Preparation And Photocatalytic Performance Of Graphene-Based Photocatalysts

Solar energy is abandant,clean and renewable energy.Recently,photocatalytic technology has attracted tremendous attention owing to its application on solving environmentental pollution and globle energy crisis.TiO₂ becomes the most extensively researched photocatalyst because of its low cost,nontoxicity and chemical stability.Howerer,its large band gap and high recombination rate of photoinduced electron-hole pairs under radiation seriously restricted the practical application of TiO₂.Therfore,it is of great significance to develop new visible light response photocatalyst by compositing with other semiconductors.Meanwhile,the introduction of other semiconductors can reduce the recombination rate of electron-hole paris.Graphene and g-C₃N₄ materials are considered as novle types of non-metallic materials which can be widely used in the field of photocatalytic technology.They are widely used as substrates for its strong adsorption capacity and enhance the adsorption of visible light,which can increase photocatalytic reaction rate.Herein high efficient visible light driven p hotocatalysts with high photocatalytic activity have been developed.The plausible machanism was proposed for photocatalytic reaction.This paper is devided into two parts:The first part: We demonstrated that N-TiO₂/NG,comprising N-TiO₂ NWs and N-doped graphene nanosheets,can be fabricated with urea through a facile hydrothermal method.The as-prepared materials were characterized by XRD,XPS,SEM,TEM,UV-Vis and so on.The results show that N from the decomposition of urea can enter not only into the lattice of TiO₂ but also into the skeleton of graphene nanosheets.The UV-Vis characterization shows that N-TiO₂/NG has visible light response.The efficiency of MB detradation using N-TiO₂/NG was 89.7% in 3 h under visible light.The kinetic constant of MB degration using N-TiO₂/NG was 0.0107 min-1,which is much high than the kinetic constants of TiO₂ and TiO₂/G.The second part: Firstly Ultrathin g-C₃N₄ nanosheets were obtained via a simply ultrasonic exfoliation method.Then TiO₂/g-C₃N₄/G composite were synthesised by photoreduction method.The as-prepared materials were characterized by XRD,XPS,SEM,TEM,UV-Vis and so on.The XRD result shows that TiO₂ NWs are composed of anatase and brookite.The specific surface area of TiO₂/g-C₃N₄/G composite is high than TiO₂ NWs and g-C₃N₄.The UV-Vis result demonstrated that TiO₂/g-C₃N₄/G composite has both visible light response and ultraviolet light response.Meanwhile,the photo-induced current is the highest of all prepared catalysts.The photoreduction efficiency of NB using TiO₂/g-C₃N₄/G was 98.1% in 4 h under irradiation with a Xe lamp,which is much high than TiO₂ NWs and g-C₃N₄.Meanwhile,TiO₂/g-C₃N₄/G composite has very high selectivity.In conclusion,TiO₂ NWs,graphene and g-C₃N₄ were fabricated as novle photocatalytic materials in this study.By means of doping and cmpositing,visible light driven photocatalysts with high photocatalytic activity have been develped for increasing photocatalytic reaction rates and application of photocatalytic technolog.