A new method for generating electricity, by simply dipping a piece of graphene sheet into a common ionic solution, is reported in Nature Communications this week. This electric energy harvesting approach could be integrated into cost-effective, self-powered sensor designs.

Attempts have been made to produce electricity with graphene based systems, but it is unconfirmed whether or not convincing or considerable amounts of electricity have been obtained. Research carried out by Wanlin Guo and colleagues now adopts a different approach. In contrast to all the previous attempts in which graphene or other carbon-based materials are completely immersed in flowing solutions, the researchers move a graphene sheet across the surface of an ionic solution, such as sodium chloride. They show that with a piece of graphene about the size of a small ruler (2 x 10 cm2), the electricity generated is approximately 10 microempheres and, while this is still a relatively small output, the authors demonstrate that it is enough to stimulate a sciatic nerve of a frog. Importantly, they also show that the electricity generated is proportional to the size of the graphene sheet and the dipping speed, suggesting that this device may be scalable.

The researchers further explain that the key to producing electricity in their experiments is to maintain a gas-liquid interface while dipping graphene. This moving gas-liquid boundary induces charge transfer in graphene, which they term‘waving potentia’,leading to electricity generation.