Elsevier

Journal of Alloys and Compounds

Volume 695, 25 February 2017, Pages 329-336
Journal of Alloys and Compounds

Self-assembled Co3O4 nanoplatelets into micro-spheres via a simple solvothermal route: Structural and electrochemical properties

https://doi.org/10.1016/j.jallcom.2016.10.174Get rights and content

Highlights

  • Synthesis of self-assembled Co3O4 nanoplatelets via a simple solvothermal route.

  • XPS studies reveals the two peaks, corresponding to the core level electrons of Co 2p3/2 and Co 2p1/2.

  • Co3O4 anode in Li-ion batteries showed a reversible capacity of 620 mA h/g after 40 cycles.

Abstract

The self-assembled Co3O4 microspheres made of nanoplatelets were prepared by a novel and simple solvothermal route. The crystal structure and morphology were characterized by X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM), respectively. The FESEM shows that the average diameter of the microspheres is about 8 μm and the thickness of individual nanoplatelets is 30–70 nm. X-ray photoelectron spectroscopy (XPS) studies reveal two strong peaks appearing at 780.6 and 797.0 eV, corresponding to the core level electrons for Co 2p3/2 and Co 2p1/2, which are characteristic XPS peaks of Co3O4 phase. The electrochemical properties of cobalt oxide nanoplatelets modified electrodes were scrutinized by cyclic voltammetry (CV) and charge-discharge profile with cycles, showing a stable reversible capacity of 620 mA h/g after 40 cycles.

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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