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Morphological Transformation of Co(OH) 2 Microspheres from Solid to Flowerlike Hollow Core–Shell Structures
Author(s) -
Qiao Ru,
Zhang Xiao Li,
Qiu Ri,
Kim Ju Chang,
Kang Young Soo
Publication year - 2009
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200800803
Subject(s) - cobalt , cobalt hydroxide , ostwald ripening , dissolution , materials science , crystallite , chemical engineering , transmission electron microscopy , scanning electron microscope , hydroxide , thermal decomposition , diffusion , nanotechnology , chemistry , metallurgy , composite material , engineering , physics , electrode , electrochemistry , thermodynamics , organic chemistry
Co(OH) 2 that blooms : Flowerlike hollow spherical architectures of cobalt hydroxide obtained through a facile solvothermal process are reported for the first time (see picture). Their growth process involves aggregation of cobalt hydroxide nanoparticles into solid spheres and a hollowing effect through subsequent dissolution‐diffusion‐redeposition of the smaller crystallites under the surface layer.We report, for the first time, a detailed investigation into the formation of highly uniform, 3D, flowerlike, hollow, spherical architectures of cobalt hydroxide through a facile solvothermal process. Various controlling parameters were examined, such as water content in starting materials, reaction time, cobalt(II) precursor concentration, and reaction temperature. On the basis of the experimental results, the formation mechanism of these flowerlike cobalt hydroxide hollow spheres involves aggregation of cobalt hydroxide building clusters into solid spheres and hollowing effect through subsequent dissolution, diffusion, and re‐deposition of the smaller crystallites under the surface layer driven by an Ostwald ripening process. Metallic cobalt hollow spheres have also been obtained by thermal decomposition of cobalt hydroxide flowers in a mixed gas of Ar+4 % H 2 at 400 °C. The morphology and composition of the products were characterized by X‐ray diffraction, field‐emission scanning electron microscopy, energy‐dispersive X‐ray spectroscopy, and (high resolution) transmission electron microscopy.