Utilizing Waste Thermocol Sheets and Rusted Iron Wires to Fabricate Carbon-Fe3 O4 Nanocomposite-Based Supercapacitors: Turning Wastes into Value-Added Materials

From waste to energy storage: post-consumer waste expanded polystyrene/rGO composite as a high performance self-standing electrode for coin cell supercapacitors

This research work aims to explore the potential usage of post-consumer waste expanded polystyrene (EPS) for the fabrication of self-standing electrodes by incorporating reduced graphene oxide (rGO) into it via a facile cost-effective mechanical mixing process. The π-π interaction between the expanded polystyrene and rGO is evidenced from FT-IR and Raman analysis. The elevated thermal stability of the EPS/rGO composite from thermogravimetric analysis (TGA) further confirms the interconnection between the rGO and EPS. This π-π stacking interaction between the rGO and the polystyrene molecules present in the polymer matrix enable the composite material to be interconnected throughout which is beneficial for the charge transport process. The symmetric coin cell supercapacitor fabricated using the EPS/rGO composite electrode can be operated with a high operating voltage of 1.6 V in aqueous KOH and Na2SO4 electrolytes. The devices fabricated with KOH and Na2SO4 electrolytes deliver an areal capacitance of 11.9 mF cm-2 and 10 mF cm-2 at the discharge current density of 0.1 mA cm-2. Further, the devices fabricated with the KOH and Na2SO4 electrolytes demonstrated remarkable rate capability of 87.1% and 99.5% after 10 000 continuous charge discharge cycles. This facile method of preparation without consuming energy or polluting the environment is a novel approach which can be scaled-up to large-scale fabrication of self-standing plastic electrodes for low-cost energy storage applications.

Nanostructurally engineered TiO2 embedded Mentha aquatica biowaste derived carbon for supercapacitor applications

The invention of cost-effective, clean, and eco-friendly energy storage technology has been capturing a lot of worldwide interest. Herein, biogenically synthesized TiO₂ nanoparticles (NPs) were ultrasonically coupled with biomass-derived activated carbon (BAC) to obtain composite (denoted as TiO₂@BAC). With the inspiration of nature, Mentha Aquatica leaves extract was employed for biogenic preparation of TiO₂ NPs, and residual solid waste (SW) after extract was subsequently utilized for BAC. It is noteworthy that, this unique intensive method does not require any harmful or toxic chemicals and solvents, and no secondary waste is generated. TEM analysis of TiO₂@BAC revealed spherical morphology of TiO₂ NPs (average size ∼ 18 nm) that were accumulated on nanosheets. Raman, XRD, and XPS manifested the successful construction of TiO₂@BAC. The electrochemical performance of the as-synthesized BAC, TiO₂ NPs, and TiO₂@BAC electrodes was tested towards supercapacitor applications. Notably, the TiO₂@BAC electrode exhibited capacitance of 149 F/g at a current density of 1 A/g, which is approximately twice than that of the bare TiO₂ electrode (76 F/g) along with excellent capacitance restoration of ∼99%. The TiO₂@BAC electrode further revealed outstanding cyclic stability, exhibiting capacitance retention of ∼90% (at 5 A/g) after 10,000 charge/discharge cycles. Furthermore, the TiO₂@BAC electrode delivered optimal specific energy density (6.96 Wh/kg) and large power density (2.07 kW/kg at 10 A/g). Moreover, the TiO₂@BAC delivers an excellent restoration and retention performances of ∼100 and ∼95% (after 10,000 cycles) at 1 A/g with ∼98% coulombic efficiency in symmetric configuration (maximum cell voltage of 1.2 V).

