Configurational entropy change-driven enhancement of thermoelectric performance in PVA-based hydrogel thermogalvanic cells

Thermogalvanic cells provide an efficient pathway for converting low-grade heat into electricity. Their performance is governed by the Seebeck coefficient, which dictates voltage output and thermoelectric efficiency. Previous efforts to enhance the Seebeck coefficient have focused on entropy contributions from solvent-induced solvation effects, while the impact of configurational entropy in quasi-solid-state networks has received limited attention. Here, we demonstrate that configurational entropy serves as an additional factor modulating the thermoelectric behavior of thermogalvanic hydrogels. Using the PVA hydrogel incorporating the Fe 2+ /Fe 3+ redox couple as a model system, we elucidate how constrained polymer networks alter redox thermodynamics. When a Fe 2+ /Fe 3+ concentration of 0.1 mol L −1 , the Seebeck coefficient in the hydrogel reaches 1.32 mV K −1 , significantly higher than that in aqueous solution (0.75 mV K −1 ). Complementary molecular dynamics simulations further demonstrate that hydrogel chains disturb the first solvation shell, broaden the radial distribution of coordinating water molecules, and increase dipole orientation disorder, thereby amplifying the configurational disparity between oxidized and reduced species. This leads to an enhanced role of configurational entropy in the ionic migration entropy. Our findings therefore highlight rational design ideas for optimizing high-performance quasi-solid-state thermogalvanic cells by quantifying the actual contribution of configurational entropy in the nano-network structure.