Unidirectional ion-transport-induced moisture-electric generation with persistent current output for self-powered monitoring systems

Abstract

Moisture-electric generators (MEGs) can directly obtain energy from ambient moisture without relying on external mechanical, thermal, or light input. This inherent compatibility with the surrounding environment makes it particularly suitable for distributed self-powered monitoring systems. However, MEGs remain limited by their low power density and insufficient operational stability under long-term or cyclic usage conditions, which hinders their practical application and large-scale deployment. Here, we present a sustained gradient MEG based on sodium alginate-vermiculite aerogels (SVA-MEG). The hygroscopic hydrogel can capture moisture at night and couple with the daytime humidity regulation capability of sodium alginate/vermiculite aerogels. The SVA-MEG utilizes synergistic humidity gradients and ion-selective transport for uninterrupted energy conversion, showing a sustained open-circuit voltage (V_OC) of 0.72 V for 30 days over a wide humidity range. Notably, a stable short-circuit current density (J_SC) exceeding 10 µA cm⁻² can be maintained for over 10 days at 90% RH. Based on this device, we have developed a wireless methane detection platform powered by an SVA-MEG array, which enables real-time methane concentration monitoring, synchronously transmitting data to both cloud platforms and mobile devices of underground workers to facilitate timely hazard alerts. This study promotes the development of a sustainable moisture-electric generator and shows potential applications in the construction of the future smart industry.