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Author: search.filters.author.Ichikawa, Satoshi

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    Hemp-Derived Hierarchical Porous Carbon with an Optimized Pore Structure by NaOH Activation for Supercapacitor Applications
    (2025-11-11)
    Bowornthommatadsana, Khemjiranee
    ;
    Klangvijit, Kanisorn
    ;
    Uwanno, Teerayut
    ;
    Phonyiem Reilly, Mayuree
    ;
    Yordsri, Visittapong
    This study focuses on converting hemp hurd, a byproduct of hemp stalk processing, into high-performance activated carbon for supercapacitor applications. Hemp hurd was pyrolyzed and subsequently activated with NaOH at various ratios (biochar:NaOH = 1:1, 1:2, 1:3, 1:4). The Hurd-4 condition (1:4 ratio) yielded the highest specific surface area, 3033 m<sup>2</sup>/g. Our findings indicate that increasing the chemical activation ratio enhances the mesopore-to-micropore volume ratio (V<inf>meso</inf>/V<inf>micro</inf>) to 1.58 while maintaining a sufficient micropore volume for ion storage. This balanced pore structure effectively increased the specific capacitance, achieving a maximum of 725 F/g at a current density of 0.3 A/g in a 1 M H<inf>2</inf>SO<inf>4</inf>electrolyte. When assembled into a coin cell with an organic electrolyte, Hurd-4 exhibited a maximum specific capacitance of 39 F/g, a maximum energy density of 34 Wh/kg, and a power density of 395 W/kg, surpassing commercial activated carbon. Additionally, the device maintained 78% capacitance retention after 10,000 cycles at a current density of 0.5 A/g. The superior electrochemical properties are attributed to the largest specific surface area, highest pore volume, and optimal mesopore volume ratio. These results demonstrate the potential of hemp hurd as a highly efficient precursor for synthesizing activated carbon for high-performance supercapacitors.
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    Preparation of activated carbon via acidic dehydration of durian husk for supercapacitor applications
    (2020-08-01)
    Ukkakimapan, Pundita
    ;
    Sattayarut, Vichuda
    ;
    Wanchaem, Thanthamrong
    ;
    Yordsri, Visittapong
    ;
    Phonyiem, Mayuree
    In this study, the preparation of activated carbons (ACs) via acidic dehydration of durian husk (DH) for supercapacitor application was investigated. The DH was dehydrated using sulfuric acid and subsequently activated by using sodium hydroxide as chemical reagent at 720 °C to obtain activated carbon (hereinafter referred to as DA). Surpassing the commercial ACs and the ACs derived from the conventional carbonization and activation (hereinafter referred to as CA), the DA exhibited superior properties in high surface area (2578 m<sup>2</sup>/g) and total pore volume (1.27 cm<sup>3</sup>/g). Moreover, besides carbon and oxygen, the DA contained sulfur and nitrogen in the carbon network. The DA can act as a suitable material for supercapacitor electrode with the specific gravimetric and volumetric capacitances of 145 F/g and 70 F/cm<sup>3</sup> in an organic electrolyte. The device also showed a promising performance with an energy density of 32 Wh/kg and a power density of 316 W/kg. These results demonstrate that the preparation of ACs via acidic dehydration of DH offers the advantages in terms of simplicity, low cost, and short-time processing to achieve heteroatom self-doped ACs with a high surface area for high-performance supercapacitors.
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