Dynamics of Reactive Oxygen Species on Cobalt-Containing Spinel Oxides in Cyclic CO Oxidation

Reactive oxygen species (ROS) are considered to be responsible for the high catalytic activity of transition metal oxides like Co3-xFexO4 in oxidation reactions, but the detailed influences of catalyst composition and morphology on...

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Autores principales:	Maik Dreyer, Anna Rabe, Eko Budiyanto, Klaus Friedel Ortega, Sharif Najafishirtari, Harun Tüysüz, Malte Behrens
Formato:	article
Lenguaje:	EN
Publicado:	MDPI AG 2021
Materias:	CO oxidation spinel Co<sub>3</sub>O<sub>4</sub> Co<sub>3-x</sub>Fe<sub>x</sub>O<sub>4</sub> oxygen activation reactive oxygen species Chemical technology TP1-1185 Chemistry QD1-999
Acceso en línea:	https://doaj.org/article/3d0d15d614594244984f2ae99543b0b0
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spelling	oai:doaj.org-article:3d0d15d614594244984f2ae99543b0b02021-11-25T17:05:44ZDynamics of Reactive Oxygen Species on Cobalt-Containing Spinel Oxides in Cyclic CO Oxidation10.3390/catal111113122073-4344https://doaj.org/article/3d0d15d614594244984f2ae99543b0b02021-10-01T00:00:00Zhttps://www.mdpi.com/2073-4344/11/11/1312https://doaj.org/toc/2073-4344Reactive oxygen species (ROS) are considered to be responsible for the high catalytic activity of transition metal oxides like Co<sub>3-x</sub>Fe<sub>x</sub>O<sub>4</sub> in oxidation reactions, but the detailed influences of catalyst composition and morphology on the formation of these reactive oxygen species are not fully understood. In the presented study, Co<sub>3</sub>O<sub>4</sub> spinels of different mesostructures, i.e., particle size, crystallinity, and specific surface area, are characterized by powder X-ray diffraction, scanning electron microscopy, and physisorption. The materials were tested in CO oxidation performed in consecutive runs and compared to a Co<sub>3-x</sub>Fe<sub>x</sub>O<sub>4</sub> composition series with a similar mesostructure to study the effects of catalyst morphology and composition on ROS formation. In the first run, the CO conversion was observed to be dominated by the exposed surface area for the pure Co-spinels, while a negative effect of Fe content in the spinels was seen. In the following oxidation run, a U-shaped conversion curve was observed for materials with high surface area, which indicated the in situ formation of ROS on those materials that were responsible for the new activity at low temperature. This activation was not stable at the higher reaction temperature but was confirmed after temperature-programmed oxidation (TPO). However, no activation after the first run was observed for low-surface-area and highly crystalline materials, and the lowest surface-area material was not even activated after TPO. Among the catalyst series studied here, a correlation of small particle size and large surface area with the ability for ROS formation is presented, and the benefit of a nanoscaled catalyst is discussed. Despite the generally negative effect of Fe, the highest relative activation was observed at intermediate Fe contents suggesting that Fe may be involved in ROS formation.Maik DreyerAnna RabeEko BudiyantoKlaus Friedel OrtegaSharif NajafishirtariHarun TüysüzMalte BehrensMDPI AGarticleCO oxidationspinelCo<sub>3</sub>O<sub>4</sub>Co<sub>3-x</sub>Fe<sub>x</sub>O<sub>4</sub>oxygen activationreactive oxygen speciesChemical technologyTP1-1185ChemistryQD1-999ENCatalysts, Vol 11, Iss 1312, p 1312 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	CO oxidation spinel Co<sub>3</sub>O<sub>4</sub> Co<sub>3-x</sub>Fe<sub>x</sub>O<sub>4</sub> oxygen activation reactive oxygen species Chemical technology TP1-1185 Chemistry QD1-999
spellingShingle	CO oxidation spinel Co<sub>3</sub>O<sub>4</sub> Co<sub>3-x</sub>Fe<sub>x</sub>O<sub>4</sub> oxygen activation reactive oxygen species Chemical technology TP1-1185 Chemistry QD1-999 Maik Dreyer Anna Rabe Eko Budiyanto Klaus Friedel Ortega Sharif Najafishirtari Harun Tüysüz Malte Behrens Dynamics of Reactive Oxygen Species on Cobalt-Containing Spinel Oxides in Cyclic CO Oxidation
