Dense porous monolithic carbon from Indonesian daikon leaf waste via NaOH–CO2 physicochemical activation for binder-free volumetric supercapacitors
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Monolith, volumetric, carbon, electrode, supercapacitor
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Abstract
High-performance volumetric supercapacitors are often limited by the trade-off between porosity and electrode density in biomass-derived carbon. Herein, binder-free monolithic carbon electrodes were produced from Indonesian daikon leaf waste through 0.5 M NaOH pretreatment followed by integrated N2–CO2 thermal processing. NaOH activation increased the surface area from 236 to 570 m2 g−1, increasing carbon purity from 88.34 to 95.45 wt% while retaining 4–5 wt% oxygen functionalities. The activated monolithic carbon electrode (VSAC) delivered a volumetric capacitance of 169 F cm−3 at 1 mV s−1 and 185 F cm−3 at 10 mA cm−2 in a symmetric two-electrode configuration without binders or conductive additives. VSAC also retained 83.2% capacitance at high scan rates and achieved 16.01 Wh L−1 at 838 W L−1. The improved performance arises from interconnected ion pathways, preserved electrode density, and surface oxygen functionalities, demonstrating a sustainable strategy for practical volumetric supercapacitors.
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Apriwandi, Sinta Mustika, W., Julnaidi, Puspita, D., Taslim, R., & Taer, E. (2026). Dense porous monolithic carbon from Indonesian daikon leaf waste via NaOH–CO2 physicochemical activation for binder-free volumetric supercapacitors. Communications in Science and Technology, 11(1), 150–161. https://doi.org/10.21924/cst.11.1.2026.2000
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References
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21. A. Phakkhawan, A. Sakulkalavek, N. Chanlek, S. Nijpanich, Self-activation of carbons derived from bio-waste cabbage for a green supercapacitor based on seawater electrolyte, Sustain. Mater. Technol. 42 (2024) e01143.
22. E. Taer, N. Yanti, W.S. Mustika, A. Apriwandi, R. Taslim, A. Agustino, Porous activated carbon monolith with nanosheet/nanofiber structure derived from the green stem of cassava for supercapacitor application, Int. J. Energy Res. 44 (2020) 1–14.
23. R. Taslim, A. Apriwandi, E. Taer, Novel Moringa oleifera Leaves 3D Porous Carbon-Based Electrode Material as a High-Performance EDLC Supercapacitor, ACS Omega 7 (2022) 36489–36502.
24. T. Yu, Q. Zhou, J. Chen, W. Ma, C. Wang, S. Fan, Y. Zhang, The synthesis of nanocellulose/B, N, F tri-doped graphene composite hydrogels for supercapacitor applications, Vacuum 222 (2024) 113036.
25. B. Tekin, Y. Topcu, Novel hemp biomass-derived activated carbon as cathode material for aqueous zinc-ion hybrid supercapacitors: Synthesis, characterization, and electrochemical performance, J. Energy Storage 77 (2024) 109879.
26. G.A. Tafete, A. Uysal, N.G. Habtu, M.K. Abera, T.A. Yemata, K.S. Duba, S. Kinayyigit, Hydrothermally synthesized nitrogen-doped hydrochar from sawdust biomass for supercapacitor electrodes, Int. J. Electrochem. Sci. 19 (2024).
27. E. Taer, L. Pratiwi, Apriwandi, W.S. Mustika, R. Taslim, Agustino, Three-dimensional pore structure of activated carbon monolithic derived from hierarchically bamboo stem for supercapacitor application, Commun. Sci. Technol. 5 (2020) 22–30.
28. W. Sun, Y. Yan, Y. Wei, J. Ma, Z. Niu, G. Hu, Catalytic Pyrolysis of Biomass: A Review of Zeolite, Carbonaceous, and Metal Oxide Catalysts, Nanomaterials 15 (2025) 1–22.
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30. E. Taer, M. Deraman, R. Taslim, Iwantono, Preparation of binderless activated carbon monolith from pre-carbonization rubber wood sawdust by controlling of carbonization and activation condition, AIP Conf. Proc. 1554 (2013) 33–37.
31. J.. Gonzalez, S. Roma, J.M. Encinar, G. Martı, Pyrolysis of various biomass residues and char utilization for the production of activated carbons, J. Anal. Appl. Pyrolysis 85 (2009) 134–141.
32. E. Taer, A. Apriwandi, Y. Yusriwandi, W.S. Mustika, Z. Zulkifli, R. Taslim, S. Sugianto, B. Kurniasih, A. Agustino, P. Dewi, Comparative study of CO2 and H2O activation in the synthesis of carbon electrode for supercapacitors, AIP Conf. Proc. 1927 (2018) 030036–1–030036–6.
33. A. Sandeep, A. V. Ravindra, Optimizing ZnCl2 activation temperature for biomass-derived porous carbons with superior energy and power density in supercapacitors, Diam. Relat. Mater. 166 (2026) 113693.
34. A. Levent, C. Saka, Stable electrode material for use in supercapacitor with iodine doping after sulfonation of mesoporous activated carbon particles based on microalgae biomass, Biomass Convers. Biorefinery 15 (2025) 20803–20816.
35. J. Serafin, M. Baca, M. Biegun, E. Mijowska, R.J. Kaleńczuk, J. Sreńscek-Nazzal, B. Michalkiewicz, Direct conversion of biomass to nanoporous activated biocarbons for high CO2 adsorption and supercapacitor applications, Appl. Surf. Sci. 497 (2019) 143722.
36. L. Szabó, X. Xu, T. Ohsawa, K. Uto, J. Henzie, I. Ichinose, M. Ebara, Ultrafine self-N-doped porous carbon nanofibers with hierarchical pore structure utilizing a biobased chitosan precursor, Int. J. Biol. Macromol. 182 (2021) 445–454.
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