A Strong Electronic Coupling between Graphene Nanosheets and Layered Titanate Nanoplates: A Soft-Chemical Route to Highly Porous Nanocomposites with Improved Photocatalytic Activity

Abstract

Strongly coupled nanocomposites of layered titanate and reduced graphene oxide (RGO) are synthesized by electrostatically derived self-assembly between negatively charged RGO nanosheets and positively charged TiO2 nanosols, which is then followed by a phase transition of the anatase TiO2 component into layered titanate. The resulting nanocomposite consists of thin 2D nanoplates of lepidocrocite-type layered titanate immobilized on the surface of RGO nanosheets. The composite formation with RGO nanosheets is effective not only in promoting the phase transition of anatase TiO2 nanosols, but also in improving the thermal stability of the layered titanate, indicating the role of RGO nanosheets as an agent for directing and stabilizing layered structures. The layered-titanate-RGO nanocomposites exhibit remarkably expanded surface area with the formation of micropores and mesopores. The composite formation with RGO nanosheets gives rise to the disappearance of the reflectance edge of layered titanate in the diffuse reflectance UV-vis spectra, indicating a strong electronic coupling between the RGO and layered titanate. The strong electronic correlation between the two components is further evidenced by the visible-light-induced generation of photocurrents after the hybridization with RGO. The layered-titanate-RGO nanocomposite shows a higher activity for the photodegradation of organic molecules than uncomposited layered titanate, underscoring the usefulness of graphene hybridization in improving the photocatalyst performance of layered titanate. The experimental findings presented here clearly demonstrate that the self-assembly of metal oxide nanoparticles with RGO 2D nanosheets is quite effective not only in synthesizing porous metal-oxide-graphene nanocomposites with improved photo-induced functionality, but also in achieving strong electronic coupling between RGO and metal oxides.