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How Surface Species Drive Product Distribution during Ammonia Oxidation : An STM and Operando APXPS Study

Ivashenko, Oleksii ; Johansson, Niclas LU ; Pettersen, Christine ; Jensen, Martin ; Zheng, Jian ; Schnadt, Joachim LU orcid and Sjåstad, Anja O. (2021) In ACS Catalysis 11. p.8261-8273
Abstract

The oxidation of ammonia is a key reaction for the production of artificial fertilizers and for environmental protection. Depending on the area of application, the catalytic reaction needs to be tuned toward the production of either N2 or NO, and this selectivity is controlled by temperature, pressure, reactant ratio, and the type of catalyst. PtRh alloys are highly useful catalytic materials for the oxidation of ammonia, and they can be employed at different reaction conditions. In contrast to pure Pt and Rh catalysts, for which a large number of studies of ammonia oxidation reaction mechanism are available, for PtRh alloys, direct spectroscopic evidence for structure-performance relationship is still lacking. To understand the... (More)

The oxidation of ammonia is a key reaction for the production of artificial fertilizers and for environmental protection. Depending on the area of application, the catalytic reaction needs to be tuned toward the production of either N2 or NO, and this selectivity is controlled by temperature, pressure, reactant ratio, and the type of catalyst. PtRh alloys are highly useful catalytic materials for the oxidation of ammonia, and they can be employed at different reaction conditions. In contrast to pure Pt and Rh catalysts, for which a large number of studies of ammonia oxidation reaction mechanism are available, for PtRh alloys, direct spectroscopic evidence for structure-performance relationship is still lacking. To understand the behavior of PtRh alloys, namely, what is their active phase under reaction conditions and how the alloy composition leads to a particular product distribution, we study the oxidation of ammonia over PtRh/Pt(111) surfaces by simultaneous operando ambient pressure X-ray photoelectron spectroscopy and mass spectrometry at 1 mbar total reaction pressure. These data are complemented by a catalyst surface characterization by scanning tunneling microscopy in ultrahigh vacuum. We establish that the predominant surface structure during NH3 oxidation strongly depends on the degree of Pt enrichment and the O2/NH3 mixing ratio. At the nanoscale, the selectivity toward N2 or NO production is driven by the surface populations of N and O species. These, in turn, are controlled by the nature of the alloying of Pt with Rh.

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author
; ; ; ; ; and
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
ammonia slip catalysis, APXPS, NOabatement, operando measurements, platinum, Pt(111), rhodium, surface alloy
in
ACS Catalysis
volume
11
pages
13 pages
publisher
The American Chemical Society (ACS)
external identifiers
  • scopus:85109452924
ISSN
2155-5435
DOI
10.1021/acscatal.1c00956
language
English
LU publication?
yes
id
69e68983-7266-46a2-8c3b-6891da9a7a2c
date added to LUP
2021-08-23 09:52:39
date last changed
2023-11-08 17:51:46
@article{69e68983-7266-46a2-8c3b-6891da9a7a2c,
  abstract     = {{<p>The oxidation of ammonia is a key reaction for the production of artificial fertilizers and for environmental protection. Depending on the area of application, the catalytic reaction needs to be tuned toward the production of either N2 or NO, and this selectivity is controlled by temperature, pressure, reactant ratio, and the type of catalyst. PtRh alloys are highly useful catalytic materials for the oxidation of ammonia, and they can be employed at different reaction conditions. In contrast to pure Pt and Rh catalysts, for which a large number of studies of ammonia oxidation reaction mechanism are available, for PtRh alloys, direct spectroscopic evidence for structure-performance relationship is still lacking. To understand the behavior of PtRh alloys, namely, what is their active phase under reaction conditions and how the alloy composition leads to a particular product distribution, we study the oxidation of ammonia over PtRh/Pt(111) surfaces by simultaneous operando ambient pressure X-ray photoelectron spectroscopy and mass spectrometry at 1 mbar total reaction pressure. These data are complemented by a catalyst surface characterization by scanning tunneling microscopy in ultrahigh vacuum. We establish that the predominant surface structure during NH3 oxidation strongly depends on the degree of Pt enrichment and the O2/NH3 mixing ratio. At the nanoscale, the selectivity toward N2 or NO production is driven by the surface populations of N and O species. These, in turn, are controlled by the nature of the alloying of Pt with Rh. </p>}},
  author       = {{Ivashenko, Oleksii and Johansson, Niclas and Pettersen, Christine and Jensen, Martin and Zheng, Jian and Schnadt, Joachim and Sjåstad, Anja O.}},
  issn         = {{2155-5435}},
  keywords     = {{ammonia slip catalysis; APXPS; NOabatement; operando measurements; platinum; Pt(111); rhodium; surface alloy}},
  language     = {{eng}},
  pages        = {{8261--8273}},
  publisher    = {{The American Chemical Society (ACS)}},
  series       = {{ACS Catalysis}},
  title        = {{How Surface Species Drive Product Distribution during Ammonia Oxidation : An STM and Operando APXPS Study}},
  url          = {{http://dx.doi.org/10.1021/acscatal.1c00956}},
  doi          = {{10.1021/acscatal.1c00956}},
  volume       = {{11}},
  year         = {{2021}},
}