# Last edited on 2018-09-05 14:38:12 by stolfilocal



Several chemical and electrochemical methods have been
employed to prepare cobalt hydroxide, for example, forced
precipitation of Co(NO3)2, direct precipitation with liquid
ammonia [8] and potassium hydroxide, [9] urea hydrolysis, [10]
and electrochemical synthesis. [11] Sampanthar and Zeng [12]
reported the synthesis of butterfly-like b-Co(OH)2 nanocrystals 
by the ethylenediamine-mediated approach. Li et al. [13] prepared b-Co(OH)2
nanostructures consisting of a mixture of nanoflakes and nanorods by the CoC2O4·2H2O 
conversion method. Recently, Liu et al. [14] synthesized single-crystalline nanosheets 
of a- and b-Co(OH)2 by using hexamethylenetetramine as a hydrolysis agent. 
Hou et al. [15] also synthesized single-crystalline b-Co(OH)2 nanosheets by
homogeneous precipitation with sodium hydroxide as the alkaline
reagent in the presence of poly(vinylpyrrolidone).

In a typical procedure, Co(NO3)2·6H2O (0.291 g, 1 mmol) was placed in a
50-mL teflon-lined autoclave and dissolved in deionized water (20 mL)
to form a pink solution at room temperature. Triethylamine (0.5–1.5 mL)
was then added dropwise with magnetic stirring, and the solution imme-
diately turned black. Next, the autoclave was filled with deionized water
up to 80% of the total volume and, after 10 min of stirring, sealed and
maintained at 100–180 C for 2–24 h without shaking or stirring. The re-
sulting products were filtered and washed with deionized water and anhy-
drous ethanol several times, and finally dried under vacuum at 60 C for
4 h. As-prepared cobalt hydroxide was calcined to produce porous nano-
sheets and nanorings of Co3O4 in air at 400–600 C for 2 h.

8] T. N. Ramesh, M. Rajamathi, P. V. Kamath, Solid State Sci. 2003, 5, 751.
[9] P. Elumalai, H. N. Vasan, N. Munichandraiah, J. Power Sources 2001, 93, 201.
[10] M. Dixit, G. N. Subbanna, P. V. Kamath, J. Mater. Chem. 1996, 6, 1429.
[11] R. S. Jayashree, P. Vishnu Kamath, J. Mater. Chem. 1999, 9, 961.
[12] J. T. Sampanthar, H. C. Zeng, J. Am. Chem. Soc. 2002, 124, 6668.
[13] X. L. Li, J. F. Liu, Y. D. Li, Mater. Chem. Phys. 2003, 80, 222.
[14] Z. Liu, R. Ma, M. Osada, K. Takada, T. Sasaki, J. Am. Chem. Soc. 2005, 127, 13869.
[15] Y. Hou, H. Kondoh, M. Shimojo, T. Kogure, T. Ohta, J. Phys. Chem. B 2005, 109, 19094.