Regulation of thermal migration channel in cellulose hydrogel to enhance thermopower

Ionic thermoelectric material is gaining increasing attention, and many attempts have been devoted to obtain huge ionic thermopower, which remains a big challenge. Herein, the idea of "ion thermal migration channel" was propose, and a high ionic thermopower was achieved by regulating the thermal migration channel in cellulose hydrogel system. It is found that the channels size as well as the channel-ion interaction played dominant roles. Initially, the channel size in cellulose/KCl hydrogel were optimized to enlarge the channel-Cl− interactions via counter-ion condensation effect, which improved the thermopower from 2.45 mV·K−1 to 8.13 mV·K−1. Then, sodium alginate as polyanion was doped and multi-valance ion cross-linking was carried out, to further enhance the channel-Cl− interaction, and a high thermopower of 22.09 mV·K−1 was realized. In addition, the cellulose based ionic thermoelectric hydrogel displayed viable basis for energy harvesting and temperature sensing as wearable flexible devices. The present work not only provides a systematic strategy for the thermopower regulation, but also supplies an applicable approach for the preparation of sustainable thermoelectric materials with biomass resources, demonstrating great potential in sustainability and green energy.