On the mechanism of hydrogen-promoted gold-catalyzed CO oxidation

The kinetics of CO oxidation, H2 oxidation and preferential CO oxidation (PrOx) over Au/Al2O3 catalysts have been investigated. The catalysts with the smallest particles (∼2 nm) are the most active for all three reactions. As previously observed, the presence of H2 greatly promotes CO oxidation, which becomes faster than CO-free H2 oxidation at low temperature. From these results and on the basis of previous works, we propose a complete PrOx mechanism. The reaction involves Au–OOH, Au–OH and Au–H intermediates, also involved in H2 oxidation, and benefits from the presence of low-coordination sites.