Next, we performed a similar experiment using a catalyst that after O150 treatment and CO/Ar pulse reduction was subsequently oxidized by a O2/Ar multipulse sequence. We had recently shown that this leads to a comparable amount of Oact species on the surface as obtained for Oact deposition via a H2/CO2/Ar pulse sequence under the same conditions . Nevertheless, there may be differences in other surface species that may affect the oxygen exchange.