Characterization of changes in the electronic structure of platinum sub-nanoclusters supported on graphene induced by...

As the sizes of noble metal catalysts, such as platinum, have been successfully minimized, fundamental insights into the electronic properties of metal sub-nanoclusters are increasingly sought for optimizing their catalytic performance. However, it is difficult to rationalize the catalytic activities of metal sub-nanoclusters owing to their more complex electronic structure compared with those of small molecules and bulky solids. In this study, the adsorption of molecular oxygen on a Pt₁₃ sub-nanocluster supported on a graphene layer was analyzed using density functional theory. Unlike bulk Pt, the Pt₁₃ sub-nanocluster has multiple adsorption sites, and the adsorption energy depends strongly on the type of adsorption site. The O₂ adsorption energy does not correlate with the transferred charge between O₂ and the Pt₁₃ moiety; therefore, to elucidate the differences in the adsorption sites, we propose an original approach for analyzing the electronic structure change in metal sub-nanoclusters caused by molecular adsorption. Our analysis of the integrated local density of state (LDOS) revealed that O₂ adsorption on the Pt₁₃ sub-nanocluster has a distinct feature, different from that on a smaller Pt₂ cluster or rather a larger Pt slab. The change in the electronic structure of the Pt₁₃ moiety was primarily observed near the Fermi level, different from that of the Pt slab whose DOS was distributed over a wide energy range. Furthermore, the change in the integrated LDOS correlated well with the O₂ adsorption energy on the Pt₁₃ sub-nanocluster.