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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]

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]

Microbial electrosynthesis (MES) presents a versatile approach for efficiently converting carbon dioxide (CO2) into valuable products. However, poor electron uptake by the microorganisms from the cathode severely limits the performance of MES. In this study, a graphitic carbon nitride (g-C3N4)-metal–organic framework (MOF) i.e. HKUST-1 composite was newly designed and synthesized as the cathode catalyst for MES operations. The physiochemical analysis such as X-ray diffraction, scanning electron microscopy (SEM), and X-ray fluorescence spectroscopy showed the successful synthesis of g-C3N4-HKUST-1, whereas electrochemical assessments revealed its enhanced kinetics for redox reactions. The g-C3N4-HKUST-1 composite displayed excellent biocompatibility to develop electroactive biohybrid catalyst for CO2 reduction. The MES with g-C3N4-HKUST-1 biohybrid demonstrated an excellent current uptake of 1.7 mA/cm2, which was noted higher as compared to the MES using g-C3N4 biohybrid (1.1 mA/cm2). Both the MESs could convert CO2 into acetic and isobutyric acid with a significantly higher yield of 0.46 g/L.d and 0.14 g/L.d respectively in MES with g-C3N4-HKUST-1 biohybrid and 0.27 g/L.d and 0.06 g/L.d, respectively in MES with g-C3N4 biohybrid. The findings of this study suggest that g-C3N4-HKUST-1 is a highly efficient catalytic material for biocathodes in MESs to significantly enhance the CO2 conversion. [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]

Metal–organic frameworks (MOFs) derived nanostructures receive immense research focus due to its high porosity, conductivity, and structural tailrolability features. In this work, porous Zeolitic Imidazole Framework‐67 (ZIF‐67) to synthesize cobalt phosphide/carbon composite (ZCoPC) that serves as a positive electrode is utilized. Furthermore, porous and conductive office paper derived carbon (OPC) are utilized as a negative electrode to make a hybrid system. The metalloid characteristics, high conductivity, and good porosity of ZCoPC material makes it a high‐performance battery like electrode. ZCoPC electrode achieves maximum specific capacity of 192.6 mAh g−1 at 1 A g−1 using 1 m potassium hydroxide (KOH) electrolyte. Furthermore, surface and diffusion charge participation investigation are also undergone for ZCoPC electrode that helps in determining the actual charge dynamics occurring in the electrode. In addition, a supercapattery device is assembled using ZCoPC as battery electrode and OPC as supercapacitor electrode. The as fabricated OPC//ZCoPC hybrid supercapattery device delivers extraordinary energy density of 31.6 Wh kg−1 with a power density of 700 W kg−1 and also a long cycle life of 92.3% even after 10,000 charge–discharge cycles. Hence, these outcomes demonstrate that the synergy of porous MOF derived metal phosphide and OPC electrodes are beneficial for supercapattery devices. [ABSTRACT FROM AUTHOR]

In the context of emerging electric devices, the demand for advanced energy storage materials has intensified. These materials must encompass both surface and diffusion-driven charge storage mechanisms. While diffusion-driven reactions offer high capacitance by utilizing the bulk of the material, their effectiveness diminishes at higher discharge rates. Conversely, surface-controlled reactions provide rapid charge/discharge rates and high power density. To strike a balance between these attributes, we devised a tri-composite material, TiO2/Carbon/MoS2 (T10/MoS2). This innovative design features a highly porous carbon core for efficient diffusion and redox-active MoS2 nanosheets on the surface. Leveraging these characteristics, the T10/MoS2 composite exhibited impressive specific capacitance (436 F/g at 5 mV/s), with a significant contribution from the diffusion-controlled process (82%). Furthermore, our symmetrical device achieved a notable energy density of ~ 50 Wh/kg at a power density of 1.3 kW/kg. This concept holds promise for extending the approach to other Metal–Organic Framework (MOF) structures, enabling enhanced diffusion-controlled processes in energy storage applications. [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]

