Potential dependent surface relaxation of the Pt(001)/electrolyte interface.

X-ray reflectivity measurements were used to determine the structure of the Pt(001)/solution interface as a function of the applied potential in alkaline and acid electrolytes. Unlike the Pt(001)/vacuum interface, the electrolyte interface was found to be unreconstructed at all potentials. The lattice spacing between the first and second layer was found to be a function of potential in the region where approximately a monolayer of H was adsorbed. The expansion was up to 2.5% of a lattice spacing (0.05 A) in alkaline electrolyte, and up to 1% of a lattice spacing in acid electrolytes