Extending Transition-Metal Carbo-Chalcogenides to Tellurium with Nb₂CTe₂

Transition-metal carbo-chalcogenides (TMCCs) are expanding the structural and chemical diversity of layered van der Waals (vdW) materials by bridging transition-metal dichalcogenides (TMDs) and transition-metal carbides (MXenes). This study reports the experimental realization of Nb₂CTe₂, the first tellurium-based TMCC phase. Using a sealed-ampule reactive synthesis strategy, Nb₂CTe₂ was obtained as the predominant phase (78.0 wt %). X-ray diffraction, scanning electron microscopy, together with atomic-resolution scanning transmission microscopy structural and chemical analysis, confirm a layered trigonal structure (P3®m1) and lamellar flake-like morphology composed of Nb-C slabs capped by Te layers. High-angle annular dark-field scanning transmission electron microscopy-derived interlayer separation, together with the previously predicted low delamination energy, supports weak out-of-plane vdW coupling. Long-term ambient exposure revealed limited chemical stability in air, with near-complete loss of the Nb₂CTe₂ phase, increased diffuse scattering, and oxidative degradation over time. This work expands the experimentally accessible TMCC family to Te-containing compositions and provides a foundation for future studies of heavy-chalcogen TMCCs and their two-dimensional derivatives.