The formation of the metal-oxide interface in the Pd/Co3O4(111) model catalyst was investigated by means of density functional theory (DFT), synchrotron radiation photoelectron spectroscopy (SRPES), and scanning tunneling microscopy (STM). The electronic metal-support interaction results in a substantial charge transfer at the interface yielding atomically dispersed Pd2+ species and partially oxidized Pdδ+ aggregates coupled with a partial reduction of Co3O4(111). Atomically dispersed Pd2+ species at the fcc site on the Co3O4(111) surface were found to be the most energetically favorable configuration. In comparison to the dispersed Pd2+ species, the formation of Pd dimers, trimers, and tetramers was found to be less favorable. The analysis of the Bader charges revealed a substantial net positive charge on Pd atoms in dimers, trimers, and tetramers which is consistent with the formation of partially oxidized Pdδ+ aggregates detected by SRPES. The analysis of the charge distribution in Co3O4(111) revealed a partial reduction of Co3+ to Co2+ cations in the first and second Co layers. According to DFT, Pdδ+ aggregates are prone to oxidation to PdO in the presence of O2 and H2O. The partially oxidized Pdδ+ and Pd4Ox aggregates form 1 to 2 monolayer thick clusters which serve as nuclei for the growth of metallic Pd0 nanoparticles. At high Pd coverage, Pd nanoparticles coalesce resulting in the growth of two-dimensional islands that densely cover the Co3O4(111) substrate.

Pd/Co3O4(111) Interface Formation

Farnesi Camellone M.;Fabris S.;Piccinin S.;
2023

Abstract

The formation of the metal-oxide interface in the Pd/Co3O4(111) model catalyst was investigated by means of density functional theory (DFT), synchrotron radiation photoelectron spectroscopy (SRPES), and scanning tunneling microscopy (STM). The electronic metal-support interaction results in a substantial charge transfer at the interface yielding atomically dispersed Pd2+ species and partially oxidized Pdδ+ aggregates coupled with a partial reduction of Co3O4(111). Atomically dispersed Pd2+ species at the fcc site on the Co3O4(111) surface were found to be the most energetically favorable configuration. In comparison to the dispersed Pd2+ species, the formation of Pd dimers, trimers, and tetramers was found to be less favorable. The analysis of the Bader charges revealed a substantial net positive charge on Pd atoms in dimers, trimers, and tetramers which is consistent with the formation of partially oxidized Pdδ+ aggregates detected by SRPES. The analysis of the charge distribution in Co3O4(111) revealed a partial reduction of Co3+ to Co2+ cations in the first and second Co layers. According to DFT, Pdδ+ aggregates are prone to oxidation to PdO in the presence of O2 and H2O. The partially oxidized Pdδ+ and Pd4Ox aggregates form 1 to 2 monolayer thick clusters which serve as nuclei for the growth of metallic Pd0 nanoparticles. At high Pd coverage, Pd nanoparticles coalesce resulting in the growth of two-dimensional islands that densely cover the Co3O4(111) substrate.
2023
Istituto Officina dei Materiali - IOM -
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/20.500.14243/472516
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