Controllable Synthesis Of Bismuth Oxyhalide Nanocatalysts With Highly Solar-Motivated Photocatalytic Activity To Decontaminate Environmental Contaminants

Bismuth oxyhalide photocatalytic materials including Bi OCl,Bi OBr and Bi OI have attracted extensive consideration as an inexpensive and advanced photocatalysts due to their attractive energy band structure and unique layered structure,which is appropriate for wide range of applications as such as solar energy conversion and environmental remediations.However,its real-world applications are still shackled by some intrinsic and intractable challenges such as low specific surface area,high photoinduced electron-hole recombination,lower separation and diffusion of charge carriers and spontaneous structural growth into large size leading to their limited photocatalytic activity.The research work in this thesis primarily emphases on the fabrication of bismuth oxyhalide photocatalysts via efficient,facile,cost-effective and environmental friendly synthetic routes.The synthesized products have extraordinary physical/chemical properties and thus exhibit the enhanced photocatalytic activity towards the decontaminate of diverse environmental pollutants.The main results and new findings in this work are summarized as follows:(1)In this chapter,unlike the conventional high temperature(110~180 oC)methods,we described the first straightforward Poly(sodium 4-styrenesulfonate)(PSS)-mediated synthetic path for the mass production of Bi OCl-UTNs in an open-vessel at room-temperature.Asprepared Bi OCl-UTNs are ultrathin(3~5 nm)with planar dimensions of 30~50 nm.The investigation about the formation process of Bi OCl-UTNs revealed that the strong electrostatic interaction occurred between [PSS]-and [Bi2O2]2+ layers which restricted the growth rate of Bi OCl nanoplates along <001> direction and results Bi OCl-UTNs.The electrolyte sedimentation process governed by Na+ ions permit the facile collection as well as mass production of Bi OClUTNs.The as-prepared Bi OCl-UTNs showed high photocatalytic activity for the decontamination of organic dyes and antibiotics.improved light absorption ability,large specific surface area,and quick separation and transmission of the photoexcited charge carriers which turn out to be the reasons for the high photocatalytic activity of Bi OCl-UTNs.(2)In this part of thesis,different from the conventional Bi OCl nanoplates having smooth surfaces(Bi OCl NPLs-SSs),we report the synthesis of unprecedented Bi OCl nanoplates with surface pits(Bi OCl NPLs-SPs)via PVP-mediated solvothermal method and displays its superior activity for the degradation of environmental pollutants.It is found that the surface pits generated in Bi OCl NPLs-SPs are due to the inhomogeneous adsorption of PVP on {001} planes of Bi OCl.Owing to the high-density surface pits,the Bi OCl NPLs-SPs displays not only large specific surface area and improved light absorption capability,but also possess plentiful low-coordination atoms,catalytic reaction active sites and adsorption sites.Such remarkable properties enable the quick separation and transfer of photoexcited carriers,resulting Bi OCl NPLs-SPs with eminent photocatalytic activity for the degradation of antibiotics(ciprofloxacin),organic dyes(Rhodamine B,methyl orange,methyl blue)and industrial chemicals(bisphenol-A).Interestingly,by adjusting halogen salts,the present method is extendable to obtain Bi OBr NPLsSPs and Bi OI NPLs-SPs with surface pits.(3)In this section of thesis,quite different from conventional Bi OCl nanoplates with individual surface-feature,we report the preparation of well-crystalline Bi OCl nanoplates enclosed by distinct triple-surface-features including ultrathin-thickness,channeled self-assembly and multiple atomic steps(Bi OCl-UCNP).Due to ultrathin thickness(2-3 nm),Bi OCl-UCNP shows improved surface area(14.4 m2g-1),narrower energy bandgap(3.05 e V)as well as provide the shorter migration route for photoinduced electrons.The plentiful snaky channels enhanced the light absorption ability and the adsorption of target molecules in Bi OCl-UCNP.The low coordinated multiple atomic steps assist as catalytic centers to accelerate the separation of photogenerated electron-holes.So,under simulated solar-light,by consuming very low amount(5 mg),Bi OCl-UCNP displays excellent efficiency(>99 %)to degrade antibiotics,organic dyes and industrial pollutants.(4)In this chapter,well-crystalline ultrathin Bi OBr nanoplates(U-BBN)are fabricated in an open-vessel at room-temperature through the support of PSS,which is supposed to be different from routinely high temperature synthetic methods.Results expose that PSS generates an intermediate PSS-Bi(OCH2CH2OH)composite by electrostatic interaction with [Bi2O2]+2 and mild down the spontaneous growth rate of Bi OBr nanoplates along <001> direction.Consequently,6~7 nm ultrathin U-BBN with 50~60 nm of planar size is produced.In addition,with large-scale synthesis,5.26 g of U-BBN is obtained having well-controlled thicknesses and size.In comparison to thick Bi OBr nanoplates(BBN),U-BBN possess high surface area,reduced energy bandgap,enhanced capacity to separate photoinduced electron-holes,and decent ability to suppress the possibility of charge recombination.As a result,under the exposure of visible light,U-BBN exhibits superior catalytic activity to not only degrade the antibiotic ciprofloxacin and rhodamine B,but it shows impressive potential to reduce Cr(VI)ions from aqueous solution.We believe that this research is not only great addition in the synthesis of semiconductor photocatalysts,but also it opens the new and effective way for the future exploration of bismuth based oxyhalide nanomaterials for other potential applications.