First-principles study of GaGeSSe monolayer: a promising photocatalyst for water splitting.

Recently, the quaternary Janus monolayers with the formula ABXY have been shown to be promising candidates for optoelectronic applications, especially in the photocatalytic water splitting reaction. Therefore, first-principles calculations were employed to investigate the photocatalytic properties of GaGeXY (X and Y represent S, Se or Te atoms) monolayers. The GaGeSSe and GaGeSeTe monolayers exhibit dynamic and thermal stability, supported by high cohesive energies (3.78-4.20 eV) and positive phonon dispersion. With a moderate Young's modulus (50.02-65.31 N m) and high Poisson's ratio (0.39-0.41), these monolayers offer a balance of stiffness and flexibility, making them suitable for flexible electronic applications. Especially, the difference in work function of 0.27 eV induces an intrinsic electric field in the GaGeSSe monolayer, making the electronic structure of this material be suitable for the photocatalytic water splitting process. With light irradiation, the oxygen evolution reaction (OER) happened simultaneously, producing electrons and H protons for the hydrogen evolution reaction (HER) to happen at a low potential barrier. Moreover, the GaGeSSe monolayer has a high absorption rate () of 10-10 cm and a high electron mobility of 430.82-461.50 cm V s. These characteristics result in a good solar-to-hydrogen of the GaGeSSe monolayer (14.80%) which is promising for use in photon-driven water splitting.