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Valorization of Macadamia Nut Shell Waste into Activated Carbons for Electrochemical Supercapacitor Electrodes
(2026-03-03)
Chaiammart, Nattapat
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Taechamahaphan, Ariya
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Chakartnarodom, Parinya
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Prakaypan, Wichit
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Ishizaki, Takahiro
Supercapacitors are promising energy storage devices owing to their high power density and excellent cycling stability. The conversion of biomass waste into activated carbon with hierarchical pore structures has emerged as a sustainable strategy for developing high-performance supercapacitor electrodes. Herein, activated carbons were synthesized from macadamia nut shell (MNS) waste via a two-step process comprising carbonization at 600 °C and subsequent chemical activation with potassium hydroxide (KOH) at 800 °C, using weight ratios of carbonized MNS to KOH of 1:1, 1:2, and 1:3. The resulting activated carbons exhibited an amorphous structure with a predominant microporosity. KOH activation substantially increased the specific surface area from 325 to 1362 m2 g–1 through gas evolution, etching, and potassium intercalation, thereby promoting the predominant micropore formation along with partial mesopore development. Increasing the KOH ratio induced greater structural disorder, widened micropores, increased the mesopore fraction, enriched C–O functionalities, and suppressed C═O and O–C═O groups. Electrochemical measurements in a 6 M KOH electrolyte using a three-electrode system revealed that the sample activated at a 1:3 ratio delivered a maximum specific capacitance of 170 F g–1 at 1 A g–1 and exhibited predominantly electric double-layer capacitor (EDLC) behavior with a minor pseudocapacitive contribution, as confirmed by power-law, Trasatti, and Dunn analyses. This performance is attributed to its large specific surface area, partially developed mesoporosity, and enhanced surface wettability. A symmetric coin-cell supercapacitor assembled using this material delivered an energy density of 5.4 W h kg–1 and a power density of 2500 W kg–1, while maintaining excellent cycling stability over 10,000 charge–discharge cycles at 3 A g–1. These results reveal the potential valorization of MNS-derived activated carbons as sustainable and efficient electrode materials for high-performance supercapacitors.
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Green Synthesis of Activated Carbons from Coconut Coir Dust via Steam Activation for Supercapacitor Electrode Applications
(2025-12-01)
Kongtip, Jirayu
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Kanjulkeat, Natapol
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Ninneit, Thanapol
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Phanapadipong, Norapat
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Chaiammart, Nattapat
Activated carbons derived from coconut coir dust were synthesized via a two-step process combining carbonization and steam activation for application as electrode materials in supercapacitors. The influence of carbonization temperature (500–700 °C) on the morphological, structural, textural, and electrochemical properties of the resulting activated carbons was systematically investigated. Increasing the carbonization temperature led to a progressive collapse of the cellular structure and formation of a more compact and thermally stable carbon matrix, while the overall morphology remained largely unchanged after steam activation. The steam-activated carbon prepared from the carbonized sample at 700 °C (SA-CCD-7) exhibited the highest specific surface area (889 m2 g−1) and a well-developed hierarchical micro–mesoporous structure. Structural analyses confirmed the amorphous nature and an increase in structural disorder after activation, consistent with the enhanced pore development. Electrochemical measurements in 6 M KOH using a three-electrode system revealed that the SA-CCD-7 displayed a typical electric double-layer capacitor (EDLC) behavior, delivering the highest specific capacitance of 86 F g−1 at 1 A g−1 and retaining 81% of its initial capacitance at 20 A g−1, demonstrating excellent rate capability. The symmetric coin-cell supercapacitor device assembled with SA-CCD-7 as the electrodes achieved an energy density of 0.9–1.2 Wh kg−1 and a power density of 50–2500 W kg−1, along with remarkable cycling stability over 10,000 cycles with negligible capacitance loss. These findings highlight steam activation of coconut coir dust as a simple, scalable, and eco-friendly approach for producing biomass-derived carbon electrodes for sustainable energy storage applications.
