pot hydrothermal route. An electrode of Mn‐BDC is prepared and employed as a supercapacitor electrode in presence of an optimized redox additive electrolyte. The proposed system has delivered a high specific capacitance of 1590 F/g at a current density of 3 A/g. The Mn‐BDC electrode retains around 82% of its initial specific capacitance even after 3000 continuous charge‐discharge cycles. [ABSTRACT FROM AUTHOR]

Abstract In pursuit of high specific capacitance and high energy density; morphology, specific surface area and conductivity of electrode material are key factors. In this context, Ni 1-x Mg x Co 2 O 4 @C (x = 0.0, 0.5) nanostructures are synthesized via facile hydrothermal route using the cotton template. Notably; the morphology altered from flowers to rods with the incorporation of cotton templates. Additionally, Mg dopant ion helps to attain greater electrical conductivity while preventing the morphology. Besides, Influence of Mg doping on the pseudocapacitance of NiCo 2 O 4 electrode was investigated by electrochemical analysis in 6 M KOH electrolyte. This remarkable synergy display superb electrochemical performance for Ni 0.5 Mg 0.5 Co 2 O 4 @C rods, i.e a high specific capacitance of 1340 Fg-1 at a current density of 1 Ag-1 and admirable cyclic stability of ∼97% up to 2000 charge-discharge cycles (at 15 Ag-1). Further, the proposed Ni 0.5 Mg 0.5 Co 2 O 4 @C rods electrode delivered high values of energy (59.5 Wh/Kg) & power (799.2 W/Kg) densities at a current density of 1 Ag-1, which is 2 times more as compared to flowers structured material. This can be attributed to increase in the specific surface area with more porous nature of rods. This work conveys the deeper understanding of the morphology and chemical composition effect on the supercapcitive performance of Ni 0.5 Mg 0.5 Co 2 O 4 @C. Thus, Ni 0.5 Mg 0.5 Co 2 O 4 @C (NMCo@C) rods may be an excellent electrode material for high-performance supercapacitor due to its exceptional electrochemical performances. Graphical abstract Image 1 Highlights • Highly porous rods structure of specific surface area of 51.78 m2g-1 is fabricated. • The specific capacitance of 1340 Fg-1 is obtained for Ni 0.5 Mg 0.5 Co 2 O 4 @C rods. • Ni 0.5 Mg 0.5 Co 2 O 4 @C rods delivers maximum energy density of 59.5 WhKg−1. • The capacitance retention of ∼97% up to 2000 charge-discharge is maintained. [ABSTRACT FROM AUTHOR]

Metal-organic frameworks (MOFs) belong to a novel class of materials with several advantages (e.g., ultrahigh porosity, tunable pore size distribution, convenience of synthesis, and structural tailor-ability). However, the insulating nature of MOFs is often recognized as a limiting factor in the extension of their applications, especially in electronic fields. In light of such limitations, various functional or conductive materials have been mixed/intercalated with MOFs to improve their potential for such applications (e.g., rechargeable batteries, optoelectronics, and supercapacitors). Lately, many of these composite materials have been recognized as next-generation electrodes for the development of efficient supercapacitors. In this review article, we have critically reviewed the recent advancements in supercapacitor applications of MOFs and their derived composite structures. Further, we have also discussed the application of various categories of electrolytes (e.g., aqueous, organic, ionic liquids, solid-state, and redox electrolytes) and their impacts on the development of MOF-based supercapacitors. [ABSTRACT FROM AUTHOR]

