Hemp-Derived Hierarchical Porous Carbon with an Optimized Pore Structure by NaOH Activation for Supercapacitor Applications

Bowornthommatadsana, Khemjiranee; Klangvijit, Kanisorn; Uwanno, Teerayut; Phonyiem Reilly, Mayuree; Yordsri, Visittapong; Chaiwat, Weerawut; Ichikawa, Satoshi; Obata, Michiko; Fujishige, Masatsugu; Takeuchi, Kenji; Wongwiriyapan, Winadda; Endo, Morinobu

doi:10.1021/acsomega.5c10175

Hemp-Derived Hierarchical Porous Carbon with an Optimized Pore Structure by NaOH Activation for Supercapacitor Applications

Author(s)

Bowornthommatadsana, Khemjiranee

Klangvijit, Kanisorn

Uwanno, Teerayut

Phonyiem Reilly, Mayuree

Yordsri, Visittapong

Chaiwat, Weerawut

Ichikawa, Satoshi

Obata, Michiko

Fujishige, Masatsugu

Takeuchi, Kenji

Wongwiriyapan, Winadda

Endo, Morinobu

Date Issued

November 11, 2025

Type

Article

DOI

10.1021/acsomega.5c10175

Abstract

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 m²/g. Our findings indicate that increasing the chemical activation ratio enhances the mesopore-to-micropore volume ratio (Vmeso/Vmicro) 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 H2SO4electrolyte. 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.

Citation

ACS Omega, 10(44), 53596-53611, 2025