Boosting Thermoelectric Performance of Thermogalvanic Hydrogels by Structure Engineering Induced by Liquid Nitrogen Quenching

Abstract Quasi‐solid thermogalvanic hydrogels hold great promise in harvesting low‐grade thermal energy, yet, they are still far from practical application owing to relatively low power output. Herein, through liquid nitrogen quenching‐induced structure engineering, a high‐performance stretchable thermogalvanic hydrogel thread with a high specific output power density of 2227.5 µW m −2 K −2 and a large thermopower of 4.5 mV K −1 is designed. After liquid nitrogen quenching, both the thermopower and electrical conductivity have been greatly improved compared to natural cooling. The excellent properties are attributed to liquid nitrogen quenching‐induced grain refinement and precipitation inhibition. It is a novel and general preparation method for high‐performance and homogeneous thermogalvanic hydrogels. Finally, a thermogalvanic hydrogel array is demonstrated to be capable of driving a low‐power motor and charging a mobile phone by low‐grade thermal energy harvesting, indicating a great potential for practical applications in human daily life.