Graphene Nanosheets as a Platform for the 2D Ordering of Metal Oxide Nanoparticles: Mesoporous 2D Aggregate of Anatase TiO2 Nanoparticles with Improved Electrode Performance

Graphene nanosheets are successfully applied as an effective platform for the 2D ordering of metal oxide nanoparticles. Mesoporous 2D aggregates of anatase TiO2 nanoparticles are synthesized by the heat treatment of the uniformly hybridized nanocomposite of layered titanatereduced graphene oxide (RGO) at elevated temperatures. The precursor layered titanateRGO nanocomposite is prepared by self-assembly of anionic RGO nanosheets and cationic TiO2 nanosols. The calcination of the as-prepared layered titanateRGO nanocomposite at 500?degrees C induces a structural and morphological change of layered titanate nanoplates into anatase TiO2 nanoparticles without significant modification of the RGO nanosheet. Increasing the heating temperature to 600?degrees C gives rise to elimination of the RGO component, leading to the formation of sheetlike porous aggregates of RGO-free TiO2 nanoparticles. The nanocomposites calcined at 500700 degrees C display promising functionality as negative electrodes for lithium ion batteries. Among the present calcined derivatives, the 2D sheet-shaped aggregate of TiO2 nanoparticles obtained from calcination at 600?degrees C delivers the greatest specific discharge capacity with good capacity retention for all current density conditions applied. Such superior electrode performance of the nanocomposite calcined at 600?degrees C is attributable both to the improved stability of the crystal structure and crystal morphology of titania and to the enhancement of Li+ ion transport through the enlargement of mesopores. The present findings clearly demonstrate the usefulness of RGO nanosheets as a platform for 2D-ordered superstructures of metal oxide nanoparticles with improved electrode performance.