Generating sustainable electricity from ambient humidity and natural evaporation has attracted tremendous interest recently as it requires no extra mechanical energy input and is deployable across all weather and geography conditions. Here, we present a device prototype for enhanced power generation from ambient humidity. This prototype uses both heterogenous materials assembled from a LiCl-loaded cellulon paper to facilitate moisture adsorption and a carbon-black-loaded cellulon paper to promote water evaporation. Exposing such a centimeter-sized device to ambient humidity can produce voltages of around 0.78 V and a current of around 7.5 μA, both of which can be sustained for more than 10 days. The enhanced electric output and durability are due to the continuous water flow that is directed by evaporation through numerous, negatively charged channels within the cellulon papers. The voltage and current exhibit an excellent scaling behavior upon device integration to sufficiently power commercial devices including even cell phones. The results open a promising prospect of sustainable electricity generation based on a synergy between spontaneous moisture adsorption and water evaporation.

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Water-evaporation-induced (WEI) electricity generation has been widely studied, but the explanation for the working mechanism remains controversial yet. In this study, porous carbon black (CB) films with multiple parallel electrodes were prepared and the voltage distribution in these films was investigated during WEI electricity generation. We found that in both toluene and ethanol CB films, voltage between neighboring electrodes increases first but then decreases with increasing height above the bulk water surface. This voltage distribution derives from similar volumetric flow rate distribution of water inside the film, which is caused by the hydrophilicity of film and water evaporation. Our results support streaming potential and present more details during WEI electricity generation. It is helpful for understanding the mechanism in other material systems as well.

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