First-PrinciplesInvestigation of Monolayer Sc₂Se₂X₂ (X = Cl, Br) as a High-PerformancePhotocatalyst for Efficient Water Splitting

Two-dimensional materials hold substantial promise for photocatalytic water splitting, primarily due to their unique structural properties and high-efficiency light absorption. However, finding such applicable materials poses a huge challenge because there are many strict requirements to meet. In this study, we employ first-principles calculations to design and evaluate two monolayers, Sc₂Se₂X₂ (X = Cl, Br), highlighting their potential as high-performance photocatalysts. these materials exhibit low activation energy barriers for water-splitting redox reactions, which facilitate high catalytic performance. The photogenerated electric field promotes oxygen adsorption, accelerating the overall reaction. The structural, mechanical, dynamical, and thermodynamic stabilities of these materials are confirmed through comprehensive analyses. With band gaps of 2.65 and 2.40 eV, respectively, these materials meet the band gap requirements for photocatalytic water splitting. Furthermore, a prominent characteristic of these materials is their significantly high electron mobility along the <i>y</i>-axis, reaching 26,560.74 and 17,634.01 cm² V^–1 s^–1, which far surpasses the hole mobility. This characteristic effectively reduces electron–hole recombination and enhances photocatalytic performance. With solar-to-hydrogen efficiencies of 13.60% and 20.58%, respectively, these materials surpass the 10% threshold required for commercial photocatalytic applications. These findings indicate that monolayer Sc₂Se₂X₂ (X = Cl, Br) has great theoretical potential for photocatalytic water splitting.