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  Operation of calcium-birnessite water-oxidation anodes: interactions of the catalyst with phosphate buffer anions

Ronge, E., Ohms, J., Roddatis, V., Jones, T., Sulzmann, F., Knop-Gericke, A., et al. (2021). Operation of calcium-birnessite water-oxidation anodes: interactions of the catalyst with phosphate buffer anions. Sustainable Energy & Fuels, 5(21), 5535-5547. doi:10.1039/D1SE01076J.

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Operation of calcium-birnessite water-oxidation anodes interactions of the catalyst with phosphate buffer anions - d1se01076j.pdf (Publisher version), 25MB
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Operation of calcium-birnessite water-oxidation anodes interactions of the catalyst with phosphate buffer anions - d1se01076j.pdf
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 Creators:
Ronge, Emanuel1, Author
Ohms, Jonas2, Author
Roddatis, Vladimir1, Author
Jones, Travis3, Author           
Sulzmann, Frederic3, Author           
Knop-Gericke, Axel3, 4, Author           
Schlögl, Robert3, 4, Author           
Kurz, Philipp2, Author
Jooss, Christian1, 5, Author
Skorupska, Katarzyna3, 4, Author           
Affiliations:
1Institut für Materialphysik, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, Göttingen 37077, Germany , ou_persistent22              
2Institut für Anorganische und Analytische Chemie, Freiburger Material forschungszentrum (FMF), Albert-Ludwigs-Universität Freiburg, Albertstraße 21, Freiburg 79104, Germany , ou_persistent22              
3Inorganic Chemistry, Fritz Haber Institute, Max Planck Society, ou_24023              
4Max-Planck-Institut für Chemische Energiekonversion, Stiftstraße 34-36, Mülheim an der Ruhr 45470, Germany , ou_persistent22              
5International Center for Advanced Energy Studies, Georg-August-Universität Göttingen, Tammannstr. 4, Göttingen 37077, Germany, ou_persistent22              

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 Abstract: Investigating the interfaces between electrolytes and electrocatalysts during electrochemical water oxidation is of great importance for an understanding of the factors influencing catalytic activity and stability. Here, the interaction of a well-established, nanocrystalline and mesoporous Ca-birnessite catalyst material (initial composition K0.2Ca0.21MnO2.21·1.4H2O, initial Mn-oxidation state ∼+3.8) with an aqueous potassium phosphate buffer electrolyte at pH 7 was studied mainly by using various electron microscopy and X-ray spectroscopy techniques. In comparison to electrolyte solutions not containing phosphate, the investigated Ca-birnessite electrodes show especially high and stable oxygen evolution activity in phosphate buffer. During electrolysis, partial ion substitutions of Ca2+ by K+ and OH/O2− by HnPO4(3−n)− were observed, leading to the formation of a stable, partially disordered Ca–K–Mn–HnPO4–H2O layer on the outer and the pore surfaces of the active electrocatalyst material. In this surface layer, Mn3+ ions are stabilized, which are often assumed to be of key importance for oxygen evolution catalysis. Furthermore, evidence for the formation of [Ca/PO4/H2O] complexes located between the [MnO6] layers of the birnessite was found using the soft Ca 2p and Ca L-edge X-ray spectroscopy. A possible way to interpret the observed, obviously very favorable “special relationship” between (hydrogen)phosphates and Ca-birnessites in electrocatalytic water oxidation would be that HnPO4(3−n)− anions are incorporated into the catalyst material where they act as stabilizing units for Mn3+ highly active centers and also as “internal bases” for the protons released during the water-oxidation reaction.

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Language(s): eng - English
 Dates: 2021-07-142021-09-242021-11-07
 Publication Status: Published online
 Pages: 13
 Publishing info: -
 Table of Contents: -
 Rev. Type: Peer
 Identifiers: DOI: 10.1039/D1SE01076J
 Degree: -

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Title: Sustainable Energy & Fuels
  Abbreviation : Sustainable Energy Fuels
Source Genre: Journal
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Publ. Info: Cambridge, UK : Royal Society of Chemistry
Pages: 13 Volume / Issue: 5 (21) Sequence Number: - Start / End Page: 5535 - 5547 Identifier: ISSN: 2398-4902
CoNE: https://pure.mpg.de/cone/journals/resource/2398-4902