Hydrogen evolution reaction of Be + H₂O (n = 5-9) based on density functional theory

Area of Science:

• Computational Chemistry
• Materials Science
• Physical Chemistry

Background:

• Beryllium clusters are of interest due to their unique electronic and structural properties.
• Understanding their interaction with water is crucial for catalysis and materials design.
• Previous studies have explored smaller beryllium clusters, but systematic investigations of larger ones (n=5-9) with water are limited.

Purpose of the Study:

• To investigate the structural evolution of beryllium clusters (Be_n, n=5-9).
• To determine the adsorption energies of Be_n@H₂O complexes.
• To elucidate the mechanism and energetics of the hydrogen evolution reaction (HER) involving Be_n and H₂O.

Main Methods:

• Density Functional Theory (DFT) calculations were employed.
• The PBE0-D3/Def2TZVP level of theory was utilized for all computations.
• Structural optimization, energy calculations, and transition state searches were performed.

Main Results:

• Global minimum structures for Be_n (n=5-9) clusters, excluding Be₇, exhibit higher point group symmetry.
• The Be₇ cluster's high symmetry was found to be unstable.
• Be₉@H₂O showed the largest adsorption energy (-1.45 eV).
• Hydrogen evolution reactions (Be_n + H₂O) are exothermic, with all intermediates and products below the equilibrium constant (EC).
• Significant energy release and structural changes occur during O-H bond cleavage in Be_n@H₂O complexes, notably in the Be₇ + H₂O reaction.
• The Be₆ + H₂O reaction involves eight transition states, with the second O-H bond cleavage being more energy-demanding than the first.
• The Be₈ + H₂O reaction proceeds through only three transition states and exhibits the highest reaction energy (-4.13 eV).

Conclusions:

• Beryllium cluster structure and stability are influenced by size and symmetry.
• Beryllium clusters effectively interact with water, facilitating hydrogen evolution.
• The hydrogen evolution reaction mechanism varies with cluster size, offering insights into catalytic activity and potential applications.