Boosting output performance in hydrogel-based moisture-electric generators via tunable solvent interactions

Abstract Hydrogels, with their hydrophilicity, flexibility, and environmental friendliness, are highly desirable for moisture-electric generators (MEGs) that harness ubiquitous moisture to generate electrical energy. As the active material layer in MEGs, hydrogels play a crucial role in absorbing atmospheric moisture and converting chemical potential energy into electricity. However, the relatively low output current of the device and the instability of hydrogels pose challenges to the development of high-performance hydrogel-based MEGs. Herein, we introduce a straightforward, feasible, cost-effective, and versatile two-step solvent displacement strategy to overcome the barrier associated with the development of MEGs. Through tunable solvent interactions of glycerol and water, the moisture absorption capability and stability of the hydrogel can be improved, while promoting favorable ion migration. Such an effective processing route not only significantly boosts the output performances but also greatly improves the long-term durability of hydrogel-based MEGs. Notably, the current output and power density of the treated MEGs can increase by up to two orders of magnitude. The mechanisms behind the intriguing observation are investigated by various characterizations and theoretical calculations. This universal strategy holds promise to be extended to various hydrogel-based MEGs. Moreover, the MEGs can be used for energy harvesting, self-powered respiratory monitoring, and non-contact humidity detection. This work offers new opportunities for advancing green energy and self-powered technologies.