Room-temperature chemical synthesis of 3-D dandelion-type nickel chloride (NiCl2@NiF) supercapattery nanostructured materials

A simple, room-temperature operable, glycerol-supported single beaker-inspired, and binder-free soft-chemical protocol has been developed to synthesize 3-D dandelion flower-type nickel chloride (NiCl₂) supercapattery (supercapacitor + battery) nanostructured electrode material from solid 3-D nickel-foam (NiF). The dandelion flower-type NiCl₂@NiF labeled as B electrode, demonstrates a battery-type electrochemical performance as obtained 1551 F·g^-1 specific capacitance (SC) and 95% cyclability over 50,000 cycles is higher than that of a setaria viridis-type NiCl₂@NiF electrode, prepared without glycerol labeled as A electrode. As a commercial market product, assembled NiCl₂@NiF@ (cathode)// BiMoO₃ (anode) pouch-type asymmetric supercapacitor energy storage device demonstrates moderate energy density and power density (28 Wh·kg^-1 and 845 W·kg^-1). By utilizing three devices in series, three different colored LEDs can be operated at full brightness. The as-proposed low temperature protocol impeccably effective and efficient on account of the low-cost, easy synthesis methodology for scalability, and high crytallinity as well as solvent-free and non-toxic as pyrolated gases were used while synthesis processing.

Macromolecular Polyethynylbenzonitrile Precursor-Based Porous Covalent Triazine Frameworks for Superior High-Rate High-Energy Supercapacitors

Porous covalent triazine framework (CTF)-based carbon materials have gained increasing attention in energy-storage applications because of their tunable structure, high chemical stability, and rich heteroatom contents. However, CTFs have thus far been exclusively synthesized from small-molecular precursors and generally show unsatisfactory supercapacitive performance. We report herein the construction of a novel range of CTFs of significantly improved supercapacitive performance from polyethynylbenzonitrile (PEBN) as a unique macromolecular precursor for the first time by ionothermal synthesis. CTF-800 synthesized at the optimized condition (800 °C; ZnCl₂/PEBN mass ratio of 3:1) shows a nanosheet-like morphology with a high yield (∼90%), high nitrogen content (>5.8%), high specific surface area (1954 m² g^-1), and optimized micropore to meso/macropore surface area ratio (42:58). As the electrode material for supercapacitor application, CTF-800 exhibits a high specific capacitance of 628 F g^-1 at 0.5 A g^-1, high-rate performance (71% of capacitance retention at 50 A g^-1), and excellent cyclic stability (96% of capacitance retention over 20 000 cycles) in a three-electrode system with aqueous 1 M H₂SO₄ electrolyte. Symmetric supercapacitor devices have been further fabricated with CTF-800 in aqueous 1 M H₂SO₄, [EMIM][BF₄], and LiPF₆ electrolytes separately. The device with the aqueous electrolyte shows the highest capacitance of 448 F g^-1 (at 0.5 A g^-1) and a high energy density of 15.5 W h kg^-1. The devices with [EMIM][BF₄] and LiPF₆ electrolytes exhibit exceptional energy densities of 70 and 78 W h kg^-1, respectively, and retain energy densities of 41 and 45 W h kg^-1, respectively, even at the high power density of 15 000 W kg^-1, confirming their high-rate high-energy performance. Meanwhile, the device with [EMIM][BF₄] electrolyte has also been demonstrated to operate well at various temperatures ranging from -20 to 60 °C with remarkable energy-storage performance.

Sulphur Source-Inspired Self-Grown 3D Ni xS y Nanostructures and Their Electrochemical Supercapacitors

Sulphur source-inspired self-grown polycrystalline and mesoporous nickel sulfide (Ni _xS _y) superstructures with vertically aligned nanomorphologies viz. rods, flakes, buds, and petals, synthesized at elevated temperatures and moderate pressures by a facile one-pot hydrothermal method on a three-dimensional Ni foam demonstrate remarkable areal specific capacitances of 7152, 4835, and 2160 F cm^-2 at current densities of 1, 2, and 5 mA cm^-2, respectively, with a cycling stability of 94% for a battery-type electrochemical supercapacitor when used as an electrode material in a supercapacitor. The Ni _xS _y//Bi₂O₃ asymmetric supercapacitor assembly exhibits an energy density of 41 W h·kg^-1 at a power density of 1399 W kg^-1 for 1 A g^-1 and was used in a three-cell series combination to operate a "GFHIM" display panel (our research institute name, Global Frontier R & D Center for Hybrid Interface Materials) composed of nearly 50 differently colored light-emitting diodes with high intensity in 1 M KOH water-alkali electrolyte. The electrochemical supercapacitor results obtained for the Ni _xS _y superstructures because of a combination of catalytically active amorphous and high mobility polycrystalline are highly comparable to those reported previously for salt-mediated and self-grown Ni _xS _y structures and morphologies.