Host–Guest Complexation of α‐Cyclodextrin and Triiodide Ions for Enhanced Performance of Ionic Thermoelectric Capacitors
Shih‐Ting Kao, Ching‐Chieh Hsu, Shao‐Huan Hong, U‐Ser Jeng, Chia‐Hsin Wang, Shih‐Huang Tung, Cheng‐Liang Liu
Abstract
Abstract Ionic thermoelectric materials have emerged as a promising avenue for harvesting low‐grade waste heat, with significant potential for applications in wearable electronics. This study introduces a novel design for ionic thermoelectric capacitors (ITECs) by incorporating host–guest complexation between α–cyclodextrin (α‐CD) and triiodide ions (I 3 − ). The strong host–guest complexation between α‐CD and I 3 − confines the diffusion of I 3 − within the cylindrical cavities of α‐CD, as evidenced by UV–vis spectroscopy and 13 C‐NMR analysis. This confinement enhances the ion mobility difference between I 3 − and sodium ions, which in turn significantly boosts the ionic thermopower of the polyvinyl alcohol/α‐CD/NaI hydrogels. Accordingly, the optimized sample achieves an impressive positive ionic thermopower of 14.24 mV K −1 and a high ionic power factor of 477.2 µW K −2 m −1 . Furthermore, the stretchable ITEC demonstrates a substantial power density of 5.9 mW m −2 . When integrated into a 3‐leg device, a stable thermovoltage of 176 mV is generated under a temperature gradient of 4.4 K, thus highlighting the potential of this system for efficient thermal energy harvesting.