Factors that influence hydrogen binding at metal-atop sites

Area of Science:

• Surface Science
• Materials Chemistry
• Computational Chemistry

Background:

• The d-band model effectively predicts adsorbate chemisorption on transition metals.
• Deviations exist for hydrogen adsorption at atop sites and on doped surfaces.
• Existing models fail to explain certain hydrogen adsorption phenomena.

Purpose of the Study:

• To develop a more comprehensive model for hydrogen adsorption on transition metal surfaces.
• To investigate factors beyond the d-band center influencing hydrogen binding energies.
• To explain discrepancies in hydrogen adsorption predictions.

Main Methods:

• Utilized density functional theory (DFT) calculations.
• Developed a multi-factor model including d-band center, d-band filling, renormalized adsorbate states, coupling matrix elements, and bond lengths.
• Applied the model to mono- and bimetallic (111) surfaces.

Main Results:

• Hydrogen adsorption at atop sites is influenced by multiple factors, not solely the d-band center.
• The model successfully correlates with DFT-calculated hydrogen binding energies.
• Lower repulsive contributions explain strong hydrogen adsorption on 5d metal surfaces.

Conclusions:

• A multi-factor model provides a more accurate description of hydrogen adsorption.
• The d-band center alone is insufficient for predicting hydrogen binding energies.
• Understanding these factors is crucial for designing catalytic materials.