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Formation of a nanoparticulate birnessite-like phase in purported molecular water oxidation catalyst systems
journal contribution
posted on 2014-07-01, 00:00 authored by R K Hocking, R Malaeb, Will GatesWill Gates, A F Patti, S L Y Chang, G Devlin, D R MacFarlane, L SpicciaThe fate of [MnIII/IV2(μ-O)2(terpy)2(H2O)2]3+ (1) under conditions typically applied to test its ability to catalyze water oxidation was studied by X-ray absorption spectroscopy and UV/Vis spectrophotometry by using [MnIII/IV2(μ-O)2(bipy)4]3+ (2) and Mn2+ as controls (terpy=2,2′:6′,2“-terpyridine, bipy=2,2′-bipyridine). The sample matrix, pH and choice of oxidizing agent were found to have a significant effect on the species formed under catalytic conditions. At low range pH values (4–6), homogeneous catalysis testing in oxone implied that 1 remains intact, whereas in clay intercalate there is strong evidence that 1 breaks down to a birnessite-like phase. In homogeneous solutions at higher pH, the results are consistent with the same birnessite-like structure identified in the clay intercalate. The use of the molecular complexes, as a source of manganese instead of simple MnII salts, was found to have the effect of slowing down oxide formation and particle aggregation in solution. The original analytical results that implied the systems are molecular are discussed in the context of these new observations.
History
Journal
ChemCatChemVolume
6Issue
7Pagination
2028 - 2038Publisher
Wiley-VCHLocation
Weinheim, GermanyPublisher DOI
ISSN
1867-3880eISSN
1867-3899Language
engPublication classification
C Journal article; C1.1 Refereed article in a scholarly journalCopyright notice
2014, Wiley-VCHUsage metrics
Keywords
homogeneous catalysismanganeseoxidationwater chemistryX-ray absorption spectroscopyScience & TechnologyPhysical SciencesChemistry, PhysicalChemistryOXYGEN-EVOLVING CENTERMANGANESE COMPLEXESHYDROGEN-PRODUCTIONFUNCTIONAL-MODELO-2 EVOLUTIONOXIDEENERGYCOBALTELECTROCATALYSTSPOLYOXOMETALATEInorganic Chemistry
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