The pyrolysis of metal-organic frameworks (MOFs) is an effective strategy for the synthesis of novel nanoporous structures for energy storage applications. In this work, the preparation of a zirconium oxide/carbon (ZrO 2 /C) nanocomposite via the pyrolysis of UiO-66 (a zirconium-based MOF) is reported for the first time. These MOF-derived metal oxide/carbon (ZrO 2 /C) materials have a great advantage in the case of supercapacitor applications over other MOFs or their derivatives as they do not need any external conductive agent. The ZrO 2 /C electrode exhibits an excellent electrochemical performance, delivering a specific capacitance of 241.5 F/g at 1 A/g current density. A 2 V symmetrical supercapacitor device is also prepared by employing a solid-state polymer gel electrolyte. The assembled device of ZrO 2 /C electrode has delivered a high energy density of around 29 Wh/kg (at a high power density of 1.5 kW/kg) while retaining almost 97% of the specific capacitance even after 2000 continuous charge/discharge cycles. • The development of efficient supercapacitor is a viable strategy to achieve energy storage devices. • Uniformly distributed oxides/carbon/oxide-carbon structures are prepared by the pyrolysis of MOF. • ZrO 2 /C composite is prepared via one-step pyrolysis of UiO-66 (zirconium-based MOF). • Superiority of a MOF-derived ZrO 2 /C composite is demonstrated in supercapacitor applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • Pencil peels is used to derive mixed phase activated carbon of high porosity and conductivity. • Asymmetrical supercapacitor is assembled using MOF derived Co 3 O 4 /WO 3 and Pencil derived activated carbon. • Asymmetrical Supercapacitor device retains long cycle life of 92.1 % after 5000 charge-discharge cycles. • The supercapacitor device shows high energy density of 50 Wh/kg at a power density of 90 W/kg. In this work, pencil peel is used to derive the mix phase activated carbon at different temperatures viz 700, 800, and 900 °C for hybrid supercapacitor applications. The derived carbon is showing the highest specific surface area for P-800 (Pencil peel@ 800 °C) sample and exhibits the graphitic and amorphous phase whose fraction can be controlled with pyrolysis temperature. Therefore, the as-prepared P-800 electrode shows the high specific capacitance of 553 F/g at a current density of 1 A/g. On the other hand, metal-organic framework (MOF) derived Cobalt-Tungsten oxide composites (Co 3 O 4 /WO 3) has been synthesized which shows a much higher specific capacitance value (544 F/g at 2 A/g) in the negative potential window. Therefore, an asymmetrical supercapacitor device has been assembled with P-800 as positive and Co 3 O 4 /WO 3 composites as a negative electrode in aqueous 1 M H 2 SO 4 (Sulfuric acid) electrolyte that delivers higher energy and power density in comparison to their symmetrical supercapacitor counterparts. [ABSTRACT FROM AUTHOR]

Covalent organic frameworks (COFs) are porous structures emerging as promising electrode materials due to their high structural diversity, controlled and wide pore network, and amenability to chemical modifications. COFs are solely composed of periodically arranged organic molecules, resulting in lightweight materials. Their inherent properties, such as extended surface area and diverse framework topologies, along with their high proclivity to chemical modification, have positioned COFs as sophisticated materials in the realm of electrochemical energy storage (EES). The modular structure of COFs facilitates the integration of key functions such as redox‐active moieties, fast charge diffusion channels, composite formation with conductive counterparts, and highly porous network for accommodating charged energy carriers, which can significantly enhance their electrochemical performance. However, ascribing intricate porosity and redox‐active functionalities to a single COF structure, while maintaining long‐term electrochemical stability, is challenging. Efforts to overcome these hurdles embrace strategies such as the implementation of reversible linkages for structural flexibility, stimuli‐responsive functionalities, and incorporating chemical groups to promote the formation of COF heterostructures. This review focuses on the recent progress of COFs in EES devices, such as batteries and supercapacitors, through a meticulous exploration of the latest strategies aimed at optimizing COFs as advanced electrodes in future EES technologies. [ABSTRACT FROM AUTHOR]

