Review on thermoelectric aerogels and their applications: progress and challenges

Thermoelectric (TE) materials and devices are able to convert direct heat to electricity and so have several uses in heat energy harvesting (power generators), wearable electronics, and local cooling. Recent advances have led to the emergence of a new class of thermoelectric materials, organic and hybrid (organic/inorganic) materials of the polymer and gel types (aerogels). These nanostructured materials, in addition to being environmentally friendly and abundant, have very low thermal conductivity, low density and specific heat and electricity transport mechanisms. Their fabrication process is less expensive than the synthesis methods of alternative materials and opens the door to previously unattainable thermoelectric module architectures, with modular shapes (surfaces/thicknesses) and sometimes with flexible properties. This study comprehensively summarizes current advancements in organic, inorganic, and composite/hybrid TE aerogels, covering the key ingredients, production technique, TE performance, as well as variables impacting TE performance and the associated mechanisms. Furthermore, the construction techniques and output performance of two typical aerogel-based TE devices/generators (TEG) are compared and examined. This paper also discusses the use of aerogel-based TEG devices in a variety of disciplines described in this review. Finally, the current obstacles and some preliminary proposals for future research potential are offered.