Modification And Properties Of Bi₂WO₆ Nanosheets Photocatalvtic Materials

At present,the problems of global ecological environment pollution and energy shortage are increasingly serious.Semiconductor photocatalysis technology has attracted extensive attention from researchers in various countries due to its outstanding advantages in energy conversion and environmental governance.Bi2WO6,as a narrow band gap photocatalytic material with unique crystal and band structure,is considered as a visible photocatalytic material with great development potential.However,the light quantum efficiency and photocatalytic activity of a single Bi2WO6 photocatalytic material still need to be further improved.Therefore,based on Bi2WO6 nanosheets,Bi2WO6 modification research is carried out from the aspects of heterogeneous element doping,surface morphology control,noble metal nanoparticle loading,etc.The main research contents and conclusions are as follows:(1)Bi2WO6 photocatalytic material was modified by hydrothermal synthesis and Nb doping.The effect of Nb doping on the structure and properties of Bi2WO6 photocatalytic material was studied.The experimental results show that the crystal structure of Bi2WO6 still belongs to orthorhombic system without obvious change when the mole fraction of Nb doping is within 7%.The introduction of a small amount of Nb element,on the one hand,widens the absorption range of visible light by introducing impurity energy levels;on the other hand,due to the difference between Nb and W orbital energy levels,oxygen vacancies will be generated on the surface of Bi2WO6,which act as electron capture agents,thus effectively improving the transport efficiency of photogenerated carriers.Under visible light,the 5%Nb doped Bi2WO6 photocatalyst showed excellent photocatalytic activity in the degradation experiments of rhodamine B and tetracycline hydrochloride.(2)Under hydrothermal reaction conditions,Bi2WO6 nanotubes photocatalytic material assembled from Bi2WO6 nanosheets was prepared with oxalic acid as raw material,and its formation mechanism and photocatalytic characteristics were studied.The results show that the three-dimensional hollow tubular morphology is grown from the solid rod intermediate produced by hydrolysis.The strong complexing property of oxalic acid is utilized to form a complex complex with Bi3+,BiWO6 nanoparticles are formed by combining the precipitated Bi3+ with WO42-,and then the nanoparticles serve as crystal nuclei to form nanotubes through self-assembly and Oswald aging.The three-dimensional hollow nanotubes morphology improves the photo-generated carrier separation efficiency of Bi2WO6 photocatalytic material,thus showing excellent visible photocatalytic activity in the photocatalytic degradation experiment of rhodamine B.(3)Ag nanoparticles were loaded on the surface of Bi2WO6 nanotubes by photo-reduction method,and the effect of nanoparticles Ag loading on the properties of Bi2WO6 was studied.The results show that Ag nanoparticles are uniformly loaded on Bi2WO6 surface,and the loading amount of nanoparticles Ag can be controlled conveniently by controlling the illumination time.Ag nanoparticles act as electron capture agents to capture photogenerated electrons and promote the separation and migration of photogenerated carriers,thus significantly improving the photocatalytic activity of Bi2WO6.The photocatalytic degradation activity of Ag-loaded Bi2WO6 nanotubes on rhodamine B is up to 2.25 times of unmodified Bi2WO6.