高压水热合成法制备纳米Co_3O_4粉末及其过程机理

High-pressure hydrothermal synthesis and growth mechanism of Co_3O_4 nanoparticles

以Co(Ac)2·4H2O为原料,采用高压水热合成法,于氧分压4MPa、200℃下水热反应20h制备纳米氧化钴粉末。采用比表面积分析仪、X射线衍射仪(XRD)、透射电镜(TEM)等对产物进行分析和表征。结果表明,产物为单一相成分的立方相尖晶石结构Co3O4,比表面积平均粒径为52.7nm,具有球形形貌特征。Co3O4的高压水热合成机理是钴离子水解产物中部分Co2+的羟基配合物被氧化成Co3+的羟基配合物,形成[Co(OH)4]2+与[Co(OH)6]3+配位多面体生长基元,随后生长基元通过缩聚反应形成近程有序的Co3O4原子团。Ac-的表面吸附有效地阻碍了Co3O4的各向异性生长与连续晶粒长大。

Spherical Co3O4 nanoparticles were prepared by high-pressure hydrothermal method using Co（Ac）2·4H2O as starting material at the reaction temperature of 200 ℃, oxygen partial pressure of 4 MPa and reaction time of 20 h. Specific surface area analyzer, XRD and TEM were employed to characterize the cobalt oxide product. It is revealed that the product consists of single Co3O4 phase with cubic spinel structure. The calculated specific surface area average size is 52.7 nm. The high-pressure hydrothermal synthesis mechanism of Co3O4 nanoparticles includes the following steps：partly oxidation of the hydrolysis product of cobalt ion which resulted in the hydroxo complex of Co^2＋ transformed into Co^3＋; the formation of the [Co（OH）4]^2- and [Co（OH）6]^3- coordination polyhedron growth units and finally the formation of the CO3O4 radical with short range order structure through the fasculation reaction. The surface adsorption of Ac^- blocks effectively the anisotropic growth and the continuous grain growth of CO3O4 particles.