Novel Working Mode of Promoting Water Diffusion Gradient via Electric Field: Endowing Moist-Electric Generator with High Humidity-Sensing Performance

Moist-electric generators (MEGs) have garnered considerable research attention in electricity generation without additional mechanical energy. Nevertheless, their practical applications in humidity sensing are limited by intrinsic limitations, including constrained water diffusivity and insufficient water ionization efficiency, which are synergistically detrimental to the output voltage and response time of the MEGs. Facilitating the directional ion migration across the sensing film is a critical way for realizing highly sensitive self-powered humidity detection with rapid response ability. Enlightened by the electric field that can drive the directional ion migration, an electric-field-enhanced MEG (E-MEG)-based humidity sensor was designed, in which a sensing film was sandwiched between two different metal electrodes. Following the working principle of moisture-induced primary batteries, an internal electric field that aligned with the water diffusive orientation was generated across the sensing film, thereby promoting the humidity sensing performance of the MEG-based sensor. The proposed E-MEG-based humidity sensor achieved an increased output voltage (955.6 mV) and decreased response time (64 s) compared to the pristine MEG-based sensor (137.1 mV/242 s) under 89.2% relative humidity (RH). This work furnishes novel research perspectives for advancing applications of MEGs in humidity detection and illuminates an innovative development in self-powered humidity-sensing technology.