Nanostructured porous cobalt oxide synthesis from Co 3 [Co(CN) 6 ] 2 and its possible applications in Lithium battery Srinivasan Harish b , Krishnamoorthy Silambarasan a , Gopi Kalaiyarasan a , Alam Venugopal Narendra Kumar a , James Joseph a,n a Electrodics and Electrocatalysis Division, CSIR – Central Electrochemical Research Institute, Karaikudi 630006, Tamil Nadu, India b Department of Chemistry, PSG Institute of Technology and Applied Research, Neelambur, Coimbatore - 641062 article info Article history: Received 8 October 2015 Received in revised form 24 November 2015 Accepted 26 November 2015 Available online 27 November 2015 Keywords: Cobalt oxide Nanoparticles Energy storage and conversion Porous material Sensors Thin films abstract The thermal decomposition and microwave heating of Co 3 [Co(CN) 6 ] 2 leads to formation of nanos- tructured porous cobalt oxide (Co 3 O 4 ). Here, we report Co 3 [Co(CN) 6 ] 2 as a novel single source precursor for the synthesis of phase pure Co 3 O 4 particles at 650 °C under mixed argon/oxygen atmosphere as evidenced from X-ray diffraction (XRD) patterns. During thermal decomposition, release of gaseous products like CO 2 ,N x O y , (CN) 2 facilitate the formation of a highly porous Co 3 O 4 whose morphology and particle size distribution were characterized using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) respectively. Porous Co 3 O 4 shows high discharge capacity of 1131 mA h g À1 with 96% coulombic efficiency against Li/Li þ reference electrode. & 2015 Elsevier B.V. All rights reserved. 1. Introduction Cobalt oxide (Co 3 O 4 ) attracts the attention of the materials researchers because of its promising applications in various fields viz., anode material for Li-ion batteries (LIBs) [1], super capacitors [2], gas sensors [3], catalytic processes [4] etc. Co 3 O 4 nanoparticles were synthesized through various routes that include the com- monly employed oxidative precipitation [5], thermal decomposi- tion [6,7], hydrothermal synthesis [8,9] etc., Synthesis of metal oxides like NiO, Co 3 O 4 , from single source precursors is a simple approach to make a porous structure for increasing material per- formance [10,11]. A few examples of single source precursors in- clude (NH 4 ) 2 Co 8 (CO 3 ) 6 (OH) 6 Á 4H 2 O [12], Co(CO 3 ) 0.5 (OH) 0.1 Á 1H 2 O [7,13], Co 4 (CO) 12 [14], prussian blue [15]. Epple's group have shown that how crystal structure of the precursor dictates the structure and morphology of the resulting products when ther- molysis was carried out under moderate temperatures [16,17]. The catalytic activity towards the formation of methanol from syn- thetic gas (CO/CO 2 /H 2 ) was studied using Cu/ZnO catalyst. Sur- prisingly, catalytic activity was not observed on Cu/ZnO catalysts synthesized from Cu[Zn(CN) 3 ] whereas the Cu/ZnO synthesized from complex containing ethylenediamine and cyanide as ligands showed 20–30% catalytic activity [17]. These observations high- light the role of the precursor in determining the crystal structure of metal oxides and their catalytic properties. In this work, we present the formation of porous Co 3 O 4 from Co 3 [Co(CN) 6 ] 2 by both thermal decomposition and microwave synthesis and its applica- tion towards Li-ion battery. 2. Results and discussion 2.1. Synthesis and characterization of Co 3 [Co(CN) 6 ] 2 The precipitate Co 3 [Co(CN) 6 ] 2 Á 12H 2 O was obtained by mixing the solutions of cobalt acetate and potassium hexacyano cobaltate (III). The product can easily be identified by its reversible color transitions in hydrated and dehydrated forms. Similar observa- tions were reported in the literature and attributed to the inter conversion of octahedral to tetrahedral co-ordination of Co 2 þ site [18]. The compound was further confirmed by using FT-IR and XRD analysis. 2.2. Phase composition analysis From TGA results (Fig. S1A), it was observed that the Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/matlet Materials Letters http://dx.doi.org/10.1016/j.matlet.2015.11.122 0167-577X/& 2015 Elsevier B.V. All rights reserved. n Corresponding author. E-mail address: jameskavalam@yahoo.com (J. Joseph). Materials Letters 165 (2016) 115–118