Cobalt Hydroxide Nanosheets and Their Thermal Decomposition to Cobalt Oxide Nanorings

Abstract

We demonstrate herein that single-crystalline beta-cobalt hydroxide (beta-Co(OH)(2)) nanosheets can be successfully synthesized in large quantities by a facile hydrothermal synthetic method with aqueous cobalt nitrate as the cobalt source and triethylamine as both an alkaline and a complexing reagent. This synthetic method has good prospects for the future large-scale production of single-crystalline beta-Co(OH)(2) nanosheets owing to its high yield, low cost, and simple reaction apparatus. Single-crystalline porous nanosheets and nanorings of cobalt oxide (Co(3)O(4)) were obtained by a thermal-decomposition method with single-crystalline beta-Co(OH)(2) nanosheets as the precursor. A probable mechanism of formation of beta-Co(OH)(2) nanosheets, porous Co(3)O(4) nanosheets, and Co(3)O(4) nanorings was proposed on the basis of the experimental results.

Polytypic transformations during the thermal decomposition of cobalt hydroxide and cobalt hydroxynitrate

“…The freshly precipitated cobalt hydroxide slurry on (i) exposure to air, (ii) ageing in alkaline solution or mother liquor results in the formation of CoOOH [13]. Nanocrystalline cobalt hydroxide platelets were prepared by the hydrothermal treatment technique in presence of amines and polyvinylpyrrolidine [14,15]. There are several reports on the thermal decomposition studies of cobalt hydroxide, cobalt oxyhydroxide and cobalt based layered double hydroxides in relation to texture, morphology by electron diffraction, X-ray diffraction, Raman spectroscopy and X-ray photoelectron spectroscopy [16][17][18][19].…”

A room temperature solution-phase process to synthesize pure phase single-crystalline hexagonal cobalt hydroxide nanoplates

“…Single-crystalline b-Co(OH) 2 nanosheets were successfully synthesized using aqueous cobalt nitrate as the cobalt source and triethylamine as both an alkaline and a complexing reagent in hydrothermal synthetic condition at 100 À180 1C for 2À 24 h [36]. Herein, we report on a facile room temperature solution-phase approach that compliments other methods as mentioned earlier for large-scale synthesis of b-Co(OH) 2 nanoplates.…”

Tuning the Morphology of Metal Oxides for Catalytic Applications

“…105,118 For the fabrication of Co 3 O 4 nanosheets or nanoplatelets, the most frequently used approach is to prepare ␤-Co(OH) 2 precursors hydrothermally, which is isostructural with brucite-like compounds and consists of a hexagonal packing of hydroxyl ions with Co II occupying alternate rows of octahedral sites, followed by thermal decomposition of these precursors at elevated temperatures. 62,[119][120][121][122][123] For example, hexagonal Co 3 O 4 nanosheets with the average thickness of 50-100 nm and the edge length of about 3 m, mainly exposing the {112} facets, were obtained by a two-step process. 62 The thickness of Co 3 O 4 nanosheets was further decreased approximately 2-3 nm when the hydrothermal synthesis was conducted in the presence of hexamethylenetetramine.…”