Coal fly ash—Municipal solid waste gasification char hybrid electrodes: Pore structure and charge-transport characteristics

Satria Pinandita
Doctoral Program of Engineering Science, Faculty of Engineering, Universitas Negeri Yogyakarta, Yogyakarta 55281, Indonesia; Department of Electrical Engineering, Faculty of Engineering, Universitas Semarang, Semarang 50196, Indonesia
Rustam Asnawi
Department of Electrical Engineering Education, Faculty of Engineering, Universitas Negeri Yogyakarta, Yogyakarta 55281, Indonesia
Mochamad Syamsiro
Department of Mechanical Engineering, Faculty of Engineering, Universitas Janabadra Yogyakarta, Yogyakarta 55231, Indonesia

Article ID: 4586

Keywords: gasification; fly ash; metal-air; pore structure; carbon

Abstract

The development of sustainable and cost-effective electrode materials is crucial for advancing metal–air battery technology and reducing dependence on conventional carbon resources. This study explores coal fly ash and Municipal Solid Waste Gasification (MSWG) char as waste-derived electrode precursors, utilizing their mineral-rich and carbonaceous characteristics to improve electrochemical performance. The objectives were to characterize the raw materials’ elemental composition and surface functional groups and to comparatively evaluate three hybrid-electrode formulations based on their pore characteristics, electrochemical response, and charge-transfer behaviour. SEM–EDX showed coal fly ash with spherical, microsphere-like particles rich in O, Si, and Al, indicating its role as a mineral-rich silicate and aluminosilicate precursor. MSWG char, however, exhibited irregular, rough, agglomerated morphology with higher carbon content, serving as the main carbon source. FTIR confirmed silicate, oxide, hydroxyl, carbonate, and carbon–mineral bonding. Among the three formulations tested, the formulation containing 20 wt.% coal fly ash (F20) showed the best overall performance, with the highest micropore surface area (1.601 m² g⁻¹) and volume (0.0006110 cm³ g⁻¹). It delivered the largest CV response, energy density of ~208 Wh kg⁻¹, power density of 17.8 W kg⁻¹, and the lowest ΔZ′ of 0.137 Ω. The descriptive results indicate that the measured performance may depend on active-pore accessibility and ion–electron transport characteristics rather than on total BET surface area alone. Further replicated experiments are required to establish the statistical reliability of the observed differences. This study advances waste-ash-derived electrodes for sustainable metal–air battery applications. The novelty of this work is the integrated composition–pore–transport evaluation of directly blended coal fly ash and MSWG char hybrid electrodes.

Published

2026-08-20

How to Cite

Pinandita, S., Asnawi, R., & Syamsiro, M. (2026). Coal fly ash—Municipal solid waste gasification char hybrid electrodes: Pore structure and charge-transport characteristics. Energy Storage and Conversion, 4(2). https://doi.org/10.59400/esc4586

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Vol. 4 No. 3 (2026): In Progress

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This work is licensed under a Creative Commons Attribution 4.0 International License.

References

[1]Rai S, Prachi P, Kant CR, et al. Metal-air batteries: From fundamental mechanisms to practical applications. Journal of Alloys and Compounds. 2025; 1033: 180805. doi: 10.1016/j.jallcom.2025.180805

[2]Timofeeva EV, Segre CU, Pour GS, et al. Aqueous air cathodes and catalysts for metal–air batteries. Current Opinion in Electrochemistry. 2023; 38: 101246. doi: 10.1016/j.coelec.2023.101246

[3]Hopkins BJ, Chervin CN, Parker JF, et al. Electrocatalyst or support? Circumventing corrosion for long-lived zinc–air batteries. Next Energy. 2023; 1(4): 100054. doi: 10.1016/j.nxener.2023.100054

[4]Gao S, Li M, Li N, et al. Porous carbon-nanostructured electrocatalysts for zinc–air batteries: from materials design to applications. Nanoscale Advances. 2025; 7(1): 60–88. doi: 10.1039/D4NA00847B

[5]Supiyeva Z, Pan X, Abbas Q. The critical role of nanostructured carbon pores in supercapacitors. Current Opinion in Electrochemistry. 2023; 39: 101249. doi: 10.1016/j.coelec.2023.101249

[6]Liu H, Zhang L. Pore-structure control of porous carbon electrode materials and energy-storage performance in water-in-salt electrolytes. Journal of Electroanalytical Chemistry. 2024; 961: 118233. doi: 10.1016/j.jelechem.2024.118233

[7]Chai Y, Hu Z, Jia W, et al. Ion transport in porous carbon electrode for supercapacitors probed by electrochemical quartz crystal microbalance. Electrochimica Acta. 2020; 356: 136780. doi: 10.1016/j.electacta.2020.136780

