Assembly of Natural Clay Minerals as Highly Robust Evaporation-Driven Power Generator

Inexhaustible natural resources, such as water, wind, moisture, and ubiquitous natural processes such as evaporation or condensation, could offer optimal energy strategies for a sustainable future. Recently, there has been a surge in interest surrounding evaporation-driven power generators (EDPs), which rely on capillary-driven water flow through permselective nanochannels, followed by evaporation into the atmosphere. Despite huge potential, existing EDPs encounter hurdles like expensive and environmentally unfriendly active materials and complex fabrication processes. Here, we introduce a bilayer membrane composed of two distinct clay minerals, vermiculite (VM) and halloysite nanotube (HNT) clay, to develop an evaporation-driven energy generator capable of generating an open-circuit potential up to 406 mV along with short circuit currents of ∼3.4 μA, resulting in a power density up to 0.85 mW/cm 3 . Due to the affordability, biocompatibility of the materials employed, and simplicity of device fabrication, this energy generator can be upscaled to power low-energy electronic devices and sensors. The all-clay power generator can withstand extreme temperatures; exposure to 180 °C did not affect its power harvesting properties. Individual energy generators are connected in series to power small electronic devices, such as humidity meters, calculators, and LEDs.