The 13th Global Conference on Polymer and Composite Materials (PCM 2026)

Abstract: Low-grade waste heat from solar radiation and industrial processes drives the development of ionic thermoelectric (i-TE) technologies that directly convert heat into electricity. Here, we report lignin-derived hydrogels as sustainable, eco-friendly i-TE materials and demonstrate a green synthesis approach to fabricate p-type and n-type components for efficient waste-heat harvesting. The crosslinked hydrogel infiltrated with 6 M KOH electrolyte exhibits p-type behavior with exceptional ionic conductivity of 226.5 mS cm⁻¹, and superior Seebeck coefficient of 13 mV K⁻¹. To enhance device efficiency and reliability, we optimized n-type performance through amine functionalization; the functionalized hydrogel infiltrated with 1 M KCl electrolyte shows a negative ionic thermopower of −7.48 mV K⁻¹ and high ionic conductivity of 39.9 mS cm⁻¹, yielding an exceptional power factor of 223.52 μW m⁻¹ K⁻². Further enhancement was achieved by integrating lignin with alginate; when infiltrated with CaCl₂ electrolyte, this composite demonstrates a remarkable negative Seebeck coefficient of −13.92 mV K⁻¹ and power factor of 876.34 μW m⁻¹ K⁻². This work highlights the immense potential of lignin-derived hydrogels for low-grade waste energy harvesting, providing a facile and scalable method for optimizing both n-type and p-type thermoelectric components and enhancing the structural and electrical reliability of high-performance n–p junctions.

Keywords: Lignin-derived hydrogel, Ionic thermoelectric material, Seebeck coefficient, p-type material, n-type material

Acknowledgements: This research was supported through the grant PID2024-160385OB-C21 funded by Ministerio de Ciencia, Innovación y Universidades MCIN/AEI/10.13039/501100011033. It also supported by Santiago Grisolia program CIGRIS/2022/132 funded by the Generalitat Valenciana.

Biography: Dr. Culebras is an Associate Professor at the University of Valencia, where he earned his PhD in Chemistry in 2017. His research focuses on organic thermoelectric materials and lignin valorization, achieving efficiency improvements of up to 1000-fold and leading to high-impact publications and patents. He has authored over 100 papers with more than 4,000 citations and has held research stays at Texas A&M University, the Max Planck Institute, and the University of Limerick. He has led and contributed to multiple national, European, and industry-funded projects, serving as Principal Investigator. Recognized with awards such as the SUSCHEM-2020 Young Researcher Award and the IRC GOI Fellowship, he has supervised numerous graduate students and collaborated with industry as a technology consultant. He also serves as a reviewer and evaluator for top journals and funding agencies across Europe and Latin America.