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Hydrothermal Synthesis of MnO2 and Hemp-Derived Activated Carbon Composites for Tailored Electrochemical Performance
(2026-07-22)
Klangvijit, Kanisorn
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Bowornthommatadsana, Khemjiranee
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Reilly, Mayuree Phonyiem
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Obata, Michiko
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Fujishige, Masatsugu
This study investigates hydrothermal synthesis of manganese dioxide composited with hemp-derived activated carbon (MnO<inf>2</inf>/AC) as electrodes for supercapacitors. The effects of key hydrothermal parameters, including carbon ratio, reaction temperature, and reaction time were systematically examined. Phase-pure α-MnO<inf>2</inf> was uniformly anchored on carbon framework. Morphology of MnO<inf>2</inf> evolved from nanowalls to well-defined nanorods with increasing reaction temperature and time. Meanwhile, the specific surface area of MnO<inf>2</inf>/AC decreased from 1712 to 1538 m2 g−1 due to partial pore blocking, while a predominantly mesoporous structure was retained. Electrochemical measurements in 1 M Na<inf>2</inf>SO<inf>4</inf> demonstrate that the optimized MnO<inf>2</inf>/AC composites achieve a specific capacitance of 216.8 F g−1 at 1 A g−1. Charge-storage mechanism analysis reveals a balanced contribution between surface-controlled capacitive processes and diffusion-controlled pseudocapacitance, which is directly correlated with preserved mesoporosity and moderate MnO<inf>2</inf> coverage. When the MnO<inf>2</inf>/AC composites were assembled into an asymmetric supercapacitor using AC as the negative electrode, the device operates stably up to 2.4 V and delivers outstanding cycling stability over 95% after 22,000 charge–discharge cycles at 5 A g−1. These results demonstrate that controlled growth of MnO<inf>2</inf>, rather than maximum oxide loading, is essential for optimizing charge-storage mechanisms and achieving high-performance biomass-derived supercapacitor electrodes.
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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
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Klangvijit, Kanisorn
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Uwanno, Teerayut
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Phonyiem Reilly, Mayuree
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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 m2/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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Laser-induced graphene electrochemical immunosensors for rapid and sensitive serological detection: A case study on dengue detection platform
(2025-06-01)
Inlumphan, Supawee
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Wongwiriyapan, Winadda
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Khemasiri, Narathon
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Rattanawarinchai, Prapakorn
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Leepheng, Piyawan
Here, we present a diagnostic on a chip platform based on laser-induced graphene (LIG) electrochemical immunosensors for serological detection. The electrochemical immunosensors are fabricated through CO<inf>2</inf> laser induction on polyimide (PI) sheets. Optimal electrochemical activity of LIG electrodes is obtained under optimized conditions of laser fluence. To verify the application, the serological detection platform was demonstrated. After functionalization with dengue virus (DENV) antigen, the LIG electrochemical immunosensors are able to sense the presence of mouse anti-flavivirus monoclonal (4G2) antibody in a wide linear working range of 25–20,000 ng/ml with the limit of detection (LOD) of 17.41 ng/ml. A specific recognition with 4G2 antibodies against with media protein and isotype is confirmed. Furthermore, the reliability of LIG electrochemical immunosensors compared to conventional enzyme-linked immunosorbent assay (ELISA) is verified through the NS1 antibodies identification in human blood serum clinical samples at room temperature. Our results highlight that the LIG-based electrode is a promising platform for electrochemical immunosensors, aimed at developing reliable and practical diagnostic tools for serological detection. These tools enable early diagnosis of infectious diseases, as well as non-invasive and rapid screening.
