Recycling Waste Rubber Into Single-Walled Carbon Nanotubes: Narrow Chirality Distribution and Hydrogen Byproduct

Abstract

Waste rubber products pose a significant threat to the Earth's ecological environment due to their non-biodegradability and long-term persistence. In this study, we present a method for converting various rubber products into single-walled carbon nanotubes (SWNTs) and hydrogen (H₂) gas via a two-stage chemical vapor deposition (CVD) system. The core of this method is a porous magnesium oxide-supported cobalt catalyst (Co/MgO) prepared via a simple impregnation method, exhibiting high metal dispersion and superior performance. In the pyrolysis stage, thermal decomposition of the rubbers generates various hydrocarbons and carbon oxides. Subsequently, in the catalysis stage, these carbon-containing substances serve as the carbon source for the synthesis of SWNTs on the Co/MgO catalyst, concurrently releasing H₂. Remarkably, under optimal reaction temperatures, the synthesized SWNTs demonstrate a narrow chirality distribution with a (8, 4) SWNT proportion of 20.1%. Moreover, this approach is also applicable to convert real waste tires, which proposes a new avenue to recycling them into high-value carbon nanomaterials and H₂, thus shedding light on mitigating the environmental challenges associated with waste rubber disposal.

Keywords

circular economy / green chemistry / hydrogen production / single-walled carbon nanotubes / waste rubber

References

[1] A. Fazli and D. Rodrigue, “Waste Rubber Recycling: A Review on the Evolution and Properties of Thermoplastic Elastomers,” Materials 13 (2020): 782.

[2] J. A. Cruz-Morales, C. Gutiérrez-Flores, D. Zárate-Saldaña, M. Burelo, H. García-Ortega, and S. Gutiérrez, “Synthetic Polyisoprene Rubber as a Mimic of Natural Rubber: Recent Advances on Synthesis, Nanocomposites, and Applications,” Polymers 15 (2023): 4074.

[3] V. K. Sharma, F. Fortuna, M. Mincarini, M. Berillo, and G. Cornacchia, “Disposal of Waste Tyres for Energy Recovery and Safe Environment,” Applied Energy 65 (2000): 381–394.

[4] D. Cui, Z. Bi, Y. Wang, et al., “Scenario Analysis of Waste Tires from China's Vehicles Future,” Journal of Cleaner Production 478 (2024): 143940.

[5] S. Maroufi, M. Mayyas, and V. Sahajwalla, “Nano-Carbons From Waste Tyre Rubber: An Insight Into Structure and Morphology,” Waste Management 69 (2017): 110–116.

[6] R. D. López-García, A. Maldonado-Reyes, M. M. Reyes-Gallegos, J. A. Rodríguez-García, C. A. Calles-Arriaga, and E. Rocha-Rangel, “Management and Disposal of Waste Tires to Develop a Company for the Manufacture of Products Based on Recycled Rubber in Tamaulipas, México,” Processes 13 (2025): 394.

[7] W. Zhao, J. He, P. Yu, X. Jiang, and L. Zhang, “Recent Progress in the Rubber Antioxidants: A Review,” Polymer Degradation and Stability 207 (2023): 110223.

[8] S. Ramarad, M. Khalid, C. T. Ratnam, A. L. Chuah, and W. Rashmi, “Waste Tire Rubber in Polymer Blends: A Review on the Evolution, Properties and Future,” Progress in Materials Science 72 (2015): 100–140.

[9] A. Kumar, R. J. Dhanorkar, S. Mohanty, and V. K. Gupta, “Advances in Recycling of Waste Vulcanized Rubber Products via Different Sustainable Approaches,” Materials Advances 5 (2024): 7584–7600.

[10] C. Sathiskumar and S. Karthikeyan, “Recycling of Waste Tires and Its Energy Storage Application of by-Products–a Review,” Sustainable Materials and Technologies 22 (2019): e00125.

