In recent years, significant attention has been directed towards single-site metal species for catalytic reactions, particularly to take advantage of atom-utilization efficiency and unique properties of single-site atoms (Joule, 2018, 2, 1242; J. Am. Chem. Soc., 2015, 137, 10484). However, preparation methods that target well-dispersed single-site atoms with high stability during catalytic processes still need to be developed. Methods to synthesize single-site atoms usually involve wet-chemistry approaches, including defect-engineering on oxide surfaces or binding site design on zeolites, but there are also new strategies, such as single-atom alloys (Science, 2012, 335, 1209). We have recently developed a metal-organic coordination strategy to achieve single-site Pt centers on oxide surfaces (J. Catal., 2018, 365, 303). The presence of suitable ligands can alter the charge state of single metal atoms and stabilize the single-site centers against migration and agglomeration. Here we report a new set of studies where we extend the surface chemistry of this approach to a broader range of metal species, including Fe, Ru, Rh, and Ir. The metal-ligand coordination and charge transfer are investigated by XPS by examining metal/ligand ratio and core-level shifts. Different metal centers and chemical states are explored to optimize conditions that can lead to active and stable catalysts. The gas phase catalysis of these systems is being examined.

Metal-ligand coordination for single-site catalysts on oxide surfaces

2019 Spring National Meeting

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