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Optimizing Electrochemical Performance: A Study of Aqueous Electrolytes with Hemp-Derived Activated Carbon for Supercapacitors
(2025-02-25)
Klangvijit, Kanisorn
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Bowornthommatadsana, Khemjiranee
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Phonyiem Reilly, Mayuree
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Uwanno, Teerayut
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Yordsri, Visittapong
This work investigates the synthesis and electrochemical performance of hemp-derived activated carbon (HAC) for supercapacitor electrode applications. HAC was prepared through NaOH chemical activation, and its electrochemical characteristics were evaluated using three different electrolytes: acidic (H<inf>2</inf>SO<inf>4</inf>), neutral (Na<inf>2</inf>SO<inf>4</inf>), and basic (KOH). The specific surface area of HAC was found to be exceptionally high, measuring 2612 m2/g, surpassing that of commercially available activated carbon (AC). Surface analysis revealed the presence of an oxygen functional group, which provided additional pseudocapacitive active sites. When 1 M H<inf>2</inf>SO<inf>4</inf> was employed as the electrolyte, HAC demonstrated a maximum specific capacitance of 594 F/g (302.4 F/cm3) at a current density of 0.3 A/g. Notably, the HAC electrode exhibited significantly higher energy density and power density, reaching values of 82 Wh/kg (135.7 mWh/cm3) and 188 W/kg (311 mW/cm3), respectively, when compared to commercial AC. These results highlight the potential of HAC as a cost-effective and high-performance electrode material, particularly when paired with H<inf>2</inf>SO<inf>4</inf> as the electrolyte due to their ideal micropore/mesopore ratio for H<inf>2</inf>SO<inf>4</inf> electrolyte access.
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Reusability, Long-Life Storage and Highly Sensitive Zirconium Nitride (ZrN) Surface-Enhanced Raman Spectroscopy (SERS) Substrate Fabricated by Reactive Gas-Timing Rf Magnetron Sputtering
(2023-12-22)
Sucheewa, Nguentra
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Wongwiriyapan, Winadda
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Rattanawarinchai, Prapakorn
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Wuttikhun, Tuksadon
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Sinthiptharakoon, Kittiphat
Transition metal nitrides (TMN) are promising material alternative to replace noble metals in the field of plasmonic applications, especially surface-enhanced Raman spectroscopy (SERS). Here we demonstrate a practical surface enhanced Raman spectroscopy (SERS) substrate using zirconium nitride (ZrN) thin films grown by reactive gas-timing (RGT) rf magnetron sputtering. The tailored properties of ZrN thin film exploited for SERS activity could be achieved to obtain a highly sensitive ZrN thin film SERS substrate with the enhancement factor (EF) of 1.24 × 106 and 4.8 %RSD at 1626 cm-1 toward methylene blue (MB) analyte which are comparable to the optimized Au sputtered thin films (EF=1.18 × 106 and with 5.1%RSD). We find that the spatial plasmonic hotspots on the surface of ZrN SERS substrate controlled by the turn-on timing of Ar:N2 sputtered gas sequence, leading to the discrete conductive surface profile, strongly relates to non-stoichiometric composition and the degree of (200)-oriented texture at the surface of ZrN thin film. Furthermore, ZrN thin film SERS substrates exhibit an excellent recyclability more than 30 cycles with simple cleaning process and a storage time longer than 6 months. The detection and reusability of ZrN SERS substrate on the low concentration of trinitrotoluene (TNT) for homeland security are also performed.
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Control of Manganese Oxide Hybrid Structure through Electrodeposition and SILAR Techniques for Supercapacitor Electrode Applications
(2023-08-01)
Klangvijit, Kanisorn
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Wongwiriyapan, Winadda
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Uwanno, Teerayut
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Obata, Michiko
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Fujishige, Masatsugu
Manganese oxide has been studied as a promising supercapacitor electrode due to its high theoretical capacitance, low cost, and environmental friendliness. Supercapacitor performance such as specific capacitance, resistance, and cycle life greatly depends on the morphology and crystal structure of manganese oxide. In this study, a Mn<inf>3</inf>O<inf>4</inf> hybrid structure was successfully synthesized using electrodeposition and successive ionic layer adsorption and reaction (SILAR) techniques which are simple, cost-effective, and low-temperature wet chemical processes. It was found that Mn<inf>3</inf>O<inf>4</inf> morphology is different depending on manganese precursors and synthesis techniques. Sea-grape-like and bird nest-like morphologies were obtained via the electrodeposition technique, while flower-like and nanoparticle morphologies were formed via the SILAR technique using manganese acetate and manganese sulfate as precursors, respectively. The hybrid structure of the nanoparticle-decorated bird nest-like heterostructure was prepared using manganese sulfate electrodeposition and subsequent SILAR deposition of manganese acetate. X-ray photoelectron spectroscopy confirmed the Mn<inf>3</inf>O<inf>4</inf> formation. Electrochemical properties of manganese oxide hybrid structure were systematically studied with cyclic voltammetry and galvanostatic charge–discharge, showing the highest areal capacitance of 390 mF cm−2 at 0.1 mA cm−2 with series and charge transfer resistances down to 4.55 and 4.91 Ω in 1 M sodium sulfate electrolyte.