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Coconut Residue-Derived Nanoporous Carbon via Hydrothermal Carbonization for Nanoporous Carbon-Based Supercapacitor Electrodes
(2025-07-01)
Ruenroengrit, Kemchat
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Kunyuan, Jumpon
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Ruttanadech, Nuttapong
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Kaewtrakulchai, Napat
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Puengjinda, Pramote
The increasing demand for sustainable and cost-effective energy storage solutions has driven interest in biomass-derived carbon materials for supercapacitor electrodes. This study explores the valorization of coconut residue (CR), an abundant agricultural waste, as a carbon precursor for nanoporous carbon (NPC) production. NPC was synthesized via hydrothermal carbonization (HTC) of CR, followed by chemical activation using potassium hydroxide (KOH) at varying temperatures (700, 800, and 900 °C). The effects of activation temperature on the structure and electrochemical performance of the NPC were systematically investigated. The activated materials exhibited amorphous, highly porous structures, with surface areas increasing alongside activation temperature—reaching a maximum of 1969 m2 g−1 at 900 °C. Electrochemical characterization was conducted using a three-electrode setup through cyclic voltammetry (CV) and galvanostatic charge–discharge (GCD) in a 1 M Na<inf>2</inf>SO<inf>4</inf> electrolyte. The sample activated at 900 °C with a CR:KOH weight ratio of 1:2.5 achieved the highest specific capacitance of 52 F g−1 at a specific current of 1 A g−1. These findings underscore the potential of CR as a low-cost and sustainable raw material for fabricating efficient electrode materials in energy storage applications.
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NiO-YSZ anode composite material derived from mechano-chemical for solid oxide fuel cells application
(2025-06-01)
Srisuwan, Thanakorn
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Puengjinda, Pramote
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Kaewtrakulchai, Napat
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Chanpee, Sirayu
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Jadsadajerm, Supachai
This study investigates the effects of calcination time, milling duration, and sintering temperature on the properties of Nickel oxide and Yttria-stabilized zirconia (NiO-YSZ) anode composite materials for solid oxide fuel cell (SOFC) applications. NiO nanoparticles were synthesized from nickel (II) sulfate (Ni(II)SO<inf>4</inf>), with X-ray diffraction (XRD) confirming a face-centered cubic (FCC) structure. The crystallite size (21 nm) was achieved after 8 hours of calcination, while prolonged durations caused particle agglomeration. Ball-milling for 12 hours produced comparatively fine particles with an average of 706 nm, though extended milling led to grain growth and aggregation. Scanning electron microscopy (SEM) revealed nano aggregation. Sintering at 1200 °C improved the densification of the NiO-YSZ layer while increasing its porosity, which enhanced the reduction of NiO to metallic nickel (Ni). Electrochemical Impedance Spectroscopy (EIS) demonstrated lower impedance and improved electrochemical performance for cells cold-sintered at 1200 °C. These findings show the importance of optimizing processing conditions to enhance the performance of NiO-YSZ anode for SOFCs, offering valuable insights for advanced energy conversion technologies.
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Chemically activated carbons derived from cashew nut shells as potential electrode materials for electrochemical supercapacitors
(2025-06-01)
Chaiammart, Nattapat
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Vignesh, Veeramuthu
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Thu, Myo Myo
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Eiad-ua, Apiluck
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Maiyalagan, Thandavarayan
Supercapacitors are widely recognized as energy storage solutions due to their high power densities and long cycle lives. Furthermore, there is growing scientific and technological interest in converting biomass waste into carbon materials for manufacturing supercapacitor electrodes. In addition to their abundance and cost-effectiveness, the appeal of carbons derived from biomass lies in their tunable porosity, which enables the rational design of carbon materials to achieve the desired performance of supercapacitors. Here, we present the synthesis of activated carbons from cashew nut shells via potassium hydroxide (KOH) activation at different temperatures (650, 750, and 850 °C). The resulting materials exhibited amorphous and predominant microporous structures. Increasing the activation temperature led to a rise in specific surface area from 1534 to 2034 m2 g−1 and an increased proportion of mesopores. The electrochemical properties of these activated carbons for supercapacitor applications were investigated by cyclic voltammetry, galvanostatic charge–discharge, and impedance spectroscopic techniques in a 1 M sodium sulfate (Na<inf>2</inf>SO<inf>4</inf>) electrolyte. Using a three-electrode system, the activated carbons treated at 750 °C exhibited a maximum specific capacitance of 106 F g−1 at a current density of 0.5 A g−1 with a good rate capability; they retained 75 % at 10 A g−1 over a 1.0 V voltage window. Furthermore, a symmetric supercapacitor coin-cell, fabricated with activated carbons treated at 750 °C as the positive and negative electrodes, demonstrated an energy density of 2.43 Wh kg−1 at a power density of 1002 W kg−1. The cell exhibited 87 % capacitance retention at 1.0 A g−1 after 10,000 cycles. This work showcases the efficient and sustainable utilization of cashew nut shells as a carbon source for supercapacitor applications and highlights their value in a circular economy.
