Synthesis of Co3O4 nanostructures using a solvothermal approach
Graphical abstract
Introduction
In the past few years, many different techniques have been developed for the preparation of nanomaterials, such as self-assembly [1], [2], coprecipitation, sol–gel methods, microemulsions, solvothermal, and so on [3], [4], [5]. Nanomaterials have been actively studied due to both scientific interests and potential applications. Among these materials, the transition metal oxides have attracted much attention due to their electrical and magnetic properties [6]. For example, unitary spinel cobalt oxide (Co3O4) stands as an important functional material, in part because of its vast applications for use in sensors, electrochemistry, pigments, catalysis, magnetism, and energy storage [7], [8]. Co3O4 nanostructures are expected to lead to even more attractive applications in conjunction with their traditional arena and nanotechnology [9], [10], [11].
Previously, Co3O4 nanostructures with various morphologies have been synthesized. He et al. synthesized monodisepersed Co3O4 nanoparticles via thermal decomposition of the intermediate product Co(NO3)2·7C6H13OH in long-carbon-chain alcohols [12], [13]. Zeng's group prepared Co3O4 nanocubes with a uniform size of ca. 47 nm in aqueous solution at 95 °C, using a nitrate-salt-mediated formation route [9], [14]. In addition, Martin and his colleagues synthesized Co3O4 nanofibers by the sol–gel method combined with a template-synthesis technique [15]. The fabrication of Co3O4 nanorods was also achieved via calcinations of precursor powders, which were prepared in an inverse microemulsion [16]. Furthermore, Selke and co-workers synthesized Co3O4 nanotubes from cobalt complexes precoated onto colloidal particles [17]. The nanostructured porous Co3O4 was also synthesized by hard templating method [18]. Zhang and co-workers prepared Co3O4 nanowires by heating a pure cobalt foil in atmosphere [19]. Co3O4/ZnO nanowire array was fabricated by photochemical coating method and a mesoporous Co3O4 core/mesoporous silica shell composite was also fabricated by depositing silica on Co3O4 superlatticed particles [20], [21]. Although different morphologies of Co3O4 nanostructure were synthesized, the preparation methods need either complicated technique or rigorous conditions. Herein, we describe a simple solvothermal way to generate high-quality Co3O4 nanostructures. In our experiments, Co3O4 micro-spheres and nanobelts are acquired, respectively, at 140 °C and at 180 °C by using basic cobalt carbonate as precursor and ammonia as solvent.
Section snippets
Experiment
All of the chemical reagents were of analytical grade and used without further purification in this experiment. The Co3O4 nanostructures were synthesized via a hydrothermal route in the presence of ammonia. Co3O4 nanobelts were synthesized as follows: Co5(OH)6(CO3)2·nH2O was added to 60 mL NH3·H2O. This solution was stirred for 30 min to ensure that Co5(OH)6(CO3)2·nH2O dissolved completely. The mixture was transferred into a stainless Teflon-lined 80 mL capacity autoclave and kept at 180 °C for 12
Characterization of Co3O4 nanostructures
Fig. 1 shows the FT-IR spectra of tricobalt tetraoxide. There are two strong bands (due to the ν(Co–O) modes) at ∼660 and ∼578 cm−1 in Fig. 1, which is a clear evidence for the presence of the crystalline Co3O4 [22]. The peaks at ∼1600 and ∼3600 cm−1 should be assigned to H2O absorbed by the samples or KBr [23]. The peaks at ∼2400 cm−1 are obvious which should be assigned to CO2 vibrant by environmental or personal. The XRD results in the next section also support this conclusion.
The phase
Conclusion
In summary, we have demonstrated a simple solvothermal method to synthesize Co3O4 micro-spheres, nanobelts and nanoplates. We have also found both the reaction temperature and the concentration of NH3·H2O to have significant effect on the morphology of the products. Co3O4 hexagonal nanoplates are also obtained by adding surfactant CTAB. The possible mechanism is proposed for the selective formation of the different morphologies. Because of the distinct advantages of solvothermal method, we
Acknowledgment
This work was supported by the Natural Science Foundation Council of China (nos. 20671011, 20331010, 90406002 and 90406024), the 111 Project (B07012) and the Key Laboratory of Structural Chemistry Foundation (no. 060017).
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2023, Journal of Magnesium and AlloysCitation Excerpt :Moreover, composite coatings containing cobalt have received considerable attention from many research groups owing to their magnetic characteristics as well as their use in developing high-strength alloys [17, 18]. In fact, variety of methods have been reported for preparing Co3O4 such as the thermal decomposition of cobalt precursors under oxidizing condition (210–815 °C) [19], chemical spray pyrolysis (300–400 °C) [20], chemical vapor deposition (CVD) [21], sol–gel [22], microemulsion [23], solvothermal [24], hard templating [25], hydrothermal [26], mechanochemical [27] and chemical combustion [28]. However, all of the above methods need relatively high reaction temperatures and the production of nanocrystalline Co3O4 is difficult and inconvenient to obtain.