Exploring Adsorption Behavior of Sulfur and Nitrogen Compounds on Transition Metal-Doped Cu (100) Surfaces: Insights from DFT and MD Simulations

International audienceWe conducted an extensive investigation using density functional theory (DFT) calculations and ReaxFF molecular dynamics (MD) simulations to elucidate the mechanisms of desulfurization and denitrogenation on Cu (100) surfaces. This study encompassed both pristine surfaces and those modified with Pt or Rh transition metals. Our primary objective was to gain a deep understanding of the adsorption behavior of thiophene (C4H4S) and pyridine (C5H5N) molecules on stepped Cu (100) surfaces, which serve as models for sulfur and nitrogen compounds. We systematically explored the interplay among water, adsorption efficiency, and surface regeneration capabilities. Using DFT, we thoroughly examined various aspects, including interaction energies, charge transfers, changes in electron density, and alterations in work function upon molecule adsorption. Notably, we observed a decrease in the interaction energy of thiophene, whereas that of pyridine increased when adsorbed on Pt/Rh-doped surfaces compared to pristine ones. Thiophene adsorption reduced the work function, potentially enhancing detectability, without causing inhibitory effects on any surface. Stepped Cu (100) surfaces demonstrated a strong affinity for thiophene, exhibiting an energy difference of approximately 86 kJ/mol. However, this trend reversed on doped surfaces, where pyridine displayed stronger adsorption than thiophene, resulting in energy differences of around 123 kJ/mol and 62 kJ/mol on Pt-Cu and Rh-Cu surfaces, respectively. Moreover, our investigation highlighted the regeneration capacity of these surfaces, indicating that all surfaces can be considered promising candidates for desulfurization, while only Cu and Pt-Cu surfaces were found to be suitable for denitrogenation. Furthermore, results from MD simulations in combination with Potential of Mean Force (PMF) simulations at 300 K, aligned with DFT calculations, confirmed the adsorption configurations of pyridine and thiophene. This analysis demonstrated the competitive advantage of thiophene over pyridine in adsorption and highlighted the inhibitory effect of water on pyridine adsorption on the Cu (100) surface

Energy barriers of single-adatoms diffusion on unreconstructed and reconstructed (110) surfaces

The present paper is aimed mainly to investigate theoretically the diffusion of Ag, Cu, Au and Pt adatoms on the (1 × 1) unreconstructed geometry for Ag, Cu and Pt (110), and reconstructed geometries ((1 × 2), (1 × 3) and (1 × 4)) for Pt and Au (110) surfaces. We consider the single adatom diffusion when additional atoms are deposited in adjacent row. For this study, we have used the molecular statics simulations combined with the embedded atom method. For several systems, we have calculated the activation barriers for hopping mechanism. For the diffusion on the unreconstructed surfaces, the trends for the activation barriers are the same for all considered systems except for Cu/Ag (110) system, where the activation barrier do not change. Further, our results indicate that additional atoms lead to a small decreasing of activation barriers for diffusion on reconstructed surfaces for some systems, while for other systems; the activation barrier remains practically unchanged