| 1. |
- Ertl, Michael, et al.
(author)
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Mössbauerite as Iron-Only Layered Oxyhydroxide Catalyst for WO3 Photoanodes
- 2019
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In: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 58:15, s. 9655-9662
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Journal article (peer-reviewed)abstract
- Mössbauerite, a trivalent iron-only layered oxyhydroxide, has been recently identified as an electrocatalyst for water oxidation. We investigated the material as potential cocatalyst for photoelectrochemical water oxidation on semiconductor photoanodes. The band edge positions of mössbauerite were determined for the first time with a combination of Mott-Schottky analysis and UV-vis diffuse reflectance spectroscopy. The positive value of the Mott-Schottky slope and the flatband potential of 0.34 V vs reversible hydrogen electrode (RHE) identifies the material as an n-type semiconductor, but bare mössbauerite does not produce noticeable photocurrent during water oxidation. Type-II heterojunction formation by facile drop-casting with WO3 thin films yielded photoanodes with amended charge carrier separation and photocurrents up to 1.22 mA cm(-2) at 1.23 V vs RHE. Mössbauerite is capable of increasing the charge carrier separation at lower potential and improving the photocurrent during photoelectrochemical water oxidation. The rise in photocurrent of the mössbauerite-functionalized WO3 photoanode thus originates from improved charge carrier separation and augmented hole collection efficiency. Our results highlight the potential of mössbauerite as a second-phase catalyst for semiconductor electrodes.
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| 2. |
- Mohideen, M. Infas H., et al.
(author)
-
Magneto-structural correlations of novel kagome-type metal organic frameworks
- 2019
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In: Journal of Materials Chemistry C. - : Royal Society of Chemistry (RSC). - 2050-7526 .- 2050-7534. ; 7:22, s. 6692-6697
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Journal article (peer-reviewed)abstract
- Here, we report the in situ formation of two novel metal organic frameworks based on copper and cobalt using tetrazole-5-carboxylate ethyl ester as the ligand synthesized by a hydrothermal route. Both MOFs show isostructural three-dimensional networks with kagome ' tilling topology and show high chemical stability. Despite the iso-structural nature, both systems show distinct magnetic features. For the Cu-based kag-MOF system, the co-existence of energetically competing ferromagnetic and antiferromagnetic interactions resulted in the establishment of a long-range ferromagnetic order sustainable up to 52 K. On the contrary, dominant antiferromagnetic interactions identified in the Co-based MOF material were responsible for an antiferromagnetic order evolving below 7 K. Importantly, chemically different metallic ions gave rise to distinct magnetic ordering with different strength and temperature-sustainability. No dynamic magnetic phenomena were observed, implying that the concentration of the metal ions within the structure exceeded the percolation limit favoring the formation of the long-range magnetic order in the studied systems. Both designed kagome ' -type MOFs were thus found to show a coexistence of high frustration and long range magnetic ordering with limited orbital quenching, resulting from the choice of the ligands and crystal arrangement. Thus, the results demonstrated the potentiality to effectively control and alter the magnetic features within the particular kagome ' -type MOF lattice due to the chemical nature and structural incorporation of individual metal ions. The presented approach offers a promising strategy to further fine tune the physical characteristics of the MOF-based systems equipping them with more competitive potential and extending their application portfolio to other fields.
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