Conquering the spatial-electronic dichotomy of MXene catalysts via surface-amorphized Mott-Schottky junctions for...

Lithium‑sulfur batteries (LSBs) suffer from the "shuttle effect" and slow redox kinetics. Although MXenes serve as competitive catalytic platforms owing to their metallic conductivity, their pristine crystalline surfaces suffer from a severe spatial-electronic dichotomy. Geometrically, rigid lattice symmetries restrict the exposed catalytic active centers exclusively to edge sites, leaving the vast basal planes catalytically dormant. Electronically, the dense coverage of highly electronegative terminal groups establishes a localized negative surface potential, inducing severe electrostatic repulsion against electron-rich polar polysulfide anions. To conquer this constraint, we present a surface engineering paradigm to construct a surface-amorphized Mo₂CT_x/a-MoO_x Mott-Schottky heterojunction via an in-situ oxidative strategy. This architecture triggers interfacial electronic reconfiguration, driving spontaneous electron migration from the semiconducting a-MoO_x overlayer into the metallic Mo₂CT_x core to achieve thermodynamic Fermi level equilibration. The resulting built-in electric field establishes a localized electron-deficient capture layer on the surface, successfully neutralizing the native electronegative electrostatic repulsion barrier of the MXene framework. Synchronously, the amorphous a-MoO_x shell disrupts crystalline steric hindrances, awakening a massive density of unsaturated Mo⁵⁺ defect states that initiate a MoS and LiO dual-anchoring chemisorption mode. Benefiting from this spatial-electronic liberation, the modified separator lowers the thermodynamic activation barriers for bidirectional sulfur conversion. LiS cells integrated with the Mo₂CT_x/a-MoO_x-modified separator deliver a high initial specific capacity of 1309.4 mAh g^-1 at 0.2C, high-rate capability up to 4C (597.2 mAh g^-1), and robust cycling stability under a sulfur loading of 6.43 mg cm^-2 (747.3 mAh g^-1 maintained after 70 cycles). This work establishes a fundamental paradigm for leveraging localized surface amorphization and Mott-Schottky charge dynamics to manipulate surface potentials and conquer interfacial repulsion in advanced energy storage applications.