Unlocking the potential of hydrogel-electrode electrical double layer for high-performance moisture-enabled electric generators

Ambient moisture-enabled generators (MEGs) present significant potential but suffer from low efficiency. This study explored the synergistic enhancement of an electrical double layer (EDL) at the hydrogel-electrode interface in hydrogel-based MEGs, which improves directional ion movement to achieve excellent performance. Our MEGs feature asymmetric electrodes made of carbon nanotubes and a poly(acrylamide-co-acrylic acid) hydrogel as the conductive medium. The interaction between the COOH-rich hygroscopic hydrogel and the salt-doped upper electrode established a humidity gradient within the hydrogel and a strong interfacial EDL. Results indicate that the generator (1 × 1 cm 2 ) achieved an open-circuit voltage of 1.3 V, an instantaneous short-circuit current of 55.7 μA/cm 2 , and a usable power output of 2.34 μW/cm 2 . It also exhibited robust environmental adaptability, maintaining 0.8 V below 30% relative humidity (RH) and over 0.65 V between −10°C and 60°C. Unlocking the potential of EDLs significantly enhances MEG performance, broadening application prospects in distributed self-powered devices and large-scale moisture-to-energy generation.