Exploring hydrogen adsorption and release in 2D M₂C-MXenes: structural and functional insights

Area of Science:

• Materials Science
• Energy Storage
• Surface Chemistry

Background:

• Two-dimensional M2C-MXenes possess unique properties like low weight and tunable surfaces, making them suitable for hydrogen energy applications.
• Understanding hydrogen interaction with these materials is crucial for developing efficient hydrogen storage solutions.

Purpose of the Study:

• To investigate hydrogen adsorption/desorption and stability in 19 pure M2C-MXenes nanosheets.
• To identify MXene compositions with optimal hydrogen binding and evolution characteristics.

Main Methods:

• Computational investigation of hydrogen adsorption energies on M2C-MXene surfaces.
• Analysis of hydrogen atom binding stability and hydrogen evolution pathways.
• Examination of stacking configurations and thermodynamic stability of hydrogenated M2C-MXenes.

Main Results:

• Hydrogen adsorption occurs mainly via physisorption, with Mn2C, Fe2C, Ag2C, and Cd2C showing the weakest adsorption energies.
• Chemisorption dominates for hydrogen atoms, leading to H2 dissociation.
• Ti2C and Zr2C exhibit the most stable hydrogen atom binding.
• Cu2C and Ag2C surfaces facilitate facile hydrogen evolution.
• Hydrogenated M2C surfaces (e.g., Co2C, Zr2C) show thermodynamic stability in FCC and HCP configurations.

Conclusions:

• Pure M2C-MXenes display diverse hydrogen utilization capabilities.
• Ti2C and Zr2C are promising for stable hydrogen atom storage.
• Cu2C and Ag2C are suitable for hydrogen release applications.
• This research provides insights for designing MXene-based materials for high-capacity hydrogen storage.