Something like: using a board with nano sized holes, water's electrons fit through the holes and an imbalance is created. Something like solar panels p and n junctions with the air's moisture. Wish I could explain it better, just skimmed an article.
As water molecules pass through the device, from an upper chamber to a lower chamber, they knock against the tiny holes’ edges, creating an electric charge imbalance between the layered chambers. In effect, it makes the device run like a battery. The whole process resembles the way clouds make electricity, which we see in the form of lightning bolts." https://www.smithsonianmag.com/smart-news/this-new-device-ge...
Can it be used in a closed circle recirculating the air with a fan? (obviously this will produce less electricity than the used to move the fan.)