N, S co-doped composite carbon aerogel derived from konjac glucomannan/fucoidan/nitrogen-enriched carbon nanotubes as electrode materials for capacitive deionization

Abstract

Natural polysaccharides derived carbon aerogels possess multiple advantages, including diverse sources, inherent heteroatom doping, abundant functional groups, and unique primitive biological channels, rendering them suitable as electrode materials in capacitive deionization (CDI). In this work, we construct a novel N, S co-doped composite carbon aerogel (FuKNCA- y) derived from konjac glucomannan (KGM)/fucoidan (Fu)/nitrogen-enriched carbon nanotubes (N-CNTs) via directional freezing method. Among them, KGM serves as both the carbon source and structural matrix, Fu acts as the S source and a secondary component, while N-CNTs provide rich N source and optimize the pore structure, significantly boosting the overall electrical conductivity. The synthesized FuKNCA- y exhibits a large specific surface area, a hierarchical porous structure, excellent mechanical properties, and N, S co-doping. These characteristics collectively improve its hydrophilicity, increase active sites, modulate the electronic structure, and ultimately lead to the improved desalination performance. Specifically, the optimal FuKNCA-6 electrode achieves a salt adsorption capacity of 32.8 mg g⁻¹ and an average salt adsorption rate of 4.02 mg g⁻¹ min⁻¹ (500 mg L⁻¹ NaCl solution and 1.2 V), with superior cycling stability. Density functional theory calculations reveal the underlying enhancement mechanism of N, S co-doping and its significant synergistic effect on CDI performance. Therefore, this work provides a new method for synthesizing advanced heteroatom-doped carbon aerogels derived from natural polysaccharides for high-performance CDI electrodes.

Keywords

Konjac glucomannan / Fucoidan / Carbon aerogels / Capacitive deionization

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

CRediT authorship contribution statement

Shaojun Liu: Writing – original draft, Formal analysis, Data curation. Jing Zhang: Writing – review & editing, Supervision. Guoran Liu: Investigation, Data curation. Xiaochan Liu: Formal analysis. Shimo Yu: Methodology. Zhipeng Yuan: Formal analysis. Xinfu Zhao: Methodology. Sijia Liu: Investigation. Kunmeng Zhu: Data curation. Xibin Yi: Supervision. Serguei Filatov: Supervision.

Acknowledgements

This work is supported by the Key Research and Development Plan of Shandong Province (2024TSGC0193, 2023TSGC0706, 2024TSGC0753), Natural Science Foundation of Shandong Province (ZR2023ME033), Science-Education-Industry Integration Innovation Pilot Project of Qilu University of Technology (2024GH09), Collaborative Innovation Center for Green Low-Carbon Materials of the Yellow River Basin for Ecological Conservation and High-Quality Development.

References

[1] K.J. Yang, T.T. Pan, N. Farhat, A.I. Felix, R.E. Waller, P.Y. Hong, J.S. Vrouwenvelder, Q.Q. Gan, Y. Han, A solar-driven atmospheric water extractor for off-grid freshwater generation and irrigation, Nat. Commun. 15 (2024) 6260, doi: 10.1038/s41467-024-50715-0.

[2] D. Li, R.M. DeConto, D. Pollard, Y.Y. Hu, Competing climate feedbacks of ice sheet freshwater discharge in a warming world, Nat. Commun. 15 (2024) 5178, doi: 10.1038/s41467-024-49604-3.

[3] J.B. Li, R.X. Wang, L.L. Han, T.Y. Wang, Y. Asakura, C.Y. Wang, X.T. Xu, Y. Yamauchi, Unveiling the neglected role of oxygen doping in nitrogen-doped carbon for enhanced capacitive deionization performance, Nat. Commun. 16 (2025) 1996, doi: 10.1038/s41467-025-56694-0.

[4] J. Landon, X. Gao, A. Omosebi, K.L. Liu, Progress and outlook for capacitive deionization technology, Curr. Opin. Chem. Eng. 25 (2019) 1-8, doi: 10.1016/j.coche.2019.06.006.

