Graphene electrodes obtain power from the impact of raindrops. Raindrops are not pure water – they contain salts that dissociate into positive and negative ions. The positively charged ions bind to the graphene surface. At the point of contact between the raindrop and the graphene, the water becomes enriched in positive ions, and the graphene becomes enriched in delocalized electrons. The difference in potential associated with this phenomenon produces a voltage and current.