Density Functional Theory Study of Transition-Metal-Doped CdS Monolayers for Hazardous Gas Sensing

With the acceleration of global industrialization and urbanization, emissions of typical toxic gases (CO, HCHO, NH₃, NO₂, and NO) have increased remarkably, creating an urgent demand for high-performance gas-sensing materials. Using first-principles calculations within the density functional theory (DFT) framework, we systematically investigated the structural stability, electronic properties, and gas-sensing performance of CdS monolayers doped with four transition metals (Os, Pd, Pt, and Ru). All doped systems exhibit negative binding energies ranging from -8.820 to -5.592 eV, and their excellent thermodynamic stability is verified by ab initio molecular dynamics simulations at 500 K. Benefiting from favorable adsorption and electronic behaviors, Os-CdS shows a high adsorption energy of -2.543 eV and a work function (WF) variation rate of 11.55% toward NO₂; Ru-CdS exhibits an adsorption energy of -3.103 eV and a sensitivity of 8.57 × 10¹ toward NO; Pt-CdS achieves an ultrahigh sensitivity of 7.09 × 10⁷ toward CO; while Pd-CdS enables ultrafast desorption of HCHO and NH₃, making it a promising candidate for efficient multigas detection. This work provides a reliable theoretical foundation for the design of high-performance CdS-based gas sensors and promotes the advancement of gas-sensing technology in environmental monitoring and industrial safety applications.