For a canonical reactive MC, the simulation approach involves two distinct types of moves: bulk moves, for which ion positions undergo random change with the acceptance probabilities determined by the standard Metropolis algorithm, and reaction protonation/deprotonation, HA ----H + + A -, moves. When a proton moves from the bulk and reacts with an active site on the surface, both electrostatic and chemical energies of the system change. The chemical energy associated with transferring a proton from the bulk to the surface is k B T ln Ka c , where K a is the surface acid dissociation constant. The change in electrostatic energy of the system can be calculated using Eq. ( ). The acceptance probability for a protonation move is then given by :