Adsorption properties of C 2 H 4 and NH 3 on MoTe 2 monolayer modified with Au n /Ag n /Cu n clusters

The sensitive and selective detection of ethylene (C2H4) and ammonia (NH3) is important for agricultural monitoring, industrial safety and environmental protection. The adsorption and gas-sensing performances of Aun/Agn/Cun (n = 1–3) cluster-modified MoTe2 monolayers toward C2H4 and NH3 were systematically investigated by first-principles calculations. All metal clusters can be stably anchored on MoTe2 through exothermic processes, narrowing the band gap from 1.259 eV for pristine MoTe2 to 0.583–1.089 eV and enhancing conductivity. Pristine MoTe2 exhibits weak physisorption of both gases (|Ead|<0.3 eV) without new bond formation, whereas cluster modification induces strong chemisorption (|Ead|>0.6 eV), with Cu-based clusters showing the highest affinities (|Ead|>0.9 eV). Considering both gas selectivity and desorption kinetics, Au2–MoTe2 is optimal for C2H4 sensing (Ead=−0.972 eV), whereas Cu3–MoTe2 and Ag3–MoTe2 are more suitable for NH3 detection (Ead = −1.391 and −1.229 eV), substantially exceeding the values for C2H4 on the same substrates. This study reveals the intrinsic mechanism of metal-cluster modification in regulating the gas adsorption selectivity of MoTe2, providing a theoretical basis for designing high-selectivity, high-sensitivity C2H4 and NH3 sensors.