Catalytic properties of Co3O4 nanoparticles for rechargeable Li/air batteries

Nanoscale Research Letters, Dec 2012

Three types of Co3O4 nanoparticles are synthesized and characterized as a catalyst for the air electrode of a Li/air battery. The shape and size of the nanoparticles are observed using scanning electron microscopy and transmission electron microscopy analyses. The formation of the Co3O4 phase is confirmed by X-ray diffraction. The electrochemical property of the air electrodes containing Co3O4 nanoparticles is significantly associated with the shape and size of the nanoparticles. It appears that the capacity of electrodes containing villiform-type Co3O4 nanoparticles is superior to that of electrodes containing cube- and flower-type Co3O4 nanoparticles. This is probably due to the sufficient pore spaces of the villiform-type Co3O4 nanoparticles.

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Catalytic properties of Co3O4 nanoparticles for rechargeable Li/air batteries

Nanoscale Research Letters Catalytic properties of Co O nanoparticles for 3 4 rechargeable Li/air batteries Kwan Su Kim 0 Yong Joon Park 0 0 Department of Advanced Materials Engineering, Kyonggi University , San 94-6, Yiui-dong, Yeongtong-gu, Suwon, Gyeonggi-do, 443-760 , Republic of Korea Three types of Co3O4 nanoparticles are synthesized and characterized as a catalyst for the air electrode of a Li/air battery. The shape and size of the nanoparticles are observed using scanning electron microscopy and transmission electron microscopy analyses. The formation of the Co3O4 phase is confirmed by X-ray diffraction. The electrochemical property of the air electrodes containing Co3O4 nanoparticles is significantly associated with the shape and size of the nanoparticles. It appears that the capacity of electrodes containing villiform-type Co3O4 nanoparticles is superior to that of electrodes containing cube- and flower-type Co3O4 nanoparticles. This is probably due to the sufficient pore spaces of the villiform-type Co3O4 nanoparticles. composites; nanostructures; chemical synthesis; electrochemical properties - Introduction A significant increase in the energy density of rechargeable batteries is required to satisfy the demands of vehicular applications and energy storage systems. One approach to solving this problem is the introduction of a new battery system having a higher energy density. Li/air batteries are potential candidates for advanced energy storage systems because of their high storage capability [1-3]. They do not store a ?cathode? in the system, which allows for a higher energy density than any other commercial rechargeable batteries. Instead, oxygen from the environment is reduced by a catalytic surface inside the air electrode. Thus, catalysts are key materials that affect the capacity, cycle life, and rate capability of such batteries. In this study, the Co3O4 nanoparticles of various shapes and structures were tested as catalysts of air electrodes for rechargeable Li/air batteries. Co3O4 with a spinel structure has attracted a considerable interest as a potential catalyst in various application fields [4-7]. In particular, this study was motivated by the notion that the catalytic efficiency of oxides is highly dependent on their morphology, size, and crystal structure [8,9]. Herein, three types of Co3O4 of various shapes and Experimental details Three types of Co3O4 nanoparticles were prepared by a hydrothermal reaction using cobalt nitrate (cube type, flower type) and cobalt chloride (villiform type), considering previous reports [10,11]. Surfactants such as urea were also added to obtain nanosized particles. X-ray diffraction [XRD] patterns of powders were measured using a Rigaku X-ray diffractometer (Rigaku Corporation, Tokyo, Japan). The microstructure of the powder was observed by field-emission scanning electron microscopy [FE-SEM] (JEOL-JSM 6500F, JEOL Ltd., Akishima, Tokyo, Japan) and field-emission transmission electron microscopy [FE-TEM] (JEOL-JEM 2100F JEOL Ltd., Akishima, Tokyo, Japan). The electrochemical performance of the air electrode containing Co3O4 nanoparticles was examined using a modified Swagelok cell, consisting of a cathode, a metallic lithium anode, a glass fiber separator, and an electrolyte of 1 M LiTFSI in EC/PC (1:1 vol.%). The cathode contained carbon (Ketjen black EC600JD, Akzo Nobel, Amsterdam, The Netherlands; approximately 1420 m2?g-1), catalysts (Co3O4 nanoparticles), and a binder (PVDF; Sigma-Aldrich, St. Louis, MO, USA). The molar ratio of carbon to catalysts was adjusted to 95:5. The binder accounted for 20 wt.% of the total electrode. The cells were assembled in an Arfilled glove box and subjected to galvanostatic cycling using a WonATech (WBCS 3000, Seocho-gu, Seoul, Korea) charge-discharge system. Experiments were carried out in 1 atm of O2 using an air chamber. Results and discussion Scanning electron microscopy [SEM] and transmission electron microscopy [TEM] were employed to investigate the shapes of the samples (Figure 1). Cube-type Co3O4 nanoparticles have a homogeneous cubic morphology (Figure 1a). The length of the nanocube was around 200 nm, and the dominant exposed plane of the cube-type Co3O4 seemed to be {001}. The villiform-type Co3O4 particles were formed by a nucleus covered with numerous micrometer-sized nanorods. In comparison with the length, the diameter of the nanorod was very small (less than 100 nm). It is interesting that the villiform-type Co3O4 has a rough surface. As shown in the TEM image (Figure 1b), the nanorods seemed to be stacked with smaller nanoparticles with a diameter of approximately 80 nm. The flower-type Co3O4 seemed to have a similar shape and size to those of the villiformtype Co3O4. However, the nanorods of the flower-type Co3O4 had a sharper end, smoother surface, and smaller diameter than those of the villiform-type Co3O4. Moreover, in contrast with the villiform-type Co3O4, the nanorods of the flo (...truncated)


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Kwan Su Kim, Yong Joon Park. Catalytic properties of Co3O4 nanoparticles for rechargeable Li/air batteries, Nanoscale Research Letters, 2012, pp. 47, Volume 7, Issue 1, DOI: 10.1186/1556-276X-7-47