Synthesis of Co₃O₄ Spinel at Ambient Conditions

Abstract

Co3O4 was prepared in aqueous solutions through a staged oxidation process. When the mole ratio of starting chemicals Co2+:OH− is ≤1:2 (Co2+ as a limiting reagent), the formation reaction follows the brucitelike phase to cobalt oxide-hydroxide, and then to cubic spinel. However, when the ratio of Co2+:OH− is > 1:2 (OH− as a limiting reagent), the reaction path changes to the brucite-like to hydrotalcite-like phase, and then to the spinel. Using the present method, Co3O4 can be formed at a temperature as low as 40 °C, and single-phase spinel Co3O4 can be prepared at 50 °C within hours under normal atmospheric pressure.

Preparation of layered double hydroxides and their applications as additives in polymers, as precursors to magnetic materials and in biology and medicine

“…68 For example, 69 calcination of a Co II Fe III III 2 O 4 spinel phases. 71,72 In addition to oxidation by calcination in air, they have also shown that calcination of Co II /Co III -NO 3 LDHs in an oxygenfree atmosphere can also afford Co II Co III 2 O 4 spinel phases; in this case, the interlayer nitrate anions act as oxidant. 73 The formation of spinel phases of the type Mg x Co II 12x Co III 2 O 4 (x = 0.0-0.9) by low-temperature (,300 uC) calcination of Mg/Co II /Co III LDH phases has also been reported.…”

Mesoporous Co3O4 and CoO@C Topotactically Transformed from Chrysanthemum‐like Co(CO3)0.5(OH)·0.11H2O and Their Lithium‐Storage Properties

“…Among them, a two‐step strategy has generated huge interest and is widely practiced, wherein cobalt‐containing solid precursors (i.e., cobalt hydroxide, cobalt nitrate hydroxide, cobalt nitrate carbonate hydroxide, cobalt hydroxyoxide, and cobalt carbonate etc.) are firstly prepared,13, 21–27, 29–41 which is followed by subsequent phase transformation to their pure metal oxide counterparts via various processes such as thermal decomposition, hydrothermal treatment or oxidation/reduction in air or a controlled atmosphere at elevated temperatures. In recent years, in particular, the synthesis of nanostructured Co 3 O 4 materials using the solid precursor Co(CO 3 ) 0.5 (OH)·0.11H 2 O has also been investigated for different applications 26, 27, 42, 43.…”

Synthesis of CoIICoIII2-xAlxO4−Al2O3 Nanocomposites via Decomposition of CoII0.73CoIII0.27(OH)2.00(NO3)0.23(CO3)0.02·0.5H2O in a Sol−Gel-Derived γ-Al2O3 Matrix

“…Very recently, we have succeeded in synthesizing the mono-transition-metal hydrotalcite-like compound Co II 0.73 Co III 0.27 (OH) 2.00 (NO 3 ) 0.23 (CO 3 ) 0.02 ·0.5H 2 O using a dynamic oxidation method . It has been observed that, due to the presence of trivalent cobalt, the above hydrotalcite-like compound can be decomposed into cubic spinel Co 3 O 4 , an important magnetic and catalytic material, at relatively low temperatures even at ambient conditions . In addition to this inorganic synthesis, we have also prepared nanometer-sized alumina materials via an organometallic sol−gel route .…”

“…In the present work, we will incorporate the hydrotalcite-like compound Co II 0.73 Co III 0.27 (OH) 2.00 (NO 3 ) 0.23 (CO 3 ) 0.02 ·0.5H 2 O into the sol−gel-derived alumina matrixes. There are two objectives in this investigation: (i) fabrication of Co II Co III 2- x Al x O 4 −Al 2 O 3 ( x ≥ 0) nanocomposites (in which at least one phase must be on the nanometer scale) using the newly synthesized cobalt hydrotalcite-like compound, in view of its low decomposition temperature, , and (ii) investigation of the thermal decomposition of hydrotalcite-like compounds in a confined space, such as in alumina matrixes in the present case. The first objective is raised owing to the fundamental interest of this magnetic material system (p-type semiconductor quantum dots embedded in an insulating matrix), while the second is directed to the general material issues of a new application of the hydrotalcite-like compounds in fabricating nanostructured materials .…”