Revolutionizing Thermal Energy Harvesting: Bio-Flex Gel Empowered by Deep Eutectic Solvent with Exceptional Thermopower and Electromagnetic Wave Absorption

Abstract

The efficient utilization of low-grade and abundant thermal sources using thermoelectric (TE) materials plays a pivotal role in enhancing the efficacy of environmental heat and energy collection and utilization. In light of sustainable development principles and capitalizing on the low thermal conductivity of biomass materials, a novel approach was proposed to integrate a green solvent (deep eutectic solvent, DES) with a bio-based nano-fiber (cellulose nanofibril, CNF) using a co-solvent evaporation method, aiming to fabricate a high-performance TE gel that exhibits excellent flexibility, mechanical properties, and scalability. Significant TE performance is realized, resulting in a high Seebeck coefficient (23.03 mV K-1) and impressive ionic conductivity (33.90 mS cm-1) at room temperature under 70% humidity. Furthermore, the incorporation of MXene demonstrates an impressive 34.3 dB electromagnetic interference (EMI) shielding efficiency, effectively safeguarding TE materials against adverse effects of external EMI during usage. Meanwhile, the gel, enriched with tannic acid, Cu ions, and MXene, ensures lasting antibacterial effectiveness, thereby mitigating bacterial attacks on the cellulose-based scaffold, which pose a significant risk of performance degradation. This study establishes a novel design pathway for the development and versatile application of high-performance, environmentally friendly, and robust TE materials.

Keywords: DES gel, Bio-derived material, Thermopower, Thermoelectrics, Energy absorption