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.