Velocity distribution of desorbing CO2 in CO oxidation on Pd(110) under steady-state conditions

The velocity and angular distributions of desorbing CO2 in CO oxidation on Pd(110) were studied under the steady-state conditions with cross-correlati on time-of-flight techniques. Sharp changes were found in both distribution s at the switching point of the rate-determining step. The velocity curves involved fast and slow components. The fast one, which was suddenly suppres sed at the switching point, showed a translational temperature from 2300 to 4000 K. The slow component was thermalized to the surface temperature. A r apid site switching for CO2 formation is proposed, in which the fast compon ent is formed on flat parts of the surface and the slow one is formed on st ructural defects. (C) 2001 Elsevier Science B.V. Ail rights reserved.