Size-dependent catalytic activity for CO oxidation over sub-nano-Au clusters

Area of Science:

• * Nanocatalysis
• * Surface Science
• * Computational Chemistry

Background:

• * Gold (Au) nanocatalysts exhibit high activity but their sub-nanometer size effects on catalysis are not well understood.
• * Understanding these size effects is crucial for designing efficient nanocatalysts.

Purpose of the Study:

• * To systematically investigate the size-dependent catalytic activity of sub-nanometer gold clusters.
• * To elucidate the relationship between geometric structure, adsorption properties, and catalytic performance in CO oxidation.

Main Methods:

• * Employed revised particle swarm optimization (RPSO) and density functional theory (DFT) to determine global-minimum structures of Au clusters (N=2-300, <2.5 nm).
• * Utilized geometric structural descriptors to link cluster features with adsorption energy and CO oxidation rates.
• * Performed high-throughput evaluation of adsorption energy and catalytic activity across various cluster sites.

Main Results:

• * A volcano-shaped relationship was observed between the mass activity of sub-nanometer Au clusters and cluster size, peaking at 0.75 nm diameter.
• * Edge and kink sites demonstrated significantly higher turnover frequencies (~10^6) compared to face sites (~10^2).
• * Weak adsorption of CO and O2 on face sites made adsorption the rate-determining step, reducing overall activity.

Conclusions:

• * Sub-nanometer gold cluster size critically influences catalytic activity, with optimal performance at ~0.75 nm.
• * Site-specific activity (edge/kink vs. face) is governed by adsorption energetics, impacting the rate-determining step.
• * This study provides fundamental mechanistic insights into the size-dependent catalysis of gold sub-nanoclusters.