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Main Title: Electrosynthesis, functional, and structural characterization of a water-oxidizing manganese oxide
Author(s): Zaharieva, Ivelina
Chernev, Petko
Risch, Marcel
Klingan, Katharina
Kohlhoff, Mike
Fischer, Anna
Dau, Holger
Type: Article
Language Code: en
Abstract: In the sustainable production of non-fossil fuels, water oxidation is pivotal. Development of efficient catalysts based on manganese is desirable because this element is earth-abundant, inexpensive, and largely non-toxic. We report an electrodeposited Mn oxide (MnCat) that catalyzes electrochemical water oxidation at neutral pH at rates that approach the level needed for direct coupling to photoactive materials. By choice of the voltage protocol we could switch between electrodeposition of inactive Mn oxides (deposition at constant anodic potentials) and synthesis of the active MnCat (deposition by voltage-cycling protocols). Electron microscopy reveals that the MnCat consists of nanoparticles (100 nm) with complex fine-structure. X-ray spectroscopy reveals that the amorphous MnCat resembles the biological paragon, the water-splitting Mn4Ca complex of photosynthesis, with respect to mean Mn oxidation state (ca. +3.8 in the MnCat) and central structural motifs. Yet the MnCat functions without calcium or other bivalent ions. Comparing the MnCat with electrodeposited Mn oxides inactive in water oxidation, we identify characteristics that likely are crucial for catalytic activity. In both inactive Mn oxides and active ones (MnCat), extensive di-μ-oxo bridging between Mn ions is observed. However in the MnCat, the voltage-cycling protocol resulted in formation of MnIII sites and prevented formation of well-ordered and unreactive MnIVO2. Structure–function relations in Mn-based water-oxidation catalysts and strategies to design catalytically active Mn-based materials are discussed. Knowledge-guided performance optimization of the MnCat could pave the road for its technological use.
Issue Date: 2012
Date Available: 28-Jun-2016
DDC Class: 690 Hausbau, Bauhandwerk
Sponsor/Funder: DFG, EXC 314, Unifying Concepts in Catalysis
EC/FP7/212508/EU/European Solar-Fuel Initiative - Renewable Hydrogen from Sun and Water. Science Linking Molecular Biomimetics and Genetics/SOLARH2
Journal Title: Energy & environmental science
Publisher: Royal Society of Chemistry
Publisher Place: Cambridge
Volume: 5
Issue: 5
Publisher DOI: 10.1039/c2ee21191b
Page Start: 7081
Page End: 7089
EISSN: 1754-5692
Notes: Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.
This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.
Appears in Collections:Inst. Chemie » Publications

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