One-pot synthesis of rice-like TiO2/graphene hydrogels as advanced electrodes for supercapacitors and the resulting aerogels as high-efficiency dye adsorbents

Rice-like titanium oxide (TiO2)/graphene hydrogel (RTGH) was synthesized using a facile one-pot hydrothermal method. During the hydrothermal process, rice-like TiO2 nanoparticles with typical diameters of 15-40 nm and lengths of 40-100 nm were formed using sodium citrate as a structure directing agent. The TiO2 nanoparticles and graphene nanosheets (GNs) self-assembled into threedimensional interconnected networks with a large surface area. COmpared with pristine graphene hydrogel (GH), P25/GH, and RTGH-blank, the strong interaction between rice-like TiO2 nanoparticles and GNs through covalent chemical bonding endowed RTGH with superior physicochemical properties, such as increased adsorption capacities and improved electrochemical performance. Results indicated that the typical RTGH exhibited a high adsorption capacity of 177.3 mg g(-1) for methylene blue (MB). The resulting aerogel, as a high-efficiency adsorbent, completed the decolorization of the MB solution within 2 h. Moreover, the typical RTGH presented high electrochemical performance with a specific capacitance of 3723 F g(-1) in a three-electrode system and 332.6 F g(-1) in a two-electrode system at a current density of 0.2 A g-1 using 1 mol L-1 H2SO4 aqueous solution as electrolyte. Furtherinore, the RTGH showed high rate capability and good stability with a capacitance retention ratio of 91.4% after 2000 charge discharge cycles and 75.4% after 120 h of floating test both at 4 A g(-1) in a two-electrode mode. Our results suggested that RTGH is a potentially useful macroscopic device for addressing current environmental and energy storage issues. (C) 2017 Elsevier Ltd. All rights reserved.