Surface termination-dependent Sc₂C MXenes: a first-principles study on photocatalytic water splitting

Area of Science:

• Materials Science
• Computational Chemistry
• Renewable Energy

Background:

• MXenes are a class of two-dimensional materials with diverse electronic properties.
• Photocatalytic water splitting is a key process for renewable hydrogen fuel production.
• Tuning the surface termination of MXenes can significantly alter their properties.

Purpose of the Study:

• To investigate the electronic properties and photocatalytic performance of Sc₂CT₂ and Janus Sc₂CXT MXenes for water splitting.
• To identify promising Sc₂C-based MXenes for efficient solar hydrogen generation.
• To understand the theoretical underpinnings of their photocatalytic activity.

Main Methods:

• Density Functional Theory (DFT) calculations were employed.
• Electronic band structures and effective masses were computed.
• Thermodynamic requirements and Gibbs free energy for water splitting were analyzed.
• Solar-to-hydrogen (STH) efficiencies were estimated.

Main Results:

• Sc₂CT₂ and Sc₂CXT MXenes exhibit tunable band gaps ranging from 0.782 to 3.000 eV.
• Sc₂CO₂ shows thermodynamic feasibility but low STH efficiency (<10%).
• Sc₂CF₂, Sc₂CH₂, and Sc₂CHF possess suitable band edge alignments for water splitting.
• Sc₂CH₂ achieved a notable 18.34% STH efficiency at pH 14.
• Light irradiation facilitates spontaneous hydrogen and oxygen evolution for Sc₂CF₂, Sc₂CH₂, and Sc₂CHF.

Conclusions:

• Sc₂C-based MXenes, particularly Sc₂CF₂, Sc₂CH₂, and Sc₂CHF, are promising candidates for photocatalytic water splitting.
• These materials demonstrate potential for efficient renewable fuel generation.
• DFT provides a valuable framework for designing advanced photocatalysts.