Orientational Water Bonding on Pt(111): Beyond the Frontier Orbital Principle

Area of Science:

• Surface Science
• Computational Chemistry
• Materials Science

Background:

• Water-metal bonding understanding traditionally relies on the frontier orbital principle, focusing on the Highest Occupied Molecular Orbital (HOMO).
• This principle primarily explains globally stable water-metal interactions on surfaces.

Purpose of the Study:

• To investigate the applicability of the frontier orbital principle to metastable water bonding configurations on metal surfaces.
• To elucidate the specific orbital interactions governing metastable water adsorption on Platinum(111) (Pt(111)).

Main Methods:

• Utilizing density functional theory (DFT) calculations to model water-metal interactions.
• Analyzing orbital shifts and electronic depopulations to identify key bonding indicators.

Main Results:

• The frontier orbital principle is insufficient for explaining metastable water bonding on Pt(111).
• HOMO-1 plays a decisive role, surpassing HOMO in orbital shifts and depopulation for metastable configurations.
• Stable configurations show σ-like overlap for both HOMO-1 and HOMO, while metastable ones exhibit a balance between σ-like (HOMO-1) and π-like (HOMO) interactions.

Conclusions:

• Orbital roles in water-metal bonding are more complex than previously understood.
• Findings challenge existing models and provide deeper insights into water-metal interactions at interfaces.
• This work bridges theoretical understanding of electrified water at electrochemical interfaces with fundamental water science on metal surfaces.