High-Performance Quasi-Solid Thermogalvanic Cells via Crown-Ether-Mediated Ion Migration

As a sustainable energy technology, the thermogalvanic cell (TGC) shows great promise in harvesting low-grade thermal energy and converting it directly into usable electricity. However, achieving a high output voltage for practical applications is still a great challenge. Recent studies have focused on achieving higher thermovoltage by increasing the entropy change of redox couples. The Soret effect (thermodiffusion) is often ignored in thermogalvanic systems. The role of the counterion of the redox couple is overlooked. Herein, we proposed that the thermovoltage of the quasi-solid thermogalvanic cell contained with K₃Fe(CN)₆/K₄Fe(CN)₆ can be increased by introducing 18-crown-6, a cationic selective complexing agent, amplifying the thermodiffusion of the cation. Thanks to the synergistic combination of the Soret effect with the thermogalvanic effect, the corresponding Seebeck coefficient of the cell was greatly boosted from 1.26 to 2.22 mV/K. The mechanism was analyzed systematically. This work may offer a promising approach to promote the thermovoltage of TGC, facilitating low-grade energy harvesting.