Summary: The pyrolysis of metal‐organic frameworks (MOFs) to derive porous nanocarbons and metal oxides has attracted scientific attention due to the advantageous properties of the final products (eg, high surface areas). In the present research, MIL‐125 (MIL = Materials of Institute Lavoisier, a Ti‐based MOF) has been subjected to a single‐step pyrolysis treatment in argon atmosphere. The combination of uniformly linked titanium metal cluster and oxygen‐enriched organic linker has acted as a template to yield a titanium dioxide (TiO2)–carbon nanocomposite. The TiO2 nanoparticles infused in carbon skeleton structure (TiO2/C) has been investigated as an electrode material for supercapacitor applications. TiO2/C electrodes have delivered an excellent electrochemical performance, for example, in terms of charging–discharging efficiency. Two equally weighed TiO2/C electrodes have been used to assemble a solid‐state symmetrical supercapacitor (SC) device, containing a gel electrolyte (poly vinyl alcohol in 1 M H2SO4). The above device has delivered a high value of energy density (43.5 Wh/kg) and an excellent power output of 0.865 kW/kg. The symmetrical SC could retain almost 95% of its initial capacitance even after 2000 charging–discharging cycles. The electrochemical performance of the TiO2/C SC was better than most MOF‐based SCs reported previously. Such performance is attributed to the synergistic combination of electrically conducting MOF‐derived carbon and redox active TiO2 nanocrystals with a large specific surface area. [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]

The present work reports the synthesis of a composite of TiO2 nanosheets (NS) with reduced graphene oxide (rGO) for supercapacitor applications. The formation of composite has been achieved via a simple one-pot hydrothermal method. The rGO/TiO2 NS composite was used to fabricate a flexible electrode which, in presence of 1 M H2SO4 as an electrolyte, has shown a high specific capacitance of 233.67 F/g at a current density of 1 A/g within a potential window of 0-1 V. This enhanced supercapacitance of the rGO/TiO2 NS electrode is attributed to the synergistic effects from TiO2 and rGO NS which help in to attain a low equivalent series resistance and enhanced ion diffusion. Furthermore, the fabricated composite electrode has displayed a long-term cyclic stability, retaining a specific capacitance of 98.2% even after 2000 charge-discharge cycles. The proposed rGO/TiO2 NS electrode has delivered high values of energy (32.454 Wh/kg) and power (716.779 W/kg) densities. Interestingly, it is possible to retrieve a sufficiently high energy density of 24.576 Wh/kg which could generate a power density value of as high as 2142.84 W/kg. The above results reveal that the herein proposed thin film composite of rGO/TiO2 NS can offer extraordinary performance as a supercapacitor electrode compared to its nanotubes or nanoparticles. [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]

The synthesis of a highly porous composite of ZIF-67 and reduced graphene oxide (rGO) using a simple stirring approach is reported. The composite has been investigated as an electrode to be assembled in a supercapacitor. In the presence of an optimized redox additive electrolyte (RAE), that is, 0.2 M K 3 [Fe(CN) 6 ] in 1 M Na 2 SO 4 , the ZIF-67/rGO composite electrode has combined the properties of improved conductivity, high specific surface area, and low resistance. The proposed composite electrode in the three-electrode system shows an ultrahigh specific capacitance of 1453 F g -1 at a current density of 4.5 A g -1 within a potential window of -0.1 to 0.5 V. Further, the ZIF-67/rGO composite electrode was used to fabricate a symmetrical supercapacitor whose operation in the presence of the RAE has delivered high values of specific capacitance (326 F g -1 at a current density of 3 A g -1 ) and energy density (25.5 W h kg -1 at a power density of 2.7 kW kg -1 ). The device could retain about 88% of its initial specific capacitance after 1000 repeated charge-discharge cycles. The practical usefulness of the device was also verified by combining two symmetrical supercapacitors in series and then lighting a white light-emitting diode (illumination for 3 min). This study, for the first time, reports the application of a ZIF-based composite (ZIF-67/rGO) in the presence of an RAE to design an efficient supercapacitor electrode. This proposed design is also scalable to a flexible symmetric device delivering high values of specific capacitance and energy density., Competing Interests: The authors declare no competing financial interest.