A n-type ionic thermoelectric hydrogel with confined cation diffusion for boosted low-grade heat harvesting

Ionic thermoelectric (i-TE) materials, based on the thermodiffusion effect, have demonstrated great potential due to their exceptional heat-to-electricity properties, low cost, and flexibility. However, a comprehensive understanding of ion transport mechanism and interaction between ion and the polymer matrix is still in its early stage. In this work, we developed a functional i-TE material with hierarchical pathways for anion by employing an interpenetrating polymer network composed of sodium polystyrene sulfonate modified polyvinyl alcohol. Notably, such specific pathway integrates coordination and electrostatic interactions between cations and functional groups, resulting in an n-type behavior of i-TE hydrogel with enhanced anion diffusion efficiency. The developed i-TE system achieves a high thermopower of −16.8 mV K−1 and an output power density of 47.8 mW m−2 at a temperature difference of 10 K. Moreover, the constructed device demonstrates high sensitivity and responsivity to varying heat input, which provides valuable insights for the design and development of potential i-TE materials and devices for low-grade heat conversion.