On reversible bonding of hydrogen molecules on platinum clusters

Area of Science:

• Computational Chemistry
• Surface Science
• Materials Science

Background:

• Understanding the interaction between hydrogen molecules and metal clusters is crucial for catalysis.
• Platinum clusters are widely used in various catalytic applications, including hydrogenation reactions.

Purpose of the Study:

• To investigate the local reactivity and binding sites of hydrogenated platinum clusters (Pt clusters).
• To elucidate the nature of hydrogen molecule (H(2)) adsorption on Pt clusters.
• To characterize the electronic properties governing H(2) binding.

Main Methods:

• Employed the regional density functional theory (DFT) method to study hydrogenated platinum clusters.
• Analyzed the electronic structure, focusing on antibond orbitals and electronic chemical potential.

Main Results:

• Identified antibond orbitals as preferential binding sites for H(2) on Pt clusters.
• Observed that these sites possess low electronic chemical potential, strong directionality, and electrophilic character.
• Formed platinum-dihydrogen (Pt-H(2)) sigma complexes through the occupation of lowest electronic chemical potential sites, associated with Pt-H antibonds (sigma(PtH) (*)).
• Demonstrated mutual stabilization between the sigma complex and the trans Pt-H bond.
• Characterized the H(2) activation on Pt clusters as an interaction stronger than physisorption or hydrogen bonding, yet weaker than chemisorption, analogous to heme-oxygen (heme-O(2)) complexes.

Conclusions:

• The electronic structure of platinum clusters dictates specific binding sites for hydrogen activation.
• The observed Pt-H(2) sigma complex formation and stabilization provide insights into hydrogenation mechanisms.
• The findings contribute to understanding hydrogen storage and catalytic processes involving platinum-based materials.