Preparation Of WO₃/g-C₃N₄ Heterojunction Modified By Different Atomic Structures And Study On Its Photocatalytic Performance

Since the beginning of the 21st century,the world is facing severe challenges from energy crisis and environmental pollution,and new materials and new technologies are urgently needed to solve energy crisis and environmental pollution problems.As a promising technology,photocatalysis can continuously convert solar energy into chemical energy under normal temperature and pressure,and realize energy production,chemical synthesis,pollutant degradation,etc,which has aroused wide interest among scientific researchers.The development of high-efficiency photocatalysts is an important key to promote the development of photocatalysis technology,and is also the core content of current photocatalysis research.Single-component materials have difficulties to simultaneously meet the requirements of visible light absorption,photo-generated carrier migration,surface reaction thermodynamic and kinetics for high-efficient photocatalysts,which limit their performance space.The heterojunction systems can take the advantages of different monomer materials as well as inhibit the recombination of photogenerated carriers through the interface carrier transfer effect,thereby obtaining the photocatalytic efficiency superior to that of monomer materials,and thus is expected to achieve efficient use of sunlight.Therefore,in the research of photocatalysis,heterojunction photocatalysts have attracted much attention.The different atomic structure states of the monomer materials(such as crystallinity,defect states,etc.)endow the monomer materials with different bulk and surface properties,which not only affect the bulk carrier migration of the monomer materials,but also affect the interface bonding of the heterojunctions and the resulting carrier transfer at the interface,affecting the photocatalytic activities of the heterojunctions.Therefore,by adjusting the atomic structure states of the monomer materials,it is anticipated to realize the construction of efficient heterojunction photocatalysts.At the same time,studying the effects of different atomic structure states on the construction of heterostructures is an important research direction for the development of heterojunction science.Graphite carbon nitride(g-C3N4)and tungsten trioxide(WO3)are two common semiconductors with visible light absorption,and they are good carriers for the study of photocatalytic heterojunction modification.Therefore,focusing on the scientific problem of heterostructure construction,this thesis adjusted the crystallinity of WO3 and the atomic structure of g-C3N4 respectively,and studied the effect of these adjustments on the WO3/g-C3N4 heterojunction photocatalyst combined with the performance results of Rhodamine B(RhB)degradation under visible light.Through the control of the ball milling process,the crystallinity of monoclinic WO3 is controlled.After the ball milling,the crystallinity of WO3 is reduced to form WO3(B).Using stirring-ultrasonication method and grinding-calcining method,g-C3N4 was compounded with WO3 and WO3(B)to construct heterojunctions.In the experiment of RhB degradation,both WO3/g-C3N4 and WO3(B)/g-C3N4 showed better photocatalytic performance than their respective monomers,indicating the effectiveness of heterostructure building.Among them,the WO3(B)/g-C3N4=10%heterojunction prepared by stirring-ultrasonication method degrades RhB at a rate of 3.58 times that of g-C3N4 under visible light conditions.The degradation rate of WO3(B)/g-C3N4=40%heterojunction under visible light conditions is 6.00 times that of g-C3N4.In comparison,the WO3(B)/g-C3N4 heterojunction shows a lower photo-generated carrier recombination probability and higher photocatalytic performance than the WO3/g-C3N4 heterojunction.The effective modification of the atomic structure of g-C3N4 was achieved based on the post thermal treatment method,and g-C3N4(PT)with better crystallinity as well as defects of nitrogen vacancies was obtained.g-C3N4(PT)shows a visible light catal ytic degradation performance of RhB significantly better than g-C3N4(1.9times).Using stirring-ultrasonication method,g-C3N4 and g-C3N4(PT)were used respectively to con struct composites with WO3.The results showed that the heterojunction effect of WO3/g-C3N4(PT)is not ideal,while WO3/g-C3N4(PT)did not have significantly better visib le light photocatalytic RhB degradation performance than WO3/g-C3N4,indicating that g-C3N4(PT)is not conducive to the construction of heterostructures.