The application of porous and conductive composite materials in energy storage devices has received great attention in the recent years. Porous materials, such as metal-organic frameworks (MOFs), possess features like large specific surface area, mesoporous structures, and multiple reaction sites that make them attractive for energy storage devices. Further, the integration of MOFs with suitable conducting agents is a promising strategy to introduce additional conductive pathways in them, which facilitates fast charge transfer. In the present work, we report synthesis and supercapacitor application of a ZIF-67/PEDOT heterostructure composite. The prepared ZIF-67/PEDOT composite, when analyzed for electrochemical performance in three-electrode systems, has delivered a specific capacitance of 106.8 F/g at a current density of 1 A/g. This value is significantly better than that attaintable with only pristine ZIF-67 electrode (34.75 F/g at 1 A/g). Extending the study, two ZIF-67/PEDOT electrodes have been used to assemble an all-solid-state symmetrical supercapacitor, which delivers excellent values of energy density (∼11 Wh/kg) and power density (200 W/kg). Hence, this work paves the way for the potential application of ZIF-67/PEDOT composite in the development of next-generation supercapacitors. Image 1 • Incorporation of PEDOT in ZIF-67 benefits high conductivity and large specific surface area. • ZIF-67/PEDOT has been explored as a supercapacitor electrode material. • The assembled 1.6 V device delivered high energy (11 Wh/kg) and power (200 W/kg) densities. • Supercapacitor device has a long cycle life (93% capacity retention even after 4000 charge-discharge cycles). [ABSTRACT FROM AUTHOR]

Carbon paper has been synthesized by paper making process followed by composite formation, and further chemically oxidized by immersing into a mixture of sulphuric acid and potassium dichromate to be used as an electrode for supercapacitor applications. XRD and Raman spectra were used to analyze the structure, and the defects in the samples respectively, in due course of oxidation. FESEM images revealed the morphology of oxidized samples to be rougher, which contributes towards increased active sites for reaction. The sample (COCP‐60) optimized via electrochemical studies, was further tested in various electrolytes to study the electrode/electrolyte interaction. It delivered a highest areal capacitance of 6.02 F/cm2 (231.5 F/g) in acidic electrolyte at a current density of 5 mA/cm2 (0.19 A/g). This findings were further corroborated by surface and diffusion contribution studies wherein it was found that diffusion is more profound with acidic electrolyte. The supercapacitor device fabricated with COCP‐60 electrode delivered an energy density of 0.41 Wh/cm2 at 2.83 W/cm2 power density with coulombic efficiency of 98 %, and cyclic stability of ∼90 % for over 5000 cycles. [ABSTRACT FROM AUTHOR]

Biowaste derived carbon materials are recently gaining attention owing to their high specific surface area (SSA) and decent electrical conductivity. Herein, pineapple peel derived porous carbon nanosheets have been synthesized at different activation temperatures (PP‐600, PP‐700 and PP‐800). This shows that its high SSA along with hierarchal pore size distribution makes it a suitable electrode material for supercapacitors. Further, the electrochemical performance of the as prepared electrode material was carried out in three different electrolytes viz. acidic (1 M H2SO4), basic (6 M KOH) and neutral (1 M Na2SO4) and among them 1 M H2SO4 electrolyte shows superior electrochemical performance. Furthermore, PP‐800 electrode material displayed highest specific capacitance of 368.8 F/g in 1 M H2SO4 electrolyte, which is much higher when tested and compared in 6 M KOH (34 F/g) and 1 M Na2SO4 (102.7 F/g) electrolytes at a constant current density of 1 A/g. Additionally, symmetrical solid‐state supercapacitor was fabricated by utilizing PP‐800 electrodes and PVA gel electrolyte, that rendered remarkable energy density of ∼43 Wh/kg at a high‐power density of ∼1 kW/kg. The as fabricated PP‐800//PP‐800 device displayed an extraordinary cycle life exhibiting capacitance retention of 83 % after 10000 ultra‐long charge‐discharge cycles. [ABSTRACT FROM AUTHOR]

