Understanding the Intrinsic Surface Reactivity of Single-Layer and Multilayer PdO(101) on Pd(100)
Journal article, 2018

We investigated the intrinsic reactivity of CO on single-layer and multilayer PdO(101) grown on Pd(100) using temperature-programmed reaction spectroscopy (TPRS) and reflection absorption infrared spectroscopy (RAIRS) experiments, as well as density functional theory (DFT) calculations. We find that CO binds more strongly on multilayer than single-layer PdO(101) (∼119 kJ/mol vs 43 kJ/mol), and that CO oxidizes negligibly on single-layer PdO(101), whereas nearly 90% of a saturated layer of CO oxidizes on multilayer PdO(101) during TPRS experiments. RAIRS further shows that CO molecules adsorb on both bridge-Pdcusand atop-Pdcussites (coordinatively unsaturated Pd sites) of single-layer PdO(101)/Pd(100), while CO binds exclusively on atop-Pdcussites of multilayer PdO(101). The DFT calculations reproduce the much stronger binding of CO on multilayer PdO(101), as well as the observed binding site preferences, and reveal that the stronger binding is entirely responsible for the higher CO oxidation activity of multilayer PdO(101)/Pd(100). We show that the O atom below the Pdcussite, present only on multilayer PdO(101), modifies the electronic states of the Pdcusatom in a way that enhances the CO-Pdcusbonding. Lastly, we show that a precursor-mediated kinetic model, with energetics determined from the present study, predicts that the intrinsic CO oxidation rates achieved on both single-layer and multilayer PdO(101)/Pd(100) can be expected to exceed the gaseous CO diffusion rate to the surface during steady-state CO oxidation at elevated pressures, even though the intrinsic reaction rates are 4-5 orders of magnitude lower on single-layer PdO(101)/Pd(100) than on multilayer PdO(101)/Pd(100).

RAIRS

DFT

surface oxide

infrared spectroscopy

PdO

palladium

Pd(100)

CO oxidation

Author

Vikram Mehar

University of Florida

Minkyu Kim

Ohio State University

M. Shipilin

Lund University

Maxime van den Bossche

Competence Centre for Catalysis (KCK)

Chalmers, Physics, Chemical Physics

Johan Gustafsson

Lund University

L. R. Merte

Malmö university

Uta Hejral

Lund University

Henrik Grönbeck

Chalmers, Physics, Chemical Physics

Competence Centre for Catalysis (KCK)

Edvin Lundgren

Lund University

A. Asthagiri

Ohio State University

Jason F. Weaver

University of Florida

ACS Catalysis

2155-5435 (eISSN)

Vol. 8 9 8553-8567

Subject Categories

Inorganic Chemistry

Theoretical Chemistry

Condensed Matter Physics

DOI

10.1021/acscatal.8b02191

More information

Latest update

12/10/2018