Oxygen exchange mechanism between isotopic CO2 and Pt/CeO2 Original Research Article

The oxygen exchange mechanism between C18O2 and CeO2 and the role of Pt in this process have been studied in an advanced TAP reactor in the 200–600 °C temperature range. For bare and Pt-containing CeO2, the exchange of the oxygen atoms of C18O2 takes place in the whole temperatures range studied, and the oxygen exchange rate increases with temperature. The proposed mechanistic pathway consists of the exchange of the oxygen atoms in the C18O2 molecule in two consecutive steps. In the case of bare CeO2, only one of the oxygen atoms of C18O2 is exchanged between 200 and 300 °C, and temperatures above 300 °C are required for the exchange of the second oxygen atom of the C18O2 molecule. Pt accelerates the exchange rate between 200 and 400 °C, mainly favouring the exchange of the second oxygen atom of the C18O2 molecule. The effect of Pt cannot be resolved at higher temperature (above 400 °C), since at high temperature the direct exchange over bare CeO2 is already fast.