10.1021/acscatal.8b05154.s002
Georgios Kyriakou
Georgios
Kyriakou
Antonio M. Márquez
Antonio M.
Márquez
Juan Pedro Holgado
Juan Pedro
Holgado
Martin J. Taylor
Martin J.
Taylor
Andrew E. H. Wheatley
Andrew
E. H. Wheatley
Joshua P. Mehta
Joshua P.
Mehta
Javier Fernández Sanz
Javier Fernández
Sanz
Simon K. Beaumont
Simon K.
Beaumont
Richard M. Lambert
Richard M.
Lambert
Comprehensive Experimental and Theoretical Study of
the CO + NO Reaction Catalyzed by Au/Ni Nanoparticles
American Chemical Society
2019
nickel oxidation state
material
method
Ni
DFT
catalyst
N recombination
importance
calculation
X-ray absorption spectroscopy
CO
N 2 formation
edge structure spectroscopy
X-ray absorption
data
oxidation state
correlation
2019-04-19 00:00:00
Dataset
https://acs.figshare.com/articles/dataset/Comprehensive_Experimental_and_Theoretical_Study_of_the_CO_NO_Reaction_Catalyzed_by_Au_Ni_Nanoparticles/8059922
The catalytic and
structural properties of five different nanoparticle
catalysts with varying Au/Ni composition were studied by six different
methods, including in situ X-ray absorption spectroscopy and density
functional theory (DFT) calculations. The as-prepared materials contained
substantial amounts of residual capping agent arising from the commonly
used synthetic procedure. Thorough removal of this material by oxidation
was essential for the acquisition of valid catalytic data. All catalysts
were highly selective toward N<sub>2</sub> formation, with 50–50
Au:Ni material being best of all. In situ X-ray absorption near edge
structure spectroscopy showed that although Au acted to moderate the
oxidation state of Ni, there was no clear correlation between catalytic
activity and nickel oxidation state. However, in situ extended X-ray
absorption fine structure spectroscopy showed a good correlation between
Au–Ni coordination number (highest for Ni<sub>50</sub>Au<sub>50</sub>) and catalytic activity. Importantly, these measurements
also demonstrated substantial and <i>reversible</i> Au/Ni
intermixing as a function of temperature between 550 °C (reaction
temperature) and 150 °C, underlining the importance of in situ
methods to the correct interpretation of reaction data. DFT calculations
on smooth, stepped, monometallic and bimetallic surfaces showed that
N + N recombination rather than NO dissociation was always rate-determining
and that the activation barrier to recombination reaction decreased
with increased Au content, thus accounting for the experimental observations.
Across the entire composition range, the oxidation state of Ni did
not correlate with activity, in disagreement with earlier work, and
theory showed that NiO itself should be catalytically inert. Au–Ni
interactions were of paramount importance in promoting N + N recombination,
the rate-limiting step.