Theoretical investigation of CO oxidation over polyoxometalate-supported Au cluster catalyst

• DFT study elucidates CO oxidation activity variation of Au/POM catalyst. • There are two different active species (O 2 – and OOH – ) for CO oxidation over Au/POM. • Surface adsorbed water produces OOH– species and very high low temperature CO oxidation activity. • In the absence of surface adsorbed water, the CO oxidation reaction proceeds using O 2 – species. A polyoxometalate-supported Au cluster catalyst (Au/POM) exhibited high catalytic activity for CO oxidation at room temperature; however, its activity decreased at the reaction temperature above 60 ℃. Density functional theory calculations were performed to elucidate the unique catalytic activities. Our calculations show that the interactions between water molecules accommodated within the defect site of the support and the O 2 adsorbed on the Au cluster generate active OOH − species. This OOH − species reacts readily with CO, resulting in high CO oxidation catalytic activity between −40 and 40 degrees Celsius. The activation barrier of CO oxidation over Au/POM in the presence of H 2 O is much lower than that in the absence of H 2 O. This is in good agreement with the experimental results, indicating that surface-adsorbed water allows for high CO oxidation catalytic activity around room temperature, whereas the activity decreases at higher temperatures owing to the desorption of surface-adsorbed water molecules.