Dynamic Behavior of Carbonate Species on Metal Oxide Surface: Oxygen Scrambling between Adsorbed Carbon Dioxide and Oxide Surface

The oxygen exchange between surface carbonate species and oxide surfaces was investigated by the temperature-programmed desorption (TPD) of C18O2 adsorbed on metal oxides, MgO, CaO, and ZrO2 at room temperature. Although desorption plots were quite different for these metal oxides, extensive oxygen exchange was commonly observed. The fraction of C16O2 in the total desorbed CO2 increased monotonically with desorption temperature, and each desorption peak in the plots for the total CO2 could not be characterized by the isotopic distribution. The difference in proportion of incorporated lattice oxygen in the total CO2 at each desorption temperature was small between the low and high concentrations of C18O2. Among these metal oxides, ZrO2 showed the highest fraction of C16O2 in the total CO2 desorbed at 400 °C when C18O2 was adsorbed on these metal oxide with same surface concentration. The value of [C16O18O]2/{[C16O2][C18O2]} was close to 4 over almost all the temperature region of desorption for all these m...