CO oxidation on TiO(2) (110) supported subnanometer gold clusters: size and shape effects

Area of Science:

• Heterogeneous catalysis
• Surface science
• Computational chemistry

Background:

• Subnanometer metal clusters are crucial in catalysis, but their size- and shape-dependent properties are not fully understood.
• Titanium dioxide (TiO2) is a widely used support material in catalysis.
• Understanding the interplay between gold cluster size, shape, and the TiO2 support is key to optimizing catalytic performance.

Purpose of the Study:

• To comprehensively study the catalytic activities of subnanometer gold clusters (Aun/TiO2, n = 1-4, 7, 16-20) for CO oxidation.
• To investigate the size- and shape-dependent catalytic behavior of gold clusters on a TiO2(110) surface.
• To elucidate the role of the TiO2 support in enhancing catalytic activity.

Main Methods:

• Density functional theory (DFT) calculations were employed to model the electronic structure and energetics of gold clusters on TiO2.
• Microkinetics analysis was used to predict reaction rates and understand reaction pathways.
• Validation of methodologies was performed by comparing DFT/microkinetics predictions with existing experimental data for benchmark systems.

Main Results:

• Catalytic activity generally increases with cluster size up to Au18.
• The hollow-cage Au18 isomer shows the highest CO oxidation activity, approximately 30 times greater than Au7/TiO2, while its pyramidal isomer is significantly less active.
• The TiO2 support enhances catalytic activity by weakening CO adsorption and facilitating O2 activation, with a hollow-cage Au18 cluster demonstrating robustness and thermal stability.

Conclusions:

• Catalytic activity of Aun/TiO2 is strongly dependent on both the size and isomeric structure of the gold clusters.
• The hollow-cage Au18 isomer represents a highly active catalytic species for CO oxidation on TiO2.
• The developed theoretical framework, including a contour plot correlating adsorption energies and reaction rates, can guide the design of efficient supported metal cluster catalysts.