description	Reactive oxygen species (ROS) are considered to be responsible for the high catalytic activity of transition metal oxides like Co<sub>3-x</sub>Fe<sub>x</sub>O<sub>4</sub> in oxidation reactions, but the detailed influences of catalyst composition and morphology on the formation of these reactive oxygen species are not fully understood. In the presented study, Co<sub>3</sub>O<sub>4</sub> spinels of different mesostructures, i.e., particle size, crystallinity, and specific surface area, are characterized by powder X-ray diffraction, scanning electron microscopy, and physisorption. The materials were tested in CO oxidation performed in consecutive runs and compared to a Co<sub>3-x</sub>Fe<sub>x</sub>O<sub>4</sub> composition series with a similar mesostructure to study the effects of catalyst morphology and composition on ROS formation. In the first run, the CO conversion was observed to be dominated by the exposed surface area for the pure Co-spinels, while a negative effect of Fe content in the spinels was seen. In the following oxidation run, a U-shaped conversion curve was observed for materials with high surface area, which indicated the in situ formation of ROS on those materials that were responsible for the new activity at low temperature. This activation was not stable at the higher reaction temperature but was confirmed after temperature-programmed oxidation (TPO). However, no activation after the first run was observed for low-surface-area and highly crystalline materials, and the lowest surface-area material was not even activated after TPO. Among the catalyst series studied here, a correlation of small particle size and large surface area with the ability for ROS formation is presented, and the benefit of a nanoscaled catalyst is discussed. Despite the generally negative effect of Fe, the highest relative activation was observed at intermediate Fe contents suggesting that Fe may be involved in ROS formation.
format	article
author	Maik Dreyer Anna Rabe Eko Budiyanto Klaus Friedel Ortega Sharif Najafishirtari Harun Tüysüz Malte Behrens
author_facet	Maik Dreyer Anna Rabe Eko Budiyanto Klaus Friedel Ortega Sharif Najafishirtari Harun Tüysüz Malte Behrens
author_sort	Maik Dreyer
title	Dynamics of Reactive Oxygen Species on Cobalt-Containing Spinel Oxides in Cyclic CO Oxidation
title_short	Dynamics of Reactive Oxygen Species on Cobalt-Containing Spinel Oxides in Cyclic CO Oxidation
title_full	Dynamics of Reactive Oxygen Species on Cobalt-Containing Spinel Oxides in Cyclic CO Oxidation
title_fullStr	Dynamics of Reactive Oxygen Species on Cobalt-Containing Spinel Oxides in Cyclic CO Oxidation
title_full_unstemmed	Dynamics of Reactive Oxygen Species on Cobalt-Containing Spinel Oxides in Cyclic CO Oxidation
title_sort	dynamics of reactive oxygen species on cobalt-containing spinel oxides in cyclic co oxidation
publisher	MDPI AG
publishDate	2021
url	https://doaj.org/article/3d0d15d614594244984f2ae99543b0b0
work_keys_str_mv	AT maikdreyer dynamicsofreactiveoxygenspeciesoncobaltcontainingspineloxidesincycliccooxidation AT annarabe dynamicsofreactiveoxygenspeciesoncobaltcontainingspineloxidesincycliccooxidation AT ekobudiyanto dynamicsofreactiveoxygenspeciesoncobaltcontainingspineloxidesincycliccooxidation AT klausfriedelortega dynamicsofreactiveoxygenspeciesoncobaltcontainingspineloxidesincycliccooxidation AT sharifnajafishirtari dynamicsofreactiveoxygenspeciesoncobaltcontainingspineloxidesincycliccooxidation AT haruntuysuz dynamicsofreactiveoxygenspeciesoncobaltcontainingspineloxidesincycliccooxidation AT maltebehrens dynamicsofreactiveoxygenspeciesoncobaltcontainingspineloxidesincycliccooxidation
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Dynamics of Reactive Oxygen Species on Cobalt-Containing Spinel Oxides in Cyclic CO Oxidation

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