10.1021/acscatal.8b04251.s001
Hanyu Ma
Hanyu
Ma
William F. Schneider
William F.
Schneider
Structure- and Temperature-Dependence of Pt-Catalyzed
Ammonia Oxidation Rates and Selectivities
American Chemical Society
2019
show rate-controlling steps
selectivity control
activation energies
N 2
step rate
Pt-Catalyzed Ammonia Oxidation Rates
ammonia oxidation rates
Pt structure
reaction network
microkinetic model parametrized
oxidize ammonia
Pt catalysts
nitric oxide
DFT results
Selectivities Ammonia oxidation
O coverages
product formation
Pt surfaces
2019-01-31 00:00:00
Journal contribution
https://acs.figshare.com/articles/journal_contribution/Structure-_and_Temperature-Dependence_of_Pt-Catalyzed_Ammonia_Oxidation_Rates_and_Selectivities/7719242
Ammonia oxidation
is operated at different temperatures over Pt
catalysts of different structures to recover different products. In
this work, we elucidate the dependency of ammonia oxidation rates
and selectivities on both Pt structure and temperature. We perform
density functional theory (DFT) computations to compare the reaction
and activation energies of elementary reactions on Pt(211) and Pt(111).
We develop a microkinetic model parametrized with the DFT results.
We show that barriers to product formation are lower on stepped Pt
than on terrace, leading to a much higher step rate at low temperature
to selectively oxidize ammonia to nitrogen. At high temperature, however,
both step and terrace perform comparably in rate to selectively produce
nitric oxide. While N<sub>2</sub> is always the thermodynamic product,
relative N and O coverages interact to make NO the kinetic product
at high temperature. The predicted rate and selectivity are consistent
with experiments. We further show rate-controlling steps on the two
Pt surfaces are different at low temperature but are the same at high
temperature. The degrees of selectivity control for elementary reactions
are comparable for the two surfaces. Finally, we demonstrate the flows
of elementary reactions in the reaction network are also structure-
and temperature-dependent.