MXene‐enhanced environmentally stable organohydrogel ionic diode toward harvesting ultralow‐frequency mechanical energy and moisture energy

Abstract With the accelerating advancement of distributed sensors and portable electronic devices in the era of big data, harvesting energy from the surrounding environment to power electrical devices has become increasingly attractive. However, most mechanical energy harvesters often require high operating frequencies to function properly. Moreover, for practical applications, the survivability of devices in harsh operating environments is a vital issue which must be addressed. Besides, the single‐stimulus responsiveness limits their further applications in complex external environments. Here, a pressure and moisture dual‐responsive ionic diode consisting of two organohydrogels with opposite charges as an energy harvester is proposed. The organohydrogel ionic diode utilizes the migration of cations and anions to form the depletion zone and followed by an enhancement of the built‐in potential along the depletion zone as a result of mechanical stress or humidity, converting ultralow‐frequency mechanical energy or moisture energy into electrical energy. Meanwhile, this mechanism is further confirmed by the finite element analysis. With the increased rectification ratio due to the introduction of MXene, the ionic diode exhibits a relatively large output current (∼10.10 μA cm −2 ) and power density (∼0.10 μW cm −2 ) at a mechanical pressure of 0.01 Hz, outperforming most currently available mechanical energy harvesters. More impressively, the incorporation of ethylene glycol provides the hydrogel ionic diode with excellent temperature tolerance and long‐term environmental stability. The organohydrogel ionic diode can also be applied as a moisture‐driven power generator and self‐powered humidity sensor. This study presents promising prospects for the efficient collection of renewable and sustainable energy and the practical application of hydrogel‐based energy harvesters in extreme environments.