Thermoelectric performance of conducting aerogels based on carbon nanotube/silver nanocomposites with ultralow thermal conductivity

Abstract

New conducting aerogels based on carbon nanotube (CNT) and silver (Ag) nanocomposites have been systematically investigated. The unique 3D network structures of the aerogels enable a remarkable reduction in their thermal conductivities. It is shown that the CNT–Ag nanocomposite aerogels (CNTANAs) possess low thermal conductivities of only 0.06 to 0.095 W m⁻¹ k⁻¹ with various Ag contents at room temperature; these values are much lower than those of other reported CNT and Ag composites with non-porous structures. Moreover, the electrical conductivities and Seebeck coefficients of the CNTANAs can be simultaneously enhanced by increasing the Ag content in the unique structure; this overcomes a drawback of bulk semiconductors wherein increasing electrical conductivity is generally accompanied by a reduced Seebeck coefficient and enhances the thermal conductivity. As a result, this strategy results in a maximum ZT value of 0.011. This ZT value is about 1 order of magnitude higher than that of the carbon aerogel and 2 orders of magnitude higher than that of the silver/polymer composites and CNT/polymer composites. At the same time, the fragile solid skeleton and highly open-cell foam structure of the CNTANAs lead to low apparent density (∼130 kg m⁻³). In this study, our study offers a new preparation method for TE materials, which will broaden the development of this facile and novel category of lightweight TE material.