Pt Cluster Nucleation on Graphene/Ir(111): Role of Defects, Diffusion, and Pathways toward Single-Atom Catalysts

Kimika Teorikoa Seminar

We investigate the nucleation mechanisms of Pt clusters on epitaxial graphene/Ir(111) by combining high-resolution X-ray photoemission spectroscopy (HR-XPS) and density functional theory (DFT) calculations. While experiments reveal predominantly planar Pt clusters, DFT predicts three-dimensional structures on pristine graphene. By modeling core-level shifts (CLS) and comparing with time-resolved XPS spectra, we identify monomers and planar clusters as the dominant species. We attempt to explained this discrpancy by the role of graphene defects, which act as strong binding sites and kinetic traps for diffusing Pt atoms, promoting planar nucleation. Building on these insights, we are attempting to establish a kinetic model that captures the interplay between monomer diffusion, defect density, and deposition rate, in order to identify conditions for stabilizing isolated Pt atoms. These results provide guidelines for tuning experimental conditions toward the realization of single-atom catalysts at relevant temperatures.