Sub‐10 nm Confined Channels in Edge‐Closed MXene Nanoribbons Boost Proton Transport for Efficient Single‐Atom Electrocatalysts

ABSTRACT Nanoribbons from atomic layers such as graphene, carbides, and nitrides (MXenes) have attracted considerable interest owing to their distinct quantum confinement effects and high surface activity. However, the controlled synthesis of MXene nanoribbons remains challenging due to their random fragmentation and poor stability. Here, an efficient stiffness‐mediated strategy is developed to fabricate unique edge‐closed MXene nanoribbons, featuring a large aspect ratio of 10∼40 and confined channels of sub‐10 nm at both edges. The key protocol involves modulating the critical collapse pressure by reducing the bending stiffness of MXene layers, thereby triggering the tube collapse of pre‐formed nanoscrolls into edge‐closed nanoribbons upon solvent evaporation. The resulting nanoribbons exhibit an enhanced polarization electric field, leading to a higher surface proton concentration and enhanced proton transport rate compared to nanoscrolls and nanosheets. As a result, these MXene nanoribbons provide an efficient platform for anchoring single‐atom Pt, achieving a low overpotential of 23 mV at 10 mA cm −2 and a Tafel slope of 25 mV dec −1 in the hydrogen evolution reaction (HER), outperforming the most reported electrocatalysts.