Preparation Of One-dimensional TiO₂/graphene Composites For Photocatalytic Degradation Of Dyes

The problem of water pollution caused by the large-scale production and widespread use of organic dyes needs to be solved.At present,photocatalytic technology is one of the green and energy-saving methods for the efficient treatment of dye wastewater.Among them,TiO₂ is one of the most promising semiconductor photocatalysts.However,conventional TiO₂ has the disadvantages of low specific surface area,wide band gap and easy recombination of photo-induced carriers,which limits its application in photocatalytic degradation of dyes.One-dimensional（1D）TiO₂nanostructures exhibit enhanced performance due to fast charge transport along the longitudinal dimension,large specific surface area,and ease of recycling.Graphene,as a new carbon material,its combination with TiO₂ can effectively improve the deficiency of TiO₂ and increase the photocatalytic performance.In this work,TiO₂ nanobelts/reduced graphene oxide（TG）composites with desirable nanostructures were successfully prepared by regulating the addition amount of Li⁺via a facile solvothermal process.The results of characterizations indicate that the introduction of 2D reduced graphene oxide（r GO）nanosheets restricts the agglomeration of 1D TiO₂ nanostructures and drives the freestanding growth of TiO₂nanobelts.Meanwhile,the addition of Li⁺not only promotes the formation of TiO₂nanobelts but also affects the distribution of TiO₂ nanobelts on the surface of r GO.The TG-2 synthesized by adding an appropriate amount of Li⁺exhibits the best photocatalytic degradation activity of these samples,even better than commercial P25photocatalyst.The excellent photocatalytic performance of TG-2 is mainly attributed to the effective separation of charge carriers promoted by the synergistic effect between uniform TiO₂ nanobelts and r GO.Additionally,TiO₂ nanobelts/nitrogen-doped graphene（TiO₂/NG）composite was prepared by solution mixing and pyrolysis.Based on the results of characterizations,it is found that the pyrolysis process at 200 ^oC effectively reduces graphene oxide,and nitrogen atoms are confirmed to be doped into graphene oxide.The specific surface area of as-synthesized TiO₂/NG composite is significantly higher than that of pristine TiO₂ nanobelts,and exhibits excellent adsorption performance for Rhodamine B.Moreover,since nitrogen doping of graphene can further promote the rapid transfer of photo-generated electrons in the composite,TiO₂/NG composite exhibits enhanced photocatalytic activity for the degradation of rhodamine B under visible light irradiation.