[5] K.X. Tang, T.Z.X. Hong, L.M. You, K. Zhou, Carbon-metal compound composite electrodes for capacitive deionization: synthesis, development and applications, J. Mater. Chem. A 7 (2019) 26693-26743, doi: 10.1039/C9TA08663C.

[6] R. Paula, S. Matthew E, K. Friedrich, B. François, Carbon electrodes for capacitive technologies, Energy Storage Mater. 16 (2019) 126-145, doi: 10.1016/j.ensm.2018.04.031.

[7] E. Joyce, J. Yusufu Abeid Chande, M. Revocatus Lazaro, K.Talam Enock, Porous carbon derived from Artocarpus heterophyllus peels for capacitive deionization electrodes, Carbon 147 (2019) 582-593, doi: 10.1016/j.carbon.2019.03.036.

[8] G.X. Huang, Q.H. Geng, W.W. Kang, Y.B. Liu, Y.Y. Li, B.L. Xing, Q.R. Liu, C.X. Zhang, Hierarchical porous carbon with optimized mesopore structure and nitrogen doping for supercapacitor electrodes, Micropor. Mesopor. Mat. 288 (2019) 109576, doi: 10.1016/j.micromeso.2019.109576.

[9] Y. Sun, S. Xue, J.H. Sun, X.X. Li, Y.C. Ou, B.H. Zhu, M. Demir, Silk-derived nitrogen-doped porous carbon electrodes with enhanced ionic conductivity for high-performance supercapacitors, J. Colloid Interface Sci. 645 (2023) 297-305, doi: 10.1016/j.jcis.2023.04.130.

[10] Q.S. Huang, L. Sheng, T. Wu, L. Huang, J. Yan, M. Li, Z.X. Chen, H.G. Zhang, Research progress on the application of carbon-based composites in capacitive deionization technology, Desalination 593 (2025) 118197, doi: 10.1016/j.desal.2024.118197.

[11] L.W. Miao, Z. Wang, J. Peng, W.Y. Deng, W.Q. Chen, Q.Z. Dai, T. Ueyama, Pseudocapacitive deionization with polypyrrole grafted CMC carbon aerogel electrodes, Sep. Purif. Technol. 296 (2022) 121441, doi: 10.1016/j.seppur.2022.121441.

[12] C.C. Ding, X.D. Wang, P. Huang, J. Yuan, Nitrogen-doped carbon aerogels derived from polyimide for high-performance supercapacitor, J. Mater. Sci. 57 (2022) 21680-21692, doi: 10.1007/s10853-022-07986-z.

[13] M.J. Chang, W.Y. Zhu, F.R. Ni, H. Wang, X. Li, L.Q. Yang, H.L. Li, J. Liu, Controllable synthesis of phenolic resin-based carbon aerogel templated by graphene oxide for high-performance supercapacitors, Colloids Surf., A 681 (2024) 132736, doi: 10.1016/j.colsurfa.2023.132736.

[14] X. Yang, B.H. Fei, J.F. Ma, X.G. Liu, S.M. Yang, G.L. Tian, Z.H. Jiang, Porous nanoplatelets wrapped carbon aerogels by pyrolysis of regenerated bamboo cellulose aerogels as supercapacitor electrodes, Carbohydr. Polym. 180 (2018) 385-392, doi: 10.1016/j.carbpol.2017.10.013.

[15] L. Wang, Q. Wu, B.Z. Zhao, Z.L. Li, Y.H. Zhang, L. Huang, S.T. Yu, Multi-functionalized carbon aerogels derived from chitosan, J. Colloid Interface Sci. 605 (2022) 790-802, doi: 10.1016/j.jcis.2021.07.132.

[16] K.J. Xie, X. Liu, H.L. Li, L. Fang, K. Xia, D.J. Yang, Y.H. Zhou, X.D. Zhang, Heteroatom tuning in agarose derived carbon aerogel for enhanced potassium ion multiple energy storage, Carbon Energy 6 (2024) e427, doi: 10.1002/cey2.427.

