Reversible Transition of Graphene from Hydrophobic to Hydrophilic in the Presence of an Electric Field

The catalytic effect of a perpendicular electric field on the reversible transition of graphene with water from hydrophobic to hydrophilic has been investigated by using first principles calculations. It is found that a negative electric field F can reduce the energy barrier for H2O dissociative adsorption on graphene, while a positive electric field has an opposite effect. Under F = −0.39 V/Å, the energy barrier becomes negative and the dissociative adsorption occurs smoothly without any potential barrier, which results in hydrophilic graphene. For the desorption of H and OH from graphene after the dissociative adsorption of the H2O molecule, the positive electric field of F = 0.36 V/Å leads to a negative desorption energy barrier and the desorption progress is present automatically, making the graphene hydrophobic again. Therefore, the electric field can act as a switch to reversibly change the graphene from hydrophobic to hydrophilic in the presence of water vapor.