Unveiling Coverage-Dependent Interactions of N-Methylaniline with the Pt(111) Surface

This study aims to elucidate the adsorption and surface chemistry of N-methylaniline (NMA) on Pt(111), using it as a model molecule to probe the activation mechanisms of aromatic amines on catalytic surfaces. Through a combination of density functional theory (DFT) calculations and experimental techniques such as temperature-programmed X-ray photoelectron spectroscopy (TP-XPS), temperature-programmed desorption (TPD), and Fourier transform infrared reflection absorption spectroscopy (FT-IRRAS), we explored the coverage-dependent behavior of NMA on Pt(111) to identify key steps in the activation process. The population of certain reaction paths is driven by a coverage-dependent balance between molecule surface charge transfer and intermolecular interactions, dictating the selective activation of specific bonds. Our findings reveal how coverage influences the orientation and bonding of NMA on the Pt(111) surface. At lower coverages, the molecule binds to the surface through the phenyl ring and activation, facilitating C-N bond cleavage to the ring under HCN formation. In comparison, at higher coverages, the molecule binds only through the nitrogen atom and desorbs intact. These insights into variable bond activation lay the groundwork for understanding the fundamental processes involved in potential heterogeneously catalyzed reactions of aromatic amines, contributing to the development of new catalytic strategies.