Self-assembled Co3O4 nanoplatelets into micro-spheres via a simple solvothermal route: Structural and electrochemical properties
Graphical abstract
Introduction
Self-assembled structures with highly specific morphology and novel properties are of great interest to chemists and materials scientists. Hierarchical nanostructures, self-organized assemblies of nanoparticles, nanorods, nanobelts as building blocks, and complex nanocrystals with well-defined shape have attracted considerable attention due to their distinctive properties [1], [2], [3], [4], [5], [6], [7], [8], [9].
Transition metal oxides are very promising class of materials, have been investigated intensively recently due to their extraordinary size dependent properties in electrical, optical and magnetic fields. Moreover, it is also anticipated to find out the suitable application in the field of catalysis, magnetic storage, energy storage and sensors etc. [10], [11], [12], [13], [14], [15], [16], [17], [18], [19], [20]. In recent years, several synthesis methods have been developed for nanomaterials, such as thermal decomposition of solid phase, chemical spray pyrolysis, microemulsions, sol-gel, coprecipitation, solvothermal and aqueous solution method [21], [22], [23], [24], [25]. Cobalt oxides (Co3O4) nanostructured materials are favorable to lead remarkable and diverse application due to their fascinating properties. Recently, a variety of novel shapes of Co3O4 such as nanoboxes [26], nanocubes [27], nanofibers [28], nanorods [29], and nanotubes [30] have been reported. Co3O4 belongs to the group VIII metal oxides having stable phase and indicates an intrinsic semiconductor [31].
Recently, enormous efforts have been made to find out the substitute novel anode materials for lithium ion batteries to enhance its performance and protection [10]. While to achieve the breakthrough in the novel anode materials production, lately more focuss was diverted mainly on the investigations nanostructured materials. Nanostructured materials have excellent properties due to their high surface-area, size effects and diverse morphologies [32]. Poizot et al. reported that electrodes made of nanoparticles of transition–metal oxides such as nickel oxides, iron oxides and cobalt oxides exhibited few times larger reversible capacities than graphite as anode materials. While performing the electrochemical properties on the metal oxide nanomaterials related lithium ion batteries (LIB's), Co3O4 nanomaterial revealed the excellent electrochemical properties among other oxide materials [33].
Rechargeable lithium ion batteries are main energy constituents of the computing and communication systems etc. and vital for various electronic devices/gadgets which frequently require backup storage. The insufficient gravimetric capacity (<370 mAhg−1) of carbon has encouraged strong research activities for alternative anode materials having large capacities at minimum potentials [34]. Currently, Co3O4 is one of very interesting energy storage materials. It has interesting application in the LIB's as an anode material and its electrochemical properties have been widely investigated. Recently F. Tao et al. reported the initial discharge capacity (i.e. 1048 mA h/g) of the cobalt oxide hollow spheres, which reduces to 100 mA h/g after 50 cycles [35]. In this work, we report a simple solvothermal route for the preparation of self-assembled Co3O4 nanoplatelets. The Co3O4 nanostructure materials were investigated as an anode material for LIB's, resulting in a high discharge capacity of 1282 mA h/g and excellent cycle durability.
Section snippets
Synthesis of Co3O4 nanostructures
All reagents were of analytical grade and used as received from Aldrich without further purification. The Co3O4 nanoplatelets were prepared by a solvothermal route. In a typical procedure, 0.1 M of Co(NO3)3·6H2O was dissolved in a beaker containing 40 ml absolute ethanol, then, 0.05 M of cetyltrimethylammonium bromide (CTAB) was introduced into the beaker with continuous stirring for about 30 min. The resulted mixture was moved into 60 ml Teflon-lined autoclave vessel. The autoclave was
Result and discussion
Fig. 1(a, b), and c depict the XRD patterns of the Co3O4 nanomaterials prepared at 150 °C for 6 h, 48 h, and without CTAB, respectively. All the diffracted peaks could be indexed to a pure phase of spinel Co3O4 (JCPDS; Card No. 43-1003) with the space group (SG) of Fd3m. The XRD studies reveal the excellent crystallinity of the Co3O4 nanostructures obtained by solvothermal route in this work. No impurity peaks were observed in the spectra, indicating the high quality of the resulted product.
The
Conclusions
The self-assembled Co3O4 nanoplatelets into microspheres were prepared by a simple solvothermal route. The FESEM revealed the average diameter of the spheres is about 8 μm and the sheet thickness is 30–70 nm. The prominent Raman peaks correspond to the Eg, F2g, Ag modes of the Co3O4 crystalline phase. X-ray photoelectron spectroscopy studies reveal the two strong peaks at 780.6 and 797.0 eV, which are characteristic of Co3O4 phase. The electrochemical properties of Co3O4 nanoplatelets as an
Acknowledgements
This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIP) (No. 2014R1A2A1A11052414. The authors would like to extend their sincere appreciation to the Deanship of Scientific Research at king Saud University for funding this Research grant No.(RG#1437-006).
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