Electronic asymmetry in Janus Ce/ThXY (X, Y = S and Se) promoting the photocatalytic oxygen evolution reaction in acidic environments

Abstract

Two-dimensional (2D) materials have emerged as promising candidates for photocatalytic water splitting due to their exceptional electronic and structural properties. While transition metal dichalcogenides (TMDs) have been widely studied, the potential of f-electron-based dichalcogenides remains underexplored. In this study, we employ first-principles density functional theory (DFT) calculations to investigate the structural stability, electronic properties, and photocatalytic performance of monolayer thorium (Th) and cerium (Ce)-based Janus dichalcogenides MXY (M = Th, Ce; X, Y = S, Se, Te). Our findings reveal that the 1T-phase is the most thermodynamically stable configuration, as f-orbitals tend to favor O_h symmetry. Band structure analysis indicates that 1T-phase Th-based compounds possess conduction and valence band positions suitable for overall water splitting, while Ce-based materials exhibit limitations due to lower conduction band minima. Optical absorption spectra highlight that ThSe₂, ThSSe, ThTe₂, ThSTe, and ThSeTe demonstrate strong visible-light absorption, making them potential photocatalysts. Additionally, free energy analysis of hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) intermediates identifies ThSTe and ThSeTe as highly active for the OER across a broad pH range. These findings provide insights into the design of f-electron-based materials for renewable energy applications and highlight their potential as next-generation photocatalysts.