THE CATALYTIC-OXIDATION OF CARBON-MONOXIDE AT THE PLATINUM ELECTROLYTE INTERFACE INVESTIGATED BY OPTICAL 2ND-HARMONIC GENERATION (SHG) - COMPARISON OF PT(111) AND PT(997) ELECTRODE SURFACES/

The anodic oxidation of CO on nominal Pt(111) and Pt(997) electrodes i n a CO-saturated 0.1 M HClO4 electrolyte is studied by optical second harmonic generation (SHG) at a wavelength of 280 nm to monitor the CO adlayer under steady-slate reaction conditions in the potential range between 50 mV and 1030 mV vs. RHE. Regarding the catalytic activity of the electrodes, two potential regimes are distinguishable: in the low potential regime, characterized by the presence of a dense CO overlay er, the reaction yield is higher on Pt(997) than on Pt(111). Positive of the overlayer stripping potential [880 mV for Pt(111) and 780 mV fo r Pt(997)] the Pt(997) electrode exhibits an inferior reactivity. The results confirm the structure sensitivity of anodic CO oxidation on Pt electrode surfaces. (C) 1998 Elsevier Science B.V. All rights reserve d.