Synthesis and characterization of chromium oxide nanocrystals via solid thermal decomposition at low temperature

doi:10.1016/j.micromeso.2007.10.044

Microporous and Mesoporous Materials

Volume 112, Issues 1–3, 1 July 2008, Pages 621-626

https://doi.org/10.1016/j.micromeso.2007.10.044 Get rights and content

Abstract

Chromium oxide nanocrystals were synthesized by solid thermal decomposition using cetyltrimethylammonium bromide (CTAB) or a triblock copolymer (P123) as template agent at low temperature. The chromium oxide nanocrystals possess lamellar phase with disordered mesopore. The template surfactants (P123 or CTAB) and hydrated water play an important bridging role in the aggregation of inorganic chromium species in the thermal decomposition of chromium nitration. The mesopores of chromium oxide are formed by eliminating CTAB or P123 from the Cr-surfactants composites with small shrinkage.

Introduction

The design and synthesis of mesostructured/mesoporous transition metal oxides have attracted considerable interests because of their potential applications in the fields of catalysis, sorption, chemical and biological separation, photonic and electronic devices, and drug delivery [1], [2], [3], [4]. However, unlike silica and aluminosilicates, mesoporous transitional metal oxides are rather difficult to prepare due to hydrolysis, redox reactions, or phase transitions and a number of different coordination numbers and oxidation states [5]. So far, well-ordered mesoporous oxides of Al, Mn, Ti, V, Zr, Sn, Nb and Ta have been reported [6], [7], [8], [9], [10], [11]. The popular synthetic routes are sol–gel method and hydrothermal method in the aqueous or non-aqueous solution [12], [13], [14]. Due to fast hydrolysis and aggregation in the solution, many synthetic methods have been developed for transitional metal oxides such as solvo-thermal method [15] and nanocasting method [16], [17], [18], [19], [20].

In our previous work, disordered nanoporous chromium oxides were prepared by solid thermal decomposition using citric acid (CA) as template and the relationship between the structure and the reaction conditions of chromium oxide was investigated [21]. The Cr₂O₃ materials obtained using CA as template possessed lamellar disordered mesopore structure with a broad pore size distribution. This might be caused by the weak template effect of CA and weak interaction between chromium precursors and CA. Although it is possible to prepare unstable lamellar phases, however, the preparation of uniformed mesoporous chromium oxide nanocrystals is more difficult.

In this study, a triblock copolymer (P123) or cetyltrimethylammonium bromide (CTAB) was used as template to synthesize mesoporous chromium oxide nanocrystals by solid thermal decomposition and the synthetic mechanism of mesoporous chromium oxide was explored. Compared to the Cr₂O₃ materials synthesized by CA, the Cr₂O₃ samples synthesized by CTAB or P123 possessed uniform pore size and more ordered structure caused by the strong interaction between templates and precursors.

Section snippets

Synthesis

Chromium oxide nanocrystals were synthesized by solid thermal decomposition method using a triblock copolymers (P123) or cetyltrimethylammonium bromide (CTAB) as template and chromium nitration as the precursor of chromium. In a typical synthesis, chromium nitration was fully mixed with P123 or CTAB surfactants. The mixtures were put into autoclave and heated in the oven at 140–200 °C for 24 h. After heating, the obtained samples were washed by distilled water and dried at 100 °C in the oven. The

Results and discussion

To identify the decomposition temperature of chromium nitrate, the thermogravimetric analysis was conducted on the chromium nitrate (Cr(NO₃)₃·9H₂O) powder under flowing air, as shown in Fig. 1. The weight loss below 100 °C is assigned to the removal of hydration water in the salt. The big weight loss from 100 to 217 °C is mainly attributed to the thermal decomposition of Cr(NO₃)₃ to form Cr₂O₃ with the 64% weight loss. A slow and steady weight loss above 450 °C is ascribed to the deoxygenation of

Conclusion

Mesoporous chromium oxide nanocrystallite with lamellar structure has been synthesized via a novel solid thermal decomposition route using P123 or CTAB as the templates. The as-synthesized chromium oxide materials possesses layered framework with intraparticle pore size in the range of 3–9 nm. In this novel thermal decomposition synthesis system, surfactants (P123 or CTAB) play an important bridging role in the aggregation of inorganic chromium species. The crystalline size, surface area and

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Synthesis and characterization of chromium oxide nanocrystals via solid thermal decomposition at low temperature

Abstract

Introduction

Section snippets

Synthesis

Results and discussion

Conclusion

Appl. Catal., A

Nature

Chem. Mater.

Angew. Chem. Int. Ed.

Angew. Chem. Int. Ed. Engl.

Angew. Chem. Int. Ed. Engl.

Science

Chem. Mater.

Angew. Chem. Int. Ed. Engl.

Angew. Chem. Int. Ed. Engl.

Angew. Chem. Int. Ed. Engl.