An Efficient Ambient‐Moisture–Driven Wearable Electrical Power Generator

Existing devices for generating electrical power from water vapor in ambient air require high levels of relative humidity (RH), cannot operate for prolonged periods, and provide insufficient output for most practical applications. Here a heterogeneous moisture‐driven electrical power generator (MODEG) is developed in the form of a free‐standing bilayer of polyelectrolyte films, one consisting of a hygroscopic matrix of graphene oxide(GO)/polyaniline(PANI) [(GO)PANI] and the other consisting of poly(diallyldimethylammonium chloride)(PDDA)‐modified fluorinated Nafion (F‐Nafion (PDDA)). One MODEG unit (1 cm(2)) can deliver a stable open‐circuit output of 0.9 V at 8 µA for more than 10 h with a matching external load. The device works over a wide range of temperature (−20 to +50 °C) and relative humidity (30% to 95% RH). It is shown that series and parallel combinations of MODEG units can directly supply sufficient power to drive commercial electronic devices such as light bulbs, supercapacitors, circuit boards, and screen displays. The (GO)PANI:F‐Nafion (PDDA) hybrid film is embedded in a mask to harvest the energy from exhaled water vapor in human breath under real‐life conditions. The device could consistently generate 450–600 mV during usual breathing, and provides sufficient power to drive medical devices, wearables, and emergency communication.