Enhancement of thermoelectric performance and mechanical reliability in electrodeposited chitosan nanofiber-bismuth telluride nanocomposite

Abstract

Thermoelectric generators (TEGs) offer a promising route for converting waste heat into electrical energy; however, the practical implementation of high-performance micro-TEGs (μTEGs) is limited by the material performance and mechanical fragility of thick bismuth telluride (Bi2Te3) films. Although thick thermoelectric layers are required to sustain sufficient temperature gradients, conventional fabrication often induces residual stress, leading to cracking and structural failure. In this work, we introduce a sustainable synthesis strategy by incorporating bio-derived chitosan nanofibers (ChNFs) into the electrodeposition process. The amino and hydroxyl functional groups of ChNFs promote interfacial bonding and nucleation, enabling the rapid growth of dense, crack-free composite films with thicknesses up to 1000 μm. The introduction of ChNFs also creates abundant phonon-scattering interfaces, significantly reducing lattice thermal conductivity from 1.48 to 0.29 W m−1 K−1 and resulting in a 303% increase in the room-temperature figure of merit (ZT), from 0.12 to 0.50. At an optimal loading of 0.0123 wt%, the composite films exhibit a 15% increase in hardness while maintaining structural integrity. These results demonstrate a multifunctional materials design strategy that simultaneously enhances thermoelectric performance, mechanical robustness, and fabrication scalability. The ChNF–Bi2Te3 nanocomposites provide a viable green pathway for developing reliable thick films for next-generation self-powered electronics and compact waste-heat harvesting systems.