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Valorization of horse manure conversion to magnetic carbon nanofiber for dye adsorption by hydrothermal treatment coupled with carbonization
(2024-06-01)
Kaewtrakulchai, Napat
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Chanpee, Sirayu
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Pasee, Warit
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Putta, Ampol
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Chutipaijit, Sutee
Pollution of water resources has recently increased as a result of expanded industrial activity. Recycling waste biomass into bio-adsorbent material offers a cheap, easy, and eco-friendly solution. In this study, magnetic carbon nanofibers (MCNF) with a highly porous structure were developed from magnetite-preloaded horse manure by hydrothermal treatment followed by carbonization using different ratios of iron (III) nitrate and iron oxide as magnetic precursors. The produced MCNF had a very porous structure with specific surface area of 435.31 m2/g and high carbon content. The magnetic characteristics of MCNF promoted by the presence of iron oxide species. The saturated magnetization of MCNF obtained from a 5:5 ratio of the magnetic precursors (iron (III) nitrate: iron oxide) was 2.48 emu/g. Synthesized MCNF was applied as a bio-adsorbent for methylene blue (MB) removal from aqueous solution, with results showing excellent dye adsorption of 92–99 %. MB adsorption was facilitated by pore filling, electrostatic contact, hydrogen bonding, and ion complexation. Experimental results indicated that the Freundlich isotherm and pseudo-second-order kinetic models concurred with the observed MB adsorption data, suggesting that the adsorption mechanism involved multilayered micropore interactions between magnetite and MB chemisorption. The resulting magnetic adsorbent was successfully removed from the aqueous solution by physical separation. Findings indicated that horse manure-derived MCNF could be used as an efficient bio-adsorbent to remove organic contaminants in wastewater.
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Size-Dependent Graphene Support for Decorating Gold Nanoparticles as a Catalyst for Hydrogen Evolution Reaction with Machine Learning-Assisted Prediction
(2023-01-01)
Saeloo, Boontarika
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Jitapunkul, Kulpavee
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Iamprasertkun, Pawin
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Panomsuwan, Gasidit
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Sirisaksoontorn, Weekit
Size-dependent two-dimensional (2D) materials (e.g., graphene) have been recently used to improve their performance in various applications such as membrane filtration, energy storage, and electrocatalysts. It has also been demonstrated that 2D nanosheets can be one of the promising support materials for decorating nanoparticles (NPs). However, the optimum nanosheet size (lateral length and thickness) for supporting NPs has not yet been explored to enhance their catalytic performance. Herein, we elucidate the mechanism behind size-dependent graphene (GP) as a support due to which gold nanoparticles (AuNPs) are used as an active catalyst for the hydrogen evolution reaction (HER). Surprisingly, the decoration of AuNPs increased with the increasing nanosheet size, counter to what is widely reported in the literature (high surface area for smaller nanosheet size). We found that a large graphene nanosheet (lGP; ∼800 nm) used as the AuNP support (lGP/AuNPs) exhibited superior performance for the HER with long-term stability. The lGP/AuNPs with a suitable content of AuNPs provides a low overpotential and a small Tafel slope, being lower than that of other reported carbon-based HER electrocatalysts. This results from highly exposed active sites of well-dispersed AuNPs on lGP giving high conductivity. The laminar structure of the stacked graphene nanosheets and the high wettability of the lGP/AuNPs electrode surface also play crucial roles in enhancing electrolytes for penetration in the electrode, suggesting a highly electrochemical surface area. Moreover, machine learning (Random Forest) was also used to reveal the essential features of the advanced catalytic material design for catalyst-based applications.
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Porous Biochar Supported Transition Metal Phosphide Catalysts for Hydrocracking of Palm Oil to Bio-Jet Fuel
(2022-10-01)
Kaewtrakulchai, Napat
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Smuthkochorn, Araya
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Manatura, Kanit
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Panomsuwan, Gasidit
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Fuji, Masayoshi
The upgrading of plant-based oils to liquid transportation fuels through the hydrotreating process has become the most attractive and promising technical pathway for producing biofuels. This work produced bio-jet fuel (C<inf>9</inf>–C<inf>14</inf> hydrocarbons) from palm olein oil through hydrocracking over varied metal phosphide supported on porous biochar catalysts. Relative metal phosphide catalysts were investigated for the highest performance for bio-jet fuel production. The palm oil’s fiber-derived porous biochar (PFC) revealed its high potential as a catalyst supporter. A series of PFC-supported cobalt, nickel, iron, and molybdenum metal phosphides (Co-P/PFC, Ni-P/PFC, Fe-P/PFC, and Mo-P/PFC) catalysts with a metal-loading content of 10 wt.% were synthesized by wet-impregnation and a reduction process. The performance of the prepared catalysts was tested for palm oil hydrocracking in a trickle-bed continuous flow reactor under fixed conditions; a reaction temperature of 420 °C, LHSV of 1 h−1, and H<inf>2</inf> pressure of 50 bar was found. The Fe-P/PFC catalyst represented the highest hydrocracking performance based on 100% conversion with 94.6% bio-jet selectivity due to its higher active phase dispersion along with high acidity, which is higher than other synthesized catalysts. Moreover, the Fe-P/PFC catalyst was found to be the most selective to C<inf>9</inf> (35.4%) and C<inf>10</inf> (37.6%) hydrocarbons.
