Harvesting Energy from Water Flow over Graphene

Water flow over carbon nanotubes has been shown to generate an induced voltage in the flow direction due to coupling of ions present in water with free charge carriers in the nanotubes. However, the induced voltages are typically of the order of a few millivolts, too small for significant power generation. Here we perform tests involving water flow with various molarities of hydrochloric acid (HCl) over few-layered graphene and report order of magnitude higher induced voltages for graphene as compared to nanotubes. The power generated by the flow of similar to 0.6 M HCl solution at similar to 0.01 m/sec was measured to be similar to 85 nW for a similar to 30 x 16 mu m size graphene film, which equates to a power per unit area of similar to 175 W/m(2). Molecular dynamics simulations indicate that the power generation is primarily caused by a net drift velocity of adsorbed Cl- ions on the continuous graphene film surface.