Unveiling the photocatalytic potential of two-dimensional ferroelastic LuSX monolayers for efficient water splitting: a first-principles discovery†

This study represents the first demonstration that two-dimensional (2D) ferroelastic (FE) materials can enhance photocatalytic applications. By comprehensive first-principles calculations, we identified the LuSX (X = Cl, Br, I) monolayers as novel FE photocatalysts for water splitting. These monolayers exhibit direct band gaps ranging from 3.67 eV to 4.09 eV, with favorable band edge alignments for photocatalytic water splitting across a range of pH values. The ferroelastic nature of LuSX enables tunable electronic properties through strain engineering, facilitating charge separation and enhancing photocatalytic efficiency. Our computations revealed their low FE switching barriers (as low as 0.12 eV per atom for LuSI) and high reversible FE strain, surpassing many known 2D materials. Furthermore, these LuSX monolayers exhibit strong UV-driven photocatalytic activity across all pH values without needing external strain. Under compressive strains, their ability to harvest a broader range of the solar spectrum is enhanced, significantly boosting their photocatalytic efficiency. These findings open up new avenues for using 2D ferroelastic materials in energy conversion applications, positioning LuSX monolayers as promising candidates for efficient, flexible photocatalysts.