Synergistic enhancement of thermoelectric properties in carbon nanotube networks via biomass lignin.

Despite interconnected uniform carbon nanotubes (CNTs) networks can lead to ultrahigh electrical conductivity, the concomitant relatively low Seebeck coefficient results in an inferior thermoelectric (TE) power factor due to the typical trade-off relationship between electrical conductivity and Seebeck coefficient. Herein, we present a facile approach to enhance the TE performance of CNT composites by embedding lignin into highly conductive CNT network via a dip-coating approach. The energy filtering effect at the CNTs/lignin interfaces enables a significant improvement in the Seebeck coefficient. Concurrently, the preservation of the CNTs conductive network structure ensures continuous pathways for carrier transport, thereby maintaining a moderate magnitude of electrical conductivity despite the incorporation of insulating lignin. Through systematic optimization of lignin concentration and soaking duration, a maximum power factor of 550.5 μW m K is achieved for the CNTs/lignin composite prepared with a 2 mg mL lignin solution for 5 min, superior to that of most reported CNTs based composite films. Considering the remarkable TE performance, a TE device comprising 5 pairs of CNTs/lignin films and Ni wires is fabricated to deliver a high output power of 220 nW at ΔT of 30 K. Moreover, the device exhibited remarkable temperature-sensing capabilities and stable voltage response, highlighting its potential application as a wearable power source and temperature sensor. This work not only provides a feasible strategy for synergistically enhancing the TE properties of CNT composites using biomass lignin, but also paves the way for the utilization of biomass lignin for wearable electronics.