Search

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]

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]

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]