[17] Z.Z. Zhai, S.S. Wang, Y.L. Xu, L.H. Zhang, X.L. Wang, H.T. Yu, B. Ren, Starch-based carbon aerogels prepared by an innovative KOH activation method for supercapacitors, Int. J. Biol. Macromol. 257 (2024) 128587, doi: 10.1016/j.ijbiomac.2023.128587.

[18] C.M. Wang, P. Zhu, Z. Huang, L. Zhang, S.A. Xie, Z.Y. Qi, Carboxymethylcellulose sodium-derived carbon aerogels for solar-driven water purification, Chemosphere 358 (2024) 142109, doi: 10.1016/j.chemosphere.2024.142109.

[19] Y.P. Hao, W.P. Zheng, Z.Y. Sun, D.M. Zhang, K.Y. Sui, P.L. Shen, P.F. Li, Q.H. Zhou, Marine polysaccharide-based composite hydrogels containing fucoidan: Preparation, physicochemical characterization, and biocompatible evaluation, Int. J. Biol. Macromol. 183 (2021) 1978-1986, doi: 10.1016/j.ijbiomac.2021.05.190.

[20] W.L. Wang, Y. Fang, X.W. Ni, K. Wu, Y.X. Wang, F.T. Jiang, S.B. Riffat, Fabrication and characterization of a novel konjac glucomannan-based air filtration aerogels strengthened by wheat straw and okara, Carbohydr. Polym. 224 (2019) 115129, doi: 10.1016/j.carbpol.2019.115129.

[21] K. Liu, R.W. Mo, W.J. Dong, W. Zhao, F.Q. Huang, Nature-derived, structure and function integrated ultra-thick carbon electrode for high-performance supercapacitors, J. Mater. Chem. A 8 (2020) 20072-20081, doi: 10.1039/D0TA06108E.

[22] X.J. Liu, H. Liu, M.J. Mi, W.Q. Kong, Y.J. Ge, J.W. Hu, Nitrogen-doped hierarchical porous carbon aerogel for high-performance capacitive deionization, Sep. Purif. Technol. 224 (2019) 44-50, doi: 10.1016/j.seppur.2019.05.010.

[23] Q.L. Liu, S.H. Bi, X.T. Xu, X.C. Xiao, Y. Lei, N, O-codoped carbon aerogel electrode improves capacitive deionization performance, J. Colloid Interface Sci. 680 (2025) 54-63, doi: 10.1016/j.jcis.2024.10.184.

[24] L. Ratcliffe, P.A. Williams, C. Viebke, J. Meadows, Physicochemical characterization of konjac glucomannan, Biomacromolecules 6 (2005) 1977-1986, doi: 10.1021/bm0492226.

[25] J.Q. Sun, M.G. Shang, M.N. Zhang, S.M. Yu, Z.P. Yuan, X.B. Yi, S. Filatov, J. Zhang, Konjac glucomannan/cellulose nanofibers composite aerogel supported HKUST-1 for CO₂ adsorption , Carbohydr. Polym. 293 (2022) 119720, doi: 10.1016/j.carbpol.2022.119720.

[26] R.X. Wang, H.H. Dong, X.Y. Li, L. Zhou, W.K. Zhu, T. Chen, Biomass encapsulated ZIF-8-derived ZnO carbon aerogels for efficient uranium extraction by synergistic adsorption-photoreduction, Chem. Eng. J. 478 (2023) 147331, doi: 10.1016/j.cej.2023.147331.

[27] T. Chen, M.X. Li, L. Zhou, X.B. Ding, D.J. Lin, T. Duan, G.C. Yang, R. He, W.K. Zhu, Bio-inspired biomass-derived carbon aerogels with superior mechanical property for oil-water separation, ACS Sustainable Chem. Eng. 8 (2020) 6458-6465, doi: 10.1021/acssuschemeng.0c00910.

