Alumina-supported sub-nanometer Pt-10 clusters: amorphization and role of the support material in a highly active CO oxidation catalyst

Catalytic CO oxidation is unveiled on size-selected Pt-10 clusters deposited on two very different ultrathin (approximate to 0.5-0.7 nm thick) alumina films: (i) a highly ordered alumina obtained under ultra-high vacuum (UHV) by oxidation of the NiAl(110) surface and (ii) amorphous alumina obtained by atomic layer deposition (ALD) on a silicon chip that is a close model of real-world supports. Notably, when exposed to realistic reaction conditions, the Pt-10/UHV-alumina system undergoes a morphological transition in both the clusters and the substrate, and becomes closely akin to Pt-10/ALD-alumina, thus reconciling UHV-type surface-science and real-world experiments. The Pt-10 clusters, thoroughly characterized via combined experimental techniques and theoretical analysis, exhibit among the highest CO oxidation activity per Pt atom reported for CO oxidation catalysts, due to the interplay of ultra-small size and support effects. A coherent interdisciplinary picture then emerges for this catalytic system.