The Efficient Charge Separation Of Materials And Its Photocatalytic Performance

Semiconductor photocatalysis has been widely applied in destruction of organic pollutants in air and water.Among the semiconductor materials,such as oxides,sulfides,nitrides and solid solutions etc.,the photocatalytic activity of single-phase photocatalysts is usually restricted by the rapid recombination of the photoexcited electron-hole pairs.To enhance the separation efficiency of photoexcited electron-hole pairs,the semiconductor composite materials?type-II and Z-scheme?were constructed.These two novel composite materials have become hot topic in recent research work on photocatalysis.The main contents of the study are as follows:?1?This work employed graphene as electron mediators to design highly efficient Z-scheme nanoheterojunctions.The photocatalytic activities of all-solid-state Z-scheme g-C₃N₄/RGO/Sb₂WO₆ nanoheterojunctions were evaluated by the degradation of Rhodamine B?RhB?.Results show that compared with the conventional g-C₃N₄,Sb₂WO₆ and g-C₃N₄-Sb₂WO₆ composites,RGO/g-C₃N₄-Sb₂WO₆ has the strongest photocatalytic performance,photocatalytic degradation rate was 91.8%.Sb₂WO₆ and RGO/ultra-thin g-C₃N₄can be connected by electrostatic force.It not only possessed strong adsorption ability,but also displayed the effective separation of photoinduced electrons and holes,there by improving the photocatalytic effect.?2?This work combined the g-C₃N₄,FeWO₄ and graphene?electron mediators?to constitute a highly efficient Z-scheme g-C₃N₄-RGO/FeWO₄ nanoheterojunctions.The photocatalytic activities of Z-scheme ultra-thin g-C₃N₄-RGO/FeWO₄ nanoheterojunctions were evaluated by the degradation of RhB.Results showed that compared with the conventional g-C₃N₄,FeWO₄ and g-C₃N₄-FeWO₄ composites,g-C₃N₄-RGO/FeWO₄ has the strongest photocatalytic performance,photocatalytic degradation rate was 95.2%.ultra-thin g-C₃N₄-RGO/FeWO₄ exhibited the best photocatalytic performance,owing to the good electron transfer ability of RGO.The introduction of RGO effectively reduced the FeWO₄ particle size and increased their contact area,which is beneficial for enhancing the charge separation.Moreover,the increased specific surface area of g-C₃N₄-RGO/FeWO₄ also enhanced the pollutant adsorption and light absorption.More importantly,the Z-scheme photocatalysts could realize the efficient charge separation,and meanwhile,preserve the reduction ability or oxidation ability of left electrons or holes.?3?Three-dimensional graphene composites?RGO?/B-TiO₂ were synthesized by one-step hydrothermol method using graphene oxide?GO?and B-TiO₂.The photocatalytic activity of the samples was evaluated by degradation of RhB.The results showed that photocatalytic performance of RGO/B-TiO₂ composites under visible light irradiation was higher than that of B-TiO₂ or TiO₂.Furthermore,the composites showed the highest photocatalytic activity when the RGO content was 1%.The introduction of RGO into B-TiO₂photocatalytic could remarkably enhance their photocatalytic activities by facilitating the electron-holes separation.?4?A facile hydrothermal approach was developed to prepare W-TiO₂/B-TiO₂ composites.The morphology,structure and optical properties of W-TiO₂/B-TiO₂ were systematically characterized and the photocatalytic activity of the smaples was evaluated by degrading RhB.The results showed that composite photocatalysts exhibited higher the photocatalytic activity than that of that of W-TiO₂ or B-TiO₂ alone.The RhB removal on W-TiO₂/B-TiO₂ can reach more than 91.2%after 180 min.The superior photocatalytic performance of W-TiO₂/B-TiO₂homojunction is owing to the formed n-n homojunction,which promoted the separation of photoinduced charge carriers and effectively suppressed their recombination,thus leading to the improved the photocatalytic efficiency.