Binding of CO and O on Low-Symmetry Pt Clusters Supported on Amorphous Silica

We quantified the impact of support interactions on the binding and interaction energies of CO and O adsorbed on Pt13 nanoclusters supported on amorphous silica surfaces through the use of density functional theory calculations. We used an accurate model for amorphous silica having two different surface silanol concentrations, corresponding to low (200 °C) and high (715 °C) surface pretreatment temperatures. We compared CO and O adsorbed on supported and freestanding Pt13 clusters. We found that Pt13 is highly susceptible to both support- and adsorbate-induced reconstruction, depending on the relaxed structure of the Pt13 cluster on the surface. Structure relaxation effects dominate over electronic effects of the support. We considered an ensemble of 50 different systems by varying the placement of the Pt13 cluster on the surfaces and by exploring a range of different binding sites for CO and O on the Pt13 cluster. In select cases, binding energy differences between supported and freestanding Pt13 are as large as 2 eV. However, the mean absolute error between supported and freestanding clusters over all systems we studied is only a few tenths of an eV. Coverage effects on coadsorption of CO and O are significantly different on supported clusters compared with the Pt(111) surface. Our results can be used for predicting when support interactions may be important for any reaction catalyzed by small metal nanoclusters.