[11] A. Wik, E. Nilsson, T. Källqvist, A. Tobiesen, and G. Dave, “Toxicity Assessment of Sequential Leachates of Tire Powder Using a Battery of Toxicity Tests and Toxicity Identification Evaluations,” Chemosphere 77 (2009): 922–927.

[12] D. Kumar, Y. Pei, B. Han, et al., “Comparative Analysis of Waste Tyre Treatment Technologies: Environmental and Economic Perspective,” Renewable and Sustainable Energy Reviews 216 (2025): 115691.

[13] Y. Zhang, C. Wu, M. A. Nahil, and P. Williams, “Pyrolysis–Catalytic Reforming/Gasification of Waste Tires for Production of Carbon Nanotubes and Hydrogen,” Energy & Fuels 29 (2015): 3328–3334.

[14] W. A. Laftah and W. A. Wan Abdul Rahman, “A Comprehensive Review of Tire Recycling Technologies and Applications,” Materials Advances 6 (2025): 4992–5010.

[15] L. Bockstal, T. Berchem, Q. Schmetz, and A. Richel, “Devulcanisation and Reclaiming of Tires and Rubber by Physical and Chemical Processes: A Review,” Journal of Cleaner Production 236 (2019): 117574.

[16] K. Formela, “Advances in Lead-Free Flexible Piezoelectric Materials for Energy and Evolving Applications,” Advanced Industrial and Engineering Polymer Research 4 (2021): 209–222.

[17] P. T. Williams, “Pyrolysis of Waste Tyres: A Review,” Waste Management 33 (2013): 1714–1728.

[18] W. Han, D. Han, and H. Chen, “Pyrolysis of Waste Tires: A Review,” Polymers 15 (2023): 1604.

[19] I. F. Elbaba, C. Wu, and P. T. Williams, “Hydrogen Production From the Pyrolysis–Gasification of Waste Tyres With a Nickel/Cerium Catalyst,” International Journal of Hydrogen Energy 36 (2011): 6628–6637.

[20] A. A. Al-Qadri, U. Ahmed, N. Ahmad, A. G. Abdul Jameel, U. Zahid, and S. R. Naqvi, “A Review of Hydrogen Generation Through Gasification and Pyrolysis of Waste Plastic and Tires: Opportunities and Challenges,” International Journal of Hydrogen Energy 77 (2024): 1185–1204.

[21] Y. Zhang, C. Wu, M. A. Nahil, and P. Williams, “High-Value Resource Recovery Products from Waste Tyres,” Proceedings of Institution of Civil Engineers: Waste and Resource Management 169 (2016): 137–145.

[22] Y. Kar, “Catalytic Pyrolysis of Car Tire Waste Using Expanded Perlite,” Waste Management 31 (2011): 1772–1782.

[23] G.-G. Choi, S.-J. Oh, and J.-S. Kim, “Clean Pyrolysis Oil From a Continuous Two-Stage Pyrolysis of Scrap Tires Using In-Situ and Ex-Situ Desulfurization,” Energy 141 (2017): 2234–2241.

[24] M. I. Jahirul, F. M. Hossain, M. G. Rasul, and A. A. Chowdhury, “A Review on the Thermochemical Recycling of Waste Tyres to Oil for Automobile Engine Application,” Energies 14 (2021): 3837.

[25] D. Sutton, B. Kelleher, and J. R. H. Ross, “Review of Literature on Catalysts for Biomass Gasification,” Fuel Processing Technology 73 (2001): 155–173.

[26] M. Zhang, S. Xu, L. Liu, et al., “Investigation of the Sulfur Enrichment Mechanism on the Catalyst in the FCC Process of Waste Tire Pyrolytic Oil,” Journal of the Energy Institute 105 (2022): 309–313.

[27] M. Paradise and T. Goswami, “Carbon Nanotubes—Production and Industrial Applications,” Materials & Design 28 (2007): 1477–1489.

