Graphene Quantum Dots Or Silver Nanoparticles Decorated Titania For Enhancing Photocatalytic Activity

Owing to low cost,easy to obtain and high chemical stability,titanium dioxide?TiO₂?has been widely used in photocatalytic field.However,TiO₂ can only absorb ultraviolet light due to intrinsic wide band gap,and the low quantum efficiency of TiO₂ photocatalysis is mainly because of high recombination of photogenerated electrons and holes.Therefore,the research on improving the photocatalytic properties of TiO₂ has become a hot topic in the field of photocatalysis.Due to the size of the relationship,as a zero dimensional materials,graphene quantum dots?GQDs?show a quantum local effect.Owing to their unique energy band structure,the GQDs decorated Ti O₂ exhibit the excellent catalytic performance.Silver?Ag?,as a noble metal,has low Fermi level.When Ag is loaded on TiO₂,the electrons and holes can be separated effectively.Besides,Ag nanoparticles local surface plasmon resonance?LSPR?on the surface of TiO₂,which can absorb visible light and improved the photocatalytic efficiency for degradation of organic dyes.Overall,the photocatalytic efficiency of TiO₂ was improved by two methods:First,the photocatalytic performance of TiO₂ was improved by loading Ag nanoparticles.Furthermore,the mesoporous Ti O₂ was prepared to increase the specific surface area and further improve its photocatalytic ability.The mesoporous TiO₂/Ag?Meso-TiO₂/Ag?photocatalyst was successfully prepared by photo-assisted method.The crystal structure,morphologies,optical properties,separation efficiency of photogenerated electron-hole pairs and photocatalytic degradation performance were characterized.Compared to meso-TiO₂,the optical absorption range of Meso-TiO₂/Ag is extended to the visible region.The photocatalytic activity of Meso-TiO₂/Ag is evaluated through the degradation of methylene blue?MB?under visible light irradiation,the Meso-TiO₂/Ag with 3%Ag exhibited excellent photodegradation efficiency,which is mainly attributed to large specific surface area,enhanced absorption of visible light and high efficiency of carrier separation and transfer rate.Second,TiO₂ nanotubes?TiO₂NT?was synthetized by a facile alkaline hydrothermal method using low cost P25.The citric acid used carbon source,thiourea as nitrogen and sulfur source to produce N and S co-doped GQDs?N,S-GQDs?.The binary composite of TiO₂NT@N,S-GQDs was achieved by physical stirring process.The TiO₂NT@N,S-GQDs composite exhibited excellent visible light photocatalytic activity for degradation of MB,the apparent rate constant of is71.9 times higher than pure TiO₂NT,indicated that the photocatalytic performance of TiO₂ can be improved significantly by decorating with N,S-GQDs.