Hydrogel-based moisture electricity generators: materials, mechanisms, and sustainable device design

Abstract

Global environmental crises and energy shortages pose a grave threat to human society. The widespread moisture offers endless source of power for sustainable electricity production. However, traditional moisture electricity generators (MEGs) encounter issues such as low power output, instability, and limited scalability. Hydrogels, with their exceptional moisture absorption and retention properties, efficient ionic transport channels, and outstanding flexibility and adaptability, provide an ideal material platform for constructing high-performance, high-stability, and scalable MEGs. Herein, a systematic overview of recent advances in hydrogel-based moisture electricity generators (HMEGs) is presented. First, the fundamental mechanisms of HMEGs are described thoroughly, including moisture–hydrogel interactions and power generation. On this basis, a mechanism-guided framework is established to explicitly correlate these processes with material selection, device design, and long-term stability. Subsequently, the selection of materials for HMEGs is introduced. Strategies to improve HMEG performance are then discussed, including the construction of porous transport pathways, the design of asymmetric gradients, the modification of electrodes, and the exploitation of synergistic effects for multi-source energy harvesting. In addition, comprehensive consideration is further given to key factors affecting device long-term stability. Applications of high-performance HMEGs in self-powered and wearable electronics, environmental monitoring, and sensing are also reviewed. Finally, we summarize the advantages of HMEGs and provide a critical analysis of current challenges and future perspectives, aiming to offer fundamental insights for the development of next-generation sustainable HMEGs.