INSITU 2ND-HARMONIC GENERATION STUDIES OF THE SURFACE-STRUCTURE OF A WELL-ORDERED PT(111) ELECTRODE

Optical second harmonic generation rotational anisotropy measurements verify that surface order is preserved when flame-annealed Pt(111) electrodes are transferred to solution with an iodine overlayer and cleaned through an iodine-CO exchange reaction and subsequent CO oxidation electrochemistry. Iodine and CO adsorption produce an anisotropic response from the surface that indicates either a reduction of the average surface symmetry from C3v to C3 or the addition of an anisotropic nonlocal contribution to the surface nonlinear susceptibility. Oxidation of the CO monolayer creates a well-ordered Pt(111) surface with a potential-dependent SHG response that suggests the presence of an adsorbed hydrogen species over a wide range of potentials. © 1990 American Chemical Society.