Capture of acidic gas molecules in metallic nanopillar array surfaces

To effectively capture the acidic fluid molecules in industrial exhaust, this study employed molecular dynamics to simulate the dynamic adsorption behavior of a mixture of carbon monoxide (CO), carbon dioxide (CO₂), hydrogen sulfide (H₂S), and water (H₂O) molecules in gold (Au) nanoslits. We systematically examined the self-diffusion coefficient (D_Z), average adsorption energy (E_a,av), and static adsorption amount (N_sa) of individual ingredients and a mixture of the adsorbates under various temperatures (T), concentrations (c), and array slit widths (d). The simulation results indicate that Au(110) has better capture capabilities with regard to H₂O and H₂S, followed by CO₂ and then finally CO. Among the various slit structures, the design of array structures with slit widths 8.15 × 5.76 Å (case C) resulted in the highest average adsorption energy and static adsorption amount for all of the adsorbates. This is due to the fact that an appropriate slit width can increase the self-diffusion coefficient of the gas molecule and provide more stable adsorption sites to capture the adsorbates. Compared to the smooth surface structure, the nanopillar array structures significantly increased the self-diffusion coefficients and the adsorption energy of specific molecules. The comprehensive molecular model is helpful to predict atomistic-level adsorption behaviors for acidic gas molecules.