Electronegativity principle for hydrogen evolution activity using first-principles calculations

Area of Science:

• Physical Chemistry
• Materials Science
• Computational Chemistry

Background:

• The Sabatier principle, using adsorption energy (ΔG_H), is a common descriptor for heterogeneous catalyst activity.
• This descriptor often fails to quantitatively predict reaction rates due to its neglect of charge transfer dynamics.
• Accurate prediction of catalytic activity is crucial for developing efficient electrocatalysts, such as for the hydrogen evolution reaction (HER).

Purpose of the Study:

• To investigate the role of interfacial charge transfer in catalytic activity for the hydrogen evolution reaction (HER).
• To identify a more accurate descriptor for predicting HER catalyst kinetics beyond traditional thermodynamic parameters.
• To establish a new principle for catalyst design based on electronic properties.

Main Methods:

• Density Functional Theory (DFT) calculations were employed.
• Both canonical and grand-canonical ensembles were utilized to model catalytic systems.
• The correlation between reaction kinetics, interfacial charge transfer, and catalyst electronic properties (Mulliken electronegativity) was analyzed.

Main Results:

• A positive correlation between reaction kinetics and interfacial charge transfer was observed for the HER.
• The grand-canonical ensemble provided a more linear Sabatier relationship for HER catalysts compared to the canonical ensemble, highlighting the importance of surface charge.
• Catalyst Mulliken electronegativity (χ) was found to be a robust descriptor, showing a linear dependence of the reaction barrier on χ across various catalysts.

Conclusions:

• Lower catalyst electronegativity leads to a lower reaction barrier and consequently a faster hydrogen evolution reaction rate.
• The proposed electronegativity principle offers a reaction route and pH-independent method for predicting and designing efficient HER catalysts.
• This work establishes interfacial charge transfer, captured by electronegativity, as a critical factor in heterogeneous catalysis.