To investigate the kinetics of proton/electron transfer, we sequentially add holes with integer charge into the system. First we tried to localize the hole between the O-O bond by changing the distance then, to avoid the errors associated with charged systems under periodic boundary conditions, we neutralize the charge associated with a hole by removing a proton from an adsorbed H 2 O molecule. This results in an adsorbed OH -on the surface of the slab.