Scalable and environmentally friendly MXene-tetrahedrites for next-generation flexible thermoelectrics

Traditional thermoelectric generators (TEGs) face scalability challenges due to high-temperature, long-duration curing processes and rare-earth/toxic chalcogenides such as bismuth telluride. Additive manufacturing has been investigated as a more time-, energy- and cost-efficient method that offers greater flexibility than traditional manufacturing techniques. Additionally, tetrahedrites are promising thermoelectric materials in high-temperature applications because they are non-toxic and earth-abundant. Herein, this work demonstrates the fabrication of scalable and sustainable Cu₁₂Sb₄S₁₃ (CAS) based composite films and flexible TEG devices (f-TEGs) with 2D MXene nanosheets using a low-thermal budget additive manufacturing approach for room temperature applications. 2D MXene nanosheets introduced energy-barrier scattering and nanoscale features to effectively increase the room-temperature ZT to 0.22, 10% higher than bulk CAS, by decoupling electrical conductivity, Seebeck coefficient, and thermal conductivity. CAS and 2D MXenes were found to be environmentally safe through a bacterial viability study. The process is used to create a 5-leg f-TEG device producing a power of 5.3 μW and a power density of 140 μW cm⁻² at a ΔT of 25 K. Therefore, this work demonstrates that combining scalable and sustainable materials and methods is an effective strategy for high-performance room-temperature f-TEGs that could potentially harvest the low waste heat energy of the human body.