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Tailoring Properties of Hafnium Nitride Thin Film via Reactive Gas-Timing RF Magnetron Sputtering for Surface Enhanced-Raman Scattering Substrates
(2022-01-01)
Sucheewa, Nguentra
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Wongwiriyapan, Winadda
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Klamchuen, Annop
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Obata, Michiko
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Fujishige, Masatsugu
This study successfully demonstrated the tailoring properties of hafnium nitride (HfN) thin films via reactive gas-timing (RGT) RF magnetron sputtering for surface-enhanced Raman spectroscopy (SERS) substrate applications. The optimal RGT sputtering condition was investigated by varying the duration time of the argon and nitrogen gas sequence. The RGT technique formed thin films with a grain size of approximately 15 nm. Additionally, the atomic ratios of nitrogen and hafnium can be controlled between 0.24 and 0.28, which is greater than the conventional technique, resulting in a high absorbance in the long wavelength region. Moreover, the HfN thin film exhibited a high Raman signal intensity with an EF of 8.5 × 104 to methylene blue molecules and was capable of being reused five times. A superior performance of HfN as a SERS substrate can be attributed to its tailored grain size and chemical composition, which results in an increase in the hot spot effect. These results demonstrate that the RGT technique is a viable method for fabricating HfN thin films with controlled properties at room temperature, which makes them an attractive material for SERS and other plasmonic applications.
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Nitrogen-doped graphene nanosheet-double-walled carbon nanotube hybrid nanostructures for high-performance supercapacitors
(2021-09-01)
Muangrat, Worawut
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Obata, Michiko
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Htay, Myo Than
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Fujishige, Masatsugu
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Dulyaseree, Paweena
A hybrid nitrogen-doped graphene nanosheet-grafted double-walled carbon nanotube (NG-DWCNT) was synthesized by chemical vapor deposition (CVD). Double-walled carbon nanotube (DWCNT) was synthesized by floating catalytic CVD using ferrocene and thiophene dissolved in ethanol. NG was directly grafted onto the DWCNT bundles by thermal CVD using mixed ethanol-urea solution. The NG possess sharp-edged petal-like structure on one-dimensional DWCNT bundle. The NG-DWCNT showed the nitrogen content of approximately 1.93 at%. The NG-DWCNT hybrid nanostructures exhibited a higher specific capacitance of 563 F g−1 than that of the DWCNT and un-doped G-DWCNT. The improvement of capacitance value is attributed to the synergic effect of the nitrogen doping together with the sharp-edged petal-like structure of the NG. The facile technique by CVD method provides a promising approach for simple and low-cost technique to synthesize the NG-DWCNT hybrid nanostructures. A hybrid carbon nanostructure of NG-DWCNT has a potential application in electrochemical conversion and energy storage devices.
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Preparation of activated carbon via acidic dehydration of durian husk for supercapacitor applications
(2020-08-01)
Ukkakimapan, Pundita
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Sattayarut, Vichuda
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Wanchaem, Thanthamrong
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Yordsri, Visittapong
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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 m2/g) and total pore volume (1.27 cm3/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/cm3 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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Investigation on electrochemical properties of sugarcane leaves-derived activated carbon by steam activation
(2020-01-01)
Ukkakimapan, Pundita
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Ukakimaparn, Prapart
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Wanchaem, Thanthamrong
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Yordsri, Visittapong
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Sattayarut, Vichuda
Sugarcane leaves (SLs) are a bio-waste from sugar production industry. To explore the value-added SLs, the SLs were used raw materials of activated carbons (ACs) by steam activation and their electrochemial properties were investigated for supercapacitor applications. The synthesis of ACs from the SLs consisted of two steps; carbonization at 500ºC and steam activation. The synthesis condition was optimized by varying activation temperature (800 and 850ºC) The porous structures were thoroughly formed on the surface after steam activation and the surface areas were reached to 630 and 639 m2 g-1 at the activation temperature of 800 and 850ºC, respectively. The SLs-derived ACs activated at 800ºC assembled in coin cell using organic electrolyte showed the highest specific capacitance of approximately 16 F g-1 with a capacitance retention of 62% when the current density increased to 1.5 A g-1. Even though there is a room to improve the electrochemical properties such as optimization of porosity and removal of inorganic component, the SLs show a potential use as raw materials of ACs for supercapacitor applications.

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