First-Principles Study on Transition Metal (Ni, Cu, Pd, Ag)-Doped NbSe ₂ for Adsorption and Sensing of Hazardous Gases

The accurate detection of hazardous gases such as methane (CH 4 ), carbon monoxide (CO), and ammonia (NH 3 ) is critical for ensuring miner safety in coal mines. Conventional gas sensors suffer from significantly reduced performance in harsh mining environments characterized by high humidity and dust levels. Two-dimensional transition metal dichalcogenides (TMDs) have emerged as promising materials for next-generation gas sensors due to their unique electronic structures and tunable surface reactivity. Using first-principles calculations, this study systematically investigates how transition metal doping (Ni, Cu, Pd, Ag) modulates the gas-sensing properties of NbSe 2 . The results demonstrate that metal doping substantially improves NbSe 2 's gas adsorption capacity. Ni-doped NbSe 2 shows optimal performance for CH 4 (-0.367 eV) and NH 3 (-1.845 eV), while Pd-doped NbSe 2 exhibits the strongest CO adsorption (-1.525 eV). Electronic structure analysis, charge transfer calculations, and work function studies reveal the structure-activity relationship between surface electron emission and gas adsorption. Notably, recovery time calculations suggest Ni-NbSe 2 maintains excellent adsorption-desorption equilibrium for CH 4 at room temperature, indicating strong practical applicability. This work elucidates the atomic-scale gas adsorption mechanisms in doped NbSe 2 , providing crucial theoretical guidance for designing advanced gas sensors for mine safety monitoring.