Efficient energy harvesting: High power wearable humidity generators with PAM-LiCl/CMC structure

Abstract

Moisture electricity generator (MEG) has gained increasing interest due to its tremendous potential applications in generating electricity from sustainable ambient moisture. However, the development of MEG for self-powered electronics is seriously hindered by the low power density of individual MEG devices. Moreover, it is highly desirable to explore the potential of MEG in wearable applications. To significantly enhance the output performance of wearable MEGs, an ionic hydrogel moisture electricity generator (IH-MEG) featuring a PAM-LiCl/CMC structure was fabricated, demonstrating an excellent combination of flexibility and high-power density. The moisture energy is produced from the phase transition of water between its gaseous state and its adsorbed state, which exhibit different enthalpy and entropy. A significant number of ions are generated upon water absorption, and the three-dimensional pore structure facilitates the rapid transport of these ions within the IH-MEG, effectively converting the chemical energy stored in the IH-MEG into electrical energy. Under normal conditions (20°C and 90 % relative humidity), the maximum output power density from an individual IH-MEG can reach as high as 113 μW·cm⁻², with an open-circuit voltage of 1.8 V and a short-circuit current of 1.2 mA, nearly doubling the previously reported values. Moreover, our IH-MEG can collect mechanical energy when pressure is applied to the device. Our achievements provide profound insights into enhancing the output performance of sustainable MEGs through the rational utilization of ion hydrogels via a simple fabrication process.