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An economically and environmentally sustainable course of action to address energy crisis concerns is to recycle discarded PET (polyethylene terephthalate) plastics into value-added products for the aforementioned application. Herein, a high surface area Cu-metal organic framework (Cu-MOF) has been synthesized through an economically feasible approach using trash PET plastic. However, electrochemical properties of pristine MOFs are hindered due to their poor stability and low intrinsic conductivity. Hence, high-performance nanocomposites of Cu-MOF with conducting polymers like PANI (polyaniline) and PPy (polypyrrole) have been synthesized via an in situ hydrothermal technique. PANI and PPy not only improve the conductivity of the nanocomposite but also create additional MOF-PANI-MOF transport channels, which ensures effective electrolyte ion transportation and hence enhances the overall electrochemical performance. Cu-MOF/PANI and Cu-MOF/PPy nanocomposites exhibit high specific capacitances of 160.5 and 132.5 F/g, respectively, at a current density of 0.5 A/g, which is more than that of pristine Cu-MOF (104.8 F/g). Furthermore, asymmetric hybrid supercapacitor devices (Cu-MOF//Cu-MOF/PANI and Cu-MOF//Cu-MOF/PPy) have been assembled that have shown immense potential as energy storage devices. The Cu-MOF//Cu-MOF/PANI hybrid device delivered a high energy density of 51.4 Wh/kg at 474 W/kg power density with outstanding cyclic stability, attenuating only 6.6% after 10 000 charge–discharge cycles. [ABSTRACT FROM AUTHOR]

Supercapacitors (SCs) based on hierarchical nanoporous framework composite materials and aqueous electrolytes are recent interests for the researchers. The structure of UiO-66 exhibits extraordinary stability and high specific surface area, but the specific capacitance of UiO-66 (139.4 F g–1 at 2 A g–1) is limited due to its moderately conducting nature. Therefore, we report a method to modify UiO-66 with pineapple peel derived activated carbon (PA-AC) to form a facile composite. Owing to the high specific surface area and good conductivity of the UiO-66/PA-AC composite, a high specific capacitance of 295.9 F g–1 at 2 A g–1 has been achieved and is well suited for supercapacitor applications. At the maximum charging voltage range of 0–1.8 V, the UiO-66/PA-AC//UiO-66/PA-AC symmetrical SC delivered a maximum energy density of 29.6 Wh kg–1 at a power density of 170 W kg–1. After 5000 repeated charge–discharge cycles at 30 A g–1, the specific capacitance of the device increased from 100% to 120% of its initial specific capacitance. This study emphasized the potential importance of incorporating MOFs into pores of biowaste derived carbon as a strategy for enhancing the charge storage kinetics of moderately conducting MOFs. [ABSTRACT FROM AUTHOR]

The commercialization of pure carbon-based supercapacitors has faced challenges due to their limited energy density. In order to overcome this challenge, the construction of carbon materials with a hierarchical pore structure has been proposed. Herein, we describe a straightforward template-free method to develop highly nanoporous activated carbon (ACs), via a one-step process where polyaniline (PANI)–polypyrrole (PPy) copolymer is carbonized/activated with KOH in a single step at temperatures ranging from 800 to 1000 °C in N2 environment to get a highly nanoporous ACs. The AC-900 material comprises a network of linked pores and a higher specific surface area of 3899.88 m2/g along with a high electrochemical surface area of 722.05 m2/g, allowing for large amounts of ion storage and quick ion transit. AC-900 has exhibited a very favorable electrochemical performance, in a 1 M H2SO4 electrolyte, a specific capacitance of 1073.9 F/g was achieved when the current density was set to 0.5 A/g. Symmetrical devices were fabricated out of two AC-900 electrodes of equivalent weight, and the results demonstrate that the AC-900//AC-900 device at a power density of approximately 868 W/kg. The device reaches a noteworthy energy density of ∼72 W h/kg, while also demonstrating very high cyclic stability with an efficiency of approximately 100% even after undergoing 6,000 charge–discharge cycles. The impressive electrochemical performance displayed by AC-900 underscores its significant potential as a polymer-derived carbon nanomaterial for electrodes in supercapacitor applications. [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]

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]

Abstract The role of redox additive electrolytes in supercapacitors is gaining an increased significance. The present research work, for the first time, investigates the supercapacitor performance of a rGO/TiO 2 nanosheet composite (prepared via facile one step hydrothermal reaction route) electrode in combination with a redox additive electrolyte, i.e., 0.2 M K 3 [Fe(CN) 6 ] in 1 M Na 2 SO 4. The synergistic effects between the porous rGO/TiO 2 nanosheet electrode and the optimized redox electrolyte have helped to achieve a significantly high specific capacitance of 1565 F/g at a current density of 3 A/g (working potential window = −0.1–0.5 V). This value of specific capacitance is much higher than achievable with the application of a plain aqueous electrolyte (e.g., 1 M Na 2 SO 4). Furthermore, rGO/TiO 2 nanosheet electrodes have been used to fabricate a symmetrical supercapacitor device which has delivered an excellent specific capacitance value of 204.5 F/g at a current density of 1.5 A/g. The device also yielded promising values of energy density (15.5 Wh/kg) and power density (1.1 kW/kg) apart from showing a long-term cyclic stability (∼87%) even after 1000 continuous charge-discharge cycles. Graphical abstract Image 1 Highlights • A composite of rGO/TiO 2 nanosheets has been explored as a supercapacitor electrode. • 0.2 M K 3 [Fe(CN) 6 ] in 1 M Na 2 SO 4 has been used as an optimized electrolyte. • Selection of above electrode and electrolyte yielded high specific capacitance. • A specific capacitance of 1565 F/g has been achieved at a current density of 3 A/g. • High values of energy (15.5 Wh/Kg) and power (1.1 kW/kg) densities were achieved. [ABSTRACT FROM AUTHOR]