[8]Christopher Selvam D, Devarajan Y, Raja T, et al. Advances in waste-derived nano-catalysts for zinc–air batteries: Enhancing OER efficiency and sustainability in energy storage. Applied Energy. 2025; 400: 126605. doi: 10.1016/j.apenergy.2025.126605

[9]He T, Tian H, Hong J, et al. From hazardous waste to high-performance anodes: Iron-Catalyzed upcycling of coal gasification slag into hierarchical porous carbon for sodium-ion batteries. Fuel. 2026; 404: 136320. doi: 10.1016/j.fuel.2025.136320

[10]Niu Y, Chen L, Guo S, et al. Porous carbon/minerals interwoven particle electrodes co-constructed by residual carbon and ash from coal gasification fine slag and its synergistic electrocatalytic mechanism. Fuel. 2024; 358: 130139. doi: 10.1016/j.fuel.2023.130139

[11]Guo Q, Li H, Wang S, et al. Experimental study on preparation of oxygen reduction catalyst from coal gasification residual carbon. Chemical Engineering Journal. 2022; 446: 137256. doi: 10.1016/j.cej.2022.137256

[12]Ma C, Fan Q, Dirican M, et al. Rational design of meso-/micro-pores for enhancing ion transportation in highly-porous carbon nanofibers used as electrode for supercapacitors. Applied Surface Science. 2021; 545: 148933. doi: 10.1016/j.apsusc.2021.148933

[13]Witte A, Garg N. Particle shape, crystallinity, and degree of polymerization of fly ash via combined SEM-EDS and Raman spectroscopy. Cement and Concrete Research. 2024; 184: 107612. doi: 10.1016/j.cemconres.2024.107612

[14]Kutchko B, Kim A. Fly ash characterization by SEM–EDS. Fuel. 2006; 85(17–18): 2537–2544. doi: 10.1016/j.fuel.2006.05.016

[15]Bhatt A, Priyadarshini S, Acharath Mohanakrishnan A, et al. Physical, chemical, and geotechnical properties of coal fly ash: A global review. Case Studies in Construction Materials. 2019; 11: e00263. doi: 10.1016/j.cscm.2019.e00263

[16]Wang H, Wang M, Zhang J, et al. Preparation of fly ash-based cobalt-iron silicate as supercapacitor electrode material. Chemical Engineering Journal. 2022; 434: 134661. doi: 10.1016/j.cej.2022.134661

[17]Fernandes DM, Abdelkader-Fernández VK, Badenhorst C, et al. Coal chars recovered from fly ash as promising electrocatalysts for oxygen reduction reaction. International Journal of Hydrogen Energy. 2021; 46(70): 34679–34688. doi: 10.1016/j.ijhydene.2021.08.009

[18]Nunes MS, Pereira C, Guedes A, et al. Assessment of coal fly ash char as a substituting material of graphite with electrocatalytic activity for the oxygen reduction reaction. Sustainable Chemistry and Pharmacy. 2022; 27: 100705. doi: 10.1016/j.scp.2022.100705

[19]Qin J, Zhang Y, Heberlein S, et al. Characterization and comparison of gasification and incineration fly ashes generated from municipal solid waste in Singapore. Waste Management. 2022; 146: 44–52. doi: 10.1016/j.wasman.2022.04.041

[20]Wang B, Gupta R, Bei L, et al. A review on gasification of municipal solid waste (MSW): Syngas production, tar formation, mineral transformation and industrial challenges. International Journal of Hydrogen Energy. 2023; 48(69): 26676–26706. doi: 10.1016/j.ijhydene.2023.03.086

[21]Sajid M, Raheem A, Ullah N, et al. Gasification of municipal solid waste: Progress, challenges, and prospects. Renewable and Sustainable Energy Reviews. 2022; 168: 112815. doi: 10.1016/j.rser.2022.112815

[22]Saini R, Deb Barma S, Srinivas Rao D, et al. Applied mineralogical investigation on coal gasification ash. Waste Management. 2023; 167: 1–12. doi: 10.1016/j.wasman.2023.05.025

[23]Wood DL, Li J, Daniel C. Prospects for reducing the processing cost of lithium ion batteries. Journal of Power Sources. 2015; 275: 234–242. doi: 10.1016/j.jpowsour.2014.11.019

[24]Baig MM, Gul IH, Baig SM, et al. The complementary advanced characterization and electrochemical techniques for electrode materials for supercapacitors. Journal of Energy Storage. 2021; 44: 103370. doi: 10.1016/j.est.2021.103370

[25]Beyers I, Bensmann A, Hanke-Rauschenbach R. Ragone plots revisited: A review of methodology and application across energy storage technologies. Journal of Energy Storage. 2023; 73: 109097. doi: 10.1016/j.est.2023.109097

[26]Velraj S, Zhu JH. Cycle life limit of carbon-based electrodes for rechargeable metal–air battery application. Journal of Electroanalytical Chemistry. 2015; 736: 76–82. doi: 10.1016/j.jelechem.2014.11.003

[27]Kang X. Critique on the “Crystallinity and selected properties of fly ash particles” by T. Matsunaga, J.K. Kim, S. Hardcastle, P.K. Rohatgi, Crystallinity and selected properties of fly ash particles, Materials Science and Engineering A, Volume 325, Issues 1–2, 28 February 2002, Pages 333–343. Materials Science and Engineering: A. 2014; 613: 414. doi: 10.1016/j.msea.2014.07.019

[28]Ismael MA, Aziz ARA, Zainal A. EZ, et al. Investigation on free-piston motion and power generation of a dual-piston air-driven expander linear generator. Energy Reports. 2021; 7: 2388–2397. doi: 10.1016/j.egyr.2021.04.035

[29]Qian Y, Liu J, Huang Z, et al. Conceptual design and system analysis of a poly-generation system for power and olefin production from natural gas. Applied Energy. 2009; 86(10): 2088–2095. doi: 10.1016/j.apenergy.2008.12.014

[30]Huang J. Diffusion impedance of electroactive materials, electrolytic solutions and porous electrodes: Warburg impedance and beyond. Electrochimica Acta. 2018; 281: 170–188. doi: 10.1016/j.electacta.2018.05.136

[31]Wang M, Chen D, Wang H, et al. A review on fly ash high-value synthesis utilization and its prospect. Green Energy and Resources. 2024; 2(1): 100062. doi: 10.1016/j.gerr.2024.100062

[32]Widayat W, Maheswari NT, Fitriani W, et al. Preparation of MgO-CaO/SiO2 catalyst from dolomite and geothermal solid waste for biodiesel production. International Journal of Renewable Energy Development. 2023; 12(3): 541–549. doi: 10.14710/ijred.2023.51573

[33]Konda K, Moodakare SB, Kumar PL, et al. Comprehensive effort on electrode slurry preparation for better electrochemical performance of LiFePO4 battery. Journal of Power Sources. 2020; 480: 228837. doi: 10.1016/j.jpowsour.2020.228837

[34]Zhuang B, Xu N, Xu X, et al. Hierarchically mesoporous Fe-N-C single-atom catalysts for efficient oxygen electrocatalysis in rechargeable zinc-air batteries. Materials Reports: Energy. 2025; 5(3): 100352. doi: 10.1016/j.matre.2025.100352

[35]Chen T, Huang S, Pei X, et al. Synergistic Co/Cu heterophase nanoparticles embedded in microporous and mesoporous carbon with hydrophobicity for high-power density zinc-air battery. Electrochimica Acta. 2025; 530: 146336. doi: 10.1016/j.electacta.2025.146336

[36]Liivand K, Sainio J, Wilson BP, et al. Overlooked residue of Li-ion battery recycling waste as high-value bifunctional oxygen electrocatalyst for Zn-air batteries. Applied Catalysis B: Environmental. 2023; 332: 122767. doi: 10.1016/j.apcatb.2023.122767

[37]Shen Z, Yu X, Yu D. Preparation and applications of coal fly ash-based catalysts: A comprehensive review. Journal of Environmental Chemical Engineering. 2025; 13(3): 116782. doi: 10.1016/j.jece.2025.116782

[38]Lasia A. Impedance of porous electrodes. Current Opinion in Electrochemistry. 2025; 54: 101764. doi: 10.1016/j.coelec.2025.101764

[39]Subbiah G, Nagappan B, Sharma S, et al. Pioneering advances in waste-derived catalysts for next-generation zinc-air batteries. Results in Engineering. 2025; 27: 106161. doi: 10.1016/j.rineng.2025.106161

[40]Tao F, Liu Y, Ren X, et al. Different surface modification methods and coating materials of zinc metal anode. Journal of Energy Chemistry. 2022; 66: 397–412. doi: 10.1016/j.jechem.2021.08.022

[41]Mollah MYA, Hess TR, Cocke DL. Surface and bulk studies of leached and unleached fly ash using XPS, SEM, EDS and FTIR techniques. Cement and Concrete Research. 1994; 24(1): 109–118. doi: 10.1016/0008-8846(94)90091-4

[42]Liu J, Li X, Jin B, et al. Optimizing porous structure of carbon electrodes for temperature-independent capacitance at sub-zero temperatures. Chemical Engineering Journal. 2022; 441: 136053. doi: 10.1016/j.cej.2022.136053

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