Two-dimensional Janus AsXY (X = Se, Te; Y = Br, I) monolayers for photocatalytic water splitting

Two-dimensional (2D) Janus materials exhibit great potential in photocatalytic applications for providing clean and renewable energy. Here, using the first principles calculations, we explore Janus AsXY (X = Se, Te; Y = Br, I) monolayers that have excellent stability and can be applied in photocatalytic water splitting. It is shown that all four Janus monolayers are indirect band-gap semiconductors with the bandgaps greater than 1.23 eV and their band edge positions straddle both sides of the water redox potential, which facilitates the prevention of carrier recombination. Meanwhile, AsXY monolayers exhibit excellent optical absorption both in the visible and the near-ultraviolet regions. Interestingly, the external potential applied to the AsXY monolayers can provide sufficient photoexcited carrier driving force for the oxygen evolution reaction and the hydrogen evolution reaction in an acidic environment. Therefore, our results reveal that Janus AsXY monolayers are promising candidates for optoelectronics and photocatalytic water splitting applications.