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Instruments / Technical Area	Publication Details	Published	Actions
B18-Core EXAFS	Metal-specific reactivity in single-atom-catalysts: CO oxidation on 4d and 5d transition metals atomically dispersed on MgO Bidyut B. Sarma , Philipp N. Plessow , Giovanni Agostini , Patricia Concepcion , Norbert Pfänder , Liqun Kang , Feng R. Wang , Felix Studt , Gonzalo Prieto Journal Of The American Chemical Society DOI: 10.1021/jacs.0c03627 Diamond Proposal Number(s): [17377, 19072] Show Abstract ▼ Abstract: Understanding and tuning the catalytic properties of metals atomically dispersed on oxides are major stepping-stones towards a rational development of single-atom catalysts (SACs). Beyond individual showcase studies, the design and synthesis of structurally regular series of SACs opens the door to systematic experimental investigations of performance as a function of metal identity. Herein, a series of single-atom catalysts based on various 4d (Ru, Rh, Pd) and 5d (Ir, Pt) transition metals has been synthesized on a common MgO carrier. Complementary experimental (X-ray absorption spectroscopy) and theoretical (Density Functional Theory) studies reveal that, regardless of the metal identity, metal cations occupy preferably octahedral coordination MgO lattice positions under step-edges, hence highly confined by the oxide support. Upon exposure to O2-lean CO oxidation conditions, FTIR spectroscopy indicates the partial de-confinement of the monoatomic metal centers driven by CO at pre-catalysis temperatures, followed by the development of surface carbonate species under steady-state conditions. These findings are supported by DFT calculations, which show the driving force and final structure for the surface metal protrusion to be metal-dependent, but point to an equivalent octahedral-coordinated M4+ carbonate species as the resting state in all cases. Experimentally, apparent reaction activation energies in the range of 96±19 kJ/mol are determined, with Pt leading to the lowest energy barrier. The results indicate that, for monoatomic sites in SACs, differences in CO oxidation reactivity enforceable via metal selection are of lower magnitude than those evidenced previously through the mechanistic involvement of adjacent redox centers on the oxide carrier, suggesting that tuning of the oxide surface chemistry is as relevant as the selection of the supported metal.	Aug 2020

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B18-Core EXAFS

Metal-specific reactivity in single-atom-catalysts: CO oxidation on 4d and 5d transition metals atomically dispersed on MgO

Bidyut B. Sarma , Philipp N. Plessow , Giovanni Agostini , Patricia Concepcion , Norbert Pfänder , Liqun Kang , Feng R. Wang , Felix Studt , Gonzalo Prieto

Journal Of The American Chemical Society

DOI: 10.1021/jacs.0c03627

Diamond Proposal Number(s): [17377, 19072]

Show Abstract ▼

Aug 2020