[28] K. Chen, G.J. Xu, R.M. Tian, J. Jiang, Y. Kuang, K. Wu, F.T. Jiang, Characterizations and great application potential for air filtration of konjac glucomannan/curdlan aerogels, Ind. Crop. Prod. 195 (2023) 116462, doi: 10.1016/j.indcrop.2023.116462.

[29] X. Yang, A.Q. Li, D. Li, P.Y. Li, L.J. Sun, Y.R. Guo, Improved physical properties of konjac glucomannan gels by co-incubating composite konjac glucomannan/xanthan systems under alkaline conditions, Food Hydrocolloids 106 (2020) 105870, doi: 10.1016/j.foodhyd.2020.105870.

[30] A. Muhamad Nur Ghoyatul, M. Petra, R. Thomas, B. Stefan, Refined linkage analysis of the sulphated marine polysaccharide fucoidan of Cladosiphon okamuranus with a focus on fucose, Carbohydr. Polym. 342 (2024) 122302, doi: 10.1016/j.carbpol.2024.122302.

[31] A.S. Silchenko, A.B. Rasin, M.I. Kusaykin, O.S. Malyarenko, N.M. Shevchenko, A.O. Zueva, A.I. Kalinovsky, T.N. Zvyagintseva, Ermakova, Modification of native fucoidan from Fucus evanescens by recombinant fucoidanase from marine bacteria Formosa algae, Carbohydr. Polym. 193 (2018) 189-195, doi: 10.1016/j.carbpol.2018.03.094.

[32] Y.F. Zheng, K.M. Chen, K.P. Jiang, F.R. Zhang, G.S. Zhu, H.R. Xu, Progress of synthetic strategies and properties of heteroatoms-doped (N, P, S, O) carbon materials for supercapacitors, J. Energy Storage 56 (2022) 105995, doi: 10.1016/j.est.2022.105995.

[33] L.X. Zhang, Q. Sun, Teng S, C.L. Wang, Y.Z. Yang, MOF-derived 3D porous carbon aerogels as an efficient adsorbent for toluene in humid air, J. Environ. Chem. Eng. 9 (6) 106722. https://doi.org/10.1016/j.jece.2021.106722.

[34] Z.P. Zhang, X.S. Shi, X.Y. Wang, Z. Zhang, Y. Wang, Encapsulating covalent organic frameworks (COFs) in cellulose aerogels for efficient iodine uptake, Sep. Purif. Technol. 309 (2023) 123108, doi: 10.1016/j.seppur.2023.123108.

[35] C.B. Liang, H. Qiu, P. Song, X.T. Shi, J. Kong, J.W. Gu, Ultra-light MXene aerogel/wood-derived porous carbon composites with wall-like “mortar/brick” structures for electromagnetic interference shielding, Sci. Bull. 65 (2020) 616-622, doi: 10.1016/j.scib.2020.02.009.

[36] M.T. Shuang, L.G. Liu, X.D. Li, L.M. Zhou, J.F. Li, Z.C. Zhong, J.H. Li, Z. Yang, A.M. Elgarahy, K.Z. Elwakeel, J.B. Ouyang, Fabrication of polyaniline-modified CNT/CS carbon aerogel composite electrode and its electrosorption performance of uranium, Sep. Purif. Technol. 377 (2025) 134296, doi: 10.1016/j.seppur.2025.134296.

[37] P. Li, W.Y. Wang, F.Y. Su, X.Y. Wang, X.L. Zhang, X.C. Zheng, N-doped interconnected porous graphene as advanced electrode material for supercapacitors, J. Alloy. Compd. 893 (2022) 162218, doi: 10.1016/j.jallcom.2021.162218.

[38] M.-T. Golmakani, E. Zamansani, M.M. Hajjari, M. Moosavi-Nasab, M. Niakousari, Curcumin-loaded gelatin/fucoidan electrospun composite: Physicochemical characterization and antioxidative application, Food Chem. X 27 (2025) 102495, doi: 10.1016/j.fochx.2025.102495.

