CeO2-supported Au-38(SR)(24) nanocluster catalysts for CO oxidation: a comparison of ligand-on and -off catalysts

The catalytic properties of atomically precise, thiolate-protected Au-38(SR)(24) (R = CH2CH2Ph) nanoclusters supported on CeO2 were investigated for CO oxidation in a fixed bed quartz reactor. Oxygen (O-2) thermal pretreatment of Au-38(SR)(24)/CeO2 at a temperature between 100 and 175 degrees C largely enhanced the catalytic activity, while pretreatment at higher temperatures (>200 degrees C) for removing thiolate instead gave rise to a somewhat lower activity than that for 175 degrees C pretreatment, and the ligand-off clusters were also found to be less stable. The CO conversion in the case of wet feed-gas (i.e. the presence of H2O vapor) was appreciably higher than the case of dry feed-gas when the reaction temperature was kept relatively low (between 60 and 80 degrees C), and interestingly the ligand-on and ligand-off catalysts exhibited opposite response to water vapor. Finally, we discussed some insights into the catalytic reaction involving the well-defined gold nanocluster catalyst.