Atomically Dispersed Catalytic Platinum Anti-Substitutions in Molybdenum Ditelluride.

Atomic defects, e.g., vacancies, substitutions, and dopants, play crucial roles in determining the functionalities of two-dimensional (2D) materials, including spin glass, single-photon emitters, and energy storage and conversion, due to the introduction of abnormal charge states and noncentrosymmetric distortion. In particular, anti-substitutions are regarded as promising topological defect types, in which substitution occurs at opposite charge sites, fundamentally modifying the atomic and electronic structures of pristine lattices. However, the fabrication of large-scale anti-substitutions remains challenging due to high formation energies and complex reaction paths. Here, we propose an approach for synthesizing atomically dispersed Pt anti-substitutions in defective 1T'-MoTe using the electrochemical exfoliation-assisted leaching-redeposition (EELR) method. Atomic-resolution scanning transmission electron microscopy (STEM) imaging reveals that Pt atoms substitute Te sites, forming unconventional Mo-Pt bonds. A rich variety of Pt anti-substitution configurations and Pt anti-substitutions coupling with Te vacancies have been fabricated by controlled electrochemical conditions. Density functional theory (DFT) calculations suggest that Pt atoms preferentially occupy the Te vacancy sites coupled with neighboring Te vacancies, stabilizing the anti-substitution configurations. The coupled Pt-Te defect complexes exhibit excellent hydrogen evolution reaction, with an overpotential of only 12.9 mV because the paired defect complexes cause charge redistribution and regulate the d-band center of the active sites as suggested by DFT. These findings introduce an effective approach for engineering atomically dispersed anti-substitutions in 2D materials, presenting new opportunities for the precise design of atomic features with targeted functionalities in catalytic and other advanced applications.