IMAGING THE OSCILLATING COOXIDATION ON PT-SURFACES WITH FIELD-ION MICROSCOPY

The oxidation of carbon monoxide on platinum surfaces is investigated by field ion microscopy (FIM) and compared to earlier work by field el ectron microscopy (FEM). The reaction gas is used as the field ion ima ging gas at pressures of < 10(-4) mbar and at temperatures of the cata lytic reaction. In FIM the surface is imaged by O2+-ions which are pre ferentially ionized at oxygen-covered surface areas. During temperatur e variations regions of bistability could be detected by FEM and FIM. Finally self-sustained isothermal oscillations of the catalytic CO-oxi dation could be measured from the periodic fluctuations of the O2+-fie ld ion current. Atomic resolution shows that the Pt-(331) planes are t he pace makers of the oscillation.