[39] S. Wu, X.T. Yan, X. Sun, S. Tian, J.J. Wang, C.Y. Liu, S.Q. Sun, L. Wu, X.F. Zhao, Q.L. Yang, S, N co-doped porous carbon materials for high performance supercapacitor, J. Energy Storage 71 (2023) 108152, doi: 10.1016/j.est.2023.108152.

[40] J.Q. Yang, X.L. Zhou, D.H. Wu, X.D. Zhao, Z. Zhou, S-doped N-rich carbon nanosheets with expanded interlayer distance as anode materials for sodium-ion batteries, Adv. Mater. 29 (2016) 1604180, doi: 10.1002/adma.201604108.

[41] W.J. Yu, J. Wang, F. Liu, Y.X. Cao, B.C. Deng, J. Li, H. Xie, J.F. Zhang, H. Tong, C.P. Liang, Self-supporting heteroatomic S/N co-doped carbon scaffold for robust lithium metal anodes, Carbon 236 (2025) 120106, doi: 10.1016/j.carbon.2025.120106.

[42] R. Chen, X.Y. Deng, C. Wang, J.Y. Du, Z.W. Zhao, W.X. Shi, W.X. Liu, J. Liu, F.Y. Cui, A newly designed graphite-polyaniline composite current collector to enhance the performance of flow electrode capacitive deionization, Chem. Eng. J. 435 (2022) 134845, doi: 10.1016/j.cej.2022.134845.

[43] J. Jiang, M.Y. Wang, W.L. Zhao, H.H. Liu, Y. Wang, P. Song, Z. Wang, Hierarchical porous carbon materials derived from N, O, S-containing bio-based polybenzoxazine for supercapacitors, Eur. Polym. J. 191 (2023) 112045, doi: 10.1016/j.eurpolymj.2023.112054.

[44] Z.J. Cui, H.H. Wang, C.L. Li, W.C. Peng, J.P. Liu, Synergy of structural engineering and dual-heteroatoms co-doping engineering boosting porous carbon toward efficient capacitive deionization, Desalination 572 (2024) 117122, doi: 10.1016/j.desal.2023.117122.

[45] W.T. Yang, J.W. Sun, D.Y. Liu, W.W. Fu, Y.B. Dong, Y.Q. Fu, Y.F. Zhu, Rational design of hierarchical structure of carbon@polyaniline composite with enhanced microwave absorption properties, Carbon 194 (2022) 114-126, doi: 10.1016/j.carbon.2022.03.061.

[46] G.J. Mu, C. Ma, X.J. Liu, W.M. Qiao, J.T. Wang, L.C. Ling, Construction of mesoporous carbon microsphere/polyaniline composites as high performance pseudocapacitive electrodes, J. Colloid Interface Sci. 573 (2020) 45-54, doi: 10.1016/j.jcis.2020.03.085.

[47] Y.J. Hu, X. Tong, H. Zhuo, L.X. Zhong, X.W. Peng, Biomass-based porous N-self-doped carbon framework/polyaniline composite with outstanding supercapacitance, ACS Sustainable Chem. Eng. 5 (2017) 8663-8674, doi: 10.1021/acssuschemeng.7b01380.

[48] L.J. Gao, S.Y. Liu, Q. Dong, C. Hu, J.S. Qiu, Sulfur & nitrogen co-doped electrospun carbon nanofibers as freestanding electrodes for membrane capacitive deionization, Sep. Purif. Technol. 295 (2022) 121280, doi: 10.1016/j.seppur.2022.121280.

[49] T. Wang, Y.J. He, Z.J. Zhao, Z.H. Zhao, X.C. Guo, S.Y. Lu, L. Zhang, Disclosing the intrinsic nature of efficient removal of antibiotics in N/S dual-doped porous carbon-based materials: The manipulation of internal electric field, Chemosphere 355 (2024) 141788, doi: 10.1016/j.chemosphere.2024.141788.

[50] M.N. Fan, Z.H. Lin, P. Zhang, X.D. Ma, K.P. Wu, M.L. Liu, X.H. Xiong, Synergistic effect of nitrogen and sulfur dual-doping endows TiO₂ with exceptional sodium storage performance , Adv. Energy Mater. 11 (2021) 2003037, doi: 10.1002/aenm.202003037.

