Cation doped cerium oxynitride with anion vacancies for Fe-based catalyst with improved activity and oxygenate tolerance for efficient synthesis of ammonia

John Humphreys; Rong Lan; Shigang Chen; Marc Walker; Yisong Han; Shanwen Tao

doi:10.1016/j.apcatb.2020.119843

Cation doped cerium oxynitride with anion vacancies for Fe-based catalyst with improved activity and oxygenate tolerance for efficient synthesis of ammonia

John Humphreys, Rong Lan, Shigang Chen, Marc Walker, Yisong Han, Shanwen Tao

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Abstract

For the first time, new Sm doped cerium oxynitrides with the formula Ce _1-zSm _zO _2-xN _y (z ≤ 0.5) are synthesized in order to maximize the concentration of anion vacancies. Single phase Sm-doped CeO _2-xN _y were confirmed by XRD, HRTEM and Rietveld refinement. These oxynitrides show a great promotion effect for the low-cost Fe catalyst for the ammonia synthesis. At 350 °C and 1 MPa, the activity of 80 wt% Fe- 20 wt% Ce _1-zSm _zO _2xN _y is one of the highest reported for non-Ru catalysts for the Haber-Bosch reaction. The apparent activation energy of the 80 wt% Fe- 20 wt% Ce _1-zSm _zO _2xN _y catalysts with z ≥ 0.3 is around 45 kJ/mol, which is in the lowest range among all reported ammonia synthesis catalysts. Introduction of nitrogen vacancies through doping may facilitate the mobility of nitrogen vacancies. This study demonstrates doped oxynitrides with a large concentration of anion vacancies, particularly nitrogen vacancies are excellent promoters/co-catalysts for ammonia synthesis.

Original language	English
Article number	119843
Number of pages	15
Journal	Applied Catalysis B: Environmental
Volume	285
Early online date	25 Dec 2020
DOIs	https://doi.org/10.1016/j.apcatb.2020.119843
Publication status	Published - 15 May 2021
Externally published	Yes

Bibliographical note

This is an Open Access article distributed under the terms of the Creative
Commons Attribution License (http://creativecommons.org/licenses/by/4.0/),
which permits unrestricted use, distribution, and reproduction in any medium,
provided the original work is properly cited..

Funder

EPSRC (Grant No. EP/G01244X/1

Keywords

Oxynitride
Nitrogen vacancy
Ammonia synthesis
Oxygenate
Activation energy

ASJC Scopus subject areas

Environmental Science(all)
Process Chemistry and Technology
Catalysis

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10.1016/j.apcatb.2020.119843Licence: CC BY

PublishedFinal published version, 7.57 MBLicence: CC BY

Cite this

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title = "Cation doped cerium oxynitride with anion vacancies for Fe-based catalyst with improved activity and oxygenate tolerance for efficient synthesis of ammonia",

abstract = "For the first time, new Sm doped cerium oxynitrides with the formula Ce 1-zSm zO 2-xN y (z ≤ 0.5) are synthesized in order to maximize the concentration of anion vacancies. Single phase Sm-doped CeO 2-xN y were confirmed by XRD, HRTEM and Rietveld refinement. These oxynitrides show a great promotion effect for the low-cost Fe catalyst for the ammonia synthesis. At 350 °C and 1 MPa, the activity of 80 wt% Fe- 20 wt% Ce 1-zSm zO 2xN y is one of the highest reported for non-Ru catalysts for the Haber-Bosch reaction. The apparent activation energy of the 80 wt% Fe- 20 wt% Ce 1-zSm zO 2xN y catalysts with z ≥ 0.3 is around 45 kJ/mol, which is in the lowest range among all reported ammonia synthesis catalysts. Introduction of nitrogen vacancies through doping may facilitate the mobility of nitrogen vacancies. This study demonstrates doped oxynitrides with a large concentration of anion vacancies, particularly nitrogen vacancies are excellent promoters/co-catalysts for ammonia synthesis. ",

keywords = "Oxynitride, Nitrogen vacancy, Ammonia synthesis, Oxygenate, Activation energy",

author = "John Humphreys and Rong Lan and Shigang Chen and Marc Walker and Yisong Han and Shanwen Tao",

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T1 - Cation doped cerium oxynitride with anion vacancies for Fe-based catalyst with improved activity and oxygenate tolerance for efficient synthesis of ammonia

AU - Humphreys, John

AU - Lan, Rong

AU - Chen, Shigang

AU - Walker, Marc

AU - Han, Yisong

AU - Tao, Shanwen

N1 - This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited..

PY - 2021/5/15

Y1 - 2021/5/15

N2 - For the first time, new Sm doped cerium oxynitrides with the formula Ce 1-zSm zO 2-xN y (z ≤ 0.5) are synthesized in order to maximize the concentration of anion vacancies. Single phase Sm-doped CeO 2-xN y were confirmed by XRD, HRTEM and Rietveld refinement. These oxynitrides show a great promotion effect for the low-cost Fe catalyst for the ammonia synthesis. At 350 °C and 1 MPa, the activity of 80 wt% Fe- 20 wt% Ce 1-zSm zO 2xN y is one of the highest reported for non-Ru catalysts for the Haber-Bosch reaction. The apparent activation energy of the 80 wt% Fe- 20 wt% Ce 1-zSm zO 2xN y catalysts with z ≥ 0.3 is around 45 kJ/mol, which is in the lowest range among all reported ammonia synthesis catalysts. Introduction of nitrogen vacancies through doping may facilitate the mobility of nitrogen vacancies. This study demonstrates doped oxynitrides with a large concentration of anion vacancies, particularly nitrogen vacancies are excellent promoters/co-catalysts for ammonia synthesis.

AB - For the first time, new Sm doped cerium oxynitrides with the formula Ce 1-zSm zO 2-xN y (z ≤ 0.5) are synthesized in order to maximize the concentration of anion vacancies. Single phase Sm-doped CeO 2-xN y were confirmed by XRD, HRTEM and Rietveld refinement. These oxynitrides show a great promotion effect for the low-cost Fe catalyst for the ammonia synthesis. At 350 °C and 1 MPa, the activity of 80 wt% Fe- 20 wt% Ce 1-zSm zO 2xN y is one of the highest reported for non-Ru catalysts for the Haber-Bosch reaction. The apparent activation energy of the 80 wt% Fe- 20 wt% Ce 1-zSm zO 2xN y catalysts with z ≥ 0.3 is around 45 kJ/mol, which is in the lowest range among all reported ammonia synthesis catalysts. Introduction of nitrogen vacancies through doping may facilitate the mobility of nitrogen vacancies. This study demonstrates doped oxynitrides with a large concentration of anion vacancies, particularly nitrogen vacancies are excellent promoters/co-catalysts for ammonia synthesis.

KW - Oxynitride

KW - Nitrogen vacancy

KW - Ammonia synthesis

KW - Oxygenate

KW - Activation energy

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Cation doped cerium oxynitride with anion vacancies for Fe-based catalyst with improved activity and oxygenate tolerance for efficient synthesis of ammonia

Abstract

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Keywords

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