Biomimetic CsCl:EG/PVA–NaOH eutectogels for high-performance ionic thermoelectrics and sustainable low-grade heat harvesting

Funding Sponsor

American University in Cairo

Author's Department

Physics Department

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https://doi.org/10.1039/d5se01406a

All Authors

Moustafa I.M. Abdelaziz Shadi A.S. Eldib Ghada E. Khedr Nageh K. Allam

Document Type

Research Article

Publication Title

Sustainable Energy and Fuels

Publication Date

1-1-2025

doi

10.1039/d5se01406a

Abstract

Developing efficient and flexible ionic thermoelectric (i-TE) materials is essential for converting low-grade waste heat into usable electrical energy. In this study, we present a new biomimetic strategy for designing high-performance eutectogels that integrate a cesium chloride–ethylene glycol deep eutectic solvent (CsCl:EG DES) with a poly(vinyl alcohol) (PVA)–sodium hydroxide (NaOH) polymer matrix. The resulting CsCl:EG/PVA–NaOH eutectogel exhibits outstanding thermoelectric performance, achieving a record-high Seebeck coefficient of 1.65 mV K−1at 355 K, significantly surpassing previously reported PVA/NaOH hydrogels and marking the first successful demonstration of thermoelectric operation in the CsCl–EG system. Comprehensive structural and morphological characterization using FTIR, SEM, and EDX confirms the formation of a robust, well-developed bicontinuous network in which CsCl:EG domains are uniformly distributed within the crosslinked PVA matrix. This architecture enables p-type thermoelectric behavior, where directional ionic transport of Na+, Cs+, Cl−, and OH−ions through interconnected percolation pathways is driven by a thermal gradient. Complementary molecular dynamics simulations (GROMACS) further validate the experimental findings, predicting a Seebeck coefficient of 2.06 mV K−1within the 298–358 K range. The simulations elucidate that the strong hydrogen-bonding network and the presence of multiple mobile ion species facilitate efficient thermodiffusion while maintaining low phonon transport. The synergistic combination of engineered ionic migration channels and phonon-scattering interfaces yields an optimal balance between a high Seebeck coefficient and low thermal conductivity. These features make the CsCl:EG/PVA–NaOH eutectogel a promising candidate for flexible, sustainable thermoelectric devices capable of harvesting low-grade waste heat under ambient conditions.

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