[28] W. Yang, W. J. Sun, W. Chu, C. F. Jiang, and J. Wen, “Synthesis of Carbon Nanotubes Using Scrap Tyre Rubber as Carbon Source,” Chinese Chemical Letters 23 (2012): 363–366.

[29] M. He, S. Zhang, and J. Zhang, “Horizontal Single-Walled Carbon Nanotube Arrays: Controlled Synthesis, Characterizations, and Applications,” Chemical Reviews 120 (2020): 12592–12684.

[30] J. L. Blackburn, T. M. Barnes, M. C. Beard, et al., “Transparent Conductive Single-Walled Carbon Nanotube Networks With Precisely Tunable Ratios of Semiconducting and Metallic Nanotubes,” ACS Nano, 2 (2008): 1266–1274.

[31] J. Z. Wang, L. Lu, M. Lotya, et al., “Development of MoS₂–CNT Composite Thin Film From Layered MoS₂ for Lithium Batteries,” Advanced Energy Materials 3 (2013): 798–805.

[32] M. M. Hamedi, A. Hajian, A. B. Fall, et al., “Highly Conducting, Strong Nanocomposites Based on Nanocellulose-Assisted Aqueous Dispersions of Single-Wall Carbon Nanotubes,” ACS Nano 8 (2014): 2467–2476.

[33] C. Qiu, Z. Zhang, M. Xiao, Y. Yang, D. Zhong, and L. M. Peng, “Scaling Carbon Nanotube Complementary Transistors to 5-nm Gate Lengths,” Science 355 (2017): 271–276.

[34] D. Zhong, Z. Zhang, L. Ding, et al., “Gigahertz Integrated Circuits Based on Carbon Nanotube Films,” Nature Electronics 1 (2018): 40–45.

[35] G. Hong, S. Diao, A. L. Antaris, and H. Dai, “Carbon Nanomaterials for Biological Imaging and Nanomedicinal Therapy,” Chemical Reviews 115 (2015): 10816–10906.

[36] M. He, S. Zhang, Q. Wu, et al., “Designing Catalysts for Chirality-Selective Synthesis of Single-Walled Carbon Nanotubes: Past Success and Future Opportunity,” Advanced Materials 31, (2019): e1800805.

[37] M. He, Y. Magnin, H. Amara, et al., “Linking Growth Mode to Lengths of Single-Walled Carbon Nanotubes,” Carbon 113 (2017): 231–236.

[38] L. P. Ding, B. McLean, Z. Xu, et al., “Why Carbon Nanotubes Grow,” Journal of the American Chemical Society 144 (2022): 5606–5613.

[39] P. V. Sushko, J. L. Gavartin, and A. L. Shluger, “Electronic Properties of Structural Defects at the MgO (001) Surface,” Journal of Physical Chemistry B 106 (2002): 2269–2276.

[40] S. Stankic, M. Müller, O. Diwald, M. Sterrer, E. Knözinger, and J. Bernardi, “Size-Dependent Optical Properties of MgO Nanocubes,” Angewandte Chemie International Edition 44 (2005): 4917–4920.

[41] E. Garrone, A. Zecchina, and F. S. Stone, “An Experimental and Theoretical Evaluation of Surface States in MgO and Other Alkaline Earth Oxides,” Philosophical Magazine B 42 (1980): 683–703.

[42] F. Han, L. Li, L. Qian, et al., “High-Temperature Growth of Chirality-Enriched, Highly Crystalline Carbon Nanotubes for Efficient Single-Chirality Separation,” Advanced Functional Materials 35 (2025): 2419702.

[43] T. Das and G. Deo, “Effects of Metal Loading and Support for Supported Cobalt Catalyst,” Catalysis Today 198 (2012): 116–124.

[44] H. Petitjean, H. Guesmi, H. Lauron-Pernot, et al., “How Surface Hydroxyls Enhance MgO Reactivity in Basic Catalysis: The Case of Methylbutynol Conversion,” ACS Catalysis 4 (2014): 4004–4014.

