Premium
A Composite Formation Route to Well‐Crystalline Manganese Oxide Nanocrystals: High Catalytic Activity of Manganate–Alumina Nanocomposites
Author(s) -
Kim Tae Woo,
Yoo Hana,
Kim In Young,
Ha HyungWook,
Han Ah Reum,
Chang JongSan,
Lee Ji Sun,
Hwang SeongJu
Publication year - 2011
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.201100218
Subject(s) - materials science , crystallinity , nanocomposite , oxide , chemical engineering , calcination , manganate , nanocrystal , inorganic chemistry , catalysis , manganese , crystallization , nanotechnology , composite material , metallurgy , organic chemistry , chemistry , power (physics) , physics , battery (electricity) , quantum mechanics , engineering
Manganese oxide nanocrystals are combined with aluminum oxide nanocrystals to improve their crystallinity via calcination without a significant increase of crystal size. A nanocomposite, consisting of two metal oxides, can be synthesized by the reaction between permanganate anions and aluminum oxyhydroxide keggin cations. The as‐prepared manganese oxide–aluminum oxide nanocomposite is X‐ray amorphous whereas heat‐treatment gives rise to the crystallization of an α ‐MnO 2 phase at 600 °C and Mn 3 O 4 /Mn 2 O 3 and γ ‐Al 2 O 3 phases at 800 °C. Electron microscopy and N 2 adsorption‐desorption‐isotherm analysis clearly demonstrate that the as‐prepared nanocomposite is composed of a porous assembly of monodisperse primary particles with a size of ∼20 nm and a surface area of >410 m 2 g −1 . Of particular interest is that the small particle size of the as‐prepared nanocomposite is well‐maintained up to 600 °C, a result of the prevention of the growth of manganate grains through nanoscale mixing with alumina grains. The calcined nanocomposite shows very‐high catalytic activity for the oxidation of cyclohexene with an extremely high conversion efficiency of >95% within 15 min. The present results show that the improvement of the crystallinity without significant crystal growth is very crucial for optimizing the catalytic activity of manganese oxide nanocrystals.