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Cattail leaf-derived nitrogen-doped carbons via hydrothermal ammonia treatment for electrocatalytic oxygen reduction in an alkaline electrolyte
(2022-07-12)
Panomsuwan, Gasidit
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Eiad-ua, Apiluck
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Kaewtrakulchai, Napat
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Seizawa, Ai
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Ishizaki, Takahiro
Cattail leaf-derived nitrogen-doped carbons (CL-NCs) were prepared by hydrothermal treatment in ammonia solution and subsequent pyrolysis for application as catalysts for the oxygen reduction reaction (ORR). The ammonia concentration was varied at 1.0, 1.5, and 2.0 M to alter the nitrogen doping content. The characterization results revealed that CL-NCs exhibited an amorphous structure, while the density of structural defects increased as the ammonia concentration increased. The CL-NC prepared without hydrothermal ammonia treatment had a nonporous structure with a low specific surface area (5 m2 g−1). With hydrothermal ammonia treatment, CL-NCs exhibited a micro–mesoporous structure with a higher surface area (113–496 m2 g−1); however, the surface area was significantly diminished at higher ammonia concentrations due to the deterioration of the pore structure. The nitrogen-doping content in CL-NCs varied from 0.65 to 1.55 atom% with the predominant ratios of pyridinic-N and graphitic-N. For electrochemical evaluation in an alkaline electrolyte (0.1 M KOH), CL-NC prepared at an ammonia concentration of 1.0 M showed the highest ORR activity among all samples, as indicated by the most positive onset potential (−0.05 V vs. Ag/AgCl) and half-wave potential (−0.22 V vs. Ag/AgCl) as well as the highest diffusion-limiting current density with a more favorable reduction via a direct four-electron pathway (n = 3.23–3.52). The ORR activity of CL-NCs had a similar trend to their specific surface area rather than nitrogen doping content, indicating the important role of surface area and porosity in enhancing the ORR activity. Moreover, it possessed excellent stability under long-term operation and exposure to methanol. The results obtained in this work could be helpful information for the further development and utilization of biomass-derived NCs for ORR catalysts.
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Nitrogen-doped carbon derived from horse manure biomass as a catalyst for the oxygen reduction reaction
(2022-06-14)
Panomsuwan, Gasidit
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Hussakan, Chadapat
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Kaewtrakulchai, Napat
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Techapiesancharoenkij, Ratchatee
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Serizawa, Ai
A massive amount of animal biomass is generated daily from livestock farms, agriculture, and food industries, causing environmental and ecological problems. The conversion of animal biomass into value-added products has recently gained considerable interest in materials science research. Herein, horse manure (HM) was utilized as a precursor for synthesizing nitrogen-doped carbons (NCs) via hydrothermal ammonia treatment and the post pyrolysis process. The ammonia concentration varied between 0.5, 1.0, and 1.5 M in the hydrothermal process. From the comprehensive characterization results, horse manure-derived nitrogen-doped carbons (HMNCs) exhibited an amorphous phase and a hierarchical nanoporous structure. The specific surface area decreased from 170.1 to 66.6 m2 g−1 as the ammonia concentration increased due to micropore deterioration. The nitrogen content was 0.90 atom% even with no ammonia treatment, indicating self-nitrogen doping. With hydrothermal ammonia treatment, the nitrogen content slightly enhanced up to 1.54 atom%. The electrocatalytic activity for the oxygen reduction reaction (ORR) of HMNCs in an alkaline solution was found to be related to nitrogen doping content and porous structure. The ORR activity of HMNCs mainly proceeded via a combination of two- and four-electron pathways. Although the ORR activity of HMNCs was still not satisfactory and comparable to that of a commercial Pt/carbon catalyst, it showed better long-term durability. The results obtained in this work provide the potential utilization of HM as a precursor for ORR catalysts and other related applications.

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