Realizing stable transition metal(111) metallene by introducing a non-metallic framework to construct 2D Janus TMB2X (X = O and S) nanostructures and investigating their hydrogen evolution catalytic performance

Abstract

Through first-principles structure search calculations, we have discovered a series of hitherto unknown two-dimensional (2D) Janus TMB₂O nanomaterials (TM = Fe, Co, Ni, Ru, Rh, Pd, Os, Ir and Pt) featuring a single atomic layer of TM-metallene as one exposed surface resembling the atomic arrangement of Pt(111) surface, which can be well stabilized by a non-metallic BO exposed surface composed of hexagonal rings. Further, by substituting S atoms for O atoms, the TMB₂S series can be derived from these nine fascinating TMB₂O structures. All eighteen intriguing 2D Janus monolayers exhibit high thermodynamic, dynamical and mechanical stabilities, as well as good conductivity. Among them, eight monolayers, involving TMB₂O (TM = Co, Ni, Ru and Os) and TMB₂S (TM = Fe, Ni, Rh and Os), demonstrate considerably high catalytic activity for hydrogen evolution reaction (HER), with the metallene-side playing a crucial role. Particularly, TMB₂O (TM = Co, Ru and Ni) and TMB₂S (TM = Rh and Os) monolayers exhibit high HER catalytic activity over a wide range of hydrogen coverage. Their active site densities reach up to 1.32 × 10¹⁵–11.64 × 10¹⁵ sites per cm², exceeding many reported materials and even the noble metal Pt. The catalytic reaction mechanisms are analyzed. This work offers new ideas for developing affordable and efficient metallene-based electrocatalysts for HER and other energy conversion processes.