Coconut-husk Derived Graphene for Supercapacitor Applications: Comparative Analysis of Polymer Gel and Aqueous Electrolytes

Herein, we propose the synthesis of reduced graphene oxide (rGO) using coconut husk as a green and natural resource for supercapacitor (SCs) applications. The electrochemical performance of graphene sheets is studied over two different electrolytes, i.e., sulfuric acid (1M) and polymer-gel electrolyte. The polyvinyl alcohol, potassium iodide, and sulfuric acid-base polymer gel electrolyte are developed using a simple solvolysis approach. The developed polymer gel electrolyte membrane shows the fine pore structure, providing appropriate channels for the ionic transportation and charge transfer within materials, alternatively enhancing the overall performance of the device in comparison to commercial polyvinyl alcohol-base membranes and polyvinyl alcohol and acid-base membranes. This is accredited to lower resistance, higher ionic conductivity of the developed materials, and electrolytes within the supercapacitor device. The electrode with 1M H2SO4 exhibits outstanding performance with a decent equivalent resistance of 4.75 Ωcm-2 and specific capacitance (Cs) of 650 Fg-1 at 1 mVs-1. Conversely, the polymer gel-containing device shows an equivalent sheet resistance (ESR), of 8 Ωcm-2 and a high specific capacitance of 500 Fg-1 at 1 mVs-1. In 1M H2SO4, the device showed 88 % cycle stability after 4400 cycles with a coulombic efficiency of 67.56 % and an energy density of 50.00 Whkg-1 with a very high-power density of 1000.00 Wkg-1 at 1 Ag-1. The polymer-gel electrolyte-containing device shows 99 % cyclic stability after 4400 cycles with a coulombic efficiency of 70.27 % and an energy density of 36.11 Whkg-1 with a power density of 996.92 Wkg-1 at 1 Ag-1.Validerad;2023;Nivå 2;2023-08-16 (joosat);Licens fulltext: CC BY-NC 3.0Funder: National Mission of Himalayan Studies (NMHS) (ref. no. GBPNI/NMHS-2019-20/MG); Sutram DST (ref no. DST/TM/WTI/WIC/2K17/82(G)), DST INSPIRE Division (ref. no. IF180347) and DST-FIST, New Delhi, India</p

Easy, Fast Self-Heating Polyurethane Nanocomposite with the Introduction of Thermally Annealed Carbon Nanotubes Using Near-Infrared Lased Irradiation

In this study, high-crystallinity single walled carbon nanotubes (H-SWNTs) were prepared by high-temperature thermal annealing at 1800 °C and a self-heating shape memory polyurethane nanocomposite with excellent self-heating characteristics was developed within a few seconds by irradiation with near-infrared rays. With a simple method (heat treatment), impurities at the surface of H-SWNTs were removed and at the same time the amorphous structure converted into a crystalline structure, improving crystallinity. Therefore, high conductivity (electric, thermal) and interfacial affinity with PU were increased, resulting in improved mechanical, thermal and electric properties. The electrical conductivity of neat polyurethane was enhanced from ~10–11 S/cm to 4.72 × 10−8 S/cm, 1.07 × 10−6 and 4.66 × 10−6 S/cm, while the thermal conductivity was enhanced up to 60% from 0.21 W/mK, 0.265 W/mK and 0.338 W/mK for the composites of 1, 3 and 5 wt%, respectively. Further, to achieve an effective photothermal effect, H-SWNTs were selected as nanofillers to reduce energy loss while increasing light-absorption efficiency. Thereafter, near-infrared rays of 818 nm were directly irradiated onto the nanocomposite film to induce photothermal properties arising from the local surface plasmon resonance effect on the CNT surface. A self-heating shape memory composite material that rapidly heated to 270 °C within 1 min was developed, even when only 3 wt.% of H-SWNTs were added. The results of this study can be used to guide the development of heat-generating coating materials and de-icing materials for the wing and body structures of automobiles or airplanes, depending on the molding method