1：Experimental Design and Method Selection:

Density functional theory (DFT) method was used to simulate the adsorption of gases on Pd-MoS2 monolayer. The spin-polarized calculations were implemented using DMol3 package. Perdew-Burke-Ernzerhof (PBE) function with generalized gradient approximation (GGA) was adopted for electron exchange and correlation. The double numerical plus polarization (DNP) was selected as the atomic orbital basis set, and the DFT semi-core pseudopotential (DSSP) method was applied to deal with the relativistic effect of transition metal atom. The Grimme method was employed for van der Waals interaction.

2：Sample Selection and Data Sources:

A 4 × 4 × 1 MoS2 monolayer supercell cleaved through (0 0 1) surface of bulk material was established, including 16 Mo and 32 S atoms with a vacuum region of 15 ?.

3：List of Experimental Equipment and Materials:

Computational simulations were performed without physical equipment.

4：Experimental Procedures and Operational Workflow:

The geometries of gas molecules and Pd-MoS2 were optimized to their most stable configuration. The adsorption energy (Ead) of each gas adsorption process was calculated.

5：Data Analysis Methods:

The Mullikan population analysis was considered to analyze the charge transfer (QT) between the target molecule and adsorbent surface. The density of state (DOS) comparison was conducted to elaborate the electronic structure.