Interface-engineered Te-Rich MoTe2/MWCNT hybrid for dual-type gas sensing: Atomic-scale insights and local bonding modulation

We report a tellurium-rich MoTe2/multiwalled carbon nanotube (MWCNT) nanocomposite synthesized via a facile one-step hydrothermal route, functioning as an efficient room- temperature dual-analyte gas sensor. Few-layer MoTe2 nanosheets decorated with excess elemental Te were uniformly anchored on a percolating MWCNT network, forming a highly conductive 2D–1D hybrid framework. The resulting sensor exhibits exceptional sensitivity toward both NO2 and NH3 gases at 25 °C, with conductance changes exceeding 100% for ~100 ppb NO2 and comparable magnitudes for ~100 ppb NH3. The detection limits reach the low-ppb to sub-ppb range, and the response–recovery times (10–30 s) rival or surpass the best reported MoTe2-based devices. Comprehensive structural and chemical characterization confirmed the composite’s multiphase and interfacial nature. X-ray diffraction and Raman spectroscopy verified the coexistence of 2H and 1T′ MoTe2 phases, while X-ray photoelectron spectroscopy revealed a high Te/Mo ratio, confirming the presence of elemental Te. Morphological analyses (SEM, STEM, BET) showed that intertwined MWCNTs form a high-surface-area, conductive scaffold for MoTe2/Te nanoparticles. Advanced atomic-resolution STEM with EDS mapping and synchrotron-based XANES/EXAFS provided direct evidence of Te-rich domains and Mo–C/Te heterointerfacial bonding, elucidating the atomic-level structure responsible for enhanced gas interactions.

The dual sensing behavior originates from the composite’s ambipolar character and numerous p- n junctions formed at MoTe2–CNT interfaces. Elemental Te and MoTe2 contribute to p-type conduction, while charge transfer and defect-induced states introduce local n-type pathways. Consequently, the sensor exhibits a positive (p-type) response toward oxidizing NO2 and a complementary negative (n-type) response toward reducing NH3. Density functional theory (DFT) simulations further clarify the mechanism: NO2 binds strongly to Te-rich edge sites, withdrawing electrons, whereas NH3 preferentially adsorbs on Mo or Te-vacancy sites, donating electrons. The substantial adsorption energies and charge transfer explain the large, reversible conductivity modulation observed experimentally.

In summary, the Te-rich MoTe2/MWCNT hybrid represents a new class of ambipolar 2D–1D nanocomposites capable of ultra-sensitive, room-temperature detection of both oxidizing and reducing gases. The synergistic effects of elemental Te doping, interfacial engineering, and heterogeneous junction formation enable superior performance and stability. This work demonstrates a unique strategy for designing multifunctional TMD/nanocarbon hybrid sensors, offering valuable insight into atomic-level interactions for advanced environmental and medical gas-sensing applications.