The interaction of carbon monoxide with clean and surface-modified zinc oxide nanoparticles: A UHV-FTIRS study

摘要

The interaction of CO with differently modified polycrystalline ZnO has been studied by FTIR spectroscopy under ultrahigh vacuum conditions (UHV-FTIRS). After exposing the clean, adsorbate-free ZnO nanoparticles to CO at 110 K we observe an intense vibrational band at 2187 cm~1 which is assigned to a majority of CO species bound to the Zn~(2+) sites on the mixed-terminated ZnO(l 010) surface. After the exposure of CO2-pretreated ZnO nanoparticles to CO at 110K, a new CO band is observed at 2215cm~(-1), which originates from CO species adsorbed on the "free" Zn sites embedded within the (2x1) tridentate carbonate structure on the ZnO(1010) surface. UHV-FTIRS data recorded at different sample temperatures demonstrate that the binding energy of CO on polycrystalline ZnO is substantially increased in the presence of pre-adsorbed CO2. The presence of hydroxyl species on the ZnO powder particles does not lead to substantial changes of the CO vibrational bands detected at 110 K under UHV conditions.