Abstract In this work, manganese MOF is synthesized using one step solvothermal method and utilized as an electrode for supercapacitor applications. The high specific surface area, chemical & thermal stability and pseudocapacitive charge storage mechanism of Mn-BDC MOF facilitates fast electronic and ionic transport. When the Mn-BDC MOF is tested as an electrode for supercapacitor applications, the electrode exhibits remarkable electrochemical performance using 1 M Na 2 SO 4 aqueous electrolyte. The Mn-BDC electrode shows a highest specific capacitance of 177.9 F/g at a current density of 0.5 A/g and 166.4 F/g at a scan rate of 1 mV/s. Further, an all-solid-state symmetrical supercapacitor is assembled using two equally weighted Mn MOF electrodes using PVA-1 M Na 2 SO 4 polymer gel electrolyte. The solid state symmetrical supercapacitor device shows a highest specific capacitance of 64.5 F/g at a current density of 0.25 A/g within an operating potential window of 0-1.5 V. Also, the device delivers an energy density and power density of 4.3 Wh/kg and 171.6 W/kg respectively along with a very high capacity retention of 98 % even after 2000 charge-discharge cycles. Therefore, the excellent electrochemical performance of Mn MOF electrodes and symmetrical device proves its superiority for practical supercapacitor applications. [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]

The ever-increasing demand for green and clean energy urge the development of cheap and efficient electrode materials for supercapacitors (SCs). In this context, several naturally abundant bio-wastes have been explored to develop porous carbons for SCs due to their easy availability, high performances, and simple processing methods. Although various BDCs are utilized for SC, the relation between the bio-waste precursor and resultant carbon materials are not very well understood. Here, we highlight how the different bio-waste precursors affect the surface characteristics of the carbon nanostructures and outlined their subsequent effect on electrochemical performances. Moreover, the surface modification of carbon materials using pre-processing, carbonization and activation methods is provided. The supercapacitive properties of activated carbons (AC) with their unique surface features derived from the different feedstock are systematically summarized. Finally, the challenges and future directions for the development of AC from bio-waste are discussed. Overall, this review provides a guide to understand how best to refine and carbonize this biomass to achieve optimum supercapacitive performance. Schematic of the used biowaste and the methodology of preparing activated carbon. Reproduced with permission from Ref. (Yue et al., 2019) Copyright 2019, Multidisciplinary Digital Publishing Institute, Ref. (Sulyman et al., 2017) Copyright 2018, American Chemical Society [Display omitted]. [ABSTRACT FROM AUTHOR]

[Display omitted] • State of the art information on core–shell MOF-based supercapacitors and batteries are explored. • CSMOF structures are discussed separately in terms of properties, synthesis and their types. • CSMOF structures for supercapacitors are compared in terms of specific capacitance, capacitance retention, energy density, and self-discharge. • CSMOF structures for batteries are compared in terms of reversible capacity, initial discharge capacity, and cyclic stability. • Besides Li-ion batteries, CSMOFs are also reviewed for Na-ion, K-ion, Li-S, Li-Se, and Li-O 2 batteries. • Critical assessment and future aspects are also explored for CSMOF based energy storage devices. Core-shell metal–organic framework (CSMOF) has attracted the attention of researchers in the material science and nanotechnology research field. The structural properties of CSMOF and their derived material include extortionate specific surface area and porosity, good structural flexibility, high stability, etc. These appealing properties make CSMOF a great alternative for various practical applications. CSMOF has shown great performance as an electrode material for energy storage applications. This review is primarily focused on the factor affecting the assemblies and synthesis of core shell structures, strategy to control the assemblies, synthesis methods, and properties of different CSMOFs for energy storage devices viz. supercapacitors (SC) and batteries. After that, different CSMOF structures are compared in terms of their performance parameters for SC including specific capacitance, capacitance retention, cyclic stability, energy density, and self-discharge.On the other hand, reversible capacity, initial discharge capacity, and cyclic stability are a few performance parameters for Li-ion batteries that are also discussed for different materials.CSMOF's applications for some other batteries like Na-ion, K-ion, Li-S, Li-Se, and Li-O 2 will likewise be discussed in other sections. Eventually, the expansion and future scope of CSMOF and its derivatives are proposed for upcoming energy storage applications. [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]