Biomass derived activated carbon (BDAC) materials are recently gaining attention as an active electrode material for alternative energy storage devices. Biomass is a rich source of carbon and blessed with high specific surface area, hierarchical pore size distribution, good conductivity, easy availability and facile synthesis approaches. These characteristics make BDAC a suitable electrode material for next generation clean and green energy applications. The review examines the recent developments in the usage of biomass derived carbon and their composites for various hybrid electrochemical capacitor (HEC) devices claiming high electrochemical performance in terms of energy and power density. It also summarizes the various synthesis strategies which lead to different morphologies that are beneficial for high performance energy storage applications. Additionally, the review also coins the existing challenges and possible solutions towards developing cost-effective and high performance HECs using biomass derived carbon-based electrodes. Finally, we speculate the future prospects of biomass derived carbon materials for energy storage applications. We expect that this review article will help in the evolution of new insights for the practical energy storage applications of biomass derived carbons. Image 1 • Various biowastes are reviewed as a potential resource for the generation of activated carbon (BDAC). • BDAC are used as one of the electrodes for Li-HEC, Na-HEC, Zn-HEC, and K-HEC. • BDAC are reviewed in terms of their need, morphologies, porosity and conductivity. • BDAC are reviewed to attain superior energy density, power density and long cycle life when used in HECs. [ABSTRACT FROM AUTHOR]

Establishing green and reliable energy resources is very important to counteract the carbon footprints and negative impact of non-renewable energy resources. Metal-organic frameworks (MOFs) are a class of porous material finding numerous applications due to their exceptional qualities, such as high surface area, low density, superior structural flexibility, and stability. Recently, increased attention has been paid to surface mounted MOFs (SURMOFs), which is nothing but thin film of MOF, as a new category in nanotechnology having unique properties compared to bulk MOFs. With the advancement of material growth and synthesis technologies, the fine tunability of film thickness, consistency, size, and geometry with a wide range of MOF complexes is possible. In this review, we recapitulate various synthesis approaches of SURMOFs including epitaxial synthesis approach, direct solvothermal method, Langmuir-Blodgett LBL deposition, Inkjet printing technique and others and then correlated the synthesis-structure-property relationship in terms of energy storage and conversion applications. Further the critical assessment and current problems of SURMOFs have been briefly discussed to explore the future opportunities in SURMOFs for energy storage and conversion applications. [Display omitted] • State of the art information on SURMOF-based energy storage and conversion devices are explored. • SURMOFs are discussed separately in terms of need, preparation and their properties. • SURMOFs as an electrode for energy storage devices are explored in supercapacitors and batteries. • SURMOFs for energy conversion devices are explored in electrocatalysis and Solar cells applications. • Critical assessment and future aspects are also explored for SURMOF based energy storage and conversion devices. [ABSTRACT FROM AUTHOR]

Carbon-based materials generated from biowaste have recently attracted interest due to their exceptional surface and conductive properties. Cow dung derived porous carbon (CDPC) with a 3D structure and linked pores is synthesized in this study, making it an alternative electrode for supercapacitors (SC). Herein, we studied the diffusion and surface charge contribution and their relationship with the scan rate. Diffusion charge contribution is more prevalent at lower scan rates. Furthermore, a large fraction of surface charge contribution of 69.2 % at a high scan rate of 100 mV/s indicates rapid electrochemical kinetics and hence high-rate performance even at higher current densities. In addition, utilizing a 1 M H 2 SO 4 electrolyte, the CDPC electrode has attained a high specific capacitance value of 210 F/g at 0.5 A/g. Furthermore, symmetrical solid-state SC device displayed high energy density of 36 Wh/kg at good power density of 800 W/kg along with remarkable cyclic stability of 92.6 % after 10,000 charge-discharge cycles. Hence, these findings demonstrate that investigating surface and diffusion charge contributions opens up new avenues for tuning the supercapacitor performance. [Display omitted] • Waste cow dung derived carbon obtained by hydrothermal carbonization and activation • Surface and diffusion charge contribution studies are performed for CDPC electrode. • Solid-state symmetrical SC assembled using two CDPC electrodes and gel electrolyte • Device retains long cycle life of 92.6 % after 10,000 charge-discharge cycles. • Device delivers high energy density of 40 Wh/kg at a power density of 907 W/kg. [ABSTRACT FROM AUTHOR]