Modification Of Hierarchically Bi₂MoO₆ Microsphere With Enhanced Photocatalytic And Adsorption Performance Via The Synergistic Effect

Semiconductor-based photocatalysis has the advantages of economy,efficiency and green for environmental treatment and remediation,thus,it is highly significant to design and develop efficient photocatalysts.Nowadays,Ti O₂ is the most widely investigated photocatalyst materials.Nevertheless,Ti O₂-based has two main drawbacks.Firstly,Ti O₂ only can be photoactivated under UV light to exhibit low solar energy conversion efficiency,which accounts for only 5% of ther energy of the sun,because of its wide band gap of 3.2 e V;Secondly,the high recombination rate of photogenerated electron-hole?e-/h+?pairs leads to low quantum efficiency.These shortcomings greatly limit its practical applications.In recent years,the Bi-based oxides photocatalyst materials and their catalytic properties have been received massive interest.In particular,Bismuth molybdate?Bi2Mo O6?,featuring a layered configuration,is the simplest member of the Aurivillius family of layered compounds,and consists of?Bi2O₂?²⁺ layers interleaved with perovskite-like?Mo O₄?^2-layers,displaying an excellent photocatalytic performance for completely degrading organic pollutants in waste water under visible light irradiation.As one of the simplest Aurivillius oxides,Bi₂MoO₆ possess a narrow band gap,ranging from 2.5 to 2.8 e V,and is capable of capturing visible light.Currently,it is has received much attention owing to its excellent photocatalytic activity,inexpensive,non-toxic and high chemical stability.In this dissertation,we focus on the low visible light utilization efficiency and high recombination of photogenerated e-/h+ pairs of Bi₂MoO₆ -based photocatalysts.By using ion doping,noble metal deposition and heterostructure construction strategies to improve its properties in repressing the recombination of photogenerated e-/h+ pairs and thereby enhance the adsorption and catalytic performance.The main works and the relevant results are as follows:First,porous Bi OBr/Bi₂MoO₆ heterostructures absorbent material were successfully fabricated,in which Bi OBr nanoparticles were deposited on the surface of the secondary nanoplate of three-dimensional porous Bi₂MoO₆ architectures through a depositionprecipitation process.The effects of initial p H,adsorbent dosage,contact time,and initial concentration were investigated.Additionally,the dynamics,thermodynamics and possible adsorption mechanism were also systematically investigated.Second,novel La and F co-doped Bi₂MoO₆ architectures were successfully synthesized via a facile solvothermal process.F atoms only replaced some of the O atoms in the [Mo O6] octahedron and thereby leading to move up the valence band?VB?edge of the Bi₂MoO₆ catalyst,decrease the band gap and broaden the absorption in the visible-light region;Meanwhile,the doped La3+ ions replaced some of the Bi3+ atoms in the?Bi2O₂?²⁺ layer.The synergistic effect of F,La-codoping are beneficial to capture the photogenerated electrons to improve the separation efficiency of the photo-induced e-/h+ and thus significantly improve photocatalytic activity.Third,a heterostructured Ag/Bi₂MoO_6-x photocatalyst was successfully synthesized via a solvothermal,calcination and photoreduction process.The effects of the calcination temperature and silver deposition on photocatalytic activity of Bi₂MoO₆ were investigated systematically.The significant improvement of the photocatalytic activity results indicated that the synergistic effect of surface oxygen defects?SOVs?and Ag nanoparticles?NPs?surface plasmonic resonance?SPR?is responsible for the efficient separation and migration of photogenerated electrons and holes,thus resulting in the remarkably improved photocatalytic activity.Fourth,a sandwich-like Z-scheme tricomponent Cd S/Ag/Bi₂MoO₆ photocatalytic system was successfully fabricated through a solvothermal,photoreduction and deposition-precipitation method.The synergistic effect of Cd S and Ag nanoparticles on the surface of Bi₂MoO₆ not only broaden the absorption in the visible-light region but also remarkably improve photocatalytic activity.