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 electron microscopy (FEM). The reaction gas is used as the field ion imaging gas at pressures of < 10(-4) mbar and at temperatures of the catalytic reaction. In FIM the surface is imaged by O2+-ions which are preferentially ionized at oxygen-covered surface areas. During temperature variations regions of bistability could be detected by FEM and FIM. Finally self-sustained isothermal oscillations of the catalytic CO-oxidation could be measured from the periodic fluctuations of the O2+-field ion current. Atomic resolution shows that the Pt-(331) planes are the pace makers of the oscillation.