Anion-cation heterostructured hydrogels for all-weather responsive electricity and water harvesting from atmospheric air

Abstract

Despite the recent boom in moisture-enabled electricity generation (MEG), it suffers from fabrication intricacy and materials inadequacy for water and energy harvesting purposes. Moreover, conventional MEGs face challenges in restricted operating humidity, inertness to subtle humidity fluctuations and inability to sustain long-lasting power output under high humidity due to limitations in hydrophilicity and hydration. Here, we exploit a unique oppositely-charged hydrogel heterojunction for electricity and fresh water harvesting from atmospheric air without trade-offs in process simplicity and humidity limits. This anion-cation heterostructure engages two oppositely polarized ions and features a self-regulating ionic gradient for MEG in a dynamically fluctuating ambient, making it not only capable of responding to sluggish and subtle humidity fluctuations but delivering undisrupted power even under extremely wet conditions. Different from other MEGs, moisture can be captured and largely stored in the hydrogel and then released as fresh water. This moisture absorption/desorption, interestingly, is accompanied by electricity generation, indicating a two-in-one strategy to address the water-energy nexus. In such a hydrogel heterojunction, multiple environmental elements like moisture, light, temperature, wind, etc., are feasibly mobilized for energy harvesting. This work provides a promising autonomous and continuous operation of an energy-water system for sustainable and decentralized purposes.