Preparation Of Black Phosphorus Composite Photocatalysts And Study On Their Visible-Light Driven Photocatalytic Hydrogen Evolution Performance

Since human being entered the 21^st century,the comprehensive utilization of solar energy has been considered as one of the most effective strategies to solve the global energy problem and improve the quality of live.It is a goal of researchers all over the world to convert solar energy into other form of energy that can be used directly.Since the development of photocatalytic technology,solar energy with the characteristics of discontinuous spatial and temporal distribution and difficult to be utilized directly can be converted into hydrogen?H₂?energy.As the H₂ energy has the advantages of easy storage and transportation,high energy density and direct utilization,photocatalytic water splitting is expected to become a new energy conversion strategy.As a novel inorganic non-metallic semiconductor material with wide optical absorption range,high carrier mobility and tunable band structure,black phosphorus?BP?has attracted more and more attention in photocatalysis and electrocatalysis.However,BP has the defects of fast photogenerated carriers recombination,low concentration of photogenerated electrons and insufficient stability,which limit it practical application of photocatalytic H₂ production.With easily preparation,good photocatalytic activity and stability,metal oxides are suitable for compounding with BP.In this paper,in order to overcome the defects of BP and further develop its photocatalytic performance,BP and metal oxides were compounded to construct suitable heterojunctions,which could improve the photocatalytic activity and stability of BP materials.A series of experimental and analysis methods were used to explore the structure,optical properties,photocatalytic activity and mechanism of the prepared samples.The main contents of this thesis are as follows:?1?BP/SnNb₂O₆?BP/SNO?nanohybrid photocatalyst was synthesized via a facile mixing strategy.XRD,SEM,HRTEM,XPS and DRS were used to investigate the crystal structure,micro-morphology,chemical state and optical absorption properties of the samples.The photocatalytic activity of BP/SNO was investigated by the H₂ evolution and organic pollutants degradation experiments under the visible-light irradiation.The results showed that the photocatalytic activity of BP/SNO was significantly enhanced compared with that of single component.BP/SNO sample with 10%?wt%?BP exhibited a photocatalytic activity of 134.5?mol·g^-1·h^-1 and good stability.The mechanism experiment and calculation demonstrated that the heterojunction between BP and SNO enhance the separation efficiency of photogenerated carriers,thus improve the photocatalytic activity of the sample.?2?BP/Co₃O₄ composite photocatalyst was prepared by a facile mixing-calcination method.To explore the crystal structure,micro-morphology and optical absorption properties of BP,Co₃O₄ and BP/Co₃O₄,XRD,SEM,AFM,XPS,DRS and other detection techniques were conducted.The H₂ evolution experiments showed that the BP/Co₃O₄ sample containing 15%?wt%?BP exhibited the highest visible H₂ production activity of 100.4?mol·g^-1·h^-1 and maintained good stability.The mechanism experiment and calculation indicated that the Z-scheme heterojunction between BP and Co₃O₄ is beneficial to the separation of photogenerated carriers,cause the improvement of photocatalytic activity of materials.?3?BP/?-Fe₂O₃ photocatalyst was synthesized via a facile mixing strategy.The crystal structure,morphology and element composition of the samples were measured by XRD,SEM,TEM,XPS,DRS and other analysis techniques.The photocatalytic activity and cyclic stability of BP/?-Fe₂O₃ samples were investigated under visible-light irradiation.The results show that the BP/?-Fe₂O₃ with 40%?wt%?BP had the highest H₂ production rate of 93.9?mol·g^-1·h^-1 and the oxygen production rate of 59.3?mol·g^-1·h^-1.Cyclic experiments showed that it has good stability.The mechanism of the sample showed that BP/?-Fe₂O₃ Z-scheme heterojunction can effectively promote the separation of photogenerated carriers,increase the concentration of carriers at H₂ and O₂ producing terminals,and thus improve the photocatalytic water splitting activity of the materials.