Three milestones in the history of CO oxidation are shown in the picture. One century ago, Langmuir investigated CO oxidation using Pt group metals which work at temperatures higher than 373 K. In the 1980s, Haruta et al. discovered that Au nanoparticles with sizes of 2 nm are active for the oxidation of CO at 200 K. In their Communication on page 2820 ff., X. Wang, T. Zhang et al. show that CO is oxidized at 173 K by Rh sub-nanoclusters supported on TiO2.
