Search

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]

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 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]

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]