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Local Atomic Arrangement and Electronic Configuration of Nanocrystalline Zinc Oxide Hybridized with Redoxable 2D Lattice of Manganese Oxide

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journal contribution
posted on 15.11.2007, 00:00 by Tae Woo Kim, Ah Reum Han, Seong-Ju Hwang, Jin-Ho Choy
Nanocrystalline zinc oxides were hybridized with the redoxable 2D lattice of layered manganese oxide through a hydrothermal reaction between the colloidal suspension of exfoliated manganese oxide nanosheets and the solution of zinc acetate. According to our analyses using powder X-ray diffraction, field emission-scanning electron microscopic, diffuse reflectance UV−vis, and N2 adsorption−desorption isotherm measurements, zinc oxide nanoparticles are intercalated in the interlayer space of layered manganese oxide, leading to the formation of 1:1 ordered heterostructure with an expanded basal spacing of ∼1.97 nm and expanded surface area of ∼60−70 m2/g. The Zn K-edge X-ray absorption spectroscopic (XAS) analyses clearly demonstrated that zinc ions in the nanohybrids are stabilized in tetrahedral geometry, and a post-calcination process on the as-prepared nanohybrid leads to a structural transformation of guest species from the loosely packed network of ZnO4 tetrahedra to the perfect wurzite-type ordering of ZnO4 tetrahedra. According to the Mn K-edge XAS investigation, the layered manganate lattice consisting of edge-shared MnO6 octahedra is well maintained with distinct variations of Mn oxidation state upon exfoliation, hybridization, and post-calcination processes. This result underscores the redox capability of the present manganate-based nanohybrid, which is contrasted with the titanate-based intercalation compounds. Judging from their unique heterostructures with redoxable manganese oxide component and expanded surface area, the present nanohybrids are expected to be applicable as electrodes for supercapacitors and lithium batteries, and heterogeneous redox catalysts.