Porous PEDOT:PSS smart thermal insulators enabling energy harvesting and detection

Abstract

In the building sector, energy independency has become an essential goal that must be achieved to contribute to carbon neutrality. This requires advanced renewable energy production measures to be applied, aside from commercialized technologies such as solar panels and wind turbines. Currently, thermal insulation panels are used in large volumes in every building structure, but commercial thermal insulators do not serve any role in active energy production. Thermoelectric (TE) materials have the ability to harvest thermal energy under any climatic condition where a thermal gradient can be applied. Therefore, replacing commercial thermal insulators with TE materials with low thermal conductivity can yield multifunctional thermal insulators that can act as simultaneous energy harvesters and insulators. Moreover, by utilizing the TE voltage generated from the Seebeck effect, the thermal insulator can also serve a solution to detect and manage overheating in energy storage systems, which can greatly improve the sustainability of buildings housing such assets. In this report, a highly porous, structurally stable porous PEDOT:PSS with a well-connected conductive network was prepared by hydrogel formation and subsequent controlled freeze-drying. The thermal insulation capability of porous PEDOT:PSS was evaluated to be comparable to commercial PU foam, with a low thermal conductivity of 0.041 W m⁻¹ K⁻¹ from a high porosity of 0.9517. TE properties and insulation ability were investigated, combined with further optimization with EtOH content variation. As a result, 90 nW cm⁻² TE power density was achieved at a stabilized ΔT of 15.16 K for a porous PEDOT:PSS with 30 wt% EtOH while maintaining low thermal conductivity which was estimated to be 0.0526 W m⁻¹ K⁻¹. Furthermore, the TE voltage response from repeated contact with a heat source was monitored, demonstrating the potential of porous PEDOT:PSS to be used as a battery overheating detection solution. The energy harvesting and detection capability of the designed porous PEDOT:PSS transforms a plain PU foam into a smart thermal insulator.