Two-dimensional multilayer M2CO2 (M = Sc, Zr, Hf) as photocatalysts for hydrogen production from water splitting: a first principles study

Currently, various two-dimensional (2D) monolayer materials have been predicted to be photocatalysts for water splitting. In the present work, the structural and electronic properties of 2D multilayer Zr2CO2, Hf2CO2 and Sc2CO2 are explored by density functional theory calculations. We found that the band gap of multilayer Zr2CO2 and Hf2CO2 becomes smaller with increasing layer number and the band edge positions demonstrate to be not suitable for driving the oxygen evolution reaction. However, applying an appropriate strain to multilayer Zr2CO2 and Hf2CO2 could make them into available photocatalysts for water splitting. For Sc2CO2, due to the built-in perpendicular electric field in monolayer Sc2CO2, there are more feasible stacking configurations of multilayer Sc2CO2, yet some of the multilayer Sc2CO2 are also proved to be potential photocatalysts for water splitting.