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Bifunctional Oxygen Reduction and Evolution Activity in Brownmillerites Ca(2)Fe((1–x))Co(x)O(5)
[Image: see text] State-of-the-art catalysts for oxygen reduction and evolution reactions (ORR and OER), which form the basis of advanced fuel cell applications, are based on noble metals such as Pt and Ir. However, high cost and scarcity of noble metals have led to an increased demand of earth-abun...
Autores principales: | , , |
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Formato: | Online Artículo Texto |
Lenguaje: | English |
Publicado: |
American Chemical Society
2019
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Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6648611/ https://www.ncbi.nlm.nih.gov/pubmed/31459309 http://dx.doi.org/10.1021/acsomega.8b02468 |
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author | Thundiyil, Shibin Kurungot, Sreekumar Devi, R. Nandini |
author_facet | Thundiyil, Shibin Kurungot, Sreekumar Devi, R. Nandini |
author_sort | Thundiyil, Shibin |
collection | PubMed |
description | [Image: see text] State-of-the-art catalysts for oxygen reduction and evolution reactions (ORR and OER), which form the basis of advanced fuel cell applications, are based on noble metals such as Pt and Ir. However, high cost and scarcity of noble metals have led to an increased demand of earth-abundant metal oxide catalysts, especially for bifunctional activity in ORR and OER. The fact that Pt and Ir or C, the cost-effective alternatives suggested, do not display satisfactory bifunctional activity has also helped in turning the interest to metal oxides which are stable under both ORR and OER conditions. Brownmillerite A(2)B(2)O(5) type oxides are promising as bifunctional oxygen electrocatalysts because of intrinsic structural features, viz., oxygen vacancy and catalytic activity of the B-site transition metal. In this study, Co-doped Ca(2)Fe(2)O(5) compounds are synthesized by the solid state method and structurally analyzed by Rietveld refinement of powder X-ray diffraction data. The compound Ca(2)Fe(2)O(5), crystallizing in the Pcmn space group has alternative FeO(4) tetrahedral and FeO(6) octahedral layers. Its Co-doped analogue, Ca(2)Fe(1.75)Co(0.25)O(5), also crystallizes in the same space group with both tetrahedral and octahedral Fe positions substituted with Co. However, Ca(2)FeCoO(5) in the Pbcm space group shows interlayer ordering with Co-rich octahedra connected to Fe-rich tetrahedra and vice versa. Oxygen bifunctional activities of these catalysts are monitored by rotating disc electrode and rotating ring disc electrode techniques in alkaline media. A close analysis of the ORR and OER was conducted through comparison of various parameters such as onset potential, current density, halfwave potential, and other kinetic parameters, which suggests that the presence of Co in the B site aids in achieving better bifunctional activity and bulk conductivity. In addition, Co(II)/Co(III) redox systems and their comparative concentrations also play a decisive role in enhancing the activity. |
format | Online Article Text |
id | pubmed-6648611 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2019 |
publisher | American Chemical Society |
record_format | MEDLINE/PubMed |
spelling | pubmed-66486112019-08-27 Bifunctional Oxygen Reduction and Evolution Activity in Brownmillerites Ca(2)Fe((1–x))Co(x)O(5) Thundiyil, Shibin Kurungot, Sreekumar Devi, R. Nandini ACS Omega [Image: see text] State-of-the-art catalysts for oxygen reduction and evolution reactions (ORR and OER), which form the basis of advanced fuel cell applications, are based on noble metals such as Pt and Ir. However, high cost and scarcity of noble metals have led to an increased demand of earth-abundant metal oxide catalysts, especially for bifunctional activity in ORR and OER. The fact that Pt and Ir or C, the cost-effective alternatives suggested, do not display satisfactory bifunctional activity has also helped in turning the interest to metal oxides which are stable under both ORR and OER conditions. Brownmillerite A(2)B(2)O(5) type oxides are promising as bifunctional oxygen electrocatalysts because of intrinsic structural features, viz., oxygen vacancy and catalytic activity of the B-site transition metal. In this study, Co-doped Ca(2)Fe(2)O(5) compounds are synthesized by the solid state method and structurally analyzed by Rietveld refinement of powder X-ray diffraction data. The compound Ca(2)Fe(2)O(5), crystallizing in the Pcmn space group has alternative FeO(4) tetrahedral and FeO(6) octahedral layers. Its Co-doped analogue, Ca(2)Fe(1.75)Co(0.25)O(5), also crystallizes in the same space group with both tetrahedral and octahedral Fe positions substituted with Co. However, Ca(2)FeCoO(5) in the Pbcm space group shows interlayer ordering with Co-rich octahedra connected to Fe-rich tetrahedra and vice versa. Oxygen bifunctional activities of these catalysts are monitored by rotating disc electrode and rotating ring disc electrode techniques in alkaline media. A close analysis of the ORR and OER was conducted through comparison of various parameters such as onset potential, current density, halfwave potential, and other kinetic parameters, which suggests that the presence of Co in the B site aids in achieving better bifunctional activity and bulk conductivity. In addition, Co(II)/Co(III) redox systems and their comparative concentrations also play a decisive role in enhancing the activity. American Chemical Society 2019-01-02 /pmc/articles/PMC6648611/ /pubmed/31459309 http://dx.doi.org/10.1021/acsomega.8b02468 Text en Copyright © 2019 American Chemical Society This is an open access article published under an ACS AuthorChoice License (http://pubs.acs.org/page/policy/authorchoice_termsofuse.html) , which permits copying and redistribution of the article or any adaptations for non-commercial purposes. |
spellingShingle | Thundiyil, Shibin Kurungot, Sreekumar Devi, R. Nandini Bifunctional Oxygen Reduction and Evolution Activity in Brownmillerites Ca(2)Fe((1–x))Co(x)O(5) |
title | Bifunctional Oxygen Reduction and Evolution Activity
in Brownmillerites Ca(2)Fe((1–x))Co(x)O(5) |
title_full | Bifunctional Oxygen Reduction and Evolution Activity
in Brownmillerites Ca(2)Fe((1–x))Co(x)O(5) |
title_fullStr | Bifunctional Oxygen Reduction and Evolution Activity
in Brownmillerites Ca(2)Fe((1–x))Co(x)O(5) |
title_full_unstemmed | Bifunctional Oxygen Reduction and Evolution Activity
in Brownmillerites Ca(2)Fe((1–x))Co(x)O(5) |
title_short | Bifunctional Oxygen Reduction and Evolution Activity
in Brownmillerites Ca(2)Fe((1–x))Co(x)O(5) |
title_sort | bifunctional oxygen reduction and evolution activity
in brownmillerites ca(2)fe((1–x))co(x)o(5) |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6648611/ https://www.ncbi.nlm.nih.gov/pubmed/31459309 http://dx.doi.org/10.1021/acsomega.8b02468 |
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