Sustainable and Clean Energy Harvesting Device Using Reversible Redox Reactions Driven Alternately by Light and Moisture

In nature, moisture and solar irradiation serve as abundant clean energy sources for advancing next-generation power generators. However, the irregular spatial-temporal distribution and alternating occurrence patterns of the dual stimuli in real-world conditions present substantial challenges to the research and development of relevant technologies. Moreover, the existing moisture-driven power generators still suffer from the problem of short power generation duration. Herein, a sustainable energy generator alternately powered by moisture and light (MLG) is demonstrated, enabled by an asymmetric design of [Fe(CN)₆]^{3 -}/[Fe(CN)₆]^{4 -} redox couple introduced into the hygroscopic hydrogel. The alternating states include two types: moisture-only effects and combined light-moisture effects with photothermal energy being dominant. The alternating moisture and light stimuli drive forward and reverse redox reactions respectively, generating a continuously alternating current output. Under pure moisture activation at 98% RH, the device exhibits peak outputs of 3.2 mA current and 0.23 V voltage. Notably, when the moisture-induced current decays to less than 100 nA after prolonged operation, a 20-min illumination at 1.5 sun intensity effectively restores the moisture-triggered current to 166 µA. The system demonstrates exceptional cycling stability under repeated light-moisture alternations, highlighting its considerable potential for sustainable energy harvesting through complementary environmental energy utilization.