Enhanced sensing characteristics of N doped and (N, O) co-doped molybdenum disulfide to detect toxic gases: a...

First-principles calculations based on density functional theory were conducted to investigate the adsorption of CO, CO₂, and NH₃ molecules on pristine, N doped, and (N, O) co-doped MoS₂ surfaces. Pristine MoS₂ systems exhibit weak physisorption with long adsorption distances, insignificant adsorption energies, and negligible charge transfer, resulting in poor gas selectivity and low electronic sensitivity toward all gases. N doping slightly enhances adsorption strength and charge exchange through defect-induced electronic modulation, improving the interaction with NH₃ but showing limited response to CO and CO₂. In contrast, (N, O) co-doping substantially reinforces molecule-substrate interactions by reducing adsorption distances and increasing charge redistribution across the surface. The (N, O) co-doped MoS₂ system exhibits pronounced work-function shifts of -1.07, -0.99, and -0.54 eV for CO, CO₂, and NH₃, respectively, together with strong energy-resolved conductivity variations, with average conductivity changes of about 30-40% for CO, 35-50% (peaks ≈70%) for CO₂, and 45-60% with maximum peaks exceeding 120% for NH₃. Compared with previous studies focusing on either N- or O-doped MoS₂, our work provides a systematic, side-by-side comparison of pristine, N-doped, and (N, O) co-doped systems and identifies (N, O) co-doping as a more effective route to simultaneously enhance sensitivity and selectivity toward CO and CO₂.