Electric field effects on the adsorption, charge transfer and vibrational state at metal electrodes:: A DFT study on H2O/Pt(111), (H2O)/Pt(100) and (H2O)2/Pt(111)

Electric field (EF) effects on an adsorbed H2O and (H2O)(2) on Pt(l Il)and (100) surfaces have been studied using density functional theory (DFT) at the B3LYP/LanL2DZ level. For the interactions between the H2O and the Pt surface (modeled as a cluster), natural bond orbital (NBO) analysis was performed. This showed that the H2O interacts strongly with the Pt surface through the higher energy level lone pair of the H2O in a parallel orientation. Geometry optimizations of the adsorbed water molecule on the Pt(111) surface were carried out, and the changes in the orientation and geometry induced by the EF are discussed. In the cases of EF = O and EF > 0, the charge transfer interaction between the H2O and the Pt surface dominates and the H2O is adsorbed at the top site. For EF < 0, the interaction between the dipole moment of the H2O and EF dominates over the charge transfer interaction. Based on the optimized geometries, we have analyzed the vibrational structure and the EF effects on the vibration of the adsorbed H2O. For the (H2O)(2) adsorbed on the Pt(lll) surface, partial-optimization calculations have been carried out and the hydrogen bonding in the dimer has been analyzed.