Electrochemical Hydrogen Evolution at the Interface of Monolayer VS₂ and Water from First-Principles Calculations

Area of Science:

• Materials Science
• Electrochemistry
• Computational Chemistry

Background:

• The hydrogen evolution reaction (HER) is crucial for clean energy production.
• Vanadium disulfide (VS2) is a promising catalyst for HER, with different phases exhibiting varying activities.
• Understanding the interfacial effects on HER activity is essential for catalyst design.

Purpose of the Study:

• To investigate the HER activity of monolayer 2H phase VS2 at the electrochemical interface with water.
• To elucidate the reaction mechanism and identify the rate-determining step.
• To compare the HER performance of 2H phase VS2 with other phases, particularly 1T phase VS2.

Main Methods:

• Density functional theory (DFT) calculations were employed.
• The study focused on the electrochemical double-layer interface.
• Simulations considered typical HER conditions, including surface hydrogen coverage and hydronium concentration.

Main Results:

• A low hydrogen coverage of 12% and high hydronium concentration of 8.3% were predicted for 2H phase VS2 under HER conditions.
• The HER proceeds via the Volmer-Heyrovsky route.
• A significant overall reaction barrier of approximately 1.0 eV was calculated for 2H phase VS2.

Conclusions:

• 2H phase VS2 exhibits considerably lower HER activity compared to 1T phase VS2.
• The 1T-to-2H phase transformation, potentially induced by reducing VS2 thickness, can significantly impair its HER performance.
• Catalyst design strategies should consider phase stability and its impact on electrochemical reactions.