A team of researchers from TAU’s Porter School of the Environment and Earth Sciences led by Prof. Colin Price in collaboration with Prof. Hadas Saaroni and doctoral student Judi Lax has found that electricity materializes in the interaction between water molecules and metal surfaces. Their research has been published in Scientific Reports.
The researchers set out to try to produce a tiny low-voltage battery that utilizes only humidity in the air, building on the findings of earlier discoveries. The scientists conducted a laboratory experiment to determine the voltage between two different metals exposed to high relative humidity, while one is grounded. “We found that there was no voltage between them when the air was dry,” Prof. Price explains. “But once the relative humidity rose above 60%, a voltage began to develop between the two isolated metal surfaces. When we lowered the humidity level to below 60%, the voltage disappeared. When we experimented outside in natural conditions, we saw the same results.
“Water is a very special molecule. During molecular collisions, it can transfer an electrical charge from one molecule to the other. Through friction, it can build up a kind of static electricity. We tried to reproduce electricity in the lab and found that different isolated metal surfaces will build up different amounts of charge from water vapour in the atmosphere, but only if the air relative humidity is above 60%. Water is normally thought of as a good conductor of electricity, not something that can build up-charge on a surface. However, it seems that things are different once the relative humidity exceeds a certain threshold,” Prof. Price says. “If a AA battery is 1.5V, there may be a practical application in the future: to develop batteries that can be charged from water vapour in the air,” Prof. Price adds.
