Two-dimensional Cr₂X₂Y₆ (X = Si, Ge; Y = S, Se, Te) family with potential application in photocatalysis

Abstract

Photocatalysis is an attractive route for energy harvesting and pollution mitigation, however, designing an optimal catalyst is rather challenging. Motivated by fundamental interest and potential applications, the investigations of two-dimensional (2D) photocatalyst are important subjects in solar energy conversion. In this work, the stability, electronic, and optical properties of 2D Cr$_2$X$_2$Y$_6$ (X = Si, Ge; Y = S, Se, Te) family are investigated to explore their photocatalytic activity for water splitting. Density functional theory (DFT) and ab-initio molecular dynamics (AIMD) calculations were employed. The electronic band structure calculations indicate that all these monolayers, except Cr$_2$Ge$_2$Te$_6$ and Cr$_2$Si$_2$Te$_6$, have an adequate bandgap, as well as suitable band-edge positions for photocatalytic water splitting reactions, specifically under acidic conditions. Moreover, the studied materials show strong capability of harvesting sunlight, that is essential for photocatalytic activity. Remarkably, Cr₂Ge₂Se₆ and Cr₂Si₂Se₆ monolayers exhibited high solar-to-hydrogen energy conversion efficiencies of 14.89% and 13.26%, respectively. The presented results pave the way for designing other electronically optimized layered photocatalysts for water splitting.