Pt/MgO catalysts with low Pt loadings were prepared from aqueous/alcohol solvents and treated at various temperatures to tune the various metal–support bonding interactions. The structures were characterized with high-energy resolution fluorescence detection (HERFD)-X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectra recorded at the Pt L<sub>III </sub>edge. The XANES data demonstrate the cationic nature of the platinum, and the EXAFS and STEM data show atomically dispersed platinum in the absence of clusters or nanoparticles in Pt/MgO samples with markedly different metal–support bonding interactions. Structural models of the catalytic species were determined with a comprehensive library of DFT-optimized structures used to guide the fitting of EXAFS data. Subsurface isolated Pt was found to be supported in MgO calcined at 700 °C, coordinating through more Pt–O bonds and with stronger metal support bonding interactions than the surface-isolated Pt that was found to be supported on MgO calcined at 400 °C. The catalysts were investigated for CO oxidation; the Pt atoms in the subsurface layer of MgO were less accessible to reactants and less active catalytically than those on the MgO surface, and they are much more stable—more resistant to sintering—than the surface platinum species—indicating that tuning the bonding interaction between isolated Pt atoms and the MgO support markedly affects the structure, activity, and stability of the catalyst.

Surface and sub-surface MgO-supported atomically dispersed platinum catalysts for CO oxidation: Characterization with X-ray absorption spectroscopy, electron microscopy, and density functional theory

ACS Spring 2022

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