Noble-Metal-Free Single-Atom Catalysts CuAl4O7-9- for CO Oxidation by O2

The single copper atom doped clusters CuAl4O7-9- can catalyze CO oxidation by O-2. The CuAl4O7-9- clusters are the first group of experimentally identified noble-metal free single atom catalysts for such a prototypical reaction. The reactions were characterized by mass spectrometry and density functional theory calculations. The CuAl4O9CO- is much more reactive than CuAl4O9- in the reaction with CO to generate CO2. One adsorbed CO is crucial to stabilize Cu of CuAl4O9- around +I oxidation state and promote the oxidation of another CO. The widely emphasized correlation between the catalytic reactivity of CO oxidation and Cu oxidation state can be understood at the strictly molecular level. The remarkable difference between Cu catalysis and noble-metal catalysis was discussed.