Carbon monoxide adsorption on silver doped gold clusters

Area of Science:

• * Physical Chemistry
• * Surface Science
• * Nanomaterials Science

Background:

• * Nanometer-sized gold particles exhibit unexpected catalytic activity, a phenomenon not fully understood.
• * Previous research primarily focused on charged, small gold clusters, leaving neutral clusters less explored.
• * Understanding the reactivity of neutral gold clusters is crucial for explaining their catalytic properties.

Purpose of the Study:

• * To investigate the size and silver-doping dependent reactivity of neutral gold clusters towards carbon monoxide adsorption.
• * To elucidate the role of electronic shell structure and silver dopants in the catalytic behavior of gold clusters.
• * To provide experimental data that can inform theoretical models of cluster reactivity.

Main Methods:

• * Gas-phase reactivity measurements using a low-pressure reaction cell at 140 K.
• * Investigation of neutral bare gold clusters (Au(n)) and silver-doped gold clusters (Au(n)Ag(m), where n = 10-45 and m = 0, 1, 2).
• * Analysis of carbon monoxide adsorption on these clusters.

Main Results:

• * Carbon monoxide adsorption probability is strongly dependent on the electronic shell structure of gold clusters, with closed shells showing highest reactivity.
• * Substitution of gold atoms with silver atoms generally reduces the reactivity of the clusters.
• * The presence of one silver atom had a minor impact on reactivity for most sizes, while two silver atoms led to a more pronounced decrease.

Conclusions:

• * Electronic shell structure significantly influences the catalytic reactivity of neutral gold clusters for CO adsorption.
• * Silver doping acts as a poison, reducing the reactivity of gold clusters, with the effect intensifying with more silver atoms.
• * Experimental findings are consistent with the Blyholder model, incorporating dopant-induced electron transfer, altered hybridization, and geometric changes.