[45] S. B. Choi, N. W. Kim, D. K. Lee, and H. Yu, “Growth Mechanism of Cubic MgO Granule via Common Ion Effect,” Journal of Nanoscience and Nanotechnology 13 (2013): 7577–7580.

[46] M. C. Biesinger, B. P. Payne, A. P. Grosvenor, L. W. M. Lau, A. R. Gersonb, and R. S. C. Smart, “Resolving Surface Chemical States in XPS Analysis of First Row Transition Metals, Oxides and Hydroxides: Cr, Mn, Fe, Co and Ni,” Applied Surface Science 257 (2021): 2717–2730.

[47] M. He, Y. Magnin, H. Jiang, et al., “Growth Modes and Chiral Selectivity of Single-Walled Carbon Nanotubes,” Nanoscale 10 (2018): 6744–6750.

[48] Q. Wu, X. Zhang, H. An, et al., “Selective Growth of (5, 4) Single-Walled Carbon Nanotubes,” Science Bulletin (forthcoming): S2095-9273(25)00761-3.

[49] M. S. Dresselhaus, G. Dresselhaus, R. Saito, and A. Jorio, “Raman Spectroscopy of Carbon Nanotubes,” Physics Reports 409 (2005): 47–99.

[50] M. He, A. I. Chernov, P. V. Fedotov, et al., “Predominant (6,5) Single-Walled Carbon Nanotube Growth on a Copper-Promoted Iron Catalyst,” Journal of the American Chemical Society 132 (2010): 13994–13996.

[51] M. He, A. I. Chernov, E. D. Obraztsova, et al., “Low Temperature Growth of SWNTs on a Nickel Catalyst by Thermal Chemical Vapor Deposition,” Nano Research 4 (2011): 334–342.

[52] V. I. Artyukhov, E. S. Penev, and B. I. Yakobson, “Why Nanotubes Grow Chiral,” Nature Communications 5 (2014): 4892.

[53] M. He, X. Wang, S. Zhang, et al., “Growth Kinetics of Single-Walled Carbon Nanotubes With a (2 n, n) Chirality Selection,” Science Advances 5 (2019): eaav9668.

[54] L. Zhang, M. He, T. W. Hansen, et al., “Growth Termination and Multiple Nucleation of Single-Wall Carbon Nanotubes Evidenced by In Situ Transmission Electron Microscopy,” ACS Nano 11 (2017): 4483–4493.

[55] H. Wang, L. Wei, F. Ren, et al., “Chiral-Selective CoSO₄/SiO₂ Catalyst for (9,8) Single-Walled Carbon Nanotube Growth,” ACS Nano 7 (2013): 614–626.

[56] L. Zhang, P. X. Hou, S. Li, et al., “In Situ TEM Observations on the Sulfur-Assisted Catalytic Growth of Single-Wall Carbon Nanotubes,” Journal of Physical Chemistry Letters 5 (2014): 1427–1432.

[57] B. Yu, C. Liu, P. X. Hou, et al., “Bulk Synthesis of Large Diameter Semiconducting Single-Walled Carbon Nanotubes by Oxygen-Assisted Floating Catalyst Chemical Vapor Deposition,” Journal of the American Chemical Society 133 (2011): 5232–5235.

[58] G. Sun, J. Kürti, P. Rajczy, M. Kertesz, J. Hafner, and G. Kresse. “Performance of the Vienna Ab Initio Simulation Package (VASP) in Chemical Applications,” Journal of Molecular Structure: THEOCHEM 624 (2008): 37–45.

[59] J. P. Perdew, K. Burke, and M. Ernzerhof, “Generalized Gradient Approximation Made Simple,” Physical Review Letters 77 (1996): 3865–3868.

[60] G. Kresse and D. Joubert, “From Ultrasoft Pseudopotentials to the Projector Augmented-Wave Method,” Physical Review B 59 (1999): 1758–1775.

[61] P. E. Blöchl, “Projector Augmented-Wave Method,” Physical Review B 50 (1994): 17953–17979.

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