Relationship between the Structures of Water on Electrode Surfaces and Electrode Potential

Abstract

Water adsorption on M(111) (M = Pt, Cu, Ni, Ru(001)) surfaces and a new double layer structure of water at a Cu(111) electrode surface were investigated by surface X-ray diffraction, scanning tunneling microscopy and infrared reflection absorption spectroscopy methods. There exists a clear relationship between a double layer structure on an electrode under an electrochemical potential controle and a simulated electric double layer structure in UHV. Water molecules in an electric double layer exhibit an ordered and a disordered structure at negative and positive electrode potentials, respectively. Therefore, potential polarization (negative or positive electrode potential application) from an equilibrium potential operates the electrified interface to cause increased or decreased ordering, orientation and charge transfer of water molecules as well as water dissociation on the electrode surfaces. The origin of an immersed gap (the difference between the UHV and electrochemical situation) is attributed to charge transfer from water molecules to metal electrodes.