Researchers from Turkey's Bilkent University discovered that graphene oxide can be reversibly reduced and oxidized using electrical stimulus. They say that graphene's band structure can be electrochemically tuned in ambient air in a two terminal planar device (due to humidity in the air). The researchers claim that if this effect can be better controlled, you could use this to create E Ink like e-paper that will be ultrafast. This could also have applications in information processing.
Here's a video showing controlled reduction and oxidation in two-terminal devices (containing multilayer graphene oxide films):