Fig. 1. CO oxidation activity of mass-selected Pt_n clusters on Al₂O₃.

a Overview of the CO₂ temperature-programmed reaction (TPR) measurements. The Pt_n-deposited surfaces were exposed to 1000 L of ¹⁸O₂ at 300 K to saturate the Pt_n clusters with ¹⁸O atoms, followed by saturation adsorption of ¹³CO at 88 K, and finally the TPR measurement was performed. The Pt coverage was 0.02 ML. b Amount of produced CO₂ from sample surface with mass-selected Pt single clusters relative to the number of Pt atoms in the cluster. The error bars were determined from multiple measurements on a single cluster size. c CO₂ TPR spectra (m/z = 47) over Pt_n/Al₂O₃. The number of produced CO₂ molecules was estimated by integrating the intensity between 100 and 500 K. d Amount of unreacted CO molecules relative to the number of Pt atoms in the cluster. e CO TPR spectra (m/z = 29) over Pt_n/Al₂O₃. f CO conversion (ratio of produced CO₂ molecules to adsorbed CO molecules) as a function of the number of Pt atoms in the cluster. The error bars in b, d, and f are standard deviation. Source data are provided as a Source Data file.