Cargando…
Factors Governing the Activity of α‐MnO(2) Catalysts in the Oxygen Evolution Reaction: Conductivity versus Exposed Surface Area of Cryptomelane
Cryptomelane (α‐(K)MnO(2)) powders were synthesized by different methods leading to only slight differences in their bulk crystal structure and chemical composition, while the BET surface area and the crystallite size differed significantly. Their performance in the oxygen evolution reaction (OER) c...
Autores principales: | , , , , , |
---|---|
Formato: | Online Artículo Texto |
Lenguaje: | English |
Publicado: |
John Wiley and Sons Inc.
2020
|
Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7540518/ https://www.ncbi.nlm.nih.gov/pubmed/32159252 http://dx.doi.org/10.1002/chem.201905090 |
_version_ | 1783591227201945600 |
---|---|
author | Heese‐Gärtlein, Justus Morales, Dulce M. Rabe, Anna Bredow, Thomas Schuhmann, Wolfgang Behrens, Malte |
author_facet | Heese‐Gärtlein, Justus Morales, Dulce M. Rabe, Anna Bredow, Thomas Schuhmann, Wolfgang Behrens, Malte |
author_sort | Heese‐Gärtlein, Justus |
collection | PubMed |
description | Cryptomelane (α‐(K)MnO(2)) powders were synthesized by different methods leading to only slight differences in their bulk crystal structure and chemical composition, while the BET surface area and the crystallite size differed significantly. Their performance in the oxygen evolution reaction (OER) covered a wide range and their sequence of increasing activity differed when electrocatalysis in alkaline electrolyte and chemical water oxidation using Ce(4+) were compared. The decisive factors that explain this difference were identified in the catalysts’ microstructure. Chemical water oxidation activity is substantially governed by the exposed surface area, while the electrocatalytic activity is determined largely by the electric conductivity, which was found to correlate with the particle morphology in terms of needle length and aspect ratio in this sample series. This correlation is rather explained by an improved conductivity due to longer needles than by structure sensitivity as was supported by reference experiments using H(2)O(2) decomposition and carbon black as additive. The most active catalyst R‐cryptomelane reached a current density of 10 mA cm(−2) at a potential 1.73 V without, and at 1.71 V in the presence of carbon black. The improvement was significantly higher for the catalyst with lower initial activity. However, the materials showed a disappointing catalytic stability during alkaline electrochemical OER, whereas the crystal structure was found to be stable at working conditions. |
format | Online Article Text |
id | pubmed-7540518 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2020 |
publisher | John Wiley and Sons Inc. |
record_format | MEDLINE/PubMed |
spelling | pubmed-75405182020-10-09 Factors Governing the Activity of α‐MnO(2) Catalysts in the Oxygen Evolution Reaction: Conductivity versus Exposed Surface Area of Cryptomelane Heese‐Gärtlein, Justus Morales, Dulce M. Rabe, Anna Bredow, Thomas Schuhmann, Wolfgang Behrens, Malte Chemistry Full Papers Cryptomelane (α‐(K)MnO(2)) powders were synthesized by different methods leading to only slight differences in their bulk crystal structure and chemical composition, while the BET surface area and the crystallite size differed significantly. Their performance in the oxygen evolution reaction (OER) covered a wide range and their sequence of increasing activity differed when electrocatalysis in alkaline electrolyte and chemical water oxidation using Ce(4+) were compared. The decisive factors that explain this difference were identified in the catalysts’ microstructure. Chemical water oxidation activity is substantially governed by the exposed surface area, while the electrocatalytic activity is determined largely by the electric conductivity, which was found to correlate with the particle morphology in terms of needle length and aspect ratio in this sample series. This correlation is rather explained by an improved conductivity due to longer needles than by structure sensitivity as was supported by reference experiments using H(2)O(2) decomposition and carbon black as additive. The most active catalyst R‐cryptomelane reached a current density of 10 mA cm(−2) at a potential 1.73 V without, and at 1.71 V in the presence of carbon black. The improvement was significantly higher for the catalyst with lower initial activity. However, the materials showed a disappointing catalytic stability during alkaline electrochemical OER, whereas the crystal structure was found to be stable at working conditions. John Wiley and Sons Inc. 2020-09-04 2020-09-21 /pmc/articles/PMC7540518/ /pubmed/32159252 http://dx.doi.org/10.1002/chem.201905090 Text en © 2020 The Authors. Published by Wiley-VCH GmbH This is an open access article under the terms of the http://creativecommons.org/licenses/by-nc/4.0/ License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes. |
spellingShingle | Full Papers Heese‐Gärtlein, Justus Morales, Dulce M. Rabe, Anna Bredow, Thomas Schuhmann, Wolfgang Behrens, Malte Factors Governing the Activity of α‐MnO(2) Catalysts in the Oxygen Evolution Reaction: Conductivity versus Exposed Surface Area of Cryptomelane |
title | Factors Governing the Activity of α‐MnO(2) Catalysts in the Oxygen Evolution Reaction: Conductivity versus Exposed Surface Area of Cryptomelane |
title_full | Factors Governing the Activity of α‐MnO(2) Catalysts in the Oxygen Evolution Reaction: Conductivity versus Exposed Surface Area of Cryptomelane |
title_fullStr | Factors Governing the Activity of α‐MnO(2) Catalysts in the Oxygen Evolution Reaction: Conductivity versus Exposed Surface Area of Cryptomelane |
title_full_unstemmed | Factors Governing the Activity of α‐MnO(2) Catalysts in the Oxygen Evolution Reaction: Conductivity versus Exposed Surface Area of Cryptomelane |
title_short | Factors Governing the Activity of α‐MnO(2) Catalysts in the Oxygen Evolution Reaction: Conductivity versus Exposed Surface Area of Cryptomelane |
title_sort | factors governing the activity of α‐mno(2) catalysts in the oxygen evolution reaction: conductivity versus exposed surface area of cryptomelane |
topic | Full Papers |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7540518/ https://www.ncbi.nlm.nih.gov/pubmed/32159252 http://dx.doi.org/10.1002/chem.201905090 |
work_keys_str_mv | AT heesegartleinjustus factorsgoverningtheactivityofamno2catalystsintheoxygenevolutionreactionconductivityversusexposedsurfaceareaofcryptomelane AT moralesdulcem factorsgoverningtheactivityofamno2catalystsintheoxygenevolutionreactionconductivityversusexposedsurfaceareaofcryptomelane AT rabeanna factorsgoverningtheactivityofamno2catalystsintheoxygenevolutionreactionconductivityversusexposedsurfaceareaofcryptomelane AT bredowthomas factorsgoverningtheactivityofamno2catalystsintheoxygenevolutionreactionconductivityversusexposedsurfaceareaofcryptomelane AT schuhmannwolfgang factorsgoverningtheactivityofamno2catalystsintheoxygenevolutionreactionconductivityversusexposedsurfaceareaofcryptomelane AT behrensmalte factorsgoverningtheactivityofamno2catalystsintheoxygenevolutionreactionconductivityversusexposedsurfaceareaofcryptomelane |