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Photocatalytic Synthesis of TiO2 and Reduced Graphene Oxide Nanocomposite for Lithium Ion Battery Jingxia Qiu, Peng Zhang, Min Ling, Sheng Li, Porun Liu, Huijun Zhao, and Shanqing Zhang* Centre for Clean Environment and Energy, Environmental Futures Centre, and Griffith School of Environment, Gold Coast Campus, Griffith University QLD 4222, Australia ABSTRACT: In this work, we synthesized graphene oxide (GO) using the improved Hummers’ oxidation method. TiO2 nanoparticles can be anchored on the GO sheets via the abundant oxygen-containing functional groups such as epoxy, hydroxyl, carbonyl, and carboxyl groups on the GO sheets. Using the TiO2 photocatalyst, the GO was photocatalytically reduced under UV illumination, leading to the production of TiO2reduced graphene oxide (TiO2-RGO) nanocomposite. The as-prepared TiO2, TiO2-GO, and TiO2-RGO nanocomposite were used to fabricate lithium ion batteries (LIBs) as the active anode materials and their corresponding lithium ion insertion/extraction performance was evaluated. The resultant LIBs of the TiO2-RGO nanocomposite possesses more stable cyclic performance, larger reversible capacity, and better rate capability, compared with that of the pure TiO2 and TiO2-GO samples. The electrochemical and materials characterization suggest that the graphene network provides efficient pathways for electron transfer, and the TiO2 nanoparticles prevent the restacking of the graphene nanosheets, resulting in the improvement in both electric conductivity and specific capacity, respectively. This work suggests that the TiO2 based photocatalytic method could be a simple, low-cost, and efficient approach for large-scale production of anode materials for lithium ion batteries. KEYWORDS: lithium ion batteries, UV photocatalysis, TiO2, reduced graphene oxide such as TiO2,15,18 SnO2,19,20 Co3O4,21 and Fe3O422 anchored on the graphene sheets could potentially resolve the problem of graphene stacking. The preparation of graphene using chemical method commonly involves the oxidation of graphite to produce graphene oxide (GO) and reduction of GO. Chemical oxidation method (e.g, the traditional Hummers’ method) is probably the most economical way to prepare GO in large quantity from natural graphite.23 Recently, an improved Hummers’ method was proposed by Tour’s group24 for the large-scale production of GO. The proposed method shows significant advantages over the Hummers’ method: it has much higher production yield, does not involve a large exothermal reaction or the production of toxic gas, produces a higher fraction of well-oxidized hydrophilic carbon material, and possesses a more regular structure. During the chemical oxidation of graphite, oxygen-containing functional groups, such as epoxy, hydroxyl, carbonyl, and carboxyl, are introduced onto the graphene sheets, which interrupts graphitic lattice and reduces the conductivity.25 In order to restore the conductivity of graphene, these functional groups are removed by chemical reduction methods, such as hydrazine,26 UV-induced reduction25 or thermal reduction,26 sonolysis.27
1. INTRODUCTION Lithium ion batteries (LIBs) have been the dominant power source for a myriad of types of portable electronic devices1 and potential power source for electric vehicles.2 To enhance LIB performance, a variety of nanomaterials, including TiO2,3,4 graphene,5−7 and its composite,8,9 has been researched as alternative electrode materials. TiO2 has been particularly attractive for large-scale energy storage, because TiO2 is an abundant, inexpensive, and environmentally benign material with various types of nanostructures available (e.g., nanotubes,10,11 nanowires,12,13 and nanosheets14). Also, TiO2 is structurally stable with a small volume change (