[51] T.T. Yan, J. Liu, H. Lei, L.Y. Shi, Z.X. An, H.S. Park, D.S. Zhang, Capacitive deionization of saline water using sandwich-like nitrogen-doped graphene composites via a self-assembling strategy, Environ. Sci: Nano 5 (2018) 2722-2730, doi: 10.1039/C8EN00629F.

[52] L. Tao, Y.P. Yang, H.L. Wang, Y.L. Zheng, H.C. Hao, W.P. Song, J. Shi, M.H. Huang, D. Mitlin, Sulfur-nitrogen rich carbon as stable high capacity potassium ion battery anode: Performance and storage mechanisms, Energy Storage Mater. 27 (2020) 212-225, doi: 10.1016/j.ensm.2020.02.004.

[53] K. Lu, H.Y. Jing, H.J. Jia, H. Qiang, F.Y. Wang, M.X. Shi, M.Z. Xia, Defect-rich N, S co-doped porous carbon with hierarchical channel network for ultrafast capacitive deionization, J. Colloid Interface Sci. 679 (2025) 262-272, doi: 10.1016/j.jcis.2024.09.241.

[54] Y.M. Qin, M.Y. Guo, S.F. Fang, L.P. Guo, H.P. Zhang, L.Y. Qi, B.L. Deng, H.F. Bao, Large-scale synthesis of N, S codoped carbon-modified Fe_0.975S composites as a novel anode for lithium/sodium ion batteries with enhanced performance , Nano Lett. 24 (2024) 11385-11392, doi: 10.1021/acs.nanolett.4c01912.

[55] G. Yi, Y.C. Lu, B.S. Zhang, Y.W. Wang, Z. Wei, J.M. Yang, J.Y. Liu, Constructing 3D hierarchical porous carbon networks via N, B co-doping and pore engineering for enhanced capacitive deionization, Desalination 601 (2025) 118591, doi: 10.1016/j.desal.2025.118591.

[56] Y.W. Jiang, Z.Y. Shen, Z.Y. Liu, H. Gong, B. Chen, Y.Y. Su, J.H. Zhou, X. Fei, Y. Li, Biomimetic biomass-based composite carbon aerogels with excellent mechanical performance for energy storage and pressure sensing in extreme environments, J. Colloid Interface Sci. 683 (2025) 786-798, doi: 10.1016/j.jcis.2024.12.051.

[57] H. Deng, Z.Q. Wang, M.J. Kim, Y. Yamauchi, S.J. Eichhorn, M.M. Titirici, L.B. Deng, Unleashing the power of capacitive deionization: Advancing ion removal with biomass-derived porous carbonaceous electrodes, Nano Energy 117 (2023) 108914, doi: 10.1016/j.nanoen.2023.108914.

[58] Y. Qiu, C.J. Zhang, R. Zhang, Z.Y. Liu, H.Z. Yang, S. Qi, Y.Z. Hou, G.W. Wen, J.L. Liu, D. Wang, Integration of pore structure modulation and B, N co-doping for enhanced capacitance deionization of biomass-derived carbon, Green Energy Environ. 8 (2023) 1488-1500, doi: 10.1016/j.gee.2023.01.005.

[59] M. Gao, W.Q. Chen, Engineering strategies toward electrodes stabilization in capacitive deionization, Coord. Chem. Rev. 505 (2024) 215695, doi: 10.1016/j.ccr.2024.215695.

[60] B.C. Qi, W.H. Chen, J. Zhang, W.Y. Xie, D.Y. Qian, Z.J. Yi, H.Z. Ma, Green dual-organic salt activation synthesis of hierarchical N, S co-doping artificial humic acid-derived porous carbon toward superior cadmium capture in asymmetric capacitive deionization, J. Environ. Manage. 392 (2025) 126681, doi: 10.1016/j.jenvman.2025.126881.