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Electricity generated from Ambient Heat by Pencils

The idea of generating electricity from ambient heat has significant meanings for both science and engineering. Here, we present an interesting idea of using pencil leads, which are made of graphite and clay, to generate electricity from the thermal motion of ions in aqueous electrolyte solution at room temperature. When two pencil leads were placed in parallel in the solutions, output power of 0.655, 1.023, 1.023 and 1.828 nW were generated in 3 M KCl, NaCl, NiCl2 and CuCl2 solutions, respectively. Besides, we also demonstrate that two pieces of reduced graphene oxide films and /or few-layer graphene films can generate much more electricity when dipped into the solutions, while there was no electrodes contact with the solution. This finding further verified that the electricity was not resulted from the chemical reaction between the electrodes and the solutions. The results also demonstrate that ambient thermal energy can be harvested with low dimensional materials, such as graphene, or with the surface of solid material without the presence of temperature gradient. However, the mechanism is still unclear.