Computational study of the electronic structures and photocatalytic water splitting performances of Janus aluminium chalcogenide monolayers

Through extensive first-principles calculations based on density functional theory, we investigate the structural stabilities, electronic and photocatalytic properties of Janus aluminium chalcogenide monolayers (Al2XY, X/Y = S, Se, and Te). Our studies reveal that these Janus Al2SSe, Al2SeTe and Al2SeTe monolayers are dynamically, thermally, and mechanically stable, and exhibit indirect semiconductor characteristics with suitable band gaps of 1.84 - 2.80 eV. Moreover, according to the calculated band alignment and optical absorption spectra, we successfully identify that the Al2SeTe monolayer would be a highly effective photocatalysts due to the adequate driving force for the water oxidation/reduction reaction and excellent visible-light harvesting ability. Furthermore, we find that the band gaps, band edge positions, and optical absorption can be remarkably modified by applying 4 % tensile strain. These findings indicate that Janus aluminium chalcogenide monolayers hold great promise as highly effective photocatalysts for water splitting.