Gas Supersaturation-Dependent Contact Angle for Bubble Nucleation in Electrochemistry

Area of Science:

• Electrochemistry
• Surface Science
• Computational Chemistry

Background:

• Surface bubble nucleation on electrodes is typically assumed to occur at a constant Young's contact angle.
• This assumption overlooks the significant impact of extreme local gas supersaturation on interfacial properties.

Purpose of the Study:

• To investigate how gas supersaturation affects the interfacial tensions governing bubble formation.
• To develop a theoretical framework for predicting bubble contact angles under supersaturation.
• To challenge the classical assumption of a constant contact angle.

Main Methods:

• Molecular dynamics simulations
• Thermodynamic analysis
• Atomistic simulations to extract interfacial parameters

Main Results:

• Gas supersaturation fundamentally alters the three interfacial tensions, leading to deviations from Young's contact angle prediction.
• Bubble contact angles can increase or decrease with supersaturation, depending on the specific gas-solvent-substrate system (e.g., N2-water-graphene vs. H2-water-Pt).
• Dimensionless interface competition parameters explain these observed differences by characterizing gas adsorption and enrichment at the liquid-solid interface.

Conclusions:

• The study establishes supersaturation-dependent interfacial thermodynamics as a critical factor in bubble nucleation.
• Findings challenge classical understanding and provide a new design principle for efficient gas-evolving electrocatalysts.
• Accurate prediction of bubble contact angles requires considering supersaturation effects.