Dispersity-dependent activity of Pd on bare and pre-oxidized Cu(111) surface

Bimetallic systems can be significantly affected in terms of the catalytic activity by their compositions as well as atomic structures. This study demonstrates that the single Pd atoms and ultrasmall clusters dispersed on the surface of Cu2O/Cu(1 1 1) exhibit significantly enhanced oxophilicity and auto-oxidizes into a checkboard-like Pd4O8 structure by grabbing oxygen atoms from the Cu2O thin film. As a comparison, the Pd ad-islands on the Cu (1 1 1) surface possess compressed lattice and present a lowered activity to oxygen, but in turn enhances the oxophilicity of the Cu substrate and leads to preferential formation of cuprous oxide overlayers on the Pd islands. The drastically different oxidative reactivity of Pd on the respective Cu2O/Cu(1 11) and Cu(1 1 1) surfaces dictate close correlations to their dispersion statuses. It thus provides a strategy for tuning the catalytic activities of similar bimetallic systems.