Enhanced Photocatalytic Activity Of Metal Oxide/g-C₃N₄ Composite By Oxygen Vacancy

In recent years,photocatalytic technology due to the advantages of direct use of sunlight,environmental protection and low cost has been widely concerned by researchers.Among them,graphite phase carbon nitride?g-C₃N₄?due to its suitable band gap,good stability and low cost has been applied in different fields,such as nitrogen fixation;degradation;organic synthesis and CO₂ reduction.However,g-C₃N₄ monomer also has some defects:?1?limited visible light absorption capacity;?2?limited photo-generated carrier migration efficiency,which affects the actual application of g-C₃N₄.Therefore,it deserves further study to improve the photo-activity of g-C₃N₄.In this paper,the photocatalytic activity of composite was significantly enhanced by combination g-C₃N₄\with metal oxides containing oxygen vacancy,our research contents are as follows:?1?SnO_2-x containing oxygen vacancy and g-C₃N₄ was prepared by solvothermal and calcination method,respectively;a series of SnO_2-x/g-C₃N₄composites?SCN?were synthesized by solvothermal method.XRD,FT-IR,XPS and SEM,TEM were used to verify the structure and observe the morphology of the composites;DRS and Photocurrent,EIS were used to verify the light absorption performance of the composites and the separation efficiency of carriers.Among them,the photocatalytic activity of the catalyst was obtained by degradation of TC,RhB and deactivation of E.coil.These experiments showed that the photocatalytic efficiency of the composite was better than that of the monomer.Among them,the optimum sample SCN-0.5 composite can effectively remove 83%of TC under 120min,decompose all of RhB under 15 min,and inactivate all of E.coil under 30 min.Capture experiments,the diagram of band gap and XPS valence band diagram confirmed that the photocatalytic mechanism of the composite is more likely to follow the Z-scheme transfer mechanism.?2?MoO_3-x containing oxygen vacancy and g-C₃N₄ was prepared by solvothermal and calcination method,respectively;a series of 1D MoO_3-x/g-C₃N₄composites?MCN?were prepared by solvothermal method.The structure and the morphology of the composite were measured by XRD,FT-IR,XPS and SEM,TEM.Photoabsorptivity and the recombination efficiency of photo-generated carrier were verified by DRS and Phototcurrent,EIS,PL.The photo-activity of MCN composites was obtained by degradation of MO and deactivation of E.coli(Among them,the kinetic constants of the optimum sample MCN-20 composite were 37.1,5.2,and 4.3times of MoO_3-x,MCN mixture,and g-C₃N₄,respectively).In addition,MCN-20composite can inactivate 100%of E.coli within 15 min,and the performance is also better than that of g-C₃N₄ and MoO_3-x.The capture experiments and the band gap diagram of the catalyst,the mott schottky curve diagram and the valence band diagram of XPS confirmed that the transfer of carriers in the composite was more consistent with the Z-scheme transfer mechanism.?3?The WO₃ and g-C₃N₄ was prepared by calcination method;WO_3-x/2Dg-C₃N₄ composite?WCN?were synthesized by one-step pyrolysis method.XRD,FT-IR,XPS and SEM,TEM were used to verify the structure and the morphology of the composites;the absorption capacity of visible light and photoelectrochemical performance were determined by DRS and Photocurrent,EIS.The photoactivity of WO_3-x/2Dg-C₃N₄ composite was verified by degradation of RhB,TC and deactivation of S.aureus.Among them,the optimum sample WCN-3composite can effectively remove 68%of TC under 100 min,decompose all of RhB under 15 min,and inactivate all of S.aureus under 30 min.The capture experiments,band gap diagram and XPS valence band diagram confirmed the possible photocatalytic mechanism,which the Z-scheme mechanism was more consistent with the transfer mechanism of carriers in the composite.The research of this paper shows that combining g-C₃N₄ and metal oxides containing oxygen vacancy can effectively broaden the light absorption range of the composite,so as to stimulate more photogenerated carriers to participate in the catalytic reaction on the surface of the material.In addition,the presence of oxygen vacancy can enhance the electrical conductivity of composite and increase the separation efficiency of photogenerated e^-and photogenerated h⁺.The heterostructure can further reduce the composite efficiency of photogenerated e^-andphotogenerated h⁺.The research in this paper provides a meaningful reference for the design and synthesize of metal oxide/g-C₃N₄ composite containing oxygen vacancy,and the composite is expected to be applied in the field of environmental purification.