Stabilization and Controllable Design of Pt(111)/(110) Metallenes via Spatial Orientation Engineering of Interfacial C-sp ³ Orbitals under Distinct BS Frameworks toward Efficient HER Catalysis

While single-atomic-layer metallenes exhibit exceptional promise as efficient catalysts, stabilizing their structures remains a fundamental challenge in materials design. Utilizing first-principles structure search, we unveiled two novel two-dimensional (2D) Janus nanostructures Pt(111)@CBS(r) and Pt(110)@CBS(c), featuring the single atomic layer of Pt(111) or Pt(110) metallene surfaces stabilized by coupling with carbon-linked boron–sulfur nonmetallic frameworks. The Pt-metallene atomic arrangement can be governed by the spatial orientation of sp3-hybridized orbitals of the C atoms linkages to the different BS-frameworks composed of either BS-hexagonal rings or BS-chains. Both unique Pt-based monolayers can possess high dynamic, thermodynamic, mechanical, and thermal stability, and metallic conductivity. Besides, they can also exhibit high catalytic activity for hydrogen evolution reaction (HER). By systematically substituting Pt with Group VIII transition metals, we have developed a series of novel 2D Janus TM(111)@CBS(r) and TM(110)@CBS(c) monolayers (TM = Ni, Ru, Rh, Pd, Os, Ir) that retain high stability and metallic conductivity. Among them, all ten TM-based monolayers (TM = Ru, Rh, Pd, Os and Ir) can demonstrate superior HER catalytic performance. Notably, the developed 2D Janus monolayers can possess the exceptional active site densities reaching 1.18 × 1015–4.06 × 1015 sites/cm2, surpassing many reported catalysts including the state-of-the-art Pt. Obviously, these TM(111)@CBS(r) and TM(110)@CBS(c) monolayers can serve as highly promising alternative HER electrocatalysts, with the unique metallene surfaces playing a crucial role. This work establishes novel strategies for stabilizing metallenes and designing high-performance metallene-based electrocatalysts, demonstrating significant promise for HER catalysis and even broader energy conversion applications.