High-thermopower polarized electrolytes enabled by methylcellulose for low-grade heat harvesting.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 35179966.
- Also identified by DOI 10.1126/sciadv.abl5318 and PMC identifier 8856612.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
Low-grade heat exists ubiquitously in the environment. Thermogalvanic cells (TGCs) are promising for converting the widespread low-grade heat directly into electricity owing to relatively high thermopowers of redox reactions. This work reports polarized electrolytes with ultrahigh thermopowers of -8.18 mV K<sup>-1</sup> for n-type and 9.62 mV K<sup>-1</sup> for p-type. The electrolyte consists of I<sup>-</sup>/I<sub>3</sub><sup>-</sup> redox couple, methylcellulose, and KCl. Thermoresponsive methylcellulose leads to polarization switching from n-type to p-type above a transition temperature due to the strong hydrophobic interaction between methylcellulose and I<sub>3</sub><sup>-</sup> ions. The giant thermopowers can be attributed to the simultaneously enhanced entropy change and concentration difference of redox couple enabled by the gelation of methylcellulose and KCl-induced complexation. The p-type TGC with the optimized electrolyte achieves a normalized maximum power density of 0.36 mW m<sup>-2</sup> K<sup>-2</sup>, which is far superior to other reported I<sup>-</sup>/I<sub>3</sub><sup>-</sup>-based TGCs. This work demonstrates cost-effective, high-thermopower polarized electrolytes for low-grade heat harvesting.