Thermoelectric Ionic Hydrogel Based on PEDOT:PSS/PAAm for Low-Grade Thermal-Energy Harvesting

The development of flexible wearable devices requires energy supply devices with high flexibility and stretchability. Thermoelectric ionic hydrogels possess characteristics of high flexibility and stretchability and can be used as heat conversion devices to transform low-grade heat energy into electrical energy. Recently, studies of ionic-thermoelectric hydrogels exhibit high thermopower (or Seebeck coefficient), but their raw materials are typically laced with strong alkalis or heavy metals, which makes them highly toxic and limits their potential applications. In order to enhance the thermopower in this study, we employed PEDOT:PSS as an n-type dopant in PAAm hydrogels to induce counterion condensation. This process immobilizes cations, thereby amplifying the ion-thermal migration rate disparity in the Soret effect and enhancing the thermopower. Furthermore, the thermoelectric performance was optimized by adjusting the dosage of the initiator ammonium persulfate (APS). The experimental results showed that the PEDOT:PSS/PAAm-based ionic hydrogel exhibited a high thermopower of −4.45 mV/K when the concentration of APS was 1 wt %. This study provides an approach for the preparation of low-toxicity, high-thermopower n-type thermoelectric ionic hydrogels.