A DFT study of electric field effects on proton transfer reactions at H+(H2O)2/Pt(111) and Ag(111)

The electric field (EF) effects on the proton transfer reaction that takes place on the surfaces of Pt(111) and Ag(111) electrodes, are studied based on density functional theory (DFT) at the level of B3LYP/LanL2DZ. According to calculations based on a ‘one-dimensional’ proton transfer model, the potential energy curve of proton transfer between two water molecules on the surfaces, depends substantially on the direction of the EF. An EF shifts the equilibrium of proton transfer in the direction of electrostatic attraction. The potential energy surface for a ‘two-dimensional’ proton transfer model, in which a proton transfers between two water molecules and the surface, revealed that an EF effectively accelerates the proton transfer from H3O+ to the surface. The rate-determining step of the proton transfer is discussed in the light of the results.