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

The electronic properties, effective masses, and photocatalytic performances for water splitting of Sc₂CT₂ and Janus Sc₂CXT (X, T = F, O, H, and OH) MXenes were systematically investigated using density functional theory (DFT). Our calculations show that Sc₂CT₂ (T = F, O, H, and OH) and Sc₂CXT (X, T = F, H, and OH) have band gaps from 0.782 to 3.000 eV. Sc₂CO₂ satisfies thermodynamic requirements for water splitting at pH 0 and 14, but its low solar-to-hydrogen (STH) efficiency (<10%) limits its practical application. In contrast, Sc₂CF₂, Sc₂CH₂ and Sc₂CHF demonstrate suitable band edge alignments and enhanced STH efficiencies at pH 7 and 14, with Sc₂CH₂ achieving a notable 18.34% STH efficiency at pH 14. Gibbs free energy calculations indicate that light irradiation enables Sc₂CF₂, Sc₂CH₂ and Sc₂CHF to catalyze spontaneous hydrogen and oxygen evolution. These combined properties make Sc₂C-based MXenes promising photocatalysts for renewable fuel generation.