Unraveling Molecular Fingerprints of Catalytic Sulfur Poisoning atthe Nanometer Scale with Near-Field Infrared Spectroscopy

:fundamental understanding of catalytic deactivation phenomenasuch as sulfur poisoning occurring on metal/metal-oxide interfaces is essential forthe development of high-performance heterogeneous catalysts with extendedlifetimes. Unambiguous identification of catalytic poisoning species requiresexperimental methods simultaneously delivering accurate information regardingadsorption sites and adsorption geometries of adsorbates with nanometer-scalespatial resolution, as well as their detailed chemical structure and surface functionalgroups. However, to date, it has not been possible to study catalytic sulfurpoisoning of metal/metal-oxide interfaces at the nanometer scale withoutsacrificing chemical definition. Here, we demonstrate that near-field nano-infraredspectroscopy can effectively identify the chemical nature, adsorption sites, and adsorption geometries of sulfur-based catalyticpoisons on a Pd(nanodisk)/Al2O3(thin-film) planar model catalyst surface at the nanometer scale. The current results reveal strikingvariations in the nature of sulfate species from one nanoparticle to another, vast alterations of sulfur poisoning on a single Pdnanoparticle as well as at the assortment of sulfate species at the active metal-metal-oxide support interfacial sites. Thesefindingsprovide critical molecular-level insights crucial for the development of long-lifetime precious metal catalysts resistant towarddeactivation by sulfur