Two-dimensional metal-free boron chalcogenides B2X3 (X = Se and Te) as photocatalysts for water splitting under visible light.

Finding photocatalysts that fully utilize the visible solar light to split water into hydrogen and oxygen has been a challenging problem for a long time. In this regard, compared to traditional three-dimensional materials, graphene-like two-dimensional materials offer many advantages such as ultra-high surface area for photochemical reactions and minimal migration distance for carriers. Herein, using density functional theory (DFT), we examine the potential of a new series of two-dimensional boron chalcogenides, B2X3 (X = S, Se, Te) as candidates for such photocatalysts. We show that B2Se3 and B2Te3 possess the ideal energy levels for photon excitation for both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). Furthermore, a bilayer van der Waals heterostructure consisting of B2Te3/B2Se3 is found to have the greatest potential for two-step photo-excitation for water splitting reaction. Our results can stimulate the synthesis of new two dimensional materials for photocatalysis.