Structure and Behavior of Water at the Electrochemical Interface Studied by Surface-Enhanced Infrared Absorption Spectroscopy

How do water molecules behave at the electrochemical interface (the charged electrode-electrolyte interface)? This is one of the most fundamental and important questions in electrochemistry, and has been discussed extensively since the first proposal of the electric double layer model by Helmholtz in 1853. In the 1960s, a general consensus was reached that water molecules orient along the electric field at the interface and change the orientation depending on the applied potential (i.e., surface charge). However, details had long been unclear. Recent developments of computational theoretical chemistry and in situ surface analytical techniques have enabled a further detailed study of the interface at a molecular level and renewed our understanding. Recent progresses has been reviewed in the manuscript by focusing on experimental data provided by surface-enhanced infrared absorption spectroscopy (SEIRAS).