Hydrogen evolution reaction in high-entropy MXenes: Insights into atomic configurations

Area of Science:

• Materials Science
• Catalysis
• Computational Chemistry

Background:

• High-entropy (HE) MXenes offer enhanced catalytic activity and stability due to diverse active sites and tunable compositions.
• Solute segregation during synthesis can lead to preferential atomic distributions, negatively impacting catalytic performance.

Purpose of the Study:

• To evaluate HE variants of M2C(-T)2 MXenes with varying surface terminations for the hydrogen evolution reaction (HER).
• To investigate the effects of compositional tuning and atomic ordering on HER performance and stability.

Main Methods:

• Density Functional Theory (DFT) calculations.
• Crystal Orbital Hamilton Population (COHP) analysis.
• Evaluation of hydrogen adsorption and diffusion energetics.

Main Results:

• Substitution of Ti with other transition metals improved H* adsorption and diffusion.
• Molybdenum (Mo) atoms exhibited short-range ordering with strong Mo-Mo interactions, facilitating H* diffusion pathways.
• Hydrogen spillover significantly reduced the Volmer-Tafel barrier for HER from 0.94 eV to 0.48 eV.
• OH-terminated HE MXenes showed good thermodynamic and mechanical stability (Young's modulus ~170 N/m, shear modulus ~68 N/m).

Conclusions:

• Engineering the composition of HE MXenes can induce favorable short-range atomic ordering.
• This ordering facilitates the hydrogen evolution reaction (HER) by creating multiple hydrogen diffusion routes.
• HE MXenes, particularly OH-terminated variants, show promise as stable and efficient electrocatalysts for HER.