Monolayer protected gold nanoparticles on ceria for an efficient CO oxidation catalyst

Since the pioneering work of Haruta et al.1 in 1987 it has been demonstrated that gold nanoparticles (AuNPs) on appropriate supports are excellent catalysts to promote oxidation processes.2 Critical features are the size and the oxidation state of the gold atoms of the clusters. It is well accepted that only gold particles with diameter lower than 5 nm are catalytically active. The crucial point is the development of simple strategies for preparing catalysts containing clusters small enough to maximize the number of metal atoms interacting with the support, in order to increase their reactivity and the catalyst stability. No general consensus exists on the oxidation state of the gold atoms at the active site. In fact, small Au clusters, cationic gold atoms at different oxidation states [Au(I), Au(III), Au(?+)], and gold atoms at the supporting interface have been claimed to be responsible for oxidation reactions.3