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Tunable Biogenic Manganese Oxides.

Authors :: Simonov AN
Hocking RK
Tao L
Gengenbach T
Williams T
Fang XY
King HJ
Bonke SA
Hoogeveen DA
Romano CA
Tebo BM
Martin LL
Casey WH
Spiccia L
Source :: Chemistry (Weinheim an der Bergstrasse, Germany) [Chemistry] 2017 Sep 27; Vol. 23 (54), pp. 13482-13492. Date of Electronic Publication: 2017 Aug 28.
Publication Year :: 2017
Abstract: Influence of the conditions for aerobic oxidation of Mn2+(aq) catalysed by the MnxEFG protein complex on the morphology, structure and reactivity of the resulting biogenic manganese oxides (MnO <subscript>x</subscript> ) is explored. Physical characterisation of MnO <subscript>x</subscript> includes scanning and transmission electron microscopy, and X-ray photoelectron and K-edge Mn, Fe X-ray absorption spectroscopy. This characterisation reveals that the MnO <subscript>x</subscript> materials share the structural features of birnessite, yet differ in the degree of structural disorder. Importantly, these biogenic products exhibit strikingly different morphologies that can be easily controlled. Changing the substrate-to-protein ratio produces MnO <subscript>x</subscript> either as nm-thin sheets, or rods with diameters below 20 nm, or a combination of the two. Mineralisation in solutions that contain Fe2+(aq) makes solids with significant disorder in the structure, while the presence of Ca2+(aq) facilitates formation of more ordered materials. The (photo)oxidation and (photo)electrocatalytic capacity of the MnO <subscript>x</subscript> minerals is examined and correlated with their structural properties.<br /> (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)