Interface Engineering of Gold Nanoclusters for CO Oxidation Catalysis.

Catalysts based on atomically precise gold nanoclusters serve as an ideal model to relate the catalytic activity to the geometrical and electronic structures as well as the ligand effect. Herein, we investigate three series of ligand (thiolate)-protected gold nanoclusters, including Au ₃₈ (SR) ₂₄ , Au ₃₆ (SR') ₂₄ , and Au ₂₅ (SR″) ₁₈ , with a focus on their interface effects using carbon monoxide (CO) oxidation as a probe reaction. The first comparison is within each series, which reveals the same trend for the three series that, rather than the bulkiness of carbon tails as commonly thought, the steric hindrance of ligands at the interface between the thiolate, Au, and CeO ₂ inhibits CO adsorption onto Au sites and hence adversely affects the activity of CO oxidation. The second comparison is between the sets Au ₃₈ (SR) ₂₄ and Au ₃₆ (SR') ₂₄ of nearly the same size, which reveals that the Au ₃₆ (SR') ₂₄ nanoclusters (with face centered cubic structure) are not sensitive to thermal pretreatment conditions, whereas the Au ₃₈ (SR) ₂₄ catalysts (icosahedral structure) are and an optimum activity is observed at a pretreatment temperature of 150 °C. Overall, the atomically precise Au _n (SR) _m nanoclusters have revealed unprecedented details on the catalytic interface and atomic structure effects. It is hoped that such insights will benefit the ultimate goal of catalysis in future design of enzymelike catalysts for environmentally friendly green catalysis.