Figure 1: Waving potential in graphene moving across the surface of seawater.

(a) Schematic illustration of the experimental set-up: moving the graphene sample on a polyester terephthalate substrate vertically across the water surface within a container. All the edges of the graphene sheet and silver emulsion electrodes are protected with silicone. (b) Typical voltage signals produced as a sample is inserted and pulled out of 0.6 M NaCl solution (~3.5 wt%) at a velocity v=3.1 cm s⁻¹.