Boosting Thermoelectric Properties of Carbon Nanotubes by Biomass Lignin for Efficient Energy Conversion and Temperature Sensing Applications

Despite carbon nanotubes (CNTs) having been extensively investigated as promising thermoelectric (TE) materials, a trade-off relationship between electrical conductivity and the Seebeck coefficient greatly impedes the enhancement of their TE efficiency. Herein, we propose a facile approach to boost the TE performance of CNTs composites, in which biomass lignin is directly incorporated into the highly conducting CNTs matrix prepared by 1-methyl-2-pyrrolidone assisted ultrasonication. Ascribing to π–π interaction between CNTs and lignin, CNTs are homogeneously distributed with an interconnected conducting network. Both the highly conductive network and energy filtering effect at the interfaces contribute to a remarkably increased Seebeck coefficient along with a moderate conductivity. Upon optimizing lignin content to 4.7 wt %, the power factor of CNTs/lignin composite films was dramatically improved to 487.1 ± 18.6 μW m–1 K–2 with a high conductivity of 3978 ± 184 S cm–1, much higher than 214.6 ± 22.9 μW m–1K–2 of neat CNTs films. Moreover, the CNTs/lignin film-based flexible thermoelectric device exhibits notable output performance and temperature monitoring capability. This study not only represents a facile strategy for boosting the TE efficiency of CNTs-based materials but also demonstrates the great potential of biomass lignin for thermoelectric applications.