Theoretical study of CO adsorption on Au/alumina substrates

Abstract Aiming to understand the role of the substrate in the adsorption of carbon monoxide on gold clusters supported on metal‐oxides, we have started a study of that process on two different alumina substrates: a fully relaxed stoichiometric (Al₂O₃)₂₀ cluster, and the Al terminated (0001) surface of α‐Al₂O₃. Here we present first principles calculations for the adsorption of CO on a gold atom supported on these alumina substrates. The (Al₂O₃)₂₀ cluster has atomic and electronic structures with similarities to those of amorphous alumina, and offers more different sites than the (0001) surface to bind gold clusters. In both cases, atomic Au adsorbs on top of a three coordinated Al atom with similar environment, being the binding energy higher in the case of the cluster substrate. CO absorbs preferentially on top of the Au atom, but in the case of cluster substrate, CO adsorbs also bridging Au and a neighbor O atom. This result suggest that the activity towards CO adsorption is larger for the Au/(amorphous‐cluster) than for Au/(0001)‐surface alumina substrate. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)