Density functional study of hydrogen binding on gold and silver-gold clusters

Area of Science:

• Computational Chemistry
• Materials Science
• Surface Science

Background:

• Understanding hydrogen interaction with metal clusters is crucial for catalysis and materials design.
• Bimetallic clusters offer tunable properties compared to monometallic counterparts.
• The influence of charge state on cluster-hydrogen binding is not fully elucidated.

Purpose of the Study:

• To theoretically investigate hydrogen binding on small bimetallic silver-gold (Ag(m)Au(n)) and pure gold (Au(n)) clusters.
• To analyze the effect of cluster composition (Ag/Au ratio) and charge state (neutral, negative, positive) on hydrogen binding.
• To determine the preferred binding sites and fragmentation pathways of cluster hydrides.

Main Methods:

• Theoretical calculations were performed on small bimetallic Ag(m)Au(n) and pure Au(n) clusters (m + n <= 5).
• Neutral, anionic, and cationic charge states were considered for cluster-hydride systems.
• Analysis included binding energies, ionization potentials, electron affinities, and vibrational frequencies.

Main Results:

• Cluster composition and charge state significantly influence the most favorable hydrogen binding site.
• Adiabatic ionization potentials, electron affinities, and hydrogen binding energies increase with higher gold content.
• Cationic clusters favor gold-containing product ejection, while anionic clusters favor silver-containing product ejection.
• The gold-hydrogen interaction is stronger than the silver-hydrogen interaction, as indicated by metal-H frequency and bond length.

Conclusions:

• The electronic and structural properties of Ag(m)Au(n) clusters are highly sensitive to composition and charge.
• Gold content plays a critical role in enhancing hydrogen binding strength and stability.
• Differential fragmentation behavior of cationic and anionic